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Sample records for early solar nebula

  1. Two different sources of water for the early solar nebula.

    Science.gov (United States)

    Kupper, Stefan; Tornow, Carmen; Gast, Philipp

    2012-06-01

    Water is essential for life. This is a trivial fact but has profound implications since the forming of life on the early Earth required water. The sources of water and the related amount of delivery depend not only on the conditions on the early Earth itself but also on the evolutionary history of the solar system. Thus we ask where and when water formed in the solar nebula-the precursor of the solar system. In this paper we explore the chemical mechanics for water formation and its expected abundance. This is achieved by studying the parental cloud core of the solar nebula and its gravitational collapse. We have identified two different sources of water for the region of Earth's accretion. The first being the sublimation of the icy mantles of dust grains formed in the parental cloud. The second source is located in the inner region of the collapsing cloud core - the so-called hot corino with a temperature of several hundred Kelvin. There, water is produced efficiently in the gas phase by reactions between neutral molecules. Additionally, we analyse the dependence of the production of water on the initial abundance ratio between carbon and oxygen.

  2. Meteorites and the physico-chemical conditions in the early solar nebula

    CERN Document Server

    Aleon, Jerome

    2008-01-01

    Chondritic meteorites constitute the most ancient rock record available in the laboratory to study the formation of the solar system and its planets. Detailed investigations of their mineralogy, petrography, chemistry and isotopic composition and comparison with other primitive solar system samples such as cometary dust particles have allowed through the years to decipher the conditions of formation of their individual components thought to have once been free-floating pieces of dust and rocks in the early solar nebula. When put in the context of astrophysical models of young stellar objects, chondritic meteorites and cometary dust bring essential insights on the astrophysical conditions prevailing in the very first stages of the solar system. Several exemples are shown in this chapter, which include (1) high temperature processes and the formation of chondrules and refractory inclusions, (2) oxygen isotopes and their bearing on photochemistry and large scale geochemical reservoirs in the nebula, (3) organosy...

  3. Origin of uranium isotope variations in early solar nebula condensates.

    Science.gov (United States)

    Tissot, François L H; Dauphas, Nicolas; Grossman, Lawrence

    2016-03-01

    High-temperature condensates found in meteorites display uranium isotopic variations ((235)U/(238)U), which complicate dating the solar system's formation and whose origin remains mysterious. It is possible that these variations are due to the decay of the short-lived radionuclide (247)Cm (t 1/2 = 15.6 My) into (235)U, but they could also be due to uranium kinetic isotopic fractionation during condensation. We report uranium isotope measurements of meteoritic refractory inclusions that reveal excesses of (235)U reaching ~+6% relative to average solar system composition, which can only be due to the decay of (247)Cm. This allows us to constrain the (247)Cm/(235)U ratio at solar system formation to (1.1 ± 0.3) × 10(-4). This value provides new clues on the universality of the nucleosynthetic r-process of rapid neutron capture.

  4. Origin of uranium isotope variations in early solar nebula condensates

    CERN Document Server

    Tissot, Francois L H; Grossman, Lawrence

    2016-01-01

    High temperature condensates found in meteorites display uranium isotopic variations (235U/238U) that complicate dating of the formation of the Solar System and whose origin remains mysterious. It is possible that these variations are due to decay of the short-lived radionuclide 247Cm (t1/2=15.6 Myr) into 235U but they could also be due to uranium kinetic isotopic fractionation during condensation. We report uranium isotope measurements of meteoritic refractory inclusions that reveal excesses of 235U reaching ~+6 % relative to average solar system composition, which can only be due to decay of 247Cm. This allows us to constrain the 247Cm/235U ratio at Solar System formation to (1.1 +- 0.3) x 10-4. This value provides new clues on the universality of nucleosynthetic r-process of rapid neutron capture.

  5. Magnetically controlled solar nebula

    Science.gov (United States)

    Stepinski, T. F.; Reyes-Ruiz, M.

    1993-01-01

    It is widely believed that a primordial solar nebula, the precursor of the Sun and its planetary system, could be best described in terms of an accretion disk. Such an accretion disk is though to be turbulent, and it is usually imagined that turbulent viscosity alone provides the torque responsible for the structure and the evolution of the nebula. However, it was found that an MHD dynamo operating in a turbulent nebula can contemporaneously produce magnetic fields capable of significantly altering or even dominating the total torque. Thus, it seems that no model of a viscous solar nebula is complete without taking magnetic fields into consideration. It was demonstrated that there are usually two distinct regions of nebular disk where a dynamo can operate: the inner region, where the magnetic field coupled to gas due to relatively high thermal ionization; and the outer region, where this coupling is achieved due to nonthermal ionization. Most models also show the existence of an intermediate region, 'the magnetic gap,' where neither thermal nor nonthermal sources can produce enough ionization to provide the necessary coupling between the magnetic field and the gas. The location and width of the gap change substantially from one model to another. At present, we can only estimate the strength of a generated magnetic field. It seems that a large-scale magnetic field is likely to be in the equipartition with the turbulent kinetic energy; however, the intense magnetic fluctuations may greatly exceed this equipartition strength on short time and length scales. To show how a dynamo-generated magnetic field changes the structure of a viscous nebula, we consider four nebula models extensively.

  6. Contraction of the solar nebula

    Science.gov (United States)

    Rawal, J. J.

    1984-10-01

    The concept of Roche limit is applied to the Laplacian theory of the origin of the solar system to study the contraction of a spherical gas cloud (solar nebula). In the process of contraction of the solar nebula, it is assumed that the phenomenon of supersonic turbulent convection described by Prentice (1978) is operative. It is found that the radius of the contracting solar nebula follows Titius-Bode law Rp = R_sun; ap, where R_sun; is the radius of the present Sun and a = 1.442. The consequences of the relation are also discussed. The aim, here, is an attempt to explain, on the basis of the concept of Roche limit, the distribution of planets in the solar system and try to understand the physics underlying it.

  7. The Spatial Distribution of Carbon Dust in the Early Solar Nebula and the Carbon Content of Planetesimals

    Science.gov (United States)

    Gail, H.-P.; Trieloff, M.

    2016-08-01

    The oxidation and pyrolysis processes in the chemically active regions of the Solar Nebula are considered that are responsible for the destruction of the pristine carbon inherited from the ISM and its conversion to hydrocarbons and ultimately to CO.

  8. Interstellar molecules - Formation in solar nebulae

    Science.gov (United States)

    Anders, E.

    1973-01-01

    Herbig's (1970) hypothesis that solar nebulae might be the principal source of interstellar grains and molecules is investigated. The investigation includes the determination of physical and chemical conditions in the early solar system. The production of organic compounds in the solar nebula is studied, and the compounds in meteorites are compared with those obtained in Miller-Urey and Fischer-Tropsch-type (FTT) reactions, taking into consideration aliphatic hydrocarbons, aromatic hydrocarbons, purines, pyrimidines, amino acids, porphyrins, and aspects of carbon-isotope fractionation. It is found that FTT reactions account reasonably well for all well-established features of organic matter in meteorites investigated. The distribution of compounds produced by FTT reactions is compared with the distribution of interstellar molecules. Biological implications of the results are considered.

  9. Organic Analysis of Catalytic Fischer-Tropsch Synthesis Products and Ordinary Chondrite Meteorites by Stepwise Pyrolysis-GCMS: Organics in the Early Solar Nebula

    Science.gov (United States)

    Locke, Darren R.; Yazzie, Cyriah A.; Burton, Aaron S.; Niles, Paul B.; Johnson, Natasha M.

    2014-01-01

    Abiotic generation of complex organic compounds, in the early solar nebula that formed our solar system, is hypothesized by some to occur via Fischer-Tropsch (FT) synthesis. In its simplest form, FT synthesis involves the low temperature (synthesis has been utilized in the gas-to-liquid process to convert syngas, produced from coal, natural gas, or biomass, into paraffin waxes that can be cracked to produce liquid diesel fuels. In general, the effect of increasing reaction temperature (>300degC) produces FT products that include lesser amounts of n-alkanes and greater alkene, alcohol, and polycyclic aromatic hydrocarbon (PAH) compounds. We have begun to experimentally investigate FT synthesis in the context of abiotic generation of organic compounds in the early solar nebula. It is generally thought that the early solar nebula included abundant hydrogen and carbon monoxide gases and nano-particulate matter such as iron and metal silicates that could have catalyzed the FT reaction. The effect of FT reaction temperature, catalyst type, and experiment duration on the resulting products is being investigated. These solid organic products are analyzed by thermal-stepwise pyrolysis-GCMS and yield the types and distribution of hydrocarbon compounds released as a function of temperature. We show how the FT products vary by reaction temperature, catalyst type, and experimental duration and compare these products to organic compounds found to be indigenous to ordinary chondrite meteorites. We hypothesize that the origin of organics in some chondritic meteorites, that represent an aggregation of materials from the early solar system, may at least in part be from FT synthesis that occurred in the early solar nebula.

  10. Chemo-dynamical deuterium fractionation in the early solar nebula: The origin of water on Earth and in asteroids and comets

    CERN Document Server

    Albertsson, T; Henning, Th

    2014-01-01

    Formation and evolution of water in the Solar System and the origin of water on Earth constitute one of the most interesting questions in astronomy. The prevailing hypothesis for the origin of water on Earth is by delivery through water-rich small Solar system bodies. In this paper, the isotopic and chemical evolution of water during the early history of the solar nebula, before the onset of planetesimal formation, is studied. A gas-grain chemical model that includes multiply-deuterated species and nuclear spin-states is combined with a steady-state solar nebula model. To calculate initial abundances, we simulated 1 Myr of evolution of a cold and dark TMC1-like prestellar core. Two time-dependent chemical models of the solar nebula are calculated over 1 Myr: (1) a laminar model and (2) a model with 2D turbulent mixing. We find that the radial outward increase of the H2O D/H ratio is shallower in the chemo-dynamical nebular model compared to the laminar model. This is related to more efficient de-fractionation...

  11. Magnetic field in the primitive solar nebula

    Science.gov (United States)

    Levy, E. H.

    1978-01-01

    Carbonaceous chondrites have apparently been magnetized in their early history in magnetic fields with intensities of 0.1 to 10 G, but the origin of the magnetizing field has remained obscured. It is suggested that the magnetic field recorded in the remanence of carbonaceous chondrites may have been produced by a self-excited hydromagnetic dynamo in the gaseous preplanetary nebula from which the solar system is thought to have formed. Recently computed models for the evolution of the preplanetary nebula, consisting of turbulent and differentially rotating gaseous disks with characteristic radial scales of several AU, are used to demonstrate the feasibility of this hypothesis. The maximum field intensity that might be realized by the dynamo production process is estimated to be as high as 1 to 10 G, taking into account two dynamical mechanisms that limit the strength of the field (the Coriolis force and ambipolar diffusion).

  12. Si isotope homogeneity of the solar nebula

    Energy Technology Data Exchange (ETDEWEB)

    Pringle, Emily A.; Savage, Paul S.; Moynier, Frédéric [Department of Earth and Planetary Sciences and McDonnell Center for the Space Sciences, Washington University in St. Louis, One Brookings Drive, St. Louis, MO 63130 (United States); Jackson, Matthew G. [Department of Earth Science, University of California, Santa Barbara, CA 93109 (United States); Barrat, Jean-Alix, E-mail: eapringle@wustl.edu, E-mail: savage@levee.wustl.edu, E-mail: pringle@ipgp.fr, E-mail: moynier@ipgp.fr, E-mail: jackson@geol.ucsb.edu, E-mail: Jean-Alix.Barrat@univ-brest.fr [Université Européenne de Bretagne, Université de Brest, CNRS UMR 6538 (Domaines Océaniques), I.U.E.M., Place Nicolas Copernic, F-29280 Plouzané Cedex (France)

    2013-12-20

    The presence or absence of variations in the mass-independent abundances of Si isotopes in bulk meteorites provides important clues concerning the evolution of the early solar system. No Si isotopic anomalies have been found within the level of analytical precision of 15 ppm in {sup 29}Si/{sup 28}Si across a wide range of inner solar system materials, including terrestrial basalts, chondrites, and achondrites. A possible exception is the angrites, which may exhibit small excesses of {sup 29}Si. However, the general absence of anomalies suggests that primitive meteorites and differentiated planetesimals formed in a reservoir that was isotopically homogenous with respect to Si. Furthermore, the lack of resolvable anomalies in the calcium-aluminum-rich inclusion measured here suggests that any nucleosynthetic anomalies in Si isotopes were erased through mixing in the solar nebula prior to the formation of refractory solids. The homogeneity exhibited by Si isotopes may have implications for the distribution of Mg isotopes in the solar nebula. Based on supernova nucleosynthetic yield calculations, the expected magnitude of heavy-isotope overabundance is larger for Si than for Mg, suggesting that any potential Mg heterogeneity, if present, exists below the 15 ppm level.

  13. Abundant Solar Nebula Solids in Comets

    Science.gov (United States)

    Messenger, S.; Keller, L. P.; Nakamura-Messenger, K.; Nguyen, A. N.; Clemett, S.

    2016-01-01

    Comets have been proposed to consist of unprocessed interstellar materials together with a variable amount of thermally annealed interstellar grains. Recent studies of cometary solids in the laboratory have shown that comets instead consist of a wide range of materials from across the protoplanetary disk, in addition to a minor complement of interstellar materials. These advances were made possible by the return of direct samples of comet 81P/Wild 2 coma dust by the NASA Stardust mission and recent advances in microscale analytical techniques. Isotopic studies of 'cometary' chondritic porous interplanetary dust particles (CP-IDPs) and comet 81P/Wild 2 Stardust samples show that preserved interstellar materials are more abundant in comets than in any class of meteorite. Identified interstellar materials include sub-micron-sized presolar silicates, oxides, and SiC dust grains and some fraction of the organic material that binds the samples together. Presolar grain abundances reach 1 weight percentage in the most stardust-rich CP-IDPs, 50 times greater than in meteorites. Yet, order of magnitude variations in presolar grain abundances among CP-IDPs suggest cometary solids experienced significant variations in the degree of processing in the solar nebula. Comets contain a surprisingly high abundance of nebular solids formed or altered at high temperatures. Comet 81P/Wild 2 samples include 10-40 micron-sized, refractory Ca- Al-rich inclusion (CAI)-, chondrule-, and ameboid olivine aggregate (AOA)-like materials. The O isotopic compositions of these refractory materials are remarkably similar to their meteoritic counterparts, ranging from 5 percent enrichments in (sup 16) O to near-terrestrial values. Comet 81P/Wild 2 and CP-IDPs also contain abundant Mg-Fe crystalline and amorphous silicates whose O isotopic compositions are also consistent with Solar System origins. Unlike meteorites, that are dominated by locally-produced materials, comets appear to be composed of

  14. Lifetime of the solar nebula constrained by meteorite paleomagnetism

    Science.gov (United States)

    Wang, Huapei; Weiss, Benjamin P.; Bai, Xue-Ning; Downey, Brynna G.; Wang, Jun; Wang, Jiajun; Suavet, Clément; Fu, Roger R.; Zucolotto, Maria E.

    2017-02-01

    A key stage in planet formation is the evolution of a gaseous and magnetized solar nebula. However, the lifetime of the nebular magnetic field and nebula are poorly constrained. We present paleomagnetic analyses of volcanic angrites demonstrating that they formed in a near-zero magnetic field (core dynamo on the angrite parent body did not initiate until about 4 to 11 million years after solar system formation.

  15. Mixing and Transport in the Solar Nebula

    Science.gov (United States)

    Boss, Alan P.

    2003-01-01

    Boss & Vanhala (2000, 2001) prepared reviews of triggered collapse and injection models, using Prudence Foster's finite differences code at very high spatial resolution (440 x 1440 cells) to demonstrate the convergence of the R-T fingers in triggered injection models. A two dimensional hydrodynamical calculation with unprecedentedly high spatial resolution (960 x 2880 zones, or almost 3 million grid points) demonstrated that it suitable shock front can both trigger the collapse of an otherwise stable presolar cloud, and inject shock front particles into the collapsing cloud through the formation of what become Rayleigh-Taylor fingers of compressed fluid layers falling into the gravitational potential well of the growing protostar. These calculations suggest that heterogeneity derived from these R-T fingers will persist down to the scale of their injection onto the surface of the solar nebula. Haghighipour developed a numerical code capable of calculating the orbital evolution of dust grains of varied sizes in a gaseous nebula, subject to Epstein and Stokes drag as well as the self-gravity of the disk. In collaboration with the PI and George W. Wetherill, Haghighipour has been involved in development of a new idea on the possibility of rapid formation of ice giant planets via the disk instability mechanism. Haghighipour studied the stability of a five-body system consisting of the Sun and four protoplanets by numerically integrating their equations of motions. Using Levison and Duncan s SWIFT integrator, Haghighipour showed that, depending on the orbital parameters of the bodies, such a system can be stable for 0.1-10 Myr. Time periods of 1 Myr or more are long enough to be consistent with the time scale proposed for the formation of giant planets by the disk instability mechanism and the photoevaporation of the gaseous envelopes of the outermost protoplanets by a nearby OB star, resulting in the formation of ice giant planets. The PI has used his three dimensional

  16. Evidence for an early nitrogen isotopic evolution in the solar nebula from volatile analyses of a CAI from the CV3 chondrite NWA 8616

    Science.gov (United States)

    Füri, Evelyn; Chaussidon, Marc; Marty, Bernard

    2015-03-01

    Nitrogen and noble gas (Ne-Ar) abundances and isotope ratios, determined by CO2 laser extraction static mass spectrometry analysis, as well as Al-Mg and O isotope data from secondary ion mass spectrometry (SIMS) analyses, are reported for a type B calcium-aluminum-rich inclusion (CAI) from the CV3 chondrite NWA 8616. The high (26Al/27Al)i ratio of (5.06 ± 0.50) × 10-5 dates the last melting event of the CAI at 39-99+109ka after "time zero", limiting the period during which high-temperature exchanges between the CAI and the nebular gas could have occurred to a very short time interval. Partial isotopic exchange with a 16O-poor reservoir resulted in Δ17O > -5‰ for melilite and anorthite, whereas spinel and Al-Ti-pyroxene retain the inferred original 16O-rich signature of the solar nebula (Δ17O ⩽ -20‰). The low 20Ne/22Ne (⩽0.83) and 36Ar/38Ar (⩽0.75) ratios of the CAI rule out the presence of any trapped planetary or solar noble gases. Cosmogenic 21Ne and 38Ar abundances are consistent with a cosmic ray exposure (CRE) age of ∼14 to 20 Ma, assuming CR fluxes similar to modern ones, without any evidence for pre-irradiation of the CAI before incorporation into the meteorite parent body. Strikingly, the CAI contains 1.4-3.4 ppm N with a δ15N value of +8‰ to +30‰. Even after correcting the measured δ15N values for cosmogenic 15N produced in situ, the CAI is highly enriched in 15N compared to the protosolar nebula (δ15NPSN = -383 ± 8‰; Marty et al., 2011), implying that the CAI-forming region was contaminated by 15N-rich material within the first 0.15 Ma of Solar System history, or, alternatively, that the CAI was ejected into the outer Solar System where it interacted with a 15N-rich reservoir.

  17. Generation of dynamo magnetic fields in the primordial solar nebula

    Science.gov (United States)

    Stepinski, Tomasz F.

    1992-01-01

    The present treatment of dynamo-generated magnetic fields in the primordial solar nebula proceeds in view of the ability of the combined action of Keplerian rotation and helical convention to generate, via alpha-omega dynamo, large-scale magnetic fields in those parts of the nebula with sufficiently high, gas-and magnetic field coupling electrical conductivity. Nebular gas electrical conductivity and the radial distribution of the local dynamo number are calculated for both a viscous-accretion disk model and the quiescent-minimum mass nebula. It is found that magnetic fields can be easily generated and maintained by alpha-omega dynamos occupying the inner and outer parts of the nebula.

  18. FORMING CHONDRITES IN A SOLAR NEBULA WITH MAGNETICALLY INDUCED TURBULENCE

    Energy Technology Data Exchange (ETDEWEB)

    Hasegawa, Yasuhiro; Turner, Neal J.; Masiero, Joseph [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Wakita, Shigeru; Matsumoto, Yuji; Oshino, Shoichi, E-mail: yasuhiro@caltech.edu [Center for Computational Astrophysics, National Astronomical Observatory of Japan, Osawa, Mitaka, Tokyo 181-8588 (Japan)

    2016-03-20

    Chondritic meteorites provide valuable opportunities to investigate the origins of the solar system. We explore impact jetting as a mechanism of chondrule formation and subsequent pebble accretion as a mechanism of accreting chondrules onto parent bodies of chondrites, and investigate how these two processes can account for the currently available meteoritic data. We find that when the solar nebula is ≤5 times more massive than the minimum-mass solar nebula at a ≃ 2–3 au and parent bodies of chondrites are ≤10{sup 24} g (≤500 km in radius) in the solar nebula, impact jetting and subsequent pebble accretion can reproduce a number of properties of the meteoritic data. The properties include the present asteroid belt mass, the formation timescale of chondrules, and the magnetic field strength of the nebula derived from chondrules in Semarkona. Since this scenario requires a first generation of planetesimals that trigger impact jetting and serve as parent bodies to accrete chondrules, the upper limit of parent bodies’ masses leads to the following implications: primordial asteroids that were originally ≥10{sup 24} g in mass were unlikely to contain chondrules, while less massive primordial asteroids likely had a chondrule-rich surface layer. The scenario developed from impact jetting and pebble accretion can therefore provide new insights into the origins of the solar system.

  19. External Photoevaporation of the Solar Nebula: Jupiter's Noble Gas Enrichments

    CERN Document Server

    Monga, Nikhil

    2014-01-01

    We present a model explaining elemental enrichments in Jupiter's atmosphere, particularly the noble gases Ar, Kr, and Xe. While He, Ne and O are depleted, seven other elements show similar enrichments ($\\sim$3 times solar, relative to H). Being volatile, Ar is difficult to fractionate from ${\\rm H}_{2}$. We argue that external photoevaporation by far ultraviolet (FUV) radiation from nearby massive stars removed ${\\rm H}_{2}$, He, and Ne from the solar nebula, but Ar and other species were retained because photoevaporation occurred at large heliocentric distances where temperatures were cold enough ($\\lt 30$ K) to trap them in amorphous water ice. As the solar nebula lost H it became relatively and uniformly enriched in other species. Our model improves on the similar model of Guillot \\& Hueso (2006). We recognize that cold temperatures alone do not trap volatiles; continuous water vapor production also is necessary. We demonstrate that FUV fluxes that photoevaporated the disk generated sufficient water va...

  20. Why convective heat transport in the solar nebula was inefficient

    Science.gov (United States)

    Cassen, P.

    1993-01-01

    The radial distributions of the effective temperatures of circumstellar disks associated with pre-main sequence (T Tauri) stars are relatively well-constrained by ground-based and spacecraft infrared photometry and radio continuum observations. If the mechanisms by which energy is transported vertically in the disks are understood, these data can be used to constrain models of the thermal structure and evolution of solar nebula. Several studies of the evolution of the solar nebula have included the calculation of the vertical transport of heat by convection. Such calculations rely on a mixing length theory of transport and some assumption regarding the vertical distribution of internal dissipation. In all cases, the results of these calculations indicate that transport by radiation dominates that by convection, even when the nebula is convectively unstable. A simple argument that demonstrates the generality (and limits) of this result, regardless of the details of mixing length theory or the precise distribution of internal heating is presented. It is based on the idea that the radiative gradient in an optically thick nebula generally does not greatly exceed the adiabatic gradient.

  1. Forming Chondrites in a Solar Nebula with Magnetically Induced Turbulence

    Science.gov (United States)

    Hasegawa, Yasuhiro; Turner, Neal J.; Masiero, Joseph R.

    2016-10-01

    Chondritic meteorites provide valuable opportunities to investigate origins of the solar system. We explore impact jetting as a mechanism to form chondrules and subsequent pebble accretion as a mechanism to accrete them onto parent bodies of chondrites, and investigate how these two processes can account for the currently available meteoritic data. We find that when the solar nebula is 1024 g in mass were unlikely to contain chondrules, while less massive primordial asteroids likely had a chondrule-rich surface layer. The scenario developed from impact jetting and pebble accretion can therefore provide new insights into origins of the solar system.

  2. Catalysis by Dust Grains in the Solar Nebula

    Science.gov (United States)

    Kress, Monika E.; Tielens, Alexander G. G. M.

    1996-01-01

    In order to determine whether grain-catalyzed reactions played an important role in the chemistry of the solar nebula, we have applied our time-dependent model of methane formation via Fischer-Tropsch catalysis to pressures from 10(exp -5) to 1 bar and temperatures from 450 to 650 K. Under these physical conditions, the reaction 3H2 + CO yields CH4 + H2O is readily catalyzed by an iron or nickel surface, whereas the same reaction is kinetically inhibited in the gas phase. Our model results indicate that under certain nebular conditions, conversion of CO to methane could be extremely efficient in the presence of iron-nickel dust grains over timescales very short compared to the lifetime of the solar nebula.

  3. Observations of the Crab Nebula with Early HAWC Data

    CERN Document Server

    Greus, Francisco Salesa

    2015-01-01

    The High Altitude Water Cherenkov (HAWC) Observatory is a TeV gamma-ray detector, completed in early 2015. HAWC started science operations in August 2013 with a third of the detector taking data. Several known gamma-ray sources have already been detected with the first HAWC data. Among these sources, the Crab Nebula, the brightest steady gamma-ray source at very high energies in our Galaxy, has been detected with high significance. In this contribution I will present the results of the observations of the Crab Nebula with HAWC, including time variability, and the detector performance based on early data.

  4. Nucleosynthesis contributions to the solar nebula

    Energy Technology Data Exchange (ETDEWEB)

    Arnould, M.

    1987-09-30

    The discovery of isotopic anomalies in meteorites suggests that the Solar System is made of material from compositionally different and imperfectly mixed reservoirs. One of them, which comprises the bulk Solar System material, is considered to be made of the well-homogenized ashes of many nucleosynthesis events. Its composition can be studied through models of the chemical evolution of the Galaxy. The main nucleosynthetic agents responsible for that evolution are very briefly reviewed, as well as the level of reliability of the model predictions. The remaining reservoir(s) contain(s) isotopically anomalous material, which probably represents only a very minute fraction of the total Solar System material. The great astrophysical importance of the existence of such reservoirs is emphasized.

  5. Interstellar Organics, the Solar Nebula, and Saturn's Satellite Phoebe

    Science.gov (United States)

    Pendleton, Y. J.; Cruikshank, D. P.

    2014-01-01

    The diffuse interstellar medium inventory of organic material (Pendleton et al. 1994, Pendleton & Allamandola 2002) was likely incorporated into the molecular cloud in which the solar nebula condensed. This provided the feedstock for the formation of the Sun, major planets, and the smaller icy bodies in the region outside Neptune's orbit (transneptunian objects, or TNOs). Saturn's satellites Phoebe, Iapetus, and Hyperion open a window to the composition of one class of TNO as revealed by the near-infrared mapping spectrometer (VIMS) on the Cassini spacecraft at Saturn. Phoebe (mean diameter 213 km) is a former TNO now orbiting Saurn. VIMS spaectral maps of PHoebe's surface reveal a complex organic spectral signature consisting of prominent aromatic (CH) and alophatic hydrocarbon (CH2, CH3) absorption bands (3.2-3.6 micrometers). Phoebe is the source of a huge debris ring encircling Saturn, and from which particles (approximately 5-20 micrometer size) spiral inward toward Saturn. They encounter Iapetus and Hperion where they mix with and blanket the native H2O ice of those two bodies. Quantitative analysis of the hydrocarbon bands on Iapetus demonstrates that aromatic CH is approximately 10 times as abundant as aliphatic CH2+CH3, significantly exceeding the strength of the aromatic signature in interplanetary dust particles, comet particles, ad in carbonaceous meteorites (Cruikshank et al. 2013). A similar excess of aromatics over aliphatics is seen in the qualitative analysis of Hyperion and Phoebe itself (Dalle Ore et al. 2012). The Iapetus aliphatic hydrocarbons show CH2/CH3 approximately 4, which is larger than the value found in the diffuse ISM (approximately 2-2.5). In so far as Phoebe is a primitive body that formed in the outer regions of the solar nebula and has preserved some of the original nebula inventory, it can be key to understanding the content and degree of procesing of the nebular material. There are other Phoebe-like TNOs that are presently

  6. Photophoretic transport of hot minerals in the solar nebula

    CERN Document Server

    Moudens, A; Petit, J -M; Wurm, G; Cordier, D; Charnoz, S

    2011-01-01

    Hot temperature minerals have been detected in a large number of comets and were also identified in the samples of Comet Wild 2 that were returned by the Stardust mission. Meanwhile, observations of the distribution of hot minerals in young stellar systems suggest that these materials were produced in the inner part of the primordial nebula and have been transported outward in the formation zone of comets. We investigate the possibility that photophoresis provides a viable mechanism to transport high-temperature materials from the inner solar system to the regions in which the comets were forming. We use a grid of time-dependent disk models of the solar nebula to quantify the distance range at which hot minerals can be transported from the inner part of the disk toward its outer regions as a function of their size and density. The particles considered here are in the form of aggregates that presumably were assembled from hot mineral individual grains ranging down to submicron sizes and formed by condensation ...

  7. The Impact of FU Orionis Outbursts and the Solar Nebula

    Science.gov (United States)

    Bell, Robbins; Young, Richard E. (Technical Monitor)

    1998-01-01

    Protostellar systems are variable on many timescales. One of the most dramatic forms of variability known to occur in low mass stellar systems is the FU Orionis outburst (Herbig 1977). Throughout a typical outburst lasting several decades, system luminosities may be a hundred times what is typical of the quiesent state. FU Orionis outburst events are thought to have significant impact on the thermal structure of the protosolar nebula; their existence has been used to explain features in the meteoritic record from thermally induced homogenization to the formation of chondrules. Until recently, the magnitude of the likely effect from such outbursts has been largely speculative due to the lack of a detailed understanding of the outburst mechanism. Recent numerical models (Bell\\& Lin 1994) have demonstrated the viability of the observational hypothesis (Hartmann\\& Kenyon 1985) that the radiation observed during outburst is emitted by a luminous circumstellar disk transporting mass at a thousand times the quiesent rate. Light curves and color and line width evolution observed in FU Orionis systems are naturally explained by time dependent outbursting model disks (Bell et al. 1995). The radial temperature structure and shape of the disk during outburst derived from these models may be used to calculate the outburst's expected impact on primitive material at various radii throughout the disk. In this review, we will begin by discussing what is known about the FU Orionis outburst phenomenon from recent observations and theory including statistically deduced outburst timescales and observed peak temperatures. Unless covered by another author, we will discuss the evidence which suggests that outburst radiation is emitted by a circumstellar disk rather than by the star and will briefly review the thermal instability as a mechanism for outburst. We will then report on recent work which investigates the likely heating of solar nebula material due to FU Orionis outbursts

  8. Early solar physics

    CERN Document Server

    Meadows, A J

    1970-01-01

    Early Solar Physics reviews developments in solar physics, particularly the advent of solar spectroscopy and the discovery of relationships between the various layers of the solar atmosphere and between the different forms of solar activity. Topics covered include solar observations during 1843; chemical analysis of the solar atmosphere; the spectrum of a solar prominence; and the solar eclipse of December 12, 1871. Spectroscopic observations of the sun are also presented. This book is comprised of 30 chapters and begins with an overview of ideas about the sun in the mid-nineteenth century, fo

  9. Refractory Metal Nuggets -- Formation of the First Condensates in the Solar Nebula

    CERN Document Server

    Liffman, Kurt; Maddison, Sarah; Brooks, Geoffrey

    2012-01-01

    As gas flowed from the solar accretion disk or solar nebula onto the proto-Sun, magnetic pressure gradients in the solar magnetosphere and the inner solar nebula provided an environment where some of this infalling flow was diverted to produce a low pressure, high temperature, gaseous, "infall" atmosphere around the inner solar nebula. The pressure in this inner disk atmosphere was mainly dependant on the accretion flow rate onto the star. High flow rates implied relatively high pressures, which decreased over time as the accretion rate decreased. In the first hundred thousand years after the formation of the solar nebula, accretional flow gas pressures were high enough to create submicron-sized Refractory Metal Nuggets (RMNs) - the precursors to Calcium Aluminum Inclusions (CAIs). Optimal temperatures and pressures for RMN formation may have occurred between 20,000 to 100,000 years after the formation of the solar nebula. It is possible that conditions were conducive to RMN/CAI formation over an eighty thous...

  10. Dark-Matter Content of Early-Type Galaxies with Planetary Nebulae

    NARCIS (Netherlands)

    Napolitano, N.R.; Romanowsky, A.J.; Coccato, L; Capaccioli, M.; Douglas, N.G.; Noordermeer, E.; Merrifield, M.R.; Kuijken, K.; Arnaboldi, M.; Gerhard, O.; Freeman, K.C.; De Lorenzi, F.; Das, P.

    2007-01-01

    Abstract. We examine the dark matter properties of nearby early-type galaxies using plane- tary nebulae (PNe) as mass probes. We have designed a specialised instrument, the Planetary Nebula Spectrograph (PN.S) operating at the William Herschel telescope, with the purpose of measuring PN velocities

  11. Kinematic properties of early-type galaxy haloes using planetary nebulae

    NARCIS (Netherlands)

    Coccato, L.; Gerhard, O.; Arnaboldi, M.; Das, P.; Douglas, N. G.; Kuijken, K.; Merrifield, M. R.; Napolitano, N. R.; Noordermeer, E.; Romanowsky, A. J.; Capaccioli, M.; Cortesi, A.; De Lorenzi, F.; Freeman, K. C.

    2009-01-01

    We present new planetary nebulae (PNe) positions, radial velocities and magnitudes for six early-type galaxies obtained with the Planetary Nebulae Spectrograph (PNS), along with derived two-dimensional velocity and velocity dispersion fields, and the alpha parameters (i.e. the number of PNe per unit

  12. Birth and early evolution of a planetary nebula

    CERN Document Server

    Bobrowsky, M; Parthasarathy, M; García-Lario, P

    1998-01-01

    The final expulsion of gas by a star as it forms a planetary nebula --- the ionized shell of gas often observed surrounding a young white dwarf --- is one of the most poorly understood stages of stellar evolution. Such nebulae form extremely rapidly (about 100 years for the ionization) and so the formation process is inherently difficult to observe. Particularly puzzling is how a spherical star can produce a highly asymmetric nebula with collimated outflows. Here we report optical observations of the Stingray Nebula which has become an ionized planetary nebula within the past few decades. We find that the collimated outflows are already evident, and we have identified the nebular structure that focuses the outflows. We have also found a companion star, reinforcing previous suspicions that binary companions play an important role in shaping planetary nebulae and changing the direction of successive outflows.

  13. Clathration of Volatiles in the Solar Nebula and Implications for the Origin of Titan's atmosphere

    CERN Document Server

    Mousis, Olivier; Thomas, Caroline; Pasek, Matthew; Marboeuf, Ulysse; Alibert, Yann; Ballenegger, Vincent; Cordier, Daniel; Ellinger, Yves; Pauzat, Francoise; Picaud, Sylvain

    2008-01-01

    We describe a scenario of Titan's formation matching the constraints imposed by its current atmospheric composition. Assuming that the abundances of all elements, including oxygen, are solar in the outer nebula, we show that the icy planetesimals were agglomerated in the feeding zone of Saturn from a mixture of clathrates with multiple guest species, so-called stochiometric hydrates such as ammonia hydrate, and pure condensates. We also use a statistical thermodynamic approach to constrain the composition of multiple guest clathrates formed in the solar nebula. We then infer that krypton and xenon, that are expected to condense in the 20-30 K temperature range in the solar nebula, are trapped in clathrates at higher temperatures than 50 K. Once formed, these ices either were accreted by Saturn or remained embedded in its surrounding subnebula until they found their way into the regular satellites growing around Saturn. In order to explain the carbon monoxide and primordial argon deficiencies of Titan's atmosp...

  14. Nonuniform viscosity in the solar nebula and large masses of Jupiter and Saturn

    OpenAIRE

    Jin, Liping

    2008-01-01

    I report a novel theory that nonuniform viscous frictional force in the solar nebula accounts for the largest mass of Jupiter and Saturn and their largest amount of H and He among the planets, two outstanding facts that are unsolved puzzles in our understanding of origin of the Solar System. It is shown that the nebula model of uniform viscosity does not match the present planet masses. By studying current known viscosity mechanisms, I show that viscosity is more efficient in the inner region...

  15. Meteorites: messengers from the early solar system.

    Science.gov (United States)

    Hofmann, Beda A

    2010-01-01

    Meteorites are fragments from solar system bodies, dominantly asteroids. A small fraction is derived from the Moon and from Mars. These rocks tell a rich history of the early solar system and range from solids little changed since the earliest phases of solid matter condensation in the solar nebula (chondrites) to material representing asteroidal metamorphism and melting, impact processes on the Moon and even aqueous alteration near the surface of Mars. Meteorites are very rare. Currently many meteorites result from searches in Antarctica and the hot deserts of North Africa and Arabia. The present high find rate likely represents a unique short-term event, asking for a careful management of this scarce scientific resource.

  16. Hydrocarbons on Saturns Satellites: Relationship to Interstellar Dust and the Solar Nebula

    Science.gov (United States)

    Cruikshank, D. P.

    2012-01-01

    To understand the origin and evolution of our Solar System, and the basic components that led to life on Earth, we study interstellar and planetary spectroscopic signatures. The possible relationship of organic material detected in carbonaceous meteorites, interplanetary dust particles (IDPs), comets and the interstellar medium have been the source of speculation over the years as the composition and processes that governed the early solar nebula have been explored to understand the extent to which primitive material survived or became processed. The Cassini VIMS has provided new data relevant to this problem. Three of Saturn's satellites, Phoebe, Iapetus, and Hyperion, are found to have aromatic and aliphatic hydrocarbons on their surfaces. The aromatic hydrocarbon signature (C-H stretching mode at 3.28 micrometers) is proportionally significantly stronger (relative to the aliphatic bands) than that seen in other Solar System bodies (e.g., comets) and materials (Stardust samples, IDPs, meteorites) and the distinctive sub-features of the 3.4 micrometer aliphatic band (CH2 and CH3 groups) are reminiscent of those widely detected throughout the diffuse ISM. Phoebe may be a captured object that originated in the region beyond the present orbit of Neptune, where the solar nebula contained a large fraction of original interstellar ice and dust that was less processed than material closer to the Sun. Debris from Phoebe now resident on Iapetus and Hyperion, as well as o Phoebe itself, thus presents a unique blend of hydrocarbons, amenable to comparisons with interstellar hydrocarbons and other Solar System materials. The dust ring surrounding Saturn, in which Phoebe is embedded, probably originated from a collision with Phoebe. Dust ring particles are the likely source of the organic-bearing materials, and perhaps the recently identified small particles of Fe detected on Saturn's satellites. Lab measurements of the absolute band strengths of representative aliphatic and

  17. Early-type objects in NGC6611 and Eagle Nebula

    CERN Document Server

    Martayan, Christophe; Hubert, Anne-Marie; Neiner, Coralie; Fremat, Yves; Baade, Dietrich; Fabregat, Juan

    2008-01-01

    An important question about Be stars is whether Be stars are born as Be stars or not. It is necessary to observe young clusters to answer this question. Observations of stars in NGC6611 and the star-formation region of Eagle Nebula have been carried out with the ESO-WFI in slitless spectroscopic mode and at the VLT-GIRAFFE. The targets for the GIRAFFE observations were pre-selected from the literature and our catalogue of emission-line stars (ELS) based on the WFI study. GIRAFFE observations allowed us to study accurately the population of the early-type stars with and without emission lines. For this study, we determined the fundamental parameters of OBA stars. We also studied the status of the objects (main sequence or pre-main sequence stars) by using IR data, membership probabilities, and location in HR diagrams. The nature of the early-type ELS in M16 is derived. The slitless observations with the WFI clearly indicate a small number of ELS in M16. We observed with GIRAFFE 101 OBA stars, among them 9 are ...

  18. Refractory Metal Nuggets - Formation of the first condensates in the Solar Nebula

    Science.gov (United States)

    Liffman, Kurt; Pignatale, Francesco C.; Maddison, Sarah; Brooks, Geoffrey

    2012-09-01

    As gas flowed from the solar accretion disk or Solar Nebula onto the proto-Sun, magnetic pressure gradients in the solar magnetosphere and the inner Solar Nebula provided an environment where some of this infalling flow was diverted to produce a low pressure, high temperature, gaseous, “infall” atmosphere around the inner Solar Nebula. The pressure in this inner disk atmosphere was mainly dependant on the accretion flow rate onto the star. High flow rates implied relatively high pressures, which decreased over time as the accretion rate decreased. In the first hundred thousand years after the formation of the Solar Nebula, accretional flow gas pressures were high enough to create submicron-sized Refractory Metal Nuggets (RMNs) - the precursors to Calcium Aluminum Inclusions (CAIs). Optimal temperatures and pressures for RMN formation may have occurred between 20,000 and 100,000 years after the formation of the Solar Nebula. It is possible that conditions were conducive to RMN/CAI formation over an 80,000 year timescale. The “infall” atmosphere and the condensation of refractory particles within this atmosphere may be observable around the inner disks of other protostellar systems. The interaction of forces from magnetic fields with the radiation pressure from the proto-Sun and the inner solar accretion disk potentially produced an optical-magnetic trap above and below the inner Solar Nebula, which provided a relatively stable environment in which the RMNs/proto-CAIs could form and grow. These RMN formation sites only existed during accretion events from the proto-solar disk onto the proto-Sun. As such, the formation and growth time of a particular RMN was dependent on the timescale of its nascent accretion event. Observational evidence suggests that RMNs were the nucleation particles for CAIs. As a consequence, the observed bimodal distribution of 26Al in CAIs, where some CAIs have 26Al while others do not, is probably due to the injection 26Al during the

  19. Solar Nebula Magnetohydrodynamic Dynamos: Kinematic Theory, Dynamical Constraints, and Magnetic Transport of Angular Momentum

    Science.gov (United States)

    Stepinski, Tomasz F.; Reyes-Ruiz, Mauricio; Vanhala, Harri A. T.

    1993-01-01

    A hydromagnetic dynamo provides the best mechanism for contemporaneously producing magnetic fields in a turbulent solar nebula. We investigate the solar nebula in the framework of a steady-state accretion disk model and establish the criteria for a viable nebular dynamo. We have found that typically a magnetic gap exists in the nebula, the region where the degree of ionization is too small for the magnetic field to couple to the gas. The location and width of this gap depend on the particular model; the supposition is that gaps cover different parts of the nebula at different evolutionary stages. We have found, from several dynamical constraints, that the generated magnetic field is likely to saturate at a strength equal to equipartition with the kinetic energy of turbulence. Maxwell stress arising from a large-scale magnetic field may significantly influence nebular structure, and Maxwell stress due to small-scale fields can actually dominate other stresses in the inner parts of the nebula. We also argue that the bulk of nebular gas, within the scale height from the midplane, is stable against Balbus-Hawley instability.

  20. The Solar Nebula on Fire: A Solution to the Carbon Deficit in the Inner Solar System

    CERN Document Server

    Lee, Jeong-Eun; Nomura, Hideko

    2010-01-01

    Despite a surface dominated by carbon-based life, the bulk composition of the Earth is dramatically carbon poor when compared to the material available at formation. Bulk carbon deficiency extends into the asteroid belt representing a fossil record of the conditions under which planets are born. The initial steps of planet formation involve the growth of primitive sub-micron silicate and carbon grains in the Solar Nebula. We present a solution wherein primordial carbon grains are preferentially destroyed by oxygen atoms ignited by heating due to stellar accretion at radii < 5 AU. This solution can account for the bulk carbon deficiency in the Earth and meteorites, the compositional gradient within the asteroid belt, and for growing evidence for similar carbon deficiency in rocks surrounding other stars.

  1. The Formation of Graphite Whiskers in the Primitive Solar Nebula

    Science.gov (United States)

    Nuth, Joseph A., III; Kimura, Yuki; Lucas, Christopher; Ferguson, Frank; Johnson, Natasha M.

    2010-01-01

    It has been suggested that carbonaceous grains are efficiently destroyed in the interstellar medium and must either reform in situ at very low pressures and temperatures or in an alternative environment more conducive to grain growth. Graphite whiskers have been discovered associated with high-temperature phases in meteorites such as calcium aluminum inclusions and chondrules, and it has been suggested that the expulsion of such material from proto stellar nebulae could significantly affect the optical properties of the average interstellar grain population. We have experimentally studied the potential for Fischer-Tropsch and Haber-Bosch type reactions to produce organic materials in protostellar systems from the abundant H2, CO, and N2 reacting on the surfaces of available silicate grains. When graphite grains are repeatedly exposed to H2, CO, and N2 at 875 K abundant graphite whiskers are observed to form on or from the surfaces of the graphite grains. In a dense, turbulent nebula, such extended whiskers are very likely to be broken off, and fragments could be ejected either in polar jets or by photon pressure after transport to the outer reaches of the nebula.

  2. TITANIUM ISOTOPE SOURCE RELATIONS AND THE EXTENT OF MIXING IN THE PROTO-SOLAR NEBULA EXAMINED BY INDEPENDENT COMPONENT ANALYSIS

    Energy Technology Data Exchange (ETDEWEB)

    Steele, Robert C. J.; Boehnke, Patrick [Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles, CA 90095 (United States)

    2015-04-01

    The Ti isotope variations observed in hibonites represent some of the largest isotope anomalies observed in the solar system. Titanium isotope compositions have previously been reported for a wide variety of different early solar system materials, including calcium, aluminum rich inclusions (CAIs) and CM hibonite grains, some of the earliest materials to form in the solar system, and bulk meteorites which formed later. These data have the potential to allow mixing of material to be traced between many different regions of the early solar system. We have used independent component analysis to examine the mixing end-members required to produce the compositions observed in the different data sets. The independent component analysis yields results identical to a linear regression for the bulk meteorites. The components identified for hibonite suggest that most of the grains are consistent with binary mixing from one of three highly anomalous nucleosynthetic sources. Comparison of these end-members show that the sources which dominate the variation of compositions in the meteorite parent body forming regions was not present in the region in which the hibonites formed. This suggests that the source which dominates variation in Ti isotope anomalies between the bulk meteorites was not present when the hibonite grains were forming. One explanation is that the bulk meteorite source may not be a primary nucleosynthetic source but was created by mixing two or more of the hibonite sources. Alternatively, the hibonite sources may have been diluted during subsequent nebula processing and are not a dominant solar system signatures.

  3. Pre-accretional sorting of grains in the outer solar nebula

    Energy Technology Data Exchange (ETDEWEB)

    Wozniakiewicz, P. J. [Earth Sciences Department, Mineral and Planetary Science Division, Natural History Museum, Cromwell Road, London SW7 5BD (United Kingdom); Bradley, J. P.; Ishii, H. A. [Institute of Geophysics and Planetary Physics, Lawrence Livermore National Laboratory, Livermore, CA 94550 (United States); Price, M. C. [School of Physical Sciences, University of Kent, Canterbury, Kent CT2 7NH (United Kingdom); Brownlee, D. E., E-mail: p.wozniakiewicz@nhm.ac.uk [Department of Astronomy, University of Washington, Seattle, WA 98195 (United States)

    2013-12-20

    Despite their micrometer-scale dimensions and nanogram masses, chondritic porous interplanetary dust particles (CP IDPs) are an important class of extraterrestrial material since their properties are consistent with a cometary origin and they show no evidence of significant post-accretional parent body alteration. Consequently, they can provide information about grain accretion in the comet-forming region of the outer solar nebula. We have previously reported our comparative study of the sizes and size distributions of crystalline silicate and sulfide grains in CP IDPs, in which we found these components exhibit a size-density relationship consistent with having been sorted together prior to accretion. Here we extend our data set and include GEMS (glass with embedded metal and sulfide), the most abundant amorphous silicate phase observed in CP IDPs. We find that while the silicate and sulfide sorting trend previously observed is maintained, the GEMS size data do not exhibit any clear relationship to these crystalline components. Therefore, GEMS do not appear to have been sorted with the silicate and sulfide crystals. The disparate sorting trends observed in GEMS and the crystalline grains in CP IDPs present an interesting challenge for modeling early transport and accretion processes. They may indicate that several sorting mechanisms operated on these CP IDP components, or alternatively, they may simply be a reflection of different source environments.

  4. Radial Transport in the Solar Nebula: Implications for Moderately Volatile Element Depletions in Chondritic Meteorites

    CERN Document Server

    Ciesla, F J

    2007-01-01

    In this paper, the possibility that the moderately volatile element depletions observed in chondritic meteorites are the results of planetesimals accreting in a solar nebula that cooled from an initially hot state (temperatures > 1350 K out to ~2-4 AU) is explored. A model is developed to track the chemical inventory of planetesimals that accrete in a viscously evolving protoplanetary disk, accounting for the redistribution of solids and vapor by advection, diffusion, and gas drag. It is found that depletion trends similar to those observed in the chondritic meteorites can be reproduced for a small range of model parameters. However, the necessary range of parameters is inconsistent with observations of disks around young stars and other constraints on meteorite parent body formation. Thus, counter to previous work, it is concluded that the global scale evolution of the solar nebula is not the cause for the observed depletion trends.

  5. Ice Lines, Planetesimal Composition and Solid Surface Density in the Solar Nebula

    CERN Document Server

    Robinson, Sarah E; Bodenheimer, Peter; Laughlin, Gregory; Turner, Neal J; Beichman, C A

    2008-01-01

    To date, there is no core accretion simulation that can successfully account for the formation of Uranus or Neptune within the observed 2-3 Myr lifetimes of protoplanetary disks. Since solid accretion rate is directly proportional to the available planetesimal surface density, one way to speed up planet formation is to take a full accounting of all the planetesimal-forming solids present in the solar nebula. By combining a viscously evolving protostellar disk with a kinetic model of ice formation, we calculate the solid surface density in the solar nebula as a function of heliocentric distance and time. We find three effects that strongly favor giant planet formation: (1) a decretion flow that brings mass from the inner solar nebula to the giant planet-forming region, (2) recent lab results (Collings et al. 2004) showing that the ammonia and water ice lines should coincide, and (3) the presence of a substantial amount of methane ice in the trans-Saturnian region. Our results show higher solid surface densitie...

  6. Accretion of Chondrules formed by Impact Jetting in Magnetically Induced Turbulent Solar Nebula

    CERN Document Server

    Hasegawa, Yasuhiro; Masiero, Joseph; Wakita, Shigeru; Matsumoto, Yuji; Oshino, Shoichi

    2016-01-01

    Chondritic meteorites provide valuable opportunities to investigate origins of the solar system. We explore impact jetting as a mechanism to form chondrules and subsequent pebble accretion as a mechanism to accrete them onto parent bodies of chondrites, and investigate how these two processes can account for the currently available meteoritic data. We find that when the solar nebula is $\\le 5$ times more massive than the minimum-mass solar nebula at $a \\simeq 2-3$ AU and parent bodies of chondrites are $\\le 10^{24}$ g ($\\le$ 500 km in radius) there, impact jetting and subsequent pebble accretion can reproduce a number of properties of the meteoritic data. The properties include the present asteroid belt mass, formation timescale of chondrules, and the magnetic field strength of the nebula derived from chondrules in Semarkona. Since this scenario requires a first generation of planetesimals that trigger impact jetting and serve as parent bodies to accrete chondrules, the upper limit of parent bodies' mass lead...

  7. Distribution of light element isotopes in Bencubbin and Weatherford meteorites: An indicator of heterogeneity in the primitive solar nebula

    Energy Technology Data Exchange (ETDEWEB)

    Blacic, J.; Maggiore, C.; Taylor, J.; Newsom, H.; Marti, K.

    1994-09-01

    The objective is to study light element isotopes, particularly {sup 15}N, in meteorites to elucidate early solar nebula processes. The approach is to use microion beams to induce characteristic nuclear reactions in specific minerals in the meteorites, and to develop isotope imaging techniques by beam rastering. Early results demonstrate the feasibility of the beam rastering technique and we have successfully measured a {delta}{sup 15}N ratio of about -50 {per_thousand} in sinoite (Si{sub 2}N{sub 2}O) in an enstatite chondrite. No conclusions can be drawn at this stage of the investigation. Ultimately, the results are important to understanding conditions during planetary formation, and in developing new analytic techniques applicable to a wide range of geophysical problems.

  8. The effect of multiple particle sizes on cooling rates of chondrules produced in large-scale shocks in the solar nebula

    CERN Document Server

    Morris, Melissa A; Desch, Steven J

    2016-01-01

    Chondrules represent one of the best probes of the physical conditions and processes acting in the early solar nebula. Proposed chondrule formation models are assessed based on their ability to match the meteoritic evidence, especially experimental constraints on their thermal histories. The model most consistent with chondrule thermal histories is passage through shock waves in the solar nebula. Existing models of heating by shocks generally yield a good first-order approximation to inferred chondrule cooling rates. However, they predict prolonged heating in the pre-shock region, which would cause volatile loss and isotopic fractionation, which are not observed. These models have typically included particles of a single (large) size, i.e., chondrule precursors, or at most, large particles accompanied by micron-sized grains. The size distribution of solids present during chondrule formation controls the opacity of the affected region, and significantly affects the thermal histories of chondrules. Micron-sized...

  9. Microquasar Jet Irradiation of the Proto-Solar Nebula?

    CERN Document Server

    Butt, Y; Butt, Yousaf; Prantzos, Nikos

    2006-01-01

    We explore the possibility that a now-extinct microquasar may have irradiated the proto-solar neighborhood, causing the 'anomalously' high local 11B/10B isotopic ratio, and comment on some observational tests of the scenario.

  10. EXTERNAL PHOTOEVAPORATION OF THE SOLAR NEBULA: JUPITER's NOBLE GAS ENRICHMENTS

    Energy Technology Data Exchange (ETDEWEB)

    Monga, Nikhil; Desch, Steven [School of Earth and Space Exploration, Arizona State University, PO Box 871404, Tempe, AZ 85287-1404 (United States)

    2015-01-01

    We present a model explaining the elemental enrichments in Jupiter's atmosphere, particularly the noble gases Ar, Kr, and Xe. While He, Ne, and O are depleted, seven other elements show similar enrichments (∼3 times solar, relative to H). Being volatile, Ar is difficult to fractionate from H{sub 2}. We argue that external photoevaporation by far-ultraviolet (FUV) radiation from nearby massive stars removed H{sub 2}, He, and Ne from the solar nebula, but Ar and other species were retained because photoevaporation occurred at large heliocentric distances where temperatures were cold enough (≲ 30 K) to trap them in amorphous water ice. As the solar nebula lost H, it became relatively and uniformly enriched in other species. Our model improves on the similar model of Guillot and Hueso. We recognize that cold temperatures alone do not trap volatiles; continuous water vapor production is also necessary. We demonstrate that FUV fluxes that photoevaporated the disk generated sufficient water vapor in regions ≲ 30 K to trap gas-phase species in amorphous water ice in solar proportions. We find more efficient chemical fractionation in the outer disk: whereas the model of Guillot and Hueso predicts a factor of three enrichment when only <2% of the disk mass remains, we find the same enrichments when 30% of the disk mass remains. Finally, we predict the presence of ∼0.1 M {sub ⊕} of water vapor in the outer solar nebula and protoplanetary disks in H II regions.

  11. Nonuniform viscosity in the solar nebula and large masses of Jupiter and Saturn

    CERN Document Server

    Jin, Liping

    2004-01-01

    I report a novel theory that nonuniform viscous frictional force in the solar nebula accounts for the largest mass of Jupiter and Saturn and their largest amount of H and He among the planets, two outstanding facts that are unsolved puzzles in our understanding of origin of the Solar System. It is shown that the nebula model of uniform viscosity does not match the present planet masses. By studying current known viscosity mechanisms, I show that viscosity is more efficient in the inner region inside Mercury and the outer region outside Jupiter-Saturn than the intermediate region. The more efficient viscosity drives faster radial inflow of material during the nebula evolution. Because the inflow in the outer region is faster than the intermediate region, the material tends to accumulate in Jupiter-Saturn region which is between the outer and intermediate region. It is demonstrated that the gas trapping time of Jovian planets is longer than the inflow time in the outer region. Therefore the gas already flows to...

  12. A sound nebula: the origin of the Solar System in the field of a standing sound wave

    CERN Document Server

    Beck, Svetlana

    2016-01-01

    According to the planetary origin conceptual model proposed in this paper, the protosun centre of the pre-solar nebula exploded, resulting in a shock wave that passed through it and then returned to the centre, generating a new explosion and shock wave. Recurrent explosions in the nebula resulted in a spherical standing sound wave, whose antinodes concentrated dust into rotating rings that transformed into planets. The extremely small angular momentum of the Sun and the tilt of its equatorial plane were caused by the asymmetry of the first, most powerful explosion. Differences between inner and outer planets are explained by the migration of solid matter, while the Oort cloud is explained by the division of the pre-solar nebula into a spherical internal nebula and an expanding spherical shell of gas. The proposed conceptual model can also explain the origin and evolution of exoplanetary systems and may be of use in searching for new planets.

  13. Organic Synthesis via Irradiation and Warming of Ice Grains in the Solar Nebula

    Science.gov (United States)

    Ciesla, Fred J.; Sanford, Scott A.

    2012-01-01

    Complex organic compounds, including many important to life on Earth, are commonly found in meteoritic and cometary samples, though their origins remain a mystery. We examined whether such molecules could be produced within the solar nebula by tracking the dynamical evolution of ice grains in the nebula and recording the environments they were exposed to. We found that icy grains originating in the outer disk, where temperatures were less than 30 K, experienced UV irradiation exposures and thermal warming similar to that which has been shown to produce complex organics in laboratory experiments. These results imply that organic compounds are natural byproducts of protoplanetary disk evolution and should be important ingredients in the formation of all planetary systems, including our own.

  14. Generating potassium abundance variations in the Solar Nebula

    CERN Document Server

    Hubbard, Alexander

    2016-01-01

    An intriguing aspect of chondritic meteorites is that they are complementary: while their separate components have wildly varying abundances, bulk chondrites have nearly solar composition. This implies that the nearly-solar reservoirs in which chondrites were born were in turn assembled from sub-reservoirs of differing compositions that birthed the different components. We focus on explaining the potassium abundance variations between chondrules even within a single chondrite, while maintaining the observed CI $^{41}$K to $^{39}$K ratios. This requires physically separating potassium and chondrules while the temperature is high enough for K to be in the gas phase. We examine several mechanisms which could drive the dust through gas and show that to do so locally would have required long (sub-orbital to many orbits) time scales; with shortest potassium depletion time scales occurring in a scenario where chondrules formed high above the midplane and settled out of the evaporated potassium. While orbital time sc...

  15. Comparing shocks in planetary nebulae with the solar wind termination shock

    CERN Document Server

    Soker, Noam; Behar, Ehud; Kastner, Joel H

    2010-01-01

    We show that suprathermal particles, termed pick-up ions (PUIs), might reduce the postshock temperature of the fast wind and jets in some planetary nebulae (PNs) and in symbiotic systems. The goal is to explain the finding that the temperature of the hot bubble formed by the post-shock gas in some PNs and symbiotic nebulae is lower, sometimes by more than an order of magnitude, than the value expected from simple hydrodynamical calculations. Although various explanations have been proposed, there is as yet no prefered solution for this low tempeature problem. PUIs have been invoked to explain the low temperature behind the termination shock of the solar wind. While in the case of the solar wind the neutral atoms that turn into PUIs penetrate the pre-shock solar wind region from the interstellar medium (ISM), in PNs the PUI source is more likely slowly moving clumps embedded in the fast wind or jets. These clumps are formed by instabilities or from backflowing cold gas. Our estimates indicate that in young PNs...

  16. Theoretical, observational, and isotopic estimates of the lifetime of the solar nebula

    Science.gov (United States)

    Podosek, Frank A.; Cassen, Patrick

    1994-01-01

    There are a variety of isotopic data for meteorites which suggest that the protostellar nebula existed and was involved in making planetary materials for some 10(exp 7) yr or more. Many cosmochemists, however, advocate alternative interpretations of such data in order to comply with a perceived constraint, from theoretical considerations, that the nebula existed only for a much shorter time, usually stated as less than or equal to 10(exp 6) yr. In this paper, we review evidence relevant to solar nebula duration which is available through three different disciplines: theoretical modeling of star formation, isotopic data from meteorites, and astronomical observations of T Tauri stars. Theoretical models based on observations of present star-forming regions indicate that stars like the Sun form by dynamical gravitational collapse of dense cores of cold molcular clouds in the interstellar clouds in the interstellar medium. The collapse to a star and disk occurs rapidly, on a time scale of the order 10(exp 5) yr. Disks evolve by dissipating energy while redistributing angular momentum, but it is difficult to predict the rate of evolution, particularly for low mass (compared to the star) disks which nonetheless still contain enough material to account for the observed planetary system. There is no compelling evidence, from available theories of disk structure and evolution, that the solar nebula must have evolved rapidly and could not have persisted for more than 1 Ma. In considering chronoloically relevant isotopic data for meteorites, we focus on three methodologies: absolute ages by U-Pb/Pb-Pb, and relative ages by short-lived radionuclides (especially Al-26) and by evolution of Sr-87/Sr-86. Two kinds of meteoritic materials-refractory inclusions such as CAIs and differential meteorites (eucrites and augrites) -- appear to have experienced potentially dateable nebular events. In both cases, the most straightforward interpretations of the available data indicate

  17. PAHs in the Ices of Saturn's Satellites: Connections to the Solar Nebula and the Interstellar Medium

    Science.gov (United States)

    Cruikshank, Dale P.; Pendleton, Yvonne J.

    2015-01-01

    Aliphatic hydrocarbons and PAHs have been observed in the interstellar medium (e.g., Allamandola et al. 1985, Pendleton et al. 1994, Pendleton & Allamandola 2002, Tielens 2013, Kwok 2008, Chiar & Pendleton 2008) The inventory of organic material in the ISM was likely incorporated into the molecular cloud in which the solar nebula condensed, contributing to the feedstock for the formation of the Sun, major planets, and the smaller icy bodies in the region outside Neptune's orbit (transneptunian objects, or TNOs). Additional organic synthesis occurred in the solar nebula (Ciesla & Sandford 2012). Saturn's satellites Phoebe, Iapetus, and Hyperion open a window to the composition of one class of TNO as revealed by the near-infrared mapping spectrometer (VIMS) on the Cassini spacecraft at Saturn. Phoebe (mean diameter 213 km) is a former TNO now orbiting Saturn (Johnson & Lunine 2005). VIMS spectral maps of Phoebe's surface reveal a complex organic spectral signature consisting of prominent aromatic (CH) and aliphatic hydrocarbon (=CH2, -CH3) absorption bands (3.2-3.6 micrometers). Phoebe is the source of a huge debris ring encircling Saturn, and from which particles ((is) approximately 5-20 micrometers size) spiral inward toward Saturn (Verbiscer et al. 2009). They encounter Iapetus and Hyperion where they mix with and blanket the native H2O ice of those two bodies. Quantitative analysis of the hydrocarbon bands on Iapetus demonstrates that aromatic CH is approximately 10 times as abundant as aliphatic CH2+CH3, significantly exceeding the strength of the aromatic signature in interplanetary dust particles, comet particles, and in carbonaceous meteorites (Cruikshank et al. 2014). A similar excess of aromatics over aliphatics is seen in the qualitative analysis of Hyperion and Phoebe itself (Dalle Ore et al. 2012). The Iapetus aliphatic hydrocarbons show CH2/CH3 (is) approximately 4, which is larger than the value found in the diffuse ISM ((is) approximately 2

  18. Dark-Matter Content of Early-Type Galaxies with Planetary Nebulae

    CERN Document Server

    Napolitano, N R; Coccato, L; Capaccioli, M; Douglas, N G; Noordermeer, E; Merrifield, M R; Kuijken, K; Arnaboldi, M; Gerhard, O; Freeman, K C; De Lorenzi, F; Das, P

    2007-01-01

    We examine the dark matter properties of nearby early-type galaxies using planetary nebulae (PNe) as mass probes. We have designed a specialised instrument, the Planetary Nebula Spectrograph (PN.S) operating at the William Herschel telescope, with the purpose of measuring PN velocities with best efficiency. The primary scientific objective of this custom-built instrument is the study of the PN kinematics in 12 ordinary round galaxies. Preliminary results showing a dearth of dark matter in ordinary galaxies (Romanowsky et al. 2003) are now confirmed by the first complete PN.S datasets. On the other hand early-type galaxies with a "regular" dark matter content are starting to be observed among the brighter PN.S target sample, thus confirming a correlation between the global dark-to-luminous mass virial ratio (f_DM=M_DM/M_star) and the galaxy luminosity and mass.

  19. 2D condensation model for the inner Solar Nebula: an enstatite-rich environment

    CERN Document Server

    Pignatale, Francesco C; Maddison, Sarah T; Brooks, Geoffrey

    2016-01-01

    Infrared observations provide the dust composition in the protoplanetary discs surface layers, but can not probe the dust chemistry in the midplane, where planet formation occurs. Meteorites show that dynamics was important in determining the dust distribution in the Solar Nebula and needs to be considered if we are to understand the global chemistry in discs. 1D radial condensation sequences can only simulate one disc layer at a time and cannot describe the global chemistry or the complexity of meteorites. To address these limitations, we compute for the first time the two dimensional distribution of condensates in the inner Solar Nebula using a thermodynamic equilibrium model, and derive timescales for vertical settling and radial migration of dust. We find two enstatite-rich zones within 1 AU from the young Sun: a band ~0.1 AU thick in the upper optically-thin layer of the disc interior to 0.8 AU, and in the optically-thick disc midplane out to ~0.4 AU. The two enstatite-rich zones support recent evidence ...

  20. Sulfurization of Iron in the Dynamic Solar Nebula and Implications for Planetary Compositions

    CERN Document Server

    Ciesla, Fred J

    2015-01-01

    One explanation for the enhanced ratio of volatiles to hydrogen in Jupiter's atmosphere compared to a a gas of solar composition is that the planet accreted volatile-bearing clathrates during its formation. Models, however, suggest that S would be over abundant if clathrates were the primary carrier of Jupiter's volatiles. This led to the suggestion that S was depleted in the outer nebula due to the formation troilite (FeS). Here, this depletion is quantitatively explored by modeling the coupled dynamical and chemical evolution of Fe grains in the solar nebula. It is found that disks that undergo rapid radial expansion from an initially compact state may allow sufficient production of FeS and carry H$_{2}$S-depleted gas outward where ices would form, providing the conditions needed for S-depleted clathrates to form. However, this expansion would also carry FeS grains to this region, which could also be incorporated into planetesimals. Thus for clathrates to be a viable source of volatiles, models must account...

  1. Non-equilibrium Condensation ina Primordial Solar Nebula: Formation of Refractory Metal Nuggets

    Science.gov (United States)

    Tanaka, Kyoko K.; Tanaka, Hidekazu; Nakazawa, Kiyoshi

    2002-11-01

    We present a theoretical investigation of non-equilibrium condensation of refractory metalsinthe primordial solar nebula, in relation to the origin of "Fremdlinges" included inCAIs. Todescribe the nucleation process of grains from vapor, weadopted asemi-phenomenological modelmodified fromthe classical nucleation theoryby the introductionof the second virial coefficient of vapor. This modelachieves excellent agreement with nucleation rate experiment. However,the second virial coefficients are unknown for a vapor of refractory metals. To overcome this, weexpress the nucleation rate by theuse of the chemical potential of dimersinsteadof the second virial coefficient. On the basis of this new nucleation theory,we have performed numerical simulations ofnon-equilibrium condensation of refractory metals andfind thattheircondensation temperatures, Tc, decrease considerably in comparison withequilibrium condensation. Even if the characteristiccooling time scale is aslarge as 1×10 5 years, the decrease in Tc isfrom 200 to 400 Kfor rare elements such as W, Re,and Os. This remarkablenon-equilibrium behaviormainly stemsfromthelow totalpressure in the primordial solar nebula. From our new modelwealso obtainthe typical size ofgrainsformed in condensation. We findthatthe cooling time should be ≳1×10 5 years for sub-micron-sized or largerrefractory metal nuggetsto form.

  2. Sublimation and reformation of icy grains in the primitive solar nebula

    Science.gov (United States)

    Lunine, Jonathan I.; Engel, Steffi; Rizk, Bashar; Horanyi, Mihaly

    1991-01-01

    The quantity of water ice that sublimates during the free fall of grains into the solar nebula from a surrounding interstellar cloud varies from over 90 percent of the grain mass as 30 AU from the nebular center to less than 10 percent at more than 100 AU. Virtually all the water that is sublimated ultimately recondenses, since the cold nebular gas lying beyond 10 AU is unable to hold more than a small portion as vapor. The return of most of the gas to solid phase near the nebular ambient temperature, of about 50 K, may result in at least two grain populations consisting, in one case, of unaltered interstellar grains which did not undergo sublimation, and in the other of water ice which cocondensed with more volatile gases at nebular ambient temperatures to yield volatile-rich amorphous phases.

  3. Meteoritic Constraints on Temperatures, Pressures, Cooling Rates, Chemical Compositions and Modes of Condensation in the Solar Nebula

    Science.gov (United States)

    Petaev, M. I.; Wood, J. A.

    2005-12-01

    Monotonic, equilibrium condensation of nebular materials from a chemically homogeneous solar nebula is unlikely. Condensation of nebular gas was quite rapid, resulting in significant deviations from chemical equilibrium between condensed phases and the residual gas. A few primitive nebular components condensed from a gas of solar composition; most of them formed in fractionated nebular systems. Local chemical variations caused by both depletion and enrichment in dust relative to gas were commonplace in the solar nebula. Local variations of nebular pressure were, in general, in the range of ~10-4 - 6×10-6 bar. Short-lived temperature excursions might have exceeded 2000 K, with the sustained temperatures in the 16O-rich nebular source regions of CAIs and AOAs being in the range of 1230-1350 K. Silicate melts might have been temporarily stable in nebular source regions heavily enriched in dust.

  4. Synthesis of refractory organic matter in the ionized gas phase of the solar nebula.

    Science.gov (United States)

    Kuga, Maïa; Marty, Bernard; Marrocchi, Yves; Tissandier, Laurent

    2015-06-01

    In the nascent solar system, primitive organic matter was a major contributor of volatile elements to planetary bodies, and could have played a key role in the development of the biosphere. However, the origin of primitive organics is poorly understood. Most scenarios advocate cold synthesis in the interstellar medium or in the outer solar system. Here, we report the synthesis of solid organics under ionizing conditions in a plasma setup from gas mixtures (H2(O)-CO-N2-noble gases) reminiscent of the protosolar nebula composition. Ionization of the gas phase was achieved at temperatures up to 1,000 K. Synthesized solid compounds share chemical and structural features with chondritic organics, and noble gases trapped during the experiments reproduce the elemental and isotopic fractionations observed in primitive organics. These results strongly suggest that both the formation of chondritic refractory organics and the trapping of noble gases took place simultaneously in the ionized areas of the protoplanetary disk, via photon- and/or electron-driven reactions and processing. Thus, synthesis of primitive organics might not have required a cold environment and could have occurred anywhere the disk is ionized, including in its warm regions. This scenario also supports N2 photodissociation as the cause of the large nitrogen isotopic range in the solar system.

  5. Radioactive Probes of the Supernova-Contaminated Solar Nebula: Evidence that the Sun was Born in a Cluster

    CERN Document Server

    Looney, L W; Fields, B D; Looney, Leslie W.; Tobin, John J.; Fields, Brian D.

    2006-01-01

    We construct a simple model for radioisotopic enrichment of the protosolar nebula by injection from a nearby supernova, based on the inverse square law for ejecta dispersion. We find that the presolar radioisotopes abundances (i.e., in solar masses) demand a nearby supernova: its distance can be no larger than 66 times the size of the protosolar nebula, at a 90% confidence level, assuming 1 solar mass of protosolar material. The relevant size of the nebula depends on its state of evolution at the time of radioactivity injection. In one scenario, a collection of low-mass stars, including our sun, formed in a group or cluster with an intermediate- to high-mass star that ended its life as a supernova while our sun was still a protostar, a starless core, or perhaps a diffuse cloud. Using recent observations of protostars to estimate the size of the protosolar nebula constrains the distance of the supernova at 0.02 to 1.6 pc. The supernova distance limit is consistent with the scales of low-mass stars formation ar...

  6. Mass-independent isotope effects in planetary atmospheres and the early solar system.

    Science.gov (United States)

    Thiemens, M H

    1999-01-15

    A class of isotope effects that alters isotope ratios on a mass-independent basis provides a tool for studying a wide range of processes in atmospheres of Earth and other planets as well as early processes in the solar nebula. The mechanism for the effect remains uncertain. Mass-independent isotopic compositions have been observed in O3, CO2, N2O, and CO in Earth's atmosphere and in carbonate from a martian meteorite, which suggests a role for mass-independent processes in the atmosphere of Mars. Observed mass-independent meteoritic oxygen and sulfur isotopic compositions may derive from chemical processes in the presolar nebula, and their distributions could provide insight into early solar system evolution.

  7. Early-type massive stars in Carina Nebula within the Gaia-ESO Survey.

    Science.gov (United States)

    Berlanas, S. R.; Herrero, A.; Martins, F.; Simón-Díaz, S.; Mahy, L.; Blomme, R.; GES WG-13

    2017-03-01

    The Gaia-ESO Survey (GES) is obtaining high quality spectra of ˜ 10^5 stars in our Galaxy, providing an homogeneous and unique overview of all the main components of the Milky Way, its formation history and the evolution of young, mature and ancient Galactic populations. Our group is in charge of the early-type massive stars that define the youngest population in the survey. In this contribution, we present the results of the quantitative spectroscopic analysis of O-type stars in the Carina Nebula within the Gaia-ESO Survey. For this aim, we have used FASTWIND and CMFGEN stellar atmosphere codes, providing stellar parameters for the current sample (GES data release iDR4).

  8. Planetary Nebulae As A Laboratory For Molecular Hydrogen in the Early Universe

    Science.gov (United States)

    Sellgren, Kris; Bromm, Volker; Dinerstein, Harriet

    2008-03-01

    We propose to obtain Spitzer IRS observations of the mid-infrared rotational lines of H2 in planetary nebulae (PNe) with very hot central stars, T > 100,000 K. Our primary motivation is to investigate the excitation and cooling of H2 exposed to UV radiation near very hot stars, which can serve as a proxy for conditions in the early universe. Cosmological simulations show that the first stellar generation (Pop. III) had high masses, > 100 Msun, and hot photospheres. The UV radiation they produced and its effect on the thermal state of the ambient H2 is relevant to subsequent star formation because stellar masses are determined by accretion processes which depend on temperature, and the metal-free primordial gas cooled primarily through excited H2. Yet the effects of this radiative feedback are uncertain: for example, whether it triggers or suppresses further star formation, and the resultant characteristic masses of second generation stars, which are key to cosmic reionization. PNe with hot central stars may be the only place where we can study the relevant microphysics. We therefore propose to obtain Spitzer spectra of such nebulae, sampling regions with a range of gas densities and radiation field dilution factors. We will use the results to derive an improved H2 cooling function to be incorporated into state of the art cosmological models. Our targets have been previously observed in the near-infrared H2 lines, so we have confidence that the lower excitation rotational lines are detectable. Evidence already exists that in some PNe the excited rotational states are overpopulated relative to standard fluorescence models, and that this may be related to the presence of Lyman-continuum photons. The observations proposed here will enable us to verify and quantify this phenomenon, and improve our understanding of H2 excitation. Spitzer is the only facility at present - and for at least the next decade - which can accomplish these goals.

  9. CO Self-Shielding as a Mechanism to Make 16O-Enriched Solids in the Solar Nebula

    Directory of Open Access Journals (Sweden)

    Joseph A. Nuth, III

    2014-05-01

    Full Text Available Photochemical self-shielding of CO has been proposed as a mechanism to produce solids observed in the modern, 16O-depleted solar system. This is distinct from the relatively 16O-enriched composition of the solar nebula, as demonstrated by the oxygen isotopic composition of the contemporary sun. While supporting the idea that self-shielding can produce local enhancements in 16O-depleted solids, we argue that complementary enhancements of 16O-enriched solids can also be produced via C16O-based, Fischer-Tropsch type (FTT catalytic processes that could produce much of the carbonaceous feedstock incorporated into accreting planetesimals. Local enhancements could explain observed 16O enrichment in calcium-aluminum-rich inclusions (CAIs, such as those from the meteorite, Isheyevo (CH/CHb, as well as in chondrules from the meteorite, Acfer 214 (CH3. CO self-shielding results in an overall increase in the 17O and 18O content of nebular solids only to the extent that there is a net loss of C16O from the solar nebula. In contrast, if C16O reacts in the nebula to produce organics and water then the net effect of the self-shielding process will be negligible for the average oxygen isotopic content of nebular solids and other mechanisms must be sought to produce the observed dichotomy between oxygen in the Sun and that in meteorites and the terrestrial planets. This illustrates that the formation and metamorphism of rocks and organics need to be considered in tandem rather than as isolated reaction networks.

  10. CO Self-Shielding as a Mechanism to Make O-16 Enriched Solids in the Solar Nebula

    Science.gov (United States)

    Nuth, Joseph A. III; Johnson, Natasha M.; Hill, Hugh G. M.

    2014-01-01

    Photochemical self-shielding of CO has been proposed as a mechanism to produce solids observed in the modern, O-16 depleted solar system. This is distinct from the relatively O-16 enriched composition of the solar nebula, as demonstrated by the oxygen isotopic composition of the contemporary sun. While supporting the idea that self-shielding can produce local enhancements in O-16 depleted solids, we argue that complementary enhancements of O-16 enriched solids can also be produced via CO-16 based, Fischer-Tropsch type (FTT) catalytic processes that could produce much of the carbonaceous feedstock incorporated into accreting planetesimals. Local enhancements could explain observed O-16 enrichment in calcium-aluminum-rich inclusions (CAIs), such as those from the meteorite, Isheyevo (CH/CHb), as well as in chondrules from the meteorite, Acfer 214 (CH3). CO selfshielding results in an overall increase in the O-17 and O-18 content of nebular solids only to the extent that there is a net loss of CO-16 from the solar nebula. In contrast, if CO-16 reacts in the nebula to produce organics and water then the net effect of the self-shielding process will be negligible for the average oxygen isotopic content of nebular solids and other mechanisms must be sought to produce the observed dichotomy between oxygen in the Sun and that in meteorites and the terrestrial planets. This illustrates that the formation and metamorphism of rocks and organics need to be considered in tandem rather than as isolated reaction networks.

  11. Stingray Nebula

    Science.gov (United States)

    1996-01-01

    This Wide Field and Planetary Camera 2 image captures the infancy of the Stingray nebula (Hen-1357), the youngest known planetary nebula. In this image, the bright central star is in the middle of the green ring of gas. Its companion star is diagonally above it at 10 o'clock. A spur of gas (green) is forming a faint bridge to the companion star due to gravitational attraction. The image also shows a ring of gas (green) surrounding the central star, with bubbles of gas to the lower left and upper right of the ring. The wind of material propelled by radiation from the hot central star has created enough pressure to blow open holes in the ends of the bubbles, allowing gas to escape. The red curved lines represent bright gas that is heated by a 'shock' caused when the central star's wind hits the walls of the bubbles. The nebula is as large as 130 solar systems, but, at its distance of 18,000 light-years, it appears only as big as a dime viewed a mile away. The Stingray is located in the direction of the southern constellation Ara (the Altar). The colors shown are actual colors emitted by nitrogen (red), oxygen (green), and hydrogen (blue).

  12. Mixing in the Solar Nebula: Implications for Isotopic Heterogeneity and Large-Scale Transport of Refractory Grains

    CERN Document Server

    Boss, Alan P

    2008-01-01

    The discovery of refractory grains amongst the particles collected from Comet 81P/Wild 2 by the Stardust spacecraft (Brownlee et al. 2006) provides the ground truth for large-scale transport of materials formed in high temperature regions close to the protosun outward to the comet-forming regions of the solar nebula. While accretion disk models driven by a generic turbulent viscosity have been invoked as a means to explain such large-scale transport, the detailed physics behind such an ``alpha'' viscosity remains unclear. We present here an alternative physical mechanism for large-scale transport in the solar nebula: gravitational torques associated with the transient spiral arms in a marginally gravitationally unstable disk, of the type that appears to be necessary to form gas giant planets. Three dimensional models are presented of the time evolution of self-gravitating disks, including radiative transfer and detailed equations of state, showing that small dust grains will be transported upstream and downst...

  13. Nucleosynthetic molybdenum isotope anomalies in iron meteorites - new evidence for thermal processing of solar nebula material

    Science.gov (United States)

    Poole, Graeme M.; Rehkämper, Mark; Coles, Barry J.; Goldberg, Tatiana; Smith, Caroline L.

    2017-09-01

    We have investigated nucleosynthetic Mo isotope anomalies in 38 different bulk iron meteorites from 11 groups, to produce by far the largest and most precise dataset available to date for such samples. All magmatic iron groups were found to display deficits in s-process Mo isotopes, with essentially constant anomalies within but significant variations between groups. Only meteorites of the non-magmatic IAB/IIICD complex revealed terrestrial Mo isotopic compositions. The improved analytical precision achieved in this study enables two isotopically distinct suites of iron meteorites to be identified. Of these, the r=p suite encompasses the IC, IIAB, IIE, IIIAB, IIIE and IVA groups and exhibits relatively modest but 'pure' s-process deficits, relative to Earth. The second r>p suite includes groups IIC, IIIF and IVB. These iron meteorites show larger s-process deficits than the r=p suite, coupled with an excess of r-process relative to p-process components. Comparison of the results with data for other elements (e.g., Cr, Ni, Ru, Ti, Zr) suggests that the Mo isotope variability is most likely produced by thermal processing and selective destruction of unstable presolar phases. An updated model is proposed, which relates the iron meteorite suites to different extents of thermal processing in the solar nebula, as governed by heliocentric distance. In detail, the r=p suite of iron meteorite parent bodies is inferred to have formed closer to the Sun, where the extent of thermal processing was similar to that experienced by terrestrial material, so that the meteorites exhibit only small s-process deficits relative to Earth. In contrast, the r>p suite formed at greater heliocentric distance, where more subtle thermal processing removed a smaller proportion of r- and p-process host phases, thereby generating larger s-process deficits relative to the terrestrial composition. In addition, the thermal conditions enabled selective destruction of p- versus r-isotope carrier phases

  14. Thermal History and Volatile Partitioning between Proto-Atmosphere and Interior of Mars Accreted in a Solar Nebula

    Science.gov (United States)

    Saito, Hiroaki; Kuramoto, Kiyoshi

    2015-11-01

    Recent precise Hf-W chronometry of Martian meteorites reveals that Mars had likely reached the half of its present mass within 3 Myr from the birth of the solar system (Dauphas and Pourmand, 2011). Hence, the accretion is considered to almost proceed within the solar nebula associated with the capture of nebula gas components. At the same time, the impact degassing may inevitably occur because impact velocity increases high enough for such degassing when a proto-planet gets larger than around lunar size. Thus, we can expect the formation of a hybrid-type proto-atmosphere that consists of nebula gas and degassed one.This study analyzes the thermal structure of this proto-atmosphere sustained by accretional heating by building a 1D radiative-convective equilibrium model. Raw materials of Mars are supposed to be volatile-rich on the basis of the geochemical systematics of Mars meteorites (Dreibus and Wanke, 1988). The composition of degassed component comprised of H2, H2O, CH4, and CO is determined by chemical equilibrium with silicate and metal under the physical condition of locally heated region generated by each impact (Kuramoto, 1997). Degassed component lies beneath the nebula gas atmosphere at altitudes below the compositional boundary height that would change depending on the amount of degassed component. The accretion time is taken to be from 1 to 6 Myr.Our model predicts that the surface temperature exceeds the liquidus temperature of rock when a proto Mars grows larger than 0.7 times of its present mass for the longest accretion time case. In this case, the magma ocean mass just after the end of accretion is 0.2 times of its present mass if heat transfer and heat sources such as short-lived radionuclides are neglected in the interior. The corresponding amount of water dissolved into the magma ocean would be around 1.8 times the present Earth ocean mass. These results suggest that the earliest Mars would be hot enough to form deep magma oceans, which

  15. GAS-PHASE SEQUESTRATION OF NOBLE GASES IN THE PROTOSOLAR NEBULA: POSSIBLE CONSEQUENCES ON THE OUTER SOLAR SYSTEM COMPOSITION

    Energy Technology Data Exchange (ETDEWEB)

    Pauzat, F.; Ellinger, Y.; Ozgurel, O. [Laboratoire de Chimie Théorique, UMR 7616-CNRS, UPMC Univ. Paris 06, F-75005 Paris (France); Mousis, O.; Ali Dib, M., E-mail: pauzat@lct.jussieu.fr, E-mail: ellinger@lct.jussieu.fr, E-mail: zge.zgerel@gmail.com, E-mail: olivier.mousis@obs-besancon.fr, E-mail: mdib@obs-besancon.fr [Institut UTINAM, CNRS/INSU, UMR 6213, Université de Franche-Comté, F-25030 Besançon Cedex (France)

    2013-11-01

    We address the problem of the sequestration of Ar, Kr, and Xe by H{sub 3}{sup +} in the gas-phase conditions encountered during the cooling of protoplanetary disks when H{sub 3}{sup +} is competing with other species present in the same environment. Using high-level ab initio simulations, we try to quantify other sequestration possibilities involving He, H{sub 5}{sup +}, H{sub 2}O, and H{sub 3}O{sup +} present in the protosolar nebula. Apart from the fact that H{sub 3}{sup +} complexes formed with heavy noble gases are found to be by far much more stable than those formed with He or H{sub 2}O, we show that H{sub 2}D{sup +} and H{sub 3}O{sup +}, both products of the reactions of H{sub 3}{sup +} with HD and H{sub 2}O, can also be efficient trapping agents for Ar, Kr, and Xe. Meanwhile, the abundance profile of H{sub 3}{sup +} in the outer part of the nebula is revisited with the use of an evolutionary accretion disk model that allows us to investigate the possibility that heavy noble gases can be sequestered by H{sub 3}{sup +} at earlier epochs than those corresponding to their trapping in planetesimals. We find that H{sub 3}{sup +} might be abundant enough in the outer protosolar nebula to trap Xe and Kr prior their condensation epochs, implying that their abundances should be solar in Saturn's current atmosphere and below the observational limit in Titan. The same scenario predicts that comets formed at high heliocentric distances should also be depleted in Kr and Xe. In situ measurements, such as those planed with the Rosetta mission on 67P/Churyumov-Gerasimenko, will be critical to check the validity of our hypotheses.

  16. Solar Index prediction methodology for early delivery

    Energy Technology Data Exchange (ETDEWEB)

    Lantz, L.J.

    1980-01-01

    Since the beginning of the Solar Index project in 1978, it has been one of the primary objectives to deliver the Indices in mid-afternoon local standard time. This was desirable because it would make it possible to have the numbers broadcast in the early evening news. A short description of the current project is presented and then a summary of the work that led to the early delivery of the Solar Index is given.

  17. Isotopic records in CM hibonites: Implications for timescales of mixing of isotope reservoirs in the solar nebula

    Science.gov (United States)

    Liu, Ming-Chang; McKeegan, Kevin D.; Goswami, Jitendra N.; Marhas, Kuljeet K.; Sahijpal, Sandeep; Ireland, Trevor R.; Davis, Andrew M.

    2009-09-01

    10Be observed in CAIs must be produced by irradiation of precursor solids in the early solar system. The lack of 26Al in PLAC hibonites indicates that significant amounts of 26Al were not formed in the same spallogenic processes that made 10Be in PLAC precursors. This is most easily understood as indicating very early formation of the PLAC hibonites, prior to the incorporation and mixing of 26Al into the solar nebula, although an alternative scenario, which invokes irradiation under different solar flare conditions, cannot be ruled out. Lithium isotopes are normal within uncertainties, probably reflecting contamination and/or postcrystallization exchange. The oxygen isotopic compositions of SHIBs and PLACs are all highly 16O-enriched, but are not derived from a homogeneous reservoir: Δ 17O values span a range of ˜-28‰ to -15‰. The ranges of 16O-enrichment in SHIBs and PLACs overlap and are less "anomalous" than the most 16O-enriched compositions found in meteorites [Kobayashi S., Imai H. and Yurimoto H. (2003) New extreme 16O-rich chondrule in the early solar system. Geochem. J.37, 663-669]. Both PLACs and SHIBs formed in 16O-enriched reservoirs characterized by small-scale heterogeneities in the gas phase. If such heterogeneities were generated by an admixture of relatively 16O-poor gas created by self-shielding during CO photolysis and transported to the hot inner regions of the accretion disk, then this process must have been initiated very early on, prior to the arrival of fresh radioactivity into the inner solar system. Oxygen isotope heterogeneities persisted throughout the formation interval of PLACs, CAI precursors, and SHIBs which could be as long as 3 × 10 5 years based on 26Al records. One SHIB and one BAG exhibit mass fractionated oxygen isotopic compositions similar to those seen in FUN inclusions and in several platy hibonite crystals [Lee T., Mayeda T. K. and Clayton R. N. (1980) Oxygen isotopic anomalies in Allende inclusion HAL. Geophys. Res

  18. Developing V-Xanes Oxybarometry for Probing Materials Formed in Reducing Environments in the Early Solar Disk

    Science.gov (United States)

    Butterworth, A. L.; Gainsforth, Z.; Jilly-Rehak, C. E.; Righter, K.; Westphal, A. J.

    2017-01-01

    Vanadium exhibits four oxidation states (V(sup 2+), V(sup 3+), V(sup 4+) and V(sup 5+)) that have been shown to preferentially partition between melt phases dependent on redox conditions, spanning oxygen fugacity across more than 10 log units. We are developing synchrotron-based x-ray absorption spectroscopy of low-fugacity standards for the determination of V oxidation state in highly reducing conditions relevant to the early solar nebula.

  19. Planetary nebulae abundances and stellar evolution

    CERN Document Server

    Pottasch, S R

    2006-01-01

    A summary is given of planetary nebulae abundances from ISO measurements. It is shown that these nebulae show abundance gradients (with galactocentric distance), which in the case of neon, argon, sulfur and oxygen (with four exceptions) are the same as HII regions and early type star abundance gradients. The abundance of these elements predicted from these gradients at the distance of the Sun from the center are exactly the solar abundance. Sulfur is the exception to this; the reason for this is discussed. The higher solar neon abundance is confirmed; this is discussed in terms of the results of helioseismology. Evidence is presented for oxygen destruction via ON cycling having occurred in the progenitors of four planetary nebulae with bilobal structure. These progenitor stars had a high mass, probably greater than 5 solar masses. This is deduced from the high values of He/H and N/H found in these nebulae. Formation of nitrogen, helium and carbon are discussed. The high mass progenitors which showed oxygen de...

  20. Fluid-induced organic synthesis in the solar nebula recorded in extraterrestrial dust from meteorites

    Science.gov (United States)

    Vollmer, Christian; Kepaptsoglou, Demie; Leitner, Jan; Busemann, Henner; Spring, Nicole H.; Ramasse, Quentin M.; Hoppe, Peter; Nittler, Larry R.

    2014-01-01

    Isotopically anomalous carbonaceous grains in extraterrestrial samples represent the most pristine organics that were delivered to the early Earth. Here we report on gentle aberration-corrected scanning transmission electron microscopy investigations of eight 15N-rich or D-rich organic grains within two carbonaceous Renazzo-type (CR) chondrites and two interplanetary dust particles (IDPs) originating from comets. Organic matter in the IDP samples is less aromatic than that in the CR chondrites, and its functional group chemistry is mainly characterized by C–O bonding and aliphatic C. Organic grains in CR chondrites are associated with carbonates and elemental Ca, which originate either from aqueous fluids or possibly an indigenous organic source. One distinct grain from the CR chondrite NWA 852 exhibits a rim structure only visible in chemical maps. The outer part is nanoglobular in shape, highly aromatic, and enriched in anomalous nitrogen. Functional group chemistry of the inner part is similar to spectra from IDP organic grains and less aromatic with nitrogen below the detection limit. The boundary between these two areas is very sharp. The direct association of both IDP-like organic matter with dominant C–O bonding environments and nanoglobular organics with dominant aromatic and C–N functionality within one unique grain provides for the first time to our knowledge strong evidence for organic synthesis in the early solar system activated by an anomalous nitrogen-containing parent body fluid. PMID:25288736

  1. Fluid-induced organic synthesis in the solar nebula recorded in extraterrestrial dust from meteorites.

    Science.gov (United States)

    Vollmer, Christian; Kepaptsoglou, Demie; Leitner, Jan; Busemann, Henner; Spring, Nicole H; Ramasse, Quentin M; Hoppe, Peter; Nittler, Larry R

    2014-10-28

    Isotopically anomalous carbonaceous grains in extraterrestrial samples represent the most pristine organics that were delivered to the early Earth. Here we report on gentle aberration-corrected scanning transmission electron microscopy investigations of eight (15)N-rich or D-rich organic grains within two carbonaceous Renazzo-type (CR) chondrites and two interplanetary dust particles (IDPs) originating from comets. Organic matter in the IDP samples is less aromatic than that in the CR chondrites, and its functional group chemistry is mainly characterized by C-O bonding and aliphatic C. Organic grains in CR chondrites are associated with carbonates and elemental Ca, which originate either from aqueous fluids or possibly an indigenous organic source. One distinct grain from the CR chondrite NWA 852 exhibits a rim structure only visible in chemical maps. The outer part is nanoglobular in shape, highly aromatic, and enriched in anomalous nitrogen. Functional group chemistry of the inner part is similar to spectra from IDP organic grains and less aromatic with nitrogen below the detection limit. The boundary between these two areas is very sharp. The direct association of both IDP-like organic matter with dominant C-O bonding environments and nanoglobular organics with dominant aromatic and C-N functionality within one unique grain provides for the first time to our knowledge strong evidence for organic synthesis in the early solar system activated by an anomalous nitrogen-containing parent body fluid.

  2. Remnants of the early solar system water enriched in heavy oxygen isotopes.

    Science.gov (United States)

    Sakamoto, Naoya; Seto, Yusuke; Itoh, Shoichi; Kuramoto, Kiyoshi; Fujino, Kiyoshi; Nagashima, Kazuhide; Krot, Alexander N; Yurimoto, Hisayoshi

    2007-07-13

    Oxygen isotopic composition of our solar system is believed to have resulted from mixing of two isotopically distinct nebular reservoirs, 16O-rich and (17,18)O-rich relative to Earth. The nature and composition of the (17,18)O-rich reservoir are poorly constrained. We report an in situ discovery of a chemically and isotopically unique material distributed ubiquitously in fine-grained matrix of a primitive carbonaceous chondrite Acfer 094. This material formed by oxidation of Fe,Ni-metal and sulfides by water either in the solar nebula or on a planetesimal. Oxygen isotopic composition of this material indicates that the water was highly enriched in 17O and 18O (delta(17,18)O(SMOW) = +180 per thousand per mil), providing the first evidence for an extremely (17,18)O-rich reservoir in the early solar system.

  3. Planetesimal clearing and size-dependent asteroid retention by secular resonance sweeping during the depletion of the solar nebula

    CERN Document Server

    Zheng, Xiaochen; Kouwenhoven, M B N

    2016-01-01

    The distribution of heavy elements is anomalously low in the asteroid main belt region compared with elsewhere in the solar system. Observational surveys also indicate a deficit in the number of small ($ \\le 50$~km size) asteroids that is two orders of magnitude lower than what is expected from the single power-law distribution that results from a collisional coagulation and fragmentation equilibrium. Here, we consider the possibility that a major fraction of the original asteroid population may have been cleared out by Jupiter's secular resonance, as it swept through the main asteroid belt during the depletion of the solar nebula. This effect leads to the excitation of the asteroids' orbital eccentricities. Concurrently, hydrodynamic drag and planet-disk tidal interaction effectively damp the eccentricities of sub-100 km-size and of super-lunar-size planetesimals, respectively. These combined effects lead to the asteroids' orbital decay and clearing from the present-day main belt region ($\\sim 2.1-3.3$~AU). ...

  4. High Energy Gamma-Ray Observations of the Crab Nebula and Pulsar with the Solar Tower Atmospheric Cherenkov Effect Experiment

    CERN Document Server

    Oser, S; Boone, L M; Chantell, M C; Conner, Z; Covault, C E; Dragovan, M; Fortin, P; Gregorich, D T; Hanna, D S; Mukherjee, R; Ong, R A; Ragan, K; Scalzo, R A; Schuette, D R; Theoret, C G; Tumer, T O; Williams, D A; Zweerink, J A

    2015-01-01

    The Solar Tower Atmospheric Cherenkov Effect Experiment (STACEE) is a new ground-based atmospheric Cherenkov telescope for gamma-ray astronomy. STACEE uses the large mirror area of a solar heliostat facility to achieve a low energy threshold. A prototype experiment which uses 32 heliostat mirrors with a total mirror area of ~ 1200\\unit{m^2} has been constructed. This prototype, called STACEE-32, was used to search for high energy gamma-ray emission from the Crab Nebula and Pulsar. Observations taken between November 1998 and February 1999 yield a strong statistical excess of gamma-like events from the Crab, with a significance of $+6.75\\sigma$ in 43 hours of on-source observing time. No evidence for pulsed emission from the Crab Pulsar was found, and the upper limit on the pulsed fraction of the observed excess was E_{th}) = (2.2 \\pm 0.6 \\pm 0.2) \\times 10^{-10}\\unit{photons cm^{-2} s^{-1}}. The observed flux is in agreement with a continuation to lower energies of the power law spectrum seen at TeV energies...

  5. Gas-grain energy transfer in solar nebula shock waves: Implications for the origin of chondrules

    Science.gov (United States)

    Hood, L. L.; Horanyi, M.

    1993-01-01

    Meteoritic chondrules provide evidence for the occurrence of rapid transient heating events in the protoplanetary nebula. Astronomical evidence suggests that gas dynamic shock waves are likely to be excited in protostellar accretion disks by processes such as protosolar mass ejections, nonaxisymmetric structures in an evolving disk, and impact on the nebula surface of infalling 'clumps' of circumstellar gas. Previous detailed calculations of gas-grain energy and momentum transfer have supported the possibility that such shock waves could have melted pre-existing chondrule-sized grains. The main requirement for grains to reach melting temperatures in shock waves with plausibly low Mach numbers is that grains existed in dust-rich zones (optical depth greater than 1) where radiative cooling of a given grain can be nearly balanced by radiation from surrounding grains. Localized dust-rich zones also provide a means of explaining the apparent small spatial scale of heating events. For example, the scale size of at least some optically thick dust-rich zones must have been relatively small (less than 10 kilometers) to be consistent with petrologic evidence for accretion of hot material onto cold chondrules. The implied number density of mm-sized grains for these zones would be greater than 30 m(exp -3). In this paper, we make several improvements of our earlier calculations to include radiation self-consistently in the shock jump conditions, and we include heating of grains due to radiation from the shocked gas. In addition, we estimate the importance of momentum feedback of dust concentrations onto the shocked gas which would tend to reduce the efficiency of gas dynamic heating of grains in the center of the dust cloud.

  6. Evidence for supernova injection into the solar nebula and the decoupling of r-process nucleosynthesis.

    Science.gov (United States)

    Brennecka, Gregory A; Borg, Lars E; Wadhwa, Meenakshi

    2013-10-22

    The isotopic composition of our Solar System reflects the blending of materials derived from numerous past nucleosynthetic events, each characterized by a distinct isotopic signature. We show that the isotopic compositions of elements spanning a large mass range in the earliest formed solids in our Solar System, calcium-aluminum-rich inclusions (CAIs), are uniform, and yet distinct from the average Solar System composition. Relative to younger objects in the Solar System, CAIs contain positive r-process anomalies in isotopes A 140. This fundamental difference in the isotopic character of CAIs around mass 140 necessitates (i) the existence of multiple sources for r-process nucleosynthesis and (ii) the injection of supernova material into a reservoir untapped by CAIs. A scenario of late supernova injection into the protoplanetary disk is consistent with formation of our Solar System in an active star-forming region of the galaxy.

  7. A thermodynamic and mechanical model for the earliest Solar System: Formation via 3-d collapse of dust in the pre-Solar nebula

    Science.gov (United States)

    Criss, R. E.; Hofmeister, A.

    2012-12-01

    The fundamental and shared rotational characteristics of the Solar System (nearly circular, co-planar orbits and mostly upright axial spins of the planets) record conditions of origin, yet are not explained by prevailing 2-dimensional disk models. Current planetary spin and orbital rotational energies (R.E.) each nearly equal and linearly depend on gravitational self-potential of formation (Ug), revealing mechanical energy conservation. We derive ΔUg ˜= ΔR.E. and stability criteria from thermodynamic principles, and parlay these relationships into a detailed model of simultaneous accretion of the protoSun and planets from the dust-bearing pre-solar nebula (PSN). Gravitational heating is insignificant because Ug is negative, the 2nd law of thermodynamics must be fulfilled, and ideal gas conditions pertain until the objects were nearly fully formed. Combined conservation of angular momentum and mechanical energy during 3-dimensional collapse of spheroidal dust shells in a contracting nebula provides ΔR.E. ˜= R.E. for the central body, whereas for formation of orbiting bodies, ΔR.E.depends on the contraction of orbits during collapse. Orbital data for the inner planets follow 0.04xR.E.f ˜= -Ug which confirms conservation of angular momentum. Measured spins of the youngest stars confirm that R.E.˜= -Ug. Heat production occurs after nearly final sizes are reached via mechanisms such as shear during differential rotation and radioactivity. We focus on the dilute stage, showing that the PSN was compositionally graded due to light molecules diffusing preferentially, providing the observed planetary chemistry, and set limits on PSN mass, density, and temperature. From measured planetary masses and orbital characteristics, accounting for dissipation of spin, we deduce mechanisms and the sequence of converting a 3-d dusty cloud to the present 2-d Solar System, and infer the evolution of dust and gas densities. Duration of events is obtained from the time

  8. A thermodynamic and mechanical model for formation of the Solar System via 3-dimensional collapse of the dusty pre-solar nebula

    Science.gov (United States)

    Hofmeister, Anne M.; Criss, Robert E.

    2012-03-01

    The fundamental and shared rotational characteristics of the Solar System (nearly circular, co-planar orbits and mostly upright axial spins of the planets) record conditions of origin, yet are not explained by prevailing 2-dimensional disk models. Current planetary spin and orbital rotational energies (R.E.) each nearly equal and linearly depend on gravitational self-potential of formation (Ug), revealing mechanical energy conservation. We derive -ΔUg≅Δ.R.E. and stability criteria from thermodynamic principles, and parlay these relationships into a detailed model of simultaneous accretion of the protoSun and planets from the dust-bearing 3-d pre-solar nebula (PSN). Gravitational heating is insignificant because Ug is negative, the 2nd law of thermodynamics must be fulfilled, and ideal gas conditions pertain to the rarified PSN until the objects were nearly fully formed. Combined conservation of angular momentum and mechanical energy during 3-dimensional collapse of spheroidal dust shells in a contracting nebula provides ΔR.E.≅R.E. for the central body, whereas for formation of orbiting bodies, ΔR.E.≅R.E.f(1-If/Ii), where I is the moment of inertia. Orbital data for the inner planets follow 0.04×R.E.f≅-Ug which confirms conservation of angular momentum. Significant loss of spin, attributed to viscous dissipation during differential rotation, masks the initial spin of the un-ignited protoSun predicted by R.E.=-Ug. Heat production occurs after nearly final sizes are reached via mechanisms such as shear during differential rotation and radioactivity. We focus on the dilute stage, showing that the PSN was compositionally graded due to light molecules diffusing preferentially, providing the observed planetary chemistry, and set limits on PSN mass, density, and temperature. From measured planetary masses and orbital characteristics, accounting for dissipation of spin, we deduce mechanisms and the sequence of converting a 3-d dusty cloud to the present 2-d

  9. Rotational studies in the Orion Nebula Cluster: from solar mass stars to brown dwarfs

    CERN Document Server

    Rodriguez-Ledesma, Maria Victoria; Eislöffel, Jochen

    2009-01-01

    Rotational studies at a variety of ages and masses are important for constraining the angular momentum evolution of young stellar objects (YSO). Of particular interest are the very low mass (VLM) stars and brown dwarfs (BDs), because of the significant lack of known rotational periods in that mass range. We provide for the first time information on rotational periods for a large sample of young VLM stars and BDs. This extensive rotational period study in the 1 Myr old Orion Nebula Cluster (ONC) is based on a deep photometric monitoring campaign using the Wide Field Imager (WFI) camera on the ESO/MPG 2.2m telescope on La Silla, Chile. Accurate I-band photometry of 2908 stars was obtained, extending three magnitudes deeper than previous studies in the ONC. We found 487 periodic variables with estimated masses between 0.5 Msun and 0.015 Msun, 124 of which are BD candidates. This is by far the most extensive and complete rotational period data set for young VLM stars and BDs. In addition, 808 objects show non-per...

  10. Probability of Capture of Irregular Satellites via Collisions Around the Gas Giant Planets as a Function of the Solar Nebula

    CERN Document Server

    Koch, F Elliott

    2011-01-01

    We investigated the probability that an inelastic collision of planetesimals within the Hill sphere of the Jovian planets could explain the presence and orbits of observed irregular satel- lites. Capture of satellites via this mechanism is highly dependent on not only the mass of the protoplanetary disk, but also the shape of the planetesimal size distribution. We performed 2000 simulations for integrated time intervals ~ 2 Myr and found that, given the currently ac- cepted value for the minimum mass solar nebula and planetesimal number density based upon the Bottke et al. (2010b) size distribution dN ~ D-1.8dD, the collision rates for the different Jovian planets range between ~ 60 and >~ 103 Myr-1 Additionally, we found that the prob- ability that these collisions remove enough orbital energy to yield a bound orbit was ~ 103 times the gravitational binding energy for objects with radii ~ 100 km. We find that, capturing irregular satellites via collisions between unbound objects can only account for ~ 0.1% o...

  11. Planetesimal Clearing and Size-dependent Asteroid Retention by Secular Resonance Sweeping during the Depletion of the Solar Nebula

    Science.gov (United States)

    Zheng, Xiaochen; Lin, Douglas N. C.; Kouwenhoven, M. B. N.

    2017-02-01

    The distribution of heavy elements is anomalously low in the asteroid main belt region compared with elsewhere in the solar system. Observational surveys also indicate a deficit in the number of small (≲50 km size) asteroids, which is two orders of magnitude lower than what is expected from the single power-law distribution that results from a collisional coagulation and fragmentation equilibrium. Here, we consider the possibility that a major fraction of the original asteroid population may have been cleared out by Jupiter’s secular resonance, as it swept through the main asteroid belt during the depletion of the solar nebula. This effect leads to the excitation of the asteroids’ orbital eccentricities. Concurrently, hydrodynamic drag and planet–disk tidal interaction effectively damp the eccentricities of sub-100 km-size and of super-lunar-size planetesimals, respectively. These combined effects lead to the asteroids’ orbital decay and clearing from the present-day main belt region (∼2.1–3.3 au). Eccentricity damping for the intermediate-size (50 to several hundreds of kilometers) planetesimals is less efficient than for small or large planetesimals. These objects therefore preferentially remain as main belt asteroids near their birthplaces, with modest asymptotic eccentricities. The smaller asteroids are the fragments of subsequent disruptive collisions at later times as suggested by the present-day asteroid families. This scenario provides a natural explanation for both the observed low surface density and the size distribution of asteroids in the main belt, without the need to invoke special planetesimal formation mechanisms. It also offers an explanation for the confined spatial extent of the terrestrial planet building blocks without the requirement of extensive migration of Jupiter, which is required in the grand-tack scenario.

  12. Stability of organic molecules against shocks in the young Solar nebula

    NARCIS (Netherlands)

    Kamp, Inga; Milosavljevic, Milica; Stempels, E

    2009-01-01

    One of the fundamental astrobiology questions is how life has formed in our Solar System. In this context the formation and stability of abiotic organic molecules such as CH(4), formic acid and amino acids, is important for understanding how organic material has formed and survived shocks and energe

  13. Pluto's structure and composition suggest origin in the solar, not a planetary, nebula

    Energy Technology Data Exchange (ETDEWEB)

    McKinnon, W.B.; Mueller, S.

    1988-09-15

    The mean density of the Pluto-Charon system is now accurately known at 1.99 +- 0.09 g cm/sup -3/, through observations of total occultations and transits. Pluto is thus very rock-rich, with a rock/(rock + H/sub 2/O-ice) mass ratio of approx. 0.68-0.80. Of four explanations for Pluto's large rock/ice ratio -formation in the inner Solar System, volatile loss during accretion, volatile loss during the large-body impact that created Charon, and formation as a large, ice-poor outer Solar System planetesimal - we show that only the last two are feasible, and that the depletion of water ice in Pluto is so severe that both explanations may be necessary.

  14. Shock wave fractionated noble gases in the early solar system

    Science.gov (United States)

    Ustinova, G. K.

    2001-08-01

    Many processes in the active star-forming regions are accompanied by strong shock waves, in acceleration by which the nuclear-active particles form the power-law energy spectrum of high rigidity: F(> E0) ˜ Eγ , with the spectral index γ ≤ 1.5-2. It must affect the production rates of spallogenic components of the isotopes, whose excitation functions depend on the shape of the energy spectrum of radiation. Thus, the isotopic signatures formed in the conditions of the strong shock wave propagation must be different from those formed in the calm environment. The early solar system incorporated all the presumed processes of the starforming stage, so that its matter had to conserve such isotopic anomalies. In previous works [1] the shock wave effects in generation of extinct radionu-clides and light elements Li, Be and B were considered. In the report some results for their evidence in the noble gas signatures are presented. Modelling the Kr isotope generation in spallation of Rb, Sr, Y and Zr with the nuclear-active particles, the energy spectrum of which was variable in the range of γ= 1.1-6.0, shows the different pace of growth of abundances of the dif-ferent Kr isotopes with decreasing . It leads to the quite diverse behaviour of the various Kr isotope ratios: the 78,80 Kr/83 Kr ratios increase, and the 82,84,86 Kr/83 Kr ratios decrease for the smaller γ. According to such criteria, for instance, the isotopically heavier SEP-Kr in the lunar ilmenites was pro-duced with the accelerated particles of the more rigid energy spectrum (γ ˜ 2) in comparison with the SW-Kr. Another important feature of the shock wave acceleration of particles is the enrichment of their specrtum with heavier ions in proportion to A/Z. Clearly, the shock wave fractionation of the noble gases, favouring the heavier isotopes, had to be inevitable. Such a fractionation depends on timing episodes of shock wave acceleration: after the n-th act of the ion acceleration their fractionation is

  15. Globular clusters and planetary nebulae kinematics and X-ray emission in the early-type galaxy NGC 5128

    Directory of Open Access Journals (Sweden)

    Samurović S.

    2006-01-01

    Full Text Available The estimates of the mass of the galaxy NGC 5128 based on the different mass tracers, globular clusters (GCs and planetary nebulae (PNe, are presented. These estimates are compared with the estimate based on the X-ray methodology and it is found that the results for the mass (and mass-to-light ratio for all three approaches are in very good agreement interior to 25 arcmin; beyond 25 arcmin the X-rays predict the mass which is too high with respect to the one found using GCs and PNe. Some possible explanations for this discrepancy were discussed. The Jeans equation is also solved and its predictions for the velocity dispersion are then compared with the observed values, which extend to ~8 effective radii in the case of the GCs and ~15 effective radii in the case of the PNe. It is found that interior to ~25 arcmin (~5 effective radii dark matter does not dominate because the total mass-to-light ratio in the B band in solar units is less than 10. Based on the GCs and PNe beyond ~25 arcmin the total mass-to-light ratio increases to ~14 (at ~80 arcmin which indicates the existence of dark matter in the outer regions of NGC 5128.

  16. Effect of External Photoevaporation on the Radial Transport of Volatiles and the Water Snowline in the Solar Nebula

    Science.gov (United States)

    Kalyaan, Anusha; Desch, Steven

    2017-01-01

    The Sun was likely born in a high mass star forming region [1]. Such a birth environment with a proximity to a nearby O or B star would photoevaporate the sun’s protoplanetary disk and cause an outward mass flow from the outer edge, as well as truncation of the disk, as seen in the Orion proplyds (although not as intensely)[2]. Photoevaporation likely explains the currently observed ~47 AU edge of the Kuiper Belt in our solar system [3], and more compellingly, the origin of certain short-lived radionuclides (such as Fe60), which cannot be successfully explained by a nebular origin [4][5]. Such a mass loss mechanism should affect the radial transport processes in the snowline region and along with temperature, has the potential to alter the location of the snowline.In this context, and in the light of recent ALMA observational results indicative of non-traditional behavior of snowlines and volatile transport in disks [6][7], this work studies what effect a photoevaporative mass loss from the outer disk may have on the volatile transport around the snowline region between ~1-10 AU in the disk. We build on the model of [8] and explore the effects of a steep photoevaporated non-uniform $\\alpha$ disk on radial transport of volatiles and small icy solids by incorporating the advection-diffusion equations as in [9] and condensation/evaporation of volatiles. We present results of these simulations, including volatile mass fluxes, ice/rock ratios, and snow line locations, in protoplanetary disks like the solar nebula.References: [1] Adams, F.C., 2010, ARAA 48,47 [2] Henney, W.J., & O’Dell, C.R., 1999, AJ, 118, 2350 [3] Trujillo,C.A. & Brown,M.E., 2001, ApJL,554,L95 [4] Hester, J.J., & Desch, S.J., 2005,ASPC, 341,107 [5] Wadhwa, M. et al. , 2007, Protostars & Planets V, 835 [5 [6] Cieza, L.A., et al., 2016, Nature,535,258 [7] Huang, J, et al. et al., 2016, ApJL, 823, L18 [8] Kalyaan, A., et al., 2015, ApJ, 815, 112 [9] Desch, S.J., et al., (in review).

  17. Planetary and meteoritic Mg/Si and d30Si variations inherited from solar nebula chemistry

    CERN Document Server

    Dauphas, Nicolas; Burkhardt, Christoph; Kobayashi, Hiroshi; Kurosawa, Kosuke

    2015-01-01

    The bulk chemical compositions of planets are uncertain, even for major elements such as Mg and Si. This is due to the fact that the samples available for study all originate from relatively shallow depths. Comparison of the stable isotope compositions of planets and meteorites can help overcome this limitation. Specifically, the non-chondritic Si isotope composition of the Earth's mantle was interpreted to reflect the presence of Si in the core, which can also explain its low density relative to pure Fe-Ni alloy. However, we have found that angrite meteorites display a heavy Si isotope composition similar to the lunar and terrestrial mantles. Because core formation in the angrite parent-body (APB) occurred under oxidizing conditions at relatively low pressure and temperature, significant incorporation of Si in the core is ruled out as an explanation for this heavy Si isotope signature. Instead, we show that equilibrium isotopic fractionation between gaseous SiO and solid forsterite at 1370 K in the solar neb...

  18. Lanthanide and actinide chemistry at high C/O ratios in the solar nebula

    Science.gov (United States)

    Lodders, Katharina; Fegley, Bruce, Jr.

    1993-01-01

    Chemical equilibrium calculations were performed to study the condensation chemistry of the REE and actinides under the highly reducing conditions which are necessary for the formation of the enstatite chondrites. Our calculations confirm that the REE and actinides condensed into oldhamite (CaS), the major REE and actinide host phase in enstatite chondrites, at a carbon-oxygen (C/O) ratio not less than 1 in an otherwise solar gas. Five basic types of REE abundance patterns, several of which are analogous to REE abundance patterns observed in the Ca, Al-rich inclusions in carbonaceous chondrites, are predicted to occur in meteoritic oldhamites. All of the reported REE patterns in oldhamites in enstatite chondrites can be interpreted in terms of our condensation calculations. The observed patterns fall into three of the five predicted categories. The reported Th and U enrichments and ratios in meteoritic oldhamites are also consistent with predictions of the condensation calculations. Pure REE sulfides are predicted to condense in the 10 exp -6 to 10 exp -9 bar range and may be found in enstatite chondrites if they formed in this pressure range.

  19. Observing nebulae

    CERN Document Server

    Griffiths, Martin

    2016-01-01

    This book enables anyone with suitable instruments to undertake an examination of nebulae and see or photograph them in detail. Nebulae, ethereal clouds of gas and dust, are among the most beautiful objects to view in the night sky. These star-forming regions are a common target for observers and photographers. Griffiths describes many of the brightest and best nebulae and includes some challenges for the more experienced observer. Readers learn the many interesting astrophysical properties of these clouds, which are an important subject of study in astronomy and astrobiology. Non-mathematical in approach, the text is easily accessible to anyone with an interest in the subject. A special feature is the inclusion of an observational guide to 70 objects personally observed or imaged by the author. The guide also includes photographs of each object for ease of identification along with their celestial coordinates, magnitudes and other pertinent information. Observing Nebulae provides a ready resource to allow an...

  20. Physical Structure of Planetary Nebulae. I. The Owl Nebula

    CERN Document Server

    Guerrero, M A; Manchado, A; Kwitter, K B

    2003-01-01

    The Owl Nebula is a triple-shell planetary nebula with the outermost shell being a faint bow-shaped halo. We have obtained deep narrow-band images and high-dispersion echelle spectra in the H-alpha, [O III], and [N II] emission lines to determine the physical structure of each shell in the nebula. These spatio-kinematic data allow us to rule out hydrodynamic models that can reproduce only the nebular morphology. Our analysis shows that the inner shell of the main nebula is slightly elongated with a bipolar cavity along its major axis, the outer nebula is a filled envelope co-expanding with the inner shell at 40 km/s, and the halo has been braked by the interstellar medium as the Owl Nebula moves through it. To explain the morphology and kinematics of the Owl Nebula, we suggest the following scenario for its formation and evolution. The early mass loss at the TP-AGB phase forms the halo, and the superwind at the end of the AGB phase forms the main nebula. The subsequent fast stellar wind compressed the superwi...

  1. Cool gaseous nebulae

    CERN Document Server

    Shaver, P A; Pottasch, S R

    1979-01-01

    The electron temperatures of diffuse gaseous nebulae have long been thought to be close to 10/sup 4/K. Much lower temperatures were derived from some of the early radio continuum and recombination line work, but these were generally considered to be wrong for a variety of reasons. While there is little doubt that the bright nebulae do indeed have temperatures of approximately 8000-9000K, there are strong indications that some nebulae of lower densities have much lower temperatures, nebulae were made in order to determine electron temperatures in the absence of such effects as collisional de-excitation, stimulated emission, and pressure broadening. Several of these nebulae have been found to have temperatures below 5000K and for two of them which are discussed (RCW94 and G339.1-0.2) absolute upper limits of approximately 4700 K are imposed by the line widths alone. (11 refs).

  2. Evidence for Mo isotope fractionation in the solar nebula and during planetary differentiation

    Science.gov (United States)

    Burkhardt, Christoph; Hin, Remco C.; Kleine, Thorsten; Bourdon, Bernard

    2014-04-01

    Mass-dependent Mo isotope fractionation has been investigated for a wide range of meteorites including chondrites (enstatite, ordinary and carbonaceous chondrites), iron meteorites, and achondrites (eucrites, angrites and martian meteorites), as well as for lunar and terrestrial samples. Magmatic iron meteorites together with enstatite, ordinary and most carbonaceous chondrites define a common δMo value of -0.16±0.02‰ (relative to the NIST SRM 3134 Mo standard), which is interpreted to reflect the Mo isotope composition of bulk planetary bodies in the inner solar system. Heavy Mo isotope compositions for IAB iron meteorites most likely reflect impact-induced evaporative losses of Mo from these meteorites. Carbonaceous chondrites define an inverse correlation between δMo and metal content, and a positive correlation between δMo and matrix abundance. These correlations are mainly defined by CM and CK chondrites, and may reflect the heterogeneous distribution of an isotopically light metal and/or an isotopically heavy matrix component in the formation region of carbonaceous chondrites. Alternatively, the elevated δMo of the CM and CK chondrites could result from the loss of volatile, isotopically light Mo oxides, that formed under oxidized conditions typical for the formation of these chondrites. The Mo isotope compositions of samples derived from the silicate portion of differentiated planetary bodies are heavy compared to the mean composition of chondrites and iron meteorites. This difference is qualitatively consistent with experimental evidence for Mo isotope fractionation between metal and silicate. The common δMo values of -0.05±0.03‰ of lunar samples derived from different geochemical reservoirs indicate the absence of significant Mo isotope fractionation by silicate differentiation or impact metamorphism/volatilization on the Moon. The most straightforward interpretation of the Mo isotope composition of the lunar mantle corresponds to the formation

  3. Precondensed matter - Key to the early solar system

    Science.gov (United States)

    Clayton, D. D.

    1978-01-01

    Explicit astrophysical details are developed for the hypothesis that chemical and isotopic anomalies in primitive solar-system samples reflect routine initial chemical conditions within precondensed matter. The central feature of this theory concerns the chemical state of presolar dust, which is regarded as never having been vaporized in the region where the most chemically primitive samples (carbonaceous meteorites) accumulated. It is suggested that the initial chemical state of heavy atoms during meteorite and planetary accumulation was distributed between a refractory-mineral component from high-temperature condensation and a volatile component resulting from cold matter adhering to preexisting grains. Thermal conditions in the solar nebula are considered along with the existence of supernova condensates and other thermal condensates in the interstellar dust. Fractionation into volatile and refractory elements is idealized in terms of four distinct interstellar components, and the fractionated precondensed matter is described.

  4. Butterfly Nebula

    Science.gov (United States)

    1997-01-01

    The Hubble Space Telescope's Wide Field and Planetary Camera 2 (WFPC2) is back at work, capturing this image of the 'butterfly wing'- shaped nebula, NGC 2346. The nebula is about 2,000 light-years away from Earth in the direction of the constellation Monoceros. It represents the spectacular 'last gasp' of a binary star system at the nebula's center. The image was taken on March 6, 1997 as part of the recommissioning of the Hubble Space Telescope's previously installed scientific instruments following the successful servicing of the HST by NASA shuttle astronauts in February. WFPC2 was installed in HST during the servicing mission in 1993. At the center of the nebula lies a pair of stars that are so close together that they orbit around each other every 16 days. This is so close that, even with Hubble, the pair of stars cannot be resolved into its two components. One component of this binary is the hot core of a star that has ejected most of its outer layers, producing the surrounding nebula. Astronomers believe that this star, when it evolved and expanded to become a red giant, actually swallowed its companion star in an act of stellar cannibalism. The resulting interaction led to a spiraling together of the two stars, culminating in ejection of the outer layers of the red giant. Most of the outer layers were ejected into a dense disk, which can still be seen in the Hubble image, surrounding the central star. Later the hot star developed a fast stellar wind. This wind, blowing out into the surrounding disk, has inflated the large, wispy hourglass-shaped wings perpendicular to the disk. These wings produce the butterfly appearance when seen in projection. The total diameter of the nebula is about one-third of a light-year, or 2 trillion miles.

  5. Response to the Comment by S.B. Simon, L. Grossman, and S.R. Sutton on "Valence state of titanium in the Wark-Lovering rim of a Leoville CAI as a record of progressive oxidation in the early Solar Nebula"

    Science.gov (United States)

    Young, Edward D.; Dyl, Kathryn A.; Simon, Justin I.

    2012-05-01

    S. Simon et al. incorrectly suggest that in earlier work we claimed there was no Ti3+ in Wark-Lovering rim pyroxenes. In neither the paper by Simon et al. (2005) nor the subsequent paper by Dyl et al. (2011) did we assert that there was no Ti3+ in rim pyroxenes. Rather, we found that many pyroxenes have Ti3+ below detection while others have lower Ti3+/Ti4+ than is typical of CAI interiors, indicating rim formation in a relatively oxidizing environment. Dyl et al. (2011) showed through exhaustive testing that the suggestion by Simon et al. (2007) that EMPA data in the paper by Simon et al. (2005) were flawed is incorrect. Here we consider each point raised in the comment by S. Simon et al. and reiterate that our electron microprobe data and the XANES data of Simon et al. (2007) agree and demonstrate a statistically significant (˜2σ) or greater difference between rim and interior pyroxene Ti3+/Ti4+. We show that the oxidation states of Ti in Wark-Lovering rim pyroxenes, the chemistry of rim pyroxenes, and the modal abundances of rim minerals are best explained by reaction between the CAI and gas that was orders of magnitude more oxidizing than the solar-like gas from which the CAIs originally formed.

  6. Water delivery in the Early Solar System

    CERN Document Server

    Dvorak, Rudolf; Süli, Áron; Sándor, Zsolt; Galiazzo, Mattia; Pilat-Lohinger, Elke

    2015-01-01

    As part of the national scientific network 'Pathways to Habitable Worlds' the delivery of water onto terrestrial planets is a key question since water is essential for the development of life as we know it. After summarizing the state of the art we show some first results of the transport of water in the early Solar System for scattered main belt objects. Hereby we investigate the questions whether planetesimals and planetesimal fragments which have gained considerable inclination due to the strong dynamical interactions in the main belt region around 2 AU can be efficient water transporting vessels. The Hungaria asteroid group is the best example that such scenarios are realistic. Assuming that the gas giants and the terrestrial planets are already formed, we monitor the collisions of scattered small bodies containing water (in the order of a few percent) with the terrestrial planets. Thus we are able to give a first estimate concerning the respective contribution of such bodies to the actual water content i...

  7. Aluminum-26 in the early solar system - Fossil or fuel

    Science.gov (United States)

    Lee, T.; Papanastassiou, D. A.; Wasserburg, G. J.

    1977-01-01

    The isotopic composition of Mg was measured in different phases of a Ca-Al-rich inclusion in the Allende meteorite. Large excesses of Mg-26 of up to 10% were found. These excesses correlate strictly with the Al-27/Mg-24 ratio for four coexisting phases with distinctive chemical compositions. Models of in situ decay of Al-26 within the solar system and of mixing of interstellar dust grains containing fossil Al-26 with normal solar system material are presented. The observed correlation provides definitive evidence for the presence of Al-26 in the early solar system. This requires either injection of freshly synthesized nucleosynthetic material into the solar system immediately before condensation and planet formation, or local production within the solar system by intense activity of the early sun. Planets promptly produced from material with the inferred Al-26/Al-27 would melt within about 300,000 years.

  8. Aluminum-26 in the early solar system - Fossil or fuel

    Science.gov (United States)

    Lee, T.; Papanastassiou, D. A.; Wasserburg, G. J.

    1977-01-01

    The isotopic composition of Mg was measured in different phases of a Ca-Al-rich inclusion in the Allende meteorite. Large excesses of Mg-26 of up to 10% were found. These excesses correlate strictly with the Al-27/Mg-24 ratio for four coexisting phases with distinctive chemical compositions. Models of in situ decay of Al-26 within the solar system and of mixing of interstellar dust grains containing fossil Al-26 with normal solar system material are presented. The observed correlation provides definitive evidence for the presence of Al-26 in the early solar system. This requires either injection of freshly synthesized nucleosynthetic material into the solar system immediately before condensation and planet formation, or local production within the solar system by intense activity of the early sun. Planets promptly produced from material with the inferred Al-26/Al-27 would melt within about 300,000 years.

  9. Planetary nebulae abundances and stellar evolution

    NARCIS (Netherlands)

    Pottasch, S. R.; Bernard-Salas, J.

    2006-01-01

    A summary is given of planetary nebulae abundances from ISO measurements. It is shown that these nebulae show abundance gradients (with galactocentric distance), which in the case of neon, argon, sulfur and oxygen (with four exceptions) are the same as HII regions and early type star abundance gradi

  10. Explaining the Noble Gas Content of the Planets: Theoretical Models for Argon-Trapping by Amorphous Ices in the Solar Nebula

    Science.gov (United States)

    Sanders, C. B.; Ciesla, F.

    2014-12-01

    The composition of planets in the modern solar system can be traced to the chemistry and physics of the solar nebula, the diffuse disk of gas and dust that surrounded the young sun immediately after its formation. Materials such as the noble gases were too volatile to be chemically incorporated by planetary embryos. Instead, it is likely that they were trapped physically and transported to the inner planets by migrating comets and planetesimals. One trapping mechanism under consideration is the capture of noble gas atoms in amorphous ices on the surface of cold grains. We created a simple numerical model to explore this mechanism, using argon as a representative volatile gas. We have demonstrated that our model reproduces experimental trapping efficiencies (ratio of the volatile atoms to water molecules in the deposited ice) when we constrain the binding energy of our representative volatile to 3500-5500K and the sticking efficiency of volatile atoms to 0.004x gas phase water pressure. Binding energy and sticking efficiency are poorly understood for most volatile substances, but this study finds that they are among the most critical when predicting the trapping of volatiles in the physical world. Constraining these parameters under nebular conditions will allow us to evaluate how much argon could have been trapped in nebular ices and ultimately assess the role of amorphous ice trapping in the origin of planetary volatiles.

  11. Blowing in the Wind: II. Creation and Redistribution of Refractory Inclusions in a Turbulent Protoplanetary Nebula

    Science.gov (United States)

    Cuzzi, Jeffrey N.; Davis, Sanford S.; Dobrovolskis, Anthony R.

    2003-01-01

    Ca-A1 rich refractory mineral inclusions (CAIs) found at 1-6% mass fraction in primitive chondrites appear to be 1-3 million years older than the dominant (chondrule) components which were accreted into the same parent bodies. A prevalent concern is that it is difficult to retain CAIs for this long against gas-drag-induced radial drift into the sun. We reassess the situation in terms of a hot inner (turbulent) nebula context for CAI formation, using analytical models of nebula evolution and particle diffusion. We show that outward radial diffusion in a weakly turbulent nebula can overwhelm inward drift, and prevent significant numbers of CAI-size particles from being lost into the sun for times on the order of 10(exp 6) years. CAIs can form early, when the inner nebula was hot, and persist in sufficient abundance to be incorporated into primitive planetesimals at a much later time. Small (less than or approximately 0.1 mm diameter) CAIs persist for longer times than large (greater than or approximately 5mm diameter ones. To obtain a quantitative match to the observed volume fractions of CAIs in chondrites, another process must be allowed for: a substantial enhancement of the inner hot nebula in silicate-forming material, which we suggest was caused by rapid inward drift of meter-sized objects. This early in nebula history, the drifting rubble would have a carbon content probably an order of magnitude larger than even the most primitive (CI) carbonaceous chondrites. Abundant carbon in the evaporating material would help keep the nebula oxygen fugacity low, plausibly solar; as inferred for the formation environment of CAIs. The associated production of a larger than canonical amount of CO2 might also play a role in mass-independent fractionation of oxygen isotopes, leaving the gas rich in O-16 as inferred from CAIs and other high temperature condensates.

  12. On collisional capture rates of irregular satellites around the gas-giant planets and the minimum mass of the solar nebula

    Science.gov (United States)

    Koch, F. Elliott; Hansen, Bradley M. S.

    2011-09-01

    We investigate the probability that an inelastic collision of planetesimals within the Hill sphere of the Jovian planets could explain the presence and orbits of observed irregular satellites. Capture of satellites via this mechanism is highly dependent on not only the mass of the protoplanetary disc, but also the shape of the planetesimal size distribution. We performed 2000 simulations for integrated time intervals ˜2 Myr and found that, given the currently accepted value for the minimum mass solar nebula and planetesimal number density based upon the Nesvorný et al. and Charnoz & Morbidelli size distribution dN˜D-3.5dD, the collision rates for the different Jovian planets range between ˜0.6 and ≳170 Myr-1 for objects with radii 1 km ≤r≤ 10 km. Additionally, we found that the probability that these collisions remove enough orbital energy to yield a bound orbit was ≲10-5 and had very little dependence on the relative size of the planetesimals. Of these collisions, the collision energy between two objects was ≳103 times the gravitational binding energy for objects with radii ˜100 km. We find that capturing irregular satellites via collisions between unbound objects can only account for ˜0.1 per cent of the observed population, hence this cannot be the sole method of producing irregular satellites.

  13. Fischer-Tropsch-Type Production of Organic Materials in the Solar Nebula: Studies Using Graphite Catalysts and Measuring the Trapping of Noble Gases

    Science.gov (United States)

    Nuth, Joseph A., III; Ferguson, Frank T.; Lucas, Christopher; Kimura, Yuki; Hohenberg, Charles

    2009-01-01

    The formation of abundant carbonaceous material in meteorites is a long standing problem and an important factor in the debate on the potential for the origin of life in other stellar systems. The Fischer-Tropsch-type (FTT) catalytic reduction of CO by hydrogen was once the preferred model for production of organic materials in the primitive solar nebula. We have demonstrated that many grain surfaces can catalyze both FTT and HB-type reactions, including amorphous iron and magnesium silicates, pure silica smokes as well as several minerals. Graphite is not a particularly good FTT catalyst, especially compared to iron powder or to amorphous iron silicate. However, like other silicates that we have studied, it gets better with exposure to CO. N2 and H2 over time: e.g., after formation of a macromolecular carbonaceous layer on the surfaces of the underlying gains. While amorphous iron silicates required only 1 or 2 experimental runs to achieve steady state reaction rates, graphite only achieved steady state after 6 or more experiments. We will present results showing the catalytic action of graphite grains increasing with increasing number of experiments and will also discuss the nature of the final "graphite" grains aster completion of our experiments.

  14. The meteoritic record of presolar and early solar system organic chemistry. [Abstract only

    Science.gov (United States)

    Cronin, John R.; Pizzarello, Sandra

    1994-01-01

    Carbon, hydrogen, and nitrogen isotopic analyses of various classes of organic compounds done in collaboration with Epstein and Krishnamurthy (Caltech) have shown these compounds to be enriched to varying degrees in the heavier isotopes. These results, in particular the large deuterium enrichments, have been interpreted as indicating an interstellar origin for the meteorite compounds or their precursors. Such isotopic fractionations, of hydrogen especially, are characteristic of low temperature ion-molecule reactions in cold interstellar clouds. There is also evidence from the large corresponding suites of alpha-amino and alpha-hydroxy acids found in meteorites suggesting that aqueous phase chemistry on the meteorite parent body played an important role in the formation of these compounds. These data support the hypothesis that interstellar compounds survived in the solar nebula at a radial distance corresponding to the asteroid belt, were incorporated into the parent body in icy, volatile-rich, planetesinals, and underwent further reactions during a period of aqueous activity within the early parent body to give the present suite of meteorite compounds. This formation hypothesis will be discussed and the results of recent isotopic and molecular analyses bearing on it will be presented.

  15. Analogs of the early solar system.

    Science.gov (United States)

    Koerner, D W

    1997-06-01

    Within the last few decades, the existence of protoplanetary disks has been inferred on the basis of emission from T Tauri stars that does not arise from a stellar photosphere. More recently, high-resolution interferometric techniques have resolved the dust continuum emission, and millimeter arrays have imaged circumstellar molecular gas. These measurements corroborate the disk interpretation; many T Tauri stars are surrounded by centrifugally supported circumstellar disks with radial sizes of order 100 AU. Further proof issues from Hubble Space Telescope images of disks that are illuminated externally. The morphology of circumstellar dust is revealed in striking detail and affirms the prevalence and dimensions of disks imaged at longer wavelengths. The fate of circumstellar material around young stars must be understood in order to discern the degree to which these disks are proto-planetary. Observational studies of circumstellar disks which are in the beginning of a dispersal phase are challenging and place great demands on astronomical techniques. Nevertheless, the connection between disks and the formation of extra-solar planets is supported by increasing circumstantial evidence. Optically thin dust continuum emission persists in T Tauri stars and is detected around some young main sequence stars. Since the dust is subject to rapid dispersal by radiation pressure and Poynting-Robertson drag, some mechanism of replenishment is required. Disks around nearby young main sequence stars show evidence for inner voids and disk asymmetries that should also disappear on short timescales. The presence of large orbiting bodies which collide and interact with the resulting debris can explain both the persistence of optically thin dust and the maintenance of otherwise-ephemeral dynamical features. Together with recent detections of extra-solar planets, these observations lend some support to the hypothesis that circumstellar disks commonly give birth to planetary systems.

  16. Dynamo magnetic field-induced angular momentum transport in protostellar nebulae - The 'minimum mass' protosolar nebula

    Science.gov (United States)

    Stepinski, T. F.; Levy, E. H.

    1990-01-01

    Magnetic torques can produce angular momentum redistribution in protostellar nebulas. Dynamo magnetic fields can be generated in differentially rotating and turbulent nebulas and can be the source of magnetic torques that transfer angular momentum from a protostar to a disk, as well as redistribute angular momentum within a disk. A magnetic field strength of 100-1000 G is needed to transport the major part of a protostar's angular momentum into a surrounding disk in a time characteristic of star formation, thus allowing formation of a solar-system size protoplanetary nebula in the usual 'minimum-mass' model of the protosolar nebula. This paper examines the possibility that a dynamo magnetic field could have induced the needed angular momentum transport from the proto-Sun to the protoplanetary nebula.

  17. Dynamo magnetic field-induced angular momentum transport in protostellar nebulae - The minimum mass protosolar nebula

    Energy Technology Data Exchange (ETDEWEB)

    Stepinski, T.F.; Levy, E.H. (Arizona Univ., Tucson (USA))

    1990-02-01

    Magnetic torques can produce angular momentum redistribution in protostellar nebulas. Dynamo magnetic fields can be generated in differentially rotating and turbulent nebulas and can be the source of magnetic torques that transfer angular momentum from a protostar to a disk, as well as redistribute angular momentum within a disk. A magnetic field strength of 100-1000 G is needed to transport the major part of a protostar's angular momentum into a surrounding disk in a time characteristic of star formation, thus allowing formation of a solar-system size protoplanetary nebula in the usual minimum-mass model of the protosolar nebula. This paper examines the possibility that a dynamo magnetic field could have induced the needed angular momentum transport from the proto-Sun to the protoplanetary nebula. 32 refs.

  18. Kinetics of Methane Clathrate Formation in the Presolar Nebula

    Science.gov (United States)

    Vu, Tuan; Choukroun, Mathieu

    2016-10-01

    Clathrate hydrates are a distinct form of water ice wherein the crystal lattice of the host water molecules forms symmetric, polyhedral cages that trap volatile guest species under appropriate pressures and temperatures. These materials are an abundant source of hydrocarbons on Earth, and have been expected to be present on a number of icy celestial bodies, including Mars, Europa, Titan, and Enceladus. Clathrates are also thought to be one of the most likely traps for volatiles during the condensation of the protostellar nebulae. Prior to the Voyager mission, the prevailing expectation was that the elemental composition of the giant planets would reflect the composition of the solar nebula and therefore be similar to solar abundances. However, spacecraft observations by Voyager, Galileo, and Cassini-Huygens, as well as ground-based observations, have revealed unexpected elemental enrichment, relative to solar abundances, of C, N, S, As, P, and noble gases in the giant planets and in comets. One of the contending explanations is the retention of these volatiles as clathrate hydrates, which may have enabled their capture early in the history of the Solar System.While the formation and stability of clathrates have been addressed theoretically and, to some extent, experimentally at relatively high pressures (10-7-10-3 bar), there is a scarcity of experimental undertaking on the kinetics of clathrate formation and their stability at the low pressures relevant to the early outer solar nebula (~10-11 bar). This study seeks to elucidate the clathrate formation kinetics under nebula-relevant conditions via a series of optical Raman experiments on ice/gas mixtures over a range of pressures and temperatures. Our work on the methane gas/ice system shows that clathrate formation occurs on a rather fast timescale (typically within minutes at 223-253 K and 30-50 bar CH4). In addition, the rate of enclathration increases with pressures and temperatures, and the activation energy

  19. Where does the huge orbital a.m. of solar and exoplanets come from? Evidence in both arenas that they get it during during nebula-borne construction, the property of new insight on the physics of gravitation

    Science.gov (United States)

    Osmaston, M. F.

    2013-09-01

    be ruled out. The near-circular orbits of all except Mercury are indeed consistent with completion in the presence of nebular gas-drag. But planetary growth by randomly directed impact would not systematically increase their orbit size and a.m. So where and how were the SS protoplanets nucleated and achieve their growth? This introduces the matter of planetary spin directions. Mercury's spin is probably irrelevant, having suffered a late giant impact (tilted and highly eccentric orbit, /3rds of its mantle missing) [8,9]. Of the 7 other planets all are prograde except Venus, whose very slow retrograde spin might be due to retrograde-capturing large amounts of the Mercury impact debris, another 2.7% of which may have built the Moon. The 98deg inclination of Uranus does not render it 'retrograde'. Restoring it by that angle makes its satellite pattern like those of the other three Giant Planets (GP). Moreover, Uranus' orbit is now as circular as its GP brethren, so the impact which tilted its axis must have been quite early, giving time for subsequent circularization by nebular action. So we are looking for a nebula-present mode of planetary construction which leads to a systematically prograde spin result. Such systematic behaviour hints strongly at gravitational nucleation. Note at once that in a Keplerian disc the vorticity is retrograde. The only place where prograde vorticity would be available in a plasma-rich protoplanetary disc is very close to the Sun and due to quasi-equatorial magnetic coupling. This point immediately strikes a chord with the exoplanet scene. There, ~23% of all those found are grouped around an orbital distance of ~10 solar radii. The proportion has changed little as the numbers grew, despite changes in detection methods. It is not a matter of ease of detection, but of why they are there at all, when Mercury, our closest-in planet, is at 83 solar radii. Some have sought to explain this as the result of inward migration due to gas drag, but

  20. A Starfish Preplanetary Nebula: IRAS 19024+0044

    Science.gov (United States)

    Sahai, Raghvendra; Sanchez Contreras, Carmen; Morris, Mark

    2005-01-01

    Using the Hubble Space Telescope, we have imaged the OH/IR star IRAS 19024+0044 (I19024) at 0.6, 0.8, 1.1, and 1.6 micrometers, as part of our surveys of candidate preplanetary nebulae. The images show a multipolar nebula of size approximately equal to 3.'7 2.'3, with at least six elongated lobes emanating from the center of the nebula. Two of the lobes show limb-brightened tips having point-symmetric structure with respect to the expected location of the central star. The central region shows two dark bands southwest and northeast of a central shallow maximum that may be either two inclined dusty toroidal structures or the dense parts of a single wide, inhomogeneous, toroid. Avery faint, surface brightness-limited, diffuse halo surrounds the lobes. Long-slit/echelle optical spectroscopy obtained at the Mount Palomar and Keck observatories shows a spatially compact source of H(alpha) emission; the H(alpha) line shows a strong, narrow, central core with very broad (+/-1000 km/sec), weak wings, and a narrower blueshifted absorption feature signifying the presence of an approximately 100 km/sec(exp -1) outflow. The spectrum is characterized by a strong, relatively featureless, continuum and lacks the strong forbidden emission lines characteristic of planetary nebulae, confirming that IRAS 19024 is a preplanetary nebula; the spectral type for the central star, although uncertain, is most likely early G. Interferometric observations of the CO J = 1 -0 line emission with the Owens Valley Radio Interferometer show a marginally resolved molecular envelope (size 5.'5 x 4.'4) with an expansion velocity of 13 km/sec (exp -1), resulting from the asymptotic giant branch (AGB) progenitor's dense, slow wind. We derive a kinematic distance of 3.5 kpc to I19024, based on its radial velocity. The bolometric flux is 7:3 x 10(exp -9) erg s(exp -1) cm(exp -2), and the luminosity 2850 L. The relatively low luminosity of I19024, in comparison with stellar evolutionary models, indicates

  1. Data Assimilation and Uncertainties in Early Solar Cycle Predictions

    Science.gov (United States)

    Kitiashvili, Irina

    2017-08-01

    Stochastic nature of solar activity variations together with our limited knowledge of the dynamo mechanism and subsurface dynamics causes uncertainty in predictions of the solar cycle. For improving the physics-based predictions we can take advantage of the mathematical data assimilation approach that allows us to take into account both, observational errors and model uncertainties, and provide estimates of the next solar cycle along with prediction uncertainties. In this study we use the Parker's migratory dynamo model together with the equation of magnetic helicity balance, which reproduces main properties of the sunspot cycles and allow us to minimize discrepancies between the observed global activity variations and the model solution. The test simulation runs show that a reliable prediction can be obtained for two phases of preceding solar cycle: 1) if the polar field reversals shortly after the solar maxima (strong toroidal field and weak poloidal field), and 2) during the solar minima (strongest poloidal and weak toroidal fields). The early estimate of Cycle 25 obtained by this method shows that this cycle will start in 2019 - 2020, reach the maximum in 2023 - 2024, and that the mean sunspot number at the maximum will be about 90 (for the v2.0 sunspot number series).

  2. New constraints on the magnetic history of the CV parent body and the solar nebula from the Kaba meteorite

    Science.gov (United States)

    Gattacceca, Jérôme; Weiss, Benjamin P.; Gounelle, Matthieu

    2016-12-01

    Recent paleomagnetic studies of Allende CV chondrite as well as thermal modeling suggest the existence of partially differentiated asteroids with outer unmelted and variably metamorphosed crusts overlying differentiated interiors. To further constrain the magnetic history of the CV parent body, we report here paleomagnetic results on Kaba CV chondrite. This meteorite contains 11 wt% pseudo-single domain magnetite, making it a rock with an excellent paleomagnetic recording capacity. Kaba appears to carry a stable natural remanent magnetization acquired on its parent body upon cooling in an internally generated magnetic field of about 3 μT from temperatures below 150 °C during thermal metamorphism about 10 to several tens of Myr after solar system formation. This strengthens the case for the existence of a molten advecting core in the CV parent body. Furthermore, we show that no significant magnetic field (i.e. lower than ∼ 0.3 μT) was present when aqueous alteration took place on the Kaba parent body around 4 to 6 Myr after solar system formation, suggesting a delay in the onset of the dynamo in the CV parent body and confirming that nebular fields had already decayed at that time.

  3. Radial pressure in the solar nebula as affecting the motions of planetesimals. [toroidal particle concentration in planetary evolution

    Science.gov (United States)

    Whipple, F. L.

    1973-01-01

    Growing planetesimals and a range of drag laws depending on the Reynolds number and on the ratio of particle size to mean free path are considered. Particles spiral in the direction of positive gradient, thus being concentrated toward toroidal concentrations of gas. The effect increases with decreasing rates of particle growth, i.e., with increasing time scales of planet formation by accretion. In the outer regions, where evidence suggests that comets were formed and Uranus and Neptune were so accumulated, the effect of the pressure gradient is to clear the forming comets from those regions. The large mass of Neptune may have developed because of this effect, perhaps Neptune's solar distance was reduced from Bode's law, and perhaps no comet belt exists beyond Neptune. In the asteroid belt, on a slow time scale, the effect may have spiraled planetesimals toward Mars and Jupiter, thus contributing to the lack of planet formation in this region.

  4. Early solar system. Early accretion of water in the inner solar system from a carbonaceous chondrite-like source.

    Science.gov (United States)

    Sarafian, Adam R; Nielsen, Sune G; Marschall, Horst R; McCubbin, Francis M; Monteleone, Brian D

    2014-10-31

    Determining the origin of water and the timing of its accretion within the inner solar system is important for understanding the dynamics of planet formation. The timing of water accretion to the inner solar system also has implications for how and when life emerged on Earth. We report in situ measurements of the hydrogen isotopic composition of the mineral apatite in eucrite meteorites, whose parent body is the main-belt asteroid 4 Vesta. These measurements sample one of the oldest hydrogen reservoirs in the solar system and show that Vesta contains the same hydrogen isotopic composition as that of carbonaceous chondrites. Taking into account the old ages of eucrite meteorites and their similarity to Earth's isotopic ratios of hydrogen, carbon, and nitrogen, we demonstrate that these volatiles could have been added early to Earth, rather than gained during a late accretion event.

  5. Lunar composition as a clue to the early history of the solar system.

    Science.gov (United States)

    Singer, S. F.

    1972-01-01

    The apparent conflict of the low iron content of the moon with the hypothesis of lunar capture is shown to be reconcilable if, in the inner solar system, iron condensations are assumed to conglomerate into planetary cores before the silicates condense to form a number of iron-poor moons. In the outer solar system, there would be no such fractionation, and, in the asteroid belt, the situation should be intermediate and quite complex. A crucial parameter is the ratio of coalescence time to cooling time, which depends on the density of the solar nebula. Also of importance are nonuniform cooling and condensation, as well as the outward transport of volatiles and their dissipation from the solar system. The model can explain also other features of the planets and asteroids.

  6. Early inner solar system origin for anomalous sulfur isotopes in differentiated protoplanets.

    Science.gov (United States)

    Antonelli, Michael A; Kim, Sang-Tae; Peters, Marc; Labidi, Jabrane; Cartigny, Pierre; Walker, Richard J; Lyons, James R; Hoek, Joost; Farquhar, James

    2014-12-16

    Achondrite meteorites have anomalous enrichments in (33)S, relative to chondrites, which have been attributed to photochemistry in the solar nebula. However, the putative photochemical reactions remain elusive, and predicted accompanying (33)S depletions have not previously been found, which could indicate an erroneous assumption regarding the origins of the (33)S anomalies, or of the bulk solar system S-isotope composition. Here, we report well-resolved anomalous (33)S depletions in IIIF iron meteorites (solar system (solar system S-isotope composition was chondritic (consistent with IAB iron meteorites, Earth, Moon, and Mars). The range of mass-independent sulfur isotope compositions may reflect spatial or temporal changes influenced by photochemical processes. A tentative correlation between S isotopes and Hf-W core segregation ages suggests that the two systems may be influenced by common factors, such as nebular location and volatile content.

  7. Pb-Pb chronometry and the early Solar System

    Science.gov (United States)

    Connelly, J. N.; Bollard, J.; Bizzarro, M.

    2017-03-01

    Of the long-lived chronometric systems, only the dual decay of 238U and 235U to 206Pb and 207Pb, respectively, have appropriate half-lives to resolve the ages of meteorites and their components formed in the first 5 Myr of the Solar System. This paper reviews the theory and methods behind this chronometer, offers criteria to critically evaluate Pb-Pb ages and presents a summary of the current state and immediate future of the chronometry of the early Solar System. We recognize that there is some debate over the age of the Solar System, but conclude that an age of 4567.30 ± 0.16 Ma based on four CAIs dated individually by the same method in two different laboratories is presently the best constrained published value. We further conclude that nebular chondrules dated by the Pb-Pb method require that they formed contemporaneously with CAIs and continued to form for at least ∼4 Myr, a conclusion that implies heterogeneous distribution of the short-lived 26Al nuclide in the protoplanetary disk. Planetesimals were already forming by ∼1 Myr after CAI formation, consistent with their growth predominantly through the accretion of chondrules. Nebular chondrule formation was completed by ∼5 Myr after CAI formation when the impact-generated Cba chondrules formed after the disk was cleared of gas and dust. We note that the absolute age of the Solar System or any single early Solar System object is not fundamental to any significant scientific question and that it is important only to know the correct relative ages of objects being used to piece together the formation history of the Solar System. As such, we point out the risks inherent in comparing Pb-Pb ages produced by different approaches in different laboratories at the level of the internal errors of individual ages. Until a cross-calibration exercise using synthetic and natural standards establishes the reproducibility between laboratories, only ages from a single laboratory, or between laboratories having

  8. Rotten Egg Nebula

    Science.gov (United States)

    1999-01-01

    Violent gas collisions that produced supersonic shock fronts in a dying star are seen in a new, detailed image from NASA's Hubble Space Telescope. The picture, taken by Hubble's Wide Field and Planetary Camera 2, is online at http://www.jpl.nasa.gov/images/wfpc . The camera was designed and built by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Stars like our Sun will eventually die and expel most of their material outward into shells of gas and dust. These shells eventually form some of the most beautiful objects in the universe, called planetary nebulae. 'This new image gives us a rare view of the early death throes of stars like our Sun. For the first time, we can see phenomena leading to the formation of planetary nebulae. Until now, this had only been predicted by theory, but had never been seen directly,' said Dr. Raghvendra Sahai, research scientist and member of the science team at JPL for the Wide Field and Planetary Camera 2. The object is sometimes called the Rotten Egg Nebula, because it contains a lot of sulphur, which would produce an awful odor if one could smell in space. The object is also known as the Calabash Nebula or by the technical name OH231.8+4.2. The densest parts of the nebula are composed of material ejected recently by the central star and accelerated in opposite directions. This material, shown as yellow in the image, is zooming away at speeds up to one and a half million kilometers per hour (one million miles per hour). Most of the star's original mass is now contained in these bipolar gas structures. A team of Spanish and American astronomers used NASA's Hubble Space Telescope to study how the gas stream rams into the surrounding material, shown in blue. They believe that such interactions dominate the formation process in planetary nebulae. Due to the high speed of the gas, shock-fronts are formed on impact and heat the surrounding gas. Although computer calculations have predicted the existence and structure of such shocks for

  9. Rotten Egg Nebula

    Science.gov (United States)

    1999-01-01

    Violent gas collisions that produced supersonic shock fronts in a dying star are seen in a new, detailed image from NASA's Hubble Space Telescope. The picture, taken by Hubble's Wide Field and Planetary Camera 2, is online at http://www.jpl.nasa.gov/images/wfpc . The camera was designed and built by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Stars like our Sun will eventually die and expel most of their material outward into shells of gas and dust. These shells eventually form some of the most beautiful objects in the universe, called planetary nebulae. 'This new image gives us a rare view of the early death throes of stars like our Sun. For the first time, we can see phenomena leading to the formation of planetary nebulae. Until now, this had only been predicted by theory, but had never been seen directly,' said Dr. Raghvendra Sahai, research scientist and member of the science team at JPL for the Wide Field and Planetary Camera 2. The object is sometimes called the Rotten Egg Nebula, because it contains a lot of sulphur, which would produce an awful odor if one could smell in space. The object is also known as the Calabash Nebula or by the technical name OH231.8+4.2. The densest parts of the nebula are composed of material ejected recently by the central star and accelerated in opposite directions. This material, shown as yellow in the image, is zooming away at speeds up to one and a half million kilometers per hour (one million miles per hour). Most of the star's original mass is now contained in these bipolar gas structures. A team of Spanish and American astronomers used NASA's Hubble Space Telescope to study how the gas stream rams into the surrounding material, shown in blue. They believe that such interactions dominate the formation process in planetary nebulae. Due to the high speed of the gas, shock-fronts are formed on impact and heat the surrounding gas. Although computer calculations have predicted the existence and structure of such shocks for

  10. The catalytic potential of cosmic dust: implications for prebiotic chemistry in the solar nebula and other protoplanetary systems.

    Science.gov (United States)

    Hill, Hugh G M; Nuth, Joseph A

    2003-01-01

    The synthesis of important prebiotic molecules is fundamentally reliant on basic starting ingredients: water, organic species [e.g., methane (CH(4))], and reduced nitrogen compounds [e.g., ammonia (NH(3)), methyl cyanide (CH(3)CN) etc.]. However, modern studies conclude that the primordial Earth's atmosphere was too rich in CO, CO(2), and water to permit efficient synthesis of such reduced molecules as envisioned by the classic Miller-Urey experiment. Other proposed sources of terrestrial nitrogen reduction, like those within submarine vent systems, also seem to be inadequate sources of chemically reduced C-H-O-N compounds. Here, we demonstrate that nebular dust analogs have impressive catalytic properties for synthesizing prebiotic molecules. Using a catalyst analogous to nebular iron silicate condensate, at temperatures ranging from 500K to 900K, we catalyzed both the Fischer-Tropsch conversion of CO and H(2) to methane and water, and the corresponding Haber-Bosch synthesis of ammonia from N(2) and H(2). Remarkably, when CO, N(2), and H(2) were allowed to react simultaneously, these syntheses also yielded nitrogen-containing organics such as methyl amine (CH(3)NH(2)), acetonitrile (CH(3)CN), and N-methyl methylene imine (H(3)CNCH(2)). A fundamental consequence of this work for astrobiology is the potential for a natural chemical pathway to produce complex chemical building blocks of life throughout our own Solar System and beyond.

  11. The Catalytic Potential of Cosmic Dust: Implications for Prebiotic Chemistry in the Solar Nebula and Other Protoplanetary Systems

    Science.gov (United States)

    Hill, Hugh G. M.; Nuth, Joseph A.

    2003-06-01

    The synthesis of important prebiotic molecules is fundamentally reliant on basic starting ingredients: water, organic species [e.g., methane (CH4)], and reduced nitrogen compounds [e.g., ammonia (NH3), methyl cyanide (CH3CN) etc.]. However, modern studies conclude that the primordial Earth's atmosphere was too rich in CO, CO2, and water to permit efficient synthesis of such reduced molecules as envisioned by the classic Miller-Urey experiment. Other proposed sources of terrestrial nitrogen reduction, like those within submarine vent systems, also seem to be inadequate sources of chemically reduced C-H-O-N compounds. Here, we demonstrate that nebular dust analogs have impressive catalytic properties for synthesizing prebiotic molecules. Using a catalyst analogous to nebular iron silicate condensate, at temperatures ranging from 500K to 900K, we catalyzed both the Fischer-Tropsch conversion of CO and H2 to methane and water, and the corresponding Haber-Bosch synthesis of ammonia from N2 and H2. Remarkably, when CO, N2, and H2 were allowed to react simultaneously, these syntheses also yielded nitrogen-containing organics such as methyl amine (CH3NH2), acetonitrile (CH3CN), and N-methyl methylene imine (H3CNCH2). A fundamental consequence of this work for astrobiology is the potential for a natural chemical pathway to produce complex chemical building blocks of life throughout our own Solar System and beyond.

  12. Corundum-hibonite inclusions and the environments of high temperature processing in the early Solar System

    Science.gov (United States)

    Needham, Andrew W.; Messenger, Scott; Han, Jangmi; Keller, Lindsay P.

    2017-01-01

    resolvable excess 26Mg while ALH-61 has a well-resolved initial 26Al/27Al ratio of 4.2 ± 0.4 × 10-5. The presence or absence of live 26Al at the time of CAI formation may record distinct chronology if 26Al was initially homogeneously distributed in the early Solar System. Alternatively, variations in 26Al/27Al ratios may reflect late injection and/or heterogeneous distribution of 26Al. Regardless of which model for 26Al distribution is correct, the data presented here indicate that formation of corundum-bearing CAIs was repeated during multiple heating and non-equilibrium condensation events throughout early Solar System history and within a single oxygen isotopic reservoir.

  13. Identification and Characterization of Early Solar system Organic Matter Preserved in Chondritic Porous Interplanetary Dust Particles

    Science.gov (United States)

    Flynn, George; Wirick, Sue; Keller, Lindsay

    2015-04-01

    The chondritic porous interplanetary dust particles (CP IDPs), collected by NASA from the Earth's stratosphere, have experienced minimal aqueous or thermal alteration since their formation. These CP IDPs are the best preserved samples of the minerals and organic matter that was present in the primitive Solar Nebula that are currently available for laboratory analysis [1]. The ~10 μm CP IDPs are aggregates of tens-of-thousands of mostly sub-micron grains of diverse compositions and mineralogies. Many of the individual mineral grains are coated by a 50 to 200 nm thick rims of carbonaceous material, and other carbonaceous material occurs as larger, discrete subunits within the particles [2]. We characterize this carbonaceous material using two high-resolution, synchrotron-based instruments: a Scanning Transmission X-ray Microscope (STXM) to locate and map the carbon and to identify its major functional groups by X-ray Absorption Near-Edge Structure (XANES) spectroscopy, and a micro-Fourier Transform Infrared (μ-FTIR) spectrometer to further characterize the functional groups by mid-infrared spectroscopy. Carbon-XANES spectroscopy identifies the rims coating the individual grains in CP IDPs as organic matter, dominated by the C=C, likely C-rings, and the C=O functional groups [3]. This structure, with the organic rims being the contact surfaces between the grains, implies a 3-step formation sequence: grain condensation, organic rim emplacement, and, finally, aggregation of the grains to form the dust particles. This suggests these organic rims formed very early in the evolution of the Solar Nebula, after grain condensation but before grain aggregation [3]. These organic rims coat grains of diverse compositions, including silicates, sulfides, and carbonates, which is inconsistent with formation by Fischer-Tropsch-like, mineral-specific catalysis, one of the mechanisms suggested for the formation of primitive organic matter. Our observations are consistent with an

  14. The Solar Radiation and Climate Experiment (SORCE) Mission Description and Early Results

    CERN Document Server

    Rottman, G; George, V

    2005-01-01

    This book describes the state-of-the art instruments for measuring the solar irradiance from soft x-ray to the near infrared and the total solar irradiance. Furthermore, the SORCE mission and early results on solar variability are presented along with papers that provide an overview of solar influences on Earth.

  15. The Stingray nebula: watching the rapid evolution of a newly born planetary nebula.

    Science.gov (United States)

    Bobrowsky, M.; Sahu, K. C.; Parthasarathy, M.; García-Lario, Pedro

    The formation and early evolution of planetary nebulae represent one of the most poorly understood phases of stellar evolution ( Kwok, 1987; Maddox, 1995). One of the youngest, the Stingray Nebula (He3-1357) ( Henize, 1967; Henize, 1976), shows all the tell-tale signs of a newly born planetary nebula: it has become ionized only within the past few decades ( Parthasarathy et al., 1993); the mass-loss from the central star has ceased within the past few years; and the central star is becoming hotter and fainter as expected from a star on its way to becoming a DA white dwarf ( Parthasarathy et al., 1995). The Stingray Nebula thus provides the ideal laboratory for examining the early structure and evolution of this class of objects. Images of the Stingray Nebula, obtained with the Hubble Space Telescope, show for the first time that its multiple expulsions of matter are focused by an equatorial ring and bubbles of gas located on opposite sides of the ring ( Bobrowsky et al., 1995). The position angle of the outflows has changed, possibly as a result of precessional motion induced by the presence of a companion star. This is consistent with the precessing jet model by Livio & Pringle (1996). Indeed, we have reported the discovery of a companion star in the Stingray Nebula ( Bobrowsky et al., 1998). Finally, we present evidence of the companion star dynamically distorting the gas in this newly-born planetary nebula.

  16. Jupiter's Role in Sculpting the Early Solar System

    Science.gov (United States)

    Naoz, Smadar

    2015-03-01

    Recent observations made by the Kepler space mission, combined with statistical analysis of existing ground and space-based data, have shown that planets somewhat bigger than the Earth - but substantially smaller than Jupiter - ;are extremely common in our Galaxy (1-4). These systems are typically found to be tightly packed, nearly coplanar, and have nearly circular orbits. Furthermore, these planets tend to have very short-period orbits, ranging from days to months. In contrast, our innermost planet, Mercury, orbits the Sun once every 88 d. Thus, taken at face value, these observations imply that the architecture of our Solar System is unique compared with the galactic population. In other words, why are there no short-period planets in our Solar System? In PNAS, Batygin and Laughlin (5) demonstrate that Jupiter is to blame. In particular, Jupiter's inward-followed-by-outward migration during the Solar System's early evolution could have driven a collisional cascade that would grind planetesimals to smaller size. Gas drag, which dominates these small planetesimals, may then have driven preexisting short-period planets into the Sun. Thus, Batygin and Laughlin (5) suggest that the terrestrial planets in our Solar System are in fact "second-generation planets," which formed after the first short-period planets were destroyed, in mass-dispersed, gas-depleted conditions (see Fig. 1 for the description of the scenario). The developed model suggests that systems with short-period Earth and super-Earth planets are anticorrelated with the existence of giant planets within the same system.

  17. The Advanced Technology Solar Telescope: design and early construction

    Science.gov (United States)

    McMullin, Joseph P.; Rimmele, Thomas R.; Keil, Stephen L.; Warner, Mark; Barden, Samuel; Bulau, Scott; Craig, Simon; Goodrich, Bret; Hansen, Eric; Hegwer, Steve; Hubbard, Robert; McBride, William; Shimko, Steve; Wöger, Friedrich; Ditsler, Jennifer

    2012-09-01

    The National Solar Observatory’s (NSO) Advanced Technology Solar Telescope (ATST) is the first large U.S. solar telescope accessible to the worldwide solar physics community to be constructed in more than 30 years. The 4-meter diameter facility will operate over a broad wavelength range (0.35 to 28 μm ), employing adaptive optics systems to achieve diffraction limited imaging and resolve features approximately 20 km on the Sun; the key observational parameters (collecting area, spatial resolution, spectral coverage, polarization accuracy, low scattered light) enable resolution of the theoretically-predicted, fine-scale magnetic features and their dynamics which modulate the radiative output of the sun and drive the release of magnetic energy from the Sun’s atmosphere in the form of flares and coronal mass ejections. In 2010, the ATST received a significant fraction of its funding for construction. In the subsequent two years, the project has hired staff and opened an office on Maui. A number of large industrial contracts have been placed throughout the world to complete the detailed designs and begin constructing the major telescope subsystems. These contracts have included the site development, AandE designs, mirrors, polishing, optic support assemblies, telescope mount and coudé rotator structures, enclosure, thermal and mechanical systems, and high-level software and controls. In addition, design development work on the instrument suite has undergone significant progress; this has included the completion of preliminary design reviews (PDR) for all five facility instruments. Permitting required for physically starting construction on the mountaintop of Haleakalā, Maui has also progressed. This paper will review the ATST goals and specifications, describe each of the major subsystems under construction, and review the contracts and lessons learned during the contracting and early construction phases. Schedules for site construction, key factory testing of

  18. Were Chondrite Parent Bodies Magnetized by the Early Solar Wind?

    Science.gov (United States)

    Oran, R.; Weiss, B. P.

    2016-12-01

    Chondrites are traditionally thought to be samples of undifferentiated bodies that never experienced large-scale melting. However, Allende and several other CV carbonaceous chondrites (Carporzen et al. 2011, Gattacceca et al., submitted) and the H chondrite Portales Valley (Bryson et al., this meeting) contain remanent magnetization acquired well after accretion. The strong intensities (tens of micro Tesla), temporal stability (lasting for several My), and late ages ( 10-100 My after solar system formation) of the magnetizations suggest they are a record of dynamos formed by a molten metallic core. This would imply that the parent bodies of these meteorites were partially differentiated, containing both melted regions and a relic chondritic crust (Abraham et al., this meeting). However, it has alternatively been proposed that CV chondrites may have been magnetized by the Interplanetary Magnetic Field (IMF) carried by the early solar wind (Tarduno et al. 2016), and which was hypothesized to be amplified at the nose of the body due to solar wind pile-up. Here we demonstrate that this scenario is unlikely, due to four main factors: 1) the magnitude of the IMF is estimated to be only 0.005 - 0.05 micro T at 1 AU for the young Sun, 2) the lack of an ionosphere and the resistivity of the crust would limit the magnetic field pile-up, 3) the time variability of the IMF in both magnitude and direction [Fig. 1A] would cuase only a fraction of the IMF to diffuse into the body [Fig. 1B], and 4) even the weak field that manages to diffuse in changes over timescales much shorter than the My timescale of magnetization acquisition and thus cannot impart a unidirectional magnetization. We demonstrate these effects quantitatively using analytical arguments, numerical simulations and analysis of solar wind in-situ measurements.

  19. Bayes’ Theorem and Early Solar Short-lived Radionuclides: The Case for an Unexceptional Origin for the Solar System

    Science.gov (United States)

    Young, Edward D.

    2016-08-01

    The presence of excesses of short-lived radionuclides in the early solar system evidenced in meteorites has been taken as testament to close encounters with exotic nucleosynthetic sources, including supernovae or AGB stars. An analysis of the likelihoods associated with different sources of these extinct nuclides in the early solar system indicates that, rather than being exotic, their abundances were typical of star-forming regions like those observed today in the Galaxy. The radiochemistry of the early solar system is therefore unexceptional, being the consequence of extensive averaging of solids from molecular clouds.

  20. Bayes' theorem and early solar short-lived radionuclides: the case for an unexceptional origin for the solar system

    CERN Document Server

    Young, Edward D

    2016-01-01

    The presence of excesses of short-lived radionuclides in the early solar system evidenced in meteorites has been taken as testament to close encounters with exotic nucleosynthetic sources, including supernovae or AGB stars. An analysis of the likelihoods associated with different sources of these extinct nuclides in the early solar system indicates that rather than being exotic, their abundances were typical of star-forming regions like those observed today in the Galaxy. The radiochemistry of the early solar system is therefore unexceptional, being the consequence of extensive averaging of molecular cloud solids.

  1. Ices in the Solar Nebula

    Science.gov (United States)

    Robinson, Sarah

    2008-05-01

    The centerpiece of this proposal is my hypothesis that other ices besides H2O help build giant planet cores. I propose a theory project on the ice composition of planet-forming regions and a related observing project on ice detection and mineralogy in debris disks. Together, the theory and observing projects will answer two questions: 1. Where are the condensation fronts of abundant volatiles located in relation to giant planet feeding zones? 2. How much does the presence of CHON ices in planetesimals speed up giant planet formation?

  2. Stable Chlorine Isotope Study: Application to Early Solar System Materials

    Science.gov (United States)

    Mala,ira. M/; Nyquist, L. E.; Reese, Y.; Shih, C-Y; Fujitani, T.; Okano, O.

    2010-01-01

    A significantly large mass fractionation between two stable chlorine isotopes is expected during planetary processes In addition, in view of the isotopic heterogeneity of other light elements, the chlorine isotopes can potentially be used as a tracer for the origins and evolutionary processes of early solar system materials. Due to analytical difficulties, however, current chlorine isotope studies on planetary materials are quite controversial among IRMS (gas source mass spectrometry) and/or TIMS (Thermal Ionization Mass Spectrometry) groups [i.e. 1-3]. Although a cross-calibration of IRMS and TIMS indicates that both techniques are sufficiently consistent with each other [4], some authors have claimed that the Cl-37/Cl-35 ratio of geological samples obtained by TIMS technique are, in general, misleadingly too high and variable compared to those of IRMS [3]. For example, almost no differences of Cl isotope composition were observed among mantle materials and carbonaceous meteorites by [3]. On the other hand, according to more recent IRMS work [2], significant Cl isotope variations are confirmed for mantle materials. Therefore, additional careful investigation of Cl isotope analyses are now required to confirm real chlorine isotope variations for planetary materials including carbonaceous chondrites [5]. A significantly large mass fractionation between two stable chlorine isotopes is expected during planetary processes In addition, in view of the isotopic heterogeneity of other light elements, the chlorine isotopes can potentially be used as a tracer for the origins and evolutionary processes of early solar system materials. Due to analytical difficulties, however, current chlorine isotope studies on planetary materials are quite controversial among IRMS (gas source mass spectrometry) and/or TIMS (Thermal Ionization Mass Spectrometry) groups [i.e. 1-3]. Although a cross-calibration of IRMS and TIMS indicates that both techniques are sufficiently consistent with each

  3. From stellar nebula to planetesimals

    CERN Document Server

    Marboeuf, Ulysse; Alibert, Yann; Cabral, Nahuel; Benz, Willy

    2014-01-01

    Solar and extrasolar comets and extrasolar planets are the subject of numerous studies in order to determine their chemical composition and internal structure. In the case of planetesimals, their compositions are important as they govern in part the composition of future planets. The present works aims at determining the chemical composition of icy planetesimals, believed to be similar to present day comets, formed in stellar systems of solar chemical composition. The main objective of this work is to provide valuable theoretical data on chemical composition for models of planetesimals and comets, and models of planet formation and evolution. We have developed a model that calculates the composition of ices formed during the cooling of the stellar nebula. Coupled with a model of refractory element formation, it allows us to determine the chemical composition and mass ratio of ices to rocks in icy planetesimals throughout in the protoplanetary disc. We provide relationships for ice line positions (for differen...

  4. Short-lived nuclei in the early Solar System: Possible AGB sources

    Energy Technology Data Exchange (ETDEWEB)

    Wasserburg, G.J. [Lunatic Asylum, Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125 (United States)]. E-mail: gjw@gps.caltech.edu; Busso, M. [Department of Physics, University of Perugia, via Pascoli, Perugia 06123 (Italy)]. E-mail: maurizio.busso@fisica.unipg.it; Gallino, R. [Department of General Physics and Sezione INFN, University of Torino, via P. Giuria 1, Turin 10125 (Italy) and Centre for Stellar and Planetary Astrophysics, School of Mathematical Sciences, Monash University, 3800 Victoria (Australia)]. E-mail: gallino@ph.unito.it; Nollett, K.M. [Physics Division, Argonne National Laboratory, Argonne, IL 60439-4843 (United States)]. E-mail: nollett@anl.gov

    2006-10-17

    The abundances of short-lived radionuclides in the early Solar System (ESS) are reviewed, as well as the methodology used in determining them. These results are compared with the inventory estimated for a uniform galactic production model. It is shown that, to within a factor of two, the observed abundances of {sup 238}U, {sup 235}U, {sup 232}Th, {sup 244}Pu, {sup 182}Hf, {sup 146}Sm, and {sup 53}Mn are roughly compatible with long-term galactic nucleosynthesis. {sup 129}I is an exception, with an ESS inventory much lower than expected from uniform production. The isotopes {sup 107}Pd, {sup 60}Fe, {sup 41}Ca, {sup 36}Cl, {sup 26}Al, and {sup 10}Be require late addition to the protosolar nebula. {sup 10}Be is the product of energetic particle irradiation of the Solar System as most probably is {sup 36}Cl. Both of these nuclei appear to be present when {sup 26}Al is absent. A late injection by a supernova (SN) cannot be responsible for most of the short-lived nuclei without excessively producing {sup 53}Mn; it can however be the source of {sup 53}Mn itself and possibly of {sup 60}Fe. If a late SN injection is responsible for these two nuclei, then there remains the problem of the origin of {sup 107}Pd and several other isotopes. Emphasis is given to an AGB star as a source of many of the nuclei, including {sup 60}Fe; this possibility is explored with a new generation of stellar models. It is shown that if the dilution factor (i.e. the ratio of the contaminating mass to the solar parental cloud mass) is f{sub 0}{approx}4x10{sup -3}, a reasonable representation for many nuclei is obtained; this requires that ({sup 60}Fe/{sup 56}Fe){sub ESS}{approx}10{sup -7} to 2x10{sup -6}. The nuclei produced by an AGB source do not include {sup 53}Mn, {sup 10}Be or {sup 36}Cl if it is very abundant. The role of irradiation is discussed with regard to {sup 26}Al, {sup 36}Cl and {sup 41}Ca, and the estimates of bulk solar abundances of these isotopes are commented on. The conflict

  5. Live iron-60 in the early solar system.

    Science.gov (United States)

    Shukolyukov, A; Lugmair, G W

    1993-02-19

    Isotopic analyses of nickel in samples from the differentiated meteorite Chervony Kut revealed the presence of relative excesses of (60)Ni ranging from 2.4 up to 50 parts per 10(4). These isotopic excesses are from the decay of the now extinct short-lived nuclide (60)Fe and provide clear evidence for the existence of (60)Fe over large scales in the early solar system. Not only was (60)Fe present at the time of melting and differentiation (that is, Fe-Ni fractionation) of the parent body of Chervony Kut but also later at the time when basaltic magma solidified at or near the surface of the planetesimal. The inferred abundance of (60)Fe suggests that its decay alone could have provided sufficient heat to melt small (diameters of several hundred kilometers) planetary bodies shortly after their accretion.

  6. A giant Ly$\\alpha$ nebula in the core of an X-ray cluster at $z=1.99$: implications for early energy injection

    CERN Document Server

    Valentino, F; Finoguenov, A; Strazzullo, V; Brun, A M C Le; Vignali, C; Bournaud, F; Dickinson, M; Renzini, A; Béthermin, M; Zanella, A; Gobat, R; Cimatti, A; Elbaz, D; Onodera, M; Pannella, M; Sargent, M T; Arimoto, N; Carollo, M; Starck, J-L

    2016-01-01

    We present the discovery of a giant $\\gtrsim$100 kpc Ly$\\alpha$ nebula detected in the core of the X-ray emitting cluster CL J1449+0856 at $z=1.99$ through Keck/LRIS narrow-band imaging. This detection extends the known relation between Ly$\\alpha$ nebulae and overdense regions of the Universe to the dense core of a $5-7\\times10^{13}$ M$_{\\odot}$ cluster. The most plausible candidates to power the nebula are two Chandra-detected AGN host cluster members. Given the physical conditions of the Ly$\\alpha$-emitting gas and the possible interplay with the X-ray phase, we argue that the Ly$\\alpha$ nebula would be short-lived ($\\lesssim10$ Myr) if not continuously replenished with cold gas at a rate of $\\gtrsim1000$ Myr. Cooling from the X-ray phase is disfavored as the replenishing mechanism, primarily because of the high Ly$\\alpha$ to X-ray luminosity ratio ($L_{\\mathrm{Ly\\alpha}}/L_{\\mathrm{X}} \\approx0.3$), $\\gtrsim10-1000\\times$ higher than in local cool-core clusters. Cosmological cold flows are disfavored by cu...

  7. A Giant Lyα Nebula in the Core of an X-Ray Cluster at Z = 1.99: Implications for Early Energy Injection

    Science.gov (United States)

    Valentino, Francesco; Daddi, Emanuele; Finoguenov, Alexis; Strazzullo, Veronica; Le Brun, Amandine; Vignali, Cristian; Bournaud, Frédéric; Dickinson, Mark; Renzini, Alvio; Béthermin, Matthieu; Zanella, Anita; Gobat, Raphaël; Cimatti, Andrea; Elbaz, David; Onodera, Masato; Pannella, Maurilio; Sargent, Mark; Arimoto, Nobuo; Carollo, Marcella; Starck, Jean-Luc

    2016-09-01

    We present the discovery of a giant ≳100 kpc Lyα nebula detected in the core of the X-ray emitting cluster CL J1449+0856 at z = 1.99 through Keck/LRIS narrow-band imaging. This detection extends the known relation between Lyα nebulae and overdense regions of the universe to the dense core of a 5-7 × 1013 M ⊙ cluster. The most plausible candidates to power the nebula are two Chandra-detected AGN host cluster members, while cooling from the X-ray phase and cosmological cold flows are disfavored primarily because of the high Lyα to X-ray luminosity ratio ({L}{Lyα }/{L}{{X}}≈ 0.3, ≳10-1000 times higher than in local cool-core clusters) and by current modeling. Given the physical conditions of the Lyα-emitting gas and the possible interplay with the X-ray phase, we argue that the Lyα nebula would be short-lived (≲10 Myr) if not continuously replenished with cold gas at a rate of ≳1000 M ⊙ yr-1. We investigate the possibility that cluster galaxies supply the required gas through outflows and we show that their total mass outflow rate matches the replenishment necessary to sustain the nebula. This scenario directly implies the extraction of energy from galaxies and its deposition in the surrounding intracluster medium (ICM), as required to explain the thermodynamic properties of local clusters. We estimate an energy injection of the order of ≈ 2 {{keV}} per particle in the ICM over a 2 Gyr interval. In our baseline calculation, AGNs provide up to 85% of the injected energy and two-thirds of the mass, while the rest is supplied by supernovae-driven winds.

  8. Pre-mare cratering and early solar system history

    Science.gov (United States)

    Wetherill, G. W.

    1977-01-01

    An evaluation of the application of the high extralunar flux in pre-mare times to more general problems of early solar system history is attempted by combining the results of dynamic studies with lunar chronological data. There is a twofold to fourfold contrast in the integral impact flux between the Apollo 14 and 16 sites and the older mare surfaces. This is judged insufficient to account for the contrasting lithology between these two sites: basalts and soil breccias in the maria, annealed breccias and impact melts in the highlands. Therefore, these rocks and their ages (3.9-4.0 b.y.) are thought to predate the surfaces in which they are found. Estimation of the flux needed to produce these lithologies, and difficulties associated with extrapolating this further back in lunar history give support to the "cataclysm" hypothesis of Tera, Papanastassiou, and Wasserburg. Dynamical studies permit separate evaluation of the possible sources for both the "normal" flux during the first 600 million years of lunar history and the "peak" that apparently occurred 4.0 billion years ago. The most likely sources for the normal flux are comets from the vicinity of Uranus and Neptune. The most promising source for the peak is tidal disruption by Earth or Venus of a Ceres-size asteroid initially in a Mars-crossing orbit. Alternative possibilities are suggested.

  9. The impact of solar UV radiation on the early biosphere

    Science.gov (United States)

    Horneck, G.

    2007-08-01

    Stratospheric ozone, photochemically produced from atmospheric oxygen, is a protective filter of the Earth's atmosphere by absorbing most of the biologically harmful UV radiation of our sun in the UV-C (190-280 nm) and short wavelength-region of the UV-B (280-315 nm). Numerous lines of isotopic and geologic evidence suggest that the Archean atmosphere was essentially anoxic. As a result the column abundance of ozone would have been insufficient to affect the surface UV radiation environment. Thus, as well as UV-B radiation, UV-C radiation would have penetrated to the Earth's surface with its associated biological consequences. The history of this ultraviolet stress for the early Earth has been determined from theoretical data and data obtained in Earth orbit on the inactivation of Bacillus subtilis spores under a simulated ozone layer of different thicknesses. Although the UV-C and UV-B regions contribute only 2 % of the entire solar extraterrestrial irradiance, photobiological experiments in space have demonstrated a high mutagenicity and lethality of this UV range to living organisms. The reason for these severe effects of extraterrestrial solar UV radiation - compared to conditions on present-day Earth - lies in the absorption characteristics of the DNA, which is the decisive target for inactivation and mutation induction at this UV range. Being a strong mutagen, UV-radiation is considered as a powerful promoter of biological evolution on the one hand, one the other hand, it may have deleterious consequences to individual cells and organisms, e.g. by causing inactivation, mutations or cancer induction. In response to potential harmful effects of environmental UV radiation, life on Earth has developed several strategies of survival, either avoiding exposure to UV radiation or restoring UV damage. Mechanisms of avoidance of exposure to UV radiation include (i) moving away from the UV radiation into shadowed areas, which requires the development of UV radiation

  10. The variable Crab Nebula

    CERN Document Server

    Tavani, Marco

    2011-01-01

    The remarkable Crab Nebula is powered by an energetic pulsar whose relativistic wind interacts with the inner parts of the Supernova Remnant SN1054. Despite low-intensity optical and X-ray variations in the inner Nebula, the Crab has been considered until now substantially stable at X-ray and gamma-ray energies. This paradigm has been shattered by the AGILE discovery in September 2010 of a very intense transient gamma-ray flare of nebular origin. For the first time, the Crab Nebula was "caught in the act" of accelerating particles up to 10^15 eV within the shortest timescale ever observed in a cosmic nebula (1 day or less). Emission between 50 MeV and a few GeV was detected with a quite hard spectrum within a short timescale. Additional analysis and recent Crab Nebula data lead to identify a total of four major flaring gamma-ray episodes detected by AGILE and Fermi during the period mid-2007/mid-2011. These observations challenge emission models of the pulsar wind interaction and particle acceleration process...

  11. A renewed search for short-lived 126Sn in the early Solar System: Hydride generation MC-ICPMS for high sensitivity Te isotopic analysis

    Science.gov (United States)

    Brennecka, Gregory A.; Borg, Lars E.; Romaniello, Stephen J.; Souders, Amanda K.; Shollenberger, Quinn R.; Marks, Naomi E.; Wadhwa, Meenakshi

    2017-03-01

    Although there is limited direct evidence for supernova input into the nascent Solar System, many models suggest it formed by the gravitational collapse of a molecular cloud that was triggered by a nearby supernova. Existing lines of evidence, mostly in the form of short-lived radionuclides present in the early Solar System, are potentially consistent with this hypothesis, but still allow for alternative explanations. Since the natural production of 126Sn is thought to occur only in supernovae and this isotope has a short half-life (126Sn→126Te, t1/2 = 235 ky), the discovery of extant 126Sn would provide unequivocal proof of supernova input to the early Solar System. Previous attempts to quantify the initial abundance of 126Sn by examining Sn-Te systematics in early solids have been hampered by difficulties in precisely measuring Te isotope ratios in these materials. Thus, here we describe a novel technique that uses hydride generation to dramatically increase the ionization efficiency of Te-an approximately 30-fold increase over previous work. This introduction system, when coupled to a MC-ICPMS, enables high-precision Te isotopic analyses on samples with expected concentrations of Sn and Te, as well as the lack of nucleosynthetic anomalies in other isotopes of Te suggest that the bulk of the Sn and Te recovered from these particular refractory inclusions is not of primary origin and thus does not represent a primary signature of Sn-Te systematics of the protosolar nebula during condensation of CAIs or their precursors. Although no evidence of supernova input was found based on Sn-Te systematics in this sample set, hydride generation represents a powerful tool that can now be used to further explore Te isotope systematics in less altered materials.

  12. Clown Face Nebula (NGC 2392)

    Science.gov (United States)

    Murdin, P.

    2000-11-01

    A planetary nebula, also known as the Eskimo Nebula, in the constellation Gemini, position RA 07 h 29.2 m, dec. +20° 55'. It is bluish, 13'' in diameter, and of ninth magnitude, with a tenth-magnitude central star. The blue-green nebula's hazy outer regions are thought to resemble an Eskimo's hood or clown's ruff....

  13. The Einstein survey of the young stars in the Orion Nebula

    Science.gov (United States)

    Zoonematkermani, S.; Caillault, J.-P.

    1987-01-01

    The Orion Nebula is the best studied site of recent star formation in the Galaxy. The complete Einstein Observatory survey of the Orion Nebula covering a 2 deg x 2 deg region centered on the Trapezium is reported. An X-ray mosaic is presented for the Nebula along with a complete X-ray catalogue for this very young cluster. Approximately 150 distinct sources were found in this 4 sq deg region; spectral types and colors were obtained for about 1/2 of the optical counterparts of these sources. Comparison of the variability of the Orion X-ray sources with those found in the Rho Ophiuchi cloud leads to the conclusion that the Orion sources' variability is also likely to result from continual flaring activities. Eleven new late B stars associated with X-ray emission far exceeding that expected from early type stars were discovered. The X-rays may originate from pre-main sequence companions to these stars; a T-Tauri star of the same age would have the correct L sub x. Comparison of the solar type stars in Orion with those in the Pleiades, the Hyades, and the field suggests that the decay of activity with age is most appropriately described by an exponential, rather than a power law fit.

  14. Utilizing Stable Isotopes and Isotopic Anomalies to Study Early Solar System Formation Processes

    Science.gov (United States)

    Simon, Justin

    2017-01-01

    Chondritic meteorites contain a diversity of particle components, i.e., chondrules and calcium-, aluminum-rich refractory inclusions (CAIs), that have survived since the formation of the Solar System. The chemical and isotopic compositions of these materials provide a record of the conditions present in the protoplanetary disk where they formed and can aid our understanding of the processes and reservoirs in which solids formed in the solar nebula, an important step leading to the accretion of planetesimals. Isotopic anomalies associated with nucleosynthetic processes are observed in these discrete materials, and can be compared to astronomical observations and astrophysical formation models of stars and more recently proplyds. The existence and size of these isotopic anomalies are typically thought to reflect a significant state of isotopic heterogeneity in the earliest Solar System, likely left over from molecular cloud heterogeneities on the grain scale, but some could also be due to late stellar injection. The homogenization of these isotopic anomalies towards planetary values can be used to track the efficiency and timescales of disk wide mixing,

  15. Giant convecting mud balls of the early solar system.

    Science.gov (United States)

    Bland, Philip A; Travis, Bryan J

    2017-07-01

    Carbonaceous asteroids may have been the precursors to the terrestrial planets, yet despite their importance, numerous attempts to model their early solar system geological history have not converged on a solution. The assumption has been that hydrothermal alteration was occurring in rocky asteroids with material properties similar to meteorites. However, these bodies would have accreted as a high-porosity aggregate of igneous clasts (chondrules) and fine-grained primordial dust, with ice filling much of the pore space. Short-lived radionuclides melted the ice, and aqueous alteration of anhydrous minerals followed. However, at the moment when the ice melted, no geological process had acted to lithify this material. It would have been a mud, rather than a rock. We tested the effect of removing the assumption of lithification. We find that if the body accretes unsorted chondrules, then large-scale mud convection is capable of producing a size-sorted chondrule population (if the body accretes an aerodynamically sorted chondrule population, then no further sorting occurs). Mud convection both moderates internal temperature and reduces variation in temperature throughout the object. As the system is thoroughly mixed, soluble elements are not fractionated, preserving primitive chemistry. Isotopic and redox heterogeneity in secondary phases over short length scales is expected, as individual particles experience a range of temperature and water-rock histories until they are brought together in their final configuration at the end of convection. These results are consistent with observations from aqueously altered meteorites (CI and CM chondrites) and spectra of primitive asteroids. The "mudball" model appears to be a general solution: Bodies spanning a ×1000 mass range show similar behavior.

  16. of Planetary Nebulae III. NGC 6781

    Directory of Open Access Journals (Sweden)

    Hugo E. Schwarz

    2006-01-01

    Full Text Available Continuing our series of papers on the three-dimensional (3D structures and accurate distances to Planetary Nebulae (PNe, we present our study of the planetary nebula NGC6781. For this object we construct a 3D photoionization model and, using the constraints provided by observational data from the literature we determine the detailed 3D structure of the nebula, the physical parameters of the ionizing source and the first precise distance. The procedure consists in simultaneously fitting all the observed emission line morphologies, integrated intensities and the two-dimensional (2D density map from the [SII] (sulfur II line ratios to the parameters generated by the model, and in an iterative way obtain the best fit for the central star parameters and the distance to NGC6781, obtaining values of 950±143 pc (parsec – astronomic distance unit and 385 LΘ (solar luminosity for the distance and luminosity of the central star respectively. Using theoretical evolutionary tracks of intermediate and low mass stars, we derive the mass of the central star of NGC6781 and its progenitor to be 0.60±0.03MΘ (solar mass and 1.5±0.5MΘ respectively.

  17. Complex molecules in the Orion Kleinmann-Low nebula

    Directory of Open Access Journals (Sweden)

    Despois D.

    2014-02-01

    Full Text Available In the framework of the delivery to the early Earth of extraterrestrial molecules, we have studied complex molecular species toward the Orion Kleinmann-Low nebula. This nebula is rich in molecules as well as in nascent stars and planetary systems. We focus here on HCOOCH3, CH3OCH3 and deuterated methanol. Upper limits on species of prebiotic interest like glycine were also obtained.

  18. Meteorites and cosmic dust: Interstellar heritage and nebular processes in the early solar system

    Directory of Open Access Journals (Sweden)

    Engrand C.

    2012-01-01

    Full Text Available Small solar system bodies like asteroids and comets have escaped planetary accretion. They are the oldest and best preserved witnesses of the formation of the solar system. Samples of these celestial bodies fall on Earth as meteorites and interplanetary dust. The STARDUST mission also recently returned to Earth cometary dust from comet 81P/Wild 2, a Jupiter Family Comet (JFC. These samples provide unique insights on the physico-chemical conditions and early processes of the solar system. They also contain some minute amount of materials inherited from the local interstellar medium that have survived the accretion processes in the solar system.

  19. Catalogues of planetary nebulae.

    Science.gov (United States)

    Acker, A.

    Firstly, the general requirements concerning catalogues are studied for planetary nebulae, in particular concerning the objects to be included in a catalogue of PN, their denominations, followed by reflexions about the afterlife and comuterized versions of a catalogue. Then, the basic elements constituting a catalogue of PN are analyzed, and the available data are looked at each time.

  20. Are protonated ions efficient sequestration agents for noble gases in the primitive nebula context?

    Science.gov (United States)

    Pauzat, Françoise; Ellinger, Yves; ozgurel, Ozge; Bacchus-montabonel, Marie-christine; Mousis, Olivier; Laboratoire de Chimie Théorique, Institut Lumière Matière, Laboratoire d'Astrophysique de Marseille

    2016-10-01

    One explanation for the deficiencies of argon, krypton and xenon observed in the atmosphere of Titan might be related to a scenario of sequestration by H3+ in the gas phase at the early evolution of the solar nebula. The chemical process implied is a radiative association, evaluated as rather efficient in the case of H3+, especially for krypton and xenon. In fact, this mechanism of chemical trapping might not be limited to H3+ only, considering that the protonated ions produced in the destruction of H3+ by its main competitors, namely H2O, CO and N2, present in the primitive nebula, might also give stable complexes with the noble gases.Here, the reactivity of the noble gases Ar, Kr, Xe, with all the protonated ions issued from H2O, CO and N2, expected to be present in the nebula with reasonably high abundances, i.e. H3O+, HCO+, HOC+, N2H+, has been studied with quantum simulation methods, quantum dynamics included. All of them give stable complexes; the rate coefficients of their radiative associations have been calculated as a function of temperature between 10 and 100 °K and found ranging from 10-18 to 10-16 cm3s-1, which can be considered as high for this type of reactions and are comparable to the rates obtained with H3+.Consequently, we can consider this process as universal for all protonated ions, which, if present in the primitive nebula as astrophysical models predict, should act as efficient sequestration agents for all three noble gases, in addition to the original H3+ captor.

  1. FeO-rich silicates and Ca,Al-rich inclusions in Qingzhen andYamato 691 (EH3) meteo-rites: Evidence for migration of mass in the solar nebula

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The Qingzhen and Yamato 691 (EH3) enstatite chondrites, which formed under extremely reducing conditions, are studied using the scanning electron microscope and electron probe microanalyzer. Both meteorites contain FeO-rich silicates and minor Ca, Al-rich inclusions. Most FeO-rich silicates are Ca-poor pyroxenes and occur as fragments in matrix. A few grains of FeO-rich silicates were found in chondrules, and FeO-rich olivine is rare. In Qingzhen, FeO-rich silicates commonly contain abundant dust-like Ni-poor metals, which probably formed through reduction of FeO. In contrast, only a few fragments of FeO-rich silicates in Yamato 691 enclose dust-like metals.This difference is consistent with a more reducing condition of Qingzhen than Yamato 691. Ca, Al-rich inclusions have similar modal compositions and mineral chemistry as their counterparts in carbonaceous chondrites. We suggest that (1)the FeO-rich silicates probably formed in oxidized regions of the solar nebula, and then moved into the enstatite chondrite locations; and (2) Ca, Al-rich inclusions in both enstatite chondrites and carbonaceous chondrites may have similar origins and reservoirs.``

  2. Statistical Mechanics and Dynamics of the Outer Solar System.I. The Jupiter/Saturn Zone

    Science.gov (United States)

    Grazier, K. R.; Newman, W. I.; Kaula, W. M.; Hyman, J. M.

    1996-01-01

    We report on numerical simulations designed to understand how the solar system evolved through a winnowing of planetesimals accreeted from the early solar nebula. This sorting process is driven by the energy and angular momentum and continues to the present day. We reconsider the existence and importance of stable niches in the Jupiter/Saturn Zone using greatly improved numerical techniques based on high-order optimized multi-step integration schemes coupled to roundoff error minimizing methods.

  3. Jovian Early Bombardment: planetesimal erosion in the inner asteroid belt

    CERN Document Server

    Turrini, Diego; Magni, Gianfranco

    2012-01-01

    The asteroid belt is an open window on the history of the Solar System, as it preserves records of both its formation process and its secular evolution. The progenitors of the present-day asteroids formed in the Solar Nebula almost contemporary to the giant planets. The actual process producing the first generation of asteroids is uncertain, strongly depending on the physical characteristics of the Solar Nebula, and the different scenarios produce very diverse initial size-frequency distributions. In this work we investigate the implications of the formation of Jupiter, plausibly the first giant planet to form, on the evolution of the primordial asteroid belt. The formation of Jupiter triggered a short but intense period of primordial bombardment, previously unaccounted for, which caused an early phase of enhanced collisional evolution in the asteroid belt. Our results indicate that this Jovian Early Bombardment caused the erosion or the disruption of bodies smaller than a threshold size, which strongly depen...

  4. Early accretion of water and volatile elements to the inner Solar System: evidence from angrites

    Science.gov (United States)

    Sarafian, Adam R.; Hauri, Erik H.; McCubbin, Francis M.; Lapen, Thomas J.; Berger, Eve L.; Nielsen, Sune G.; Marschall, Horst R.; Gaetani, Glenn A.; Righter, Kevin; Sarafian, Emily

    2017-04-01

    Inner Solar System bodies are depleted in volatile elements relative to chondrite meteorites, yet the source(s) and mechanism(s) of volatile-element depletion and/or enrichment are poorly constrained. The timing, mechanisms and quantities of volatile elements present in the early inner Solar System have vast implications for diverse processes, from planetary differentiation to the emergence of life. We report major, trace and volatile-element contents of a glass bead derived from the D'Orbigny angrite, the hydrogen isotopic composition of this glass bead and that of coexisting olivine and silicophosphates, and the 207Pb-206Pb age of the silicophosphates, 4568 ± 20 Ma. We use volatile saturation models to demonstrate that the angrite parent body must have been a major body in the early inner Solar System. We further show via mixing calculations that all inner Solar System bodies accreted volatile elements with carbonaceous chondrite H and N isotope signatures extremely early in Solar System history. Only a small portion (if any) of comets and gaseous nebular H species contributed to the volatile content of the inner Solar System bodies. This article is part of the themed issue 'The origin, history and role of water in the evolution of the inner Solar System'.

  5. Early accretion of water and volatile elements to the inner Solar System: evidence from angrites.

    Science.gov (United States)

    Sarafian, Adam R; Hauri, Erik H; McCubbin, Francis M; Lapen, Thomas J; Berger, Eve L; Nielsen, Sune G; Marschall, Horst R; Gaetani, Glenn A; Righter, Kevin; Sarafian, Emily

    2017-05-28

    Inner Solar System bodies are depleted in volatile elements relative to chondrite meteorites, yet the source(s) and mechanism(s) of volatile-element depletion and/or enrichment are poorly constrained. The timing, mechanisms and quantities of volatile elements present in the early inner Solar System have vast implications for diverse processes, from planetary differentiation to the emergence of life. We report major, trace and volatile-element contents of a glass bead derived from the D'Orbigny angrite, the hydrogen isotopic composition of this glass bead and that of coexisting olivine and silicophosphates, and the (207)Pb-(206)Pb age of the silicophosphates, 4568 ± 20 Ma. We use volatile saturation models to demonstrate that the angrite parent body must have been a major body in the early inner Solar System. We further show via mixing calculations that all inner Solar System bodies accreted volatile elements with carbonaceous chondrite H and N isotope signatures extremely early in Solar System history. Only a small portion (if any) of comets and gaseous nebular H species contributed to the volatile content of the inner Solar System bodies.This article is part of the themed issue 'The origin, history and role of water in the evolution of the inner Solar System'. © 2017 The Author(s).

  6. Dusty globules in the Crab Nebula

    CERN Document Server

    Grenman, Tiia; Elfgren, Erik

    2016-01-01

    From existing broad-band images obtained with the Hubble Space Telescope, we located 92 globules, for which we derived positions, dimensions, orientations, extinctions, masses, proper motions, and their distributions. The globules have mean radii ranging from 400 to 2000 AU and are not resolved in current infrared images of the nebula. The extinction law for dust grains in these globules matches a normal interstellar extinction law. Derived masses of dust range from 1 to 60 x 10^(-6) solar masses, and the total mass contained in globules constitute a fraction of approximately 2% or less of the total dust content of the nebula. The globules are spread over the outer part of the nebula, and a fraction of them coincide in position with emission filaments, where we find elongated globules that are aligned with these filaments. Only 10% of the globules are coincident in position with the numerous H2-emitting knots found in previous studies. All globules move outwards from the centre with transversal velocities of ...

  7. The Solar Eclipse Predictions of Chiljeongsam-Oepyeon in Early Choseon

    Science.gov (United States)

    Ahn, Young Sook; Lee, Yong Sam

    2004-12-01

    The history books of East Asia about astronomical phenomena have the more records of the solar eclipse frequently than any other ones. It is because traditionally, the solar eclipse meaned the fate of dynasty and the king's rule. The Sun, the biggest thing in the heaven symbolized the king, and the solar eclipse foresaw that the king had the problem in private including the body, and the country might suffer from difficulties in a great scale. So the king and all of the ministers used to gather to hold a ceremony named Gusikrye which solar eclipse may pass safely. Consequently, kings always had concernments on collecting informations of solar eclipse. Inspite of importance of solar eclipse predictions, but at the beginning of the Choseon, the predictions of the solar eclipse didn't fit. King Sejong compiled the Chiljeongsan-naepion and the Chiljeongsan-oepyeon to calculate the celestial phenomena including the solar eclipse. By the publications of these two books, the calendar making system of Choseon was firmly established. The Chiljeongsan-oepyeon adopted Huihui calendar of Arabia. The Solar eclipse predictions of Chiljeongsan-oepyeon were relative correct compared to modern method in early Choseon dynasty.

  8. Thermal and chemical evolution in the early solar system as recorded by FUN CAIs: Part I - Petrology, mineral chemistry, and isotopic composition of Allende FUN CAI CMS-1

    Science.gov (United States)

    Williams, C. D.; Ushikubo, T.; Bullock, E. S.; Janney, P. E.; Hines, R. R.; Kita, N. T.; Hervig, R. L.; MacPherson, G. J.; Mendybaev, R. A.; Richter, F. M.; Wadhwa, M.

    2017-03-01

    Detailed petrologic, geochemical and isotopic analyses of a new FUN CAI from the Allende CV3 meteorite (designated CMS-1) indicate that it formed by extensive melting and evaporation of primitive precursor material(s). The precursor material(s) condensed in a 16O-rich region (δ17O and δ18O ∼ -49‰) of the inner solar nebula dominated by gas of solar composition at total pressures of ∼10-3-10-6 bar. Subsequent melting of the precursor material(s) was accompanied by evaporative loss of magnesium, silicon and oxygen resulting in large mass-dependent isotope fractionations in these elements (δ25Mg = 30.71-39.26‰, δ29Si = 14.98-16.65‰, and δ18O = -41.57 to -15.50‰). This evaporative loss resulted in a bulk composition similar to that of compact Type A and Type B CAIs, but very distinct from the composition of the original precursor condensate(s). Kinetic fractionation factors and the measured mass-dependent fractionation of silicon and magnesium in CMS-1 suggest that ∼80% of the silicon and ∼85% of the magnesium were lost from its precursor material(s) through evaporative processes. These results suggest that the precursor material(s) of normal and FUN CAIs condensed in similar environments, but subsequently evolved under vastly different conditions such as total gas pressure. The chemical and isotopic differences between normal and FUN CAIs could be explained by sorting of early solar system materials into distinct physical and chemical regimes, in conjunction with discrete heating events, within the protoplanetary disk.

  9. A large bubble around the Crab Nebula

    Science.gov (United States)

    Romani, Roger W.; Reach, William T.; Koo, Bon Chul; Heiles, Carl

    1990-01-01

    IRAS and 21 cm observations of the interstellar medium around the Crab nebula show evidence of a large bubble surrounded by a partial shell. If located at the canonical 2 kpc distance of the Crab pulsar, the shell is estimated to have a radius of about 90 pc and to contain about 50,000 solar masses of swept-up gas. The way in which interior conditions of this bubble can have important implications for observations of the Crab are described, and the fashion in which presupernova evolution of the pulsar progenitor has affected its local environment is described.

  10. Fe/Ni ratio in the Ant Nebula Mz 3

    CERN Document Server

    Zhang, Y

    2006-01-01

    We have analyzed the [Fe II] and [Ni II] emission lines in the bipolar planetary nebula Mz~3. We find that the [Fe II] and [Ni II] lines arise exclusively from the central regions. Fluorescence excitation in the formation process of these lines is negligible for this low-excitation nebula. From the [Fe II]/[Ni II] ratio, we obtain a higher Fe/Ni abundance ratio with respect to the solar value. The current result provides further supporting evidence for Mz 3 as a symbiotic Mira.

  11. The formation of the solar system by gravitational instability: Prediction of a new planet or another Kuiper-type belt

    OpenAIRE

    Griv, Evgeny; Gedalin, Michael

    2004-01-01

    The early gas-dust solar nebula is considered: the gasdynamic theory is used to study the gravitational Jeans-type instability in its protoplanetary disk. The implications for the origin of the solar system are discussed. It is shown that a collective process, forming the basis of the gravitational instability hypothesis, solves with surprising simplicity the two main problems of the dynamical characteristics of the system, which are associated with its observed spacing and orbital momentum d...

  12. Microcrystals and Amorphous Material in Comets and Primitive Meteorites: Keys to Understanding Processes in the Early Solar System

    Science.gov (United States)

    Nuth, J. A.; Brearley, A. J.; Scott, E. R. D.

    2004-01-01

    Comets, fine-grained matrices of chondrites, and chondritic interplanetary dust particles (IDPs) are each composed of both crystalline and amorphous silicates. The primitive solar nebula, in which comets and asteroids accreted, was formed from the collapsed core of a Giant Molecular Cloud, that, in turn, condensed from materials present in the interstellar medium (ISM). Despite observations that reveal the presence of crystalline magnesium silicate minerals in the shells of very high mass-loss-rate stars [1,2], typical silicate grains in the ISM are most likely to be amorphous, given their relatively long residence time in such a high radiation environment. An upper limit of 3% crystalline grains can be derived from their non-detection in spectra of ISM solids [3]. If the vast majority of grains that enter the primitive solar nebula are amorphous, then the observation of crystalline dust in comets and primitive chondrite matrices indicates the action of specific processes required to transform the amorphous starting materials into the crystals that are observed.

  13. Early Mission Power Assessment of the Dawn Solar Array

    Science.gov (United States)

    Stella, Paul M.; DiStefano, Salvatore; Rayman, Marc D.; Ulloa-Severino, Antonio

    2009-01-01

    NASA's Discovery Mission Dawn was launched in September 2007. Dawn will be the first to orbit two asteroids on a single voyage. The solar array for the Dawn mission will provide power under greatly varying illumination and temperature conditions. Dawn's ion propulsion system (IPS) will provide the spacecraft with enough thrust to reach Vesta and Ceres and orbit both. The demanding mission would be impossible without ion propulsion -- a mission only to the asteroid Vesta (and not including Ceres) would require a much more massive spacecraft and, a much larger launch vehicle.

  14. Early Mission Power Assessment of the Dawn Solar Array

    Science.gov (United States)

    Stella, Paul M.; DiStefano, Salvatore; Rayman, Marc D.; Ulloa-Severino, Antonio

    2009-01-01

    NASA's Discovery Mission Dawn was launched in September 2007. Dawn will be the first to orbit two asteroids on a single voyage. The solar array for the Dawn mission will provide power under greatly varying illumination and temperature conditions. Dawn's ion propulsion system (IPS) will provide the spacecraft with enough thrust to reach Vesta and Ceres and orbit both. The demanding mission would be impossible without ion propulsion -- a mission only to the asteroid Vesta (and not including Ceres) would require a much more massive spacecraft and, a much larger launch vehicle.

  15. Infrared reflection nebulae in Orion Molecular Cloud 2

    Science.gov (United States)

    Pendleton, Yvonne; Werner, M. W.; Capps, R.; Lester, D.

    1986-01-01

    New observations of Orion Molecular Cloud 2 have been made from 1 to 100 microns using the NASA Infrared Telescope Facility and the Kuiper Airborne Observatory. An extensive program of polarimetry, photometry, and spectrophotometry has shown that the extended emission regions associated with two of the previously known near-infrared sources, IRS 1 and IRS 4, are infrared reflection nebulae, and that the compact sources IRS 1 and IRS 4 are the main luminosity sources in the cloud. The constraints from the far-infrared observations and an analysis of the scattered light from the IRS 1 nebula show that OMC-2/IRS 1 can be characterized by L of 500 solar luminosities or less and T of roughly 1000 K. The near-infrared albedo of the grains in the IRS 1 nebula is greater than 0.08.

  16. SBS 1150+599A an extremely oxygen-poor planetary nebula in the Galactic halo?

    CERN Document Server

    Tovmassian, G H; Chavushyan, V H; Zharikov, S V; Gutíerrez, C; Prada, F

    2001-01-01

    We report results of a spectrophotometric study of SBS 1150+599A and discuss the nature of this object based upon our data. Our study shows that SBS 1150+599A is most probably a planetary nebula located in the Galactic halo and not a cataclysmic variable as originally proposed by the authors of the Second Byurakan Survey from low resolution spectroscopy. We have further elaborated on the properties of SBS 1150+599A (now becoming PN G135.9+55.9) with tools used for planetary nebula analysis. Our photoionization models show that, in order to match the observational constraints, the oxygen abundance in the nebula is probably extremely low, around 1/500 solar, which is one order of magnitude lower than the most oxygen-poor planetary nebulae known so far. This finding has strong implications on our understanding of the formation of planetary nebulae and of the evolution of the Galactic halo.

  17. Ghost Head Nebula

    Science.gov (United States)

    1999-01-01

    Looking like a colorful holiday card, a new image from NASA's Hubble Space Telescope reveals a vibrant green and red nebula far from Earth. The image of NGC 2080, taken by Hubble's Wide Field and Planetary Camera 2, designed and built by NASA's Jet Propulsion Laboratory, Pasadena, Calif., is available online at http://www.jpl.nasa.gov/images/wfpc . Images like this help astronomers investigate star formation in nebulas. NGC 2080, nicknamed 'The Ghost Head Nebula,' is one of a chain of star-forming regions lying south of the 30 Doradus nebula in the Large Magellanic Cloud. 30 Doradus is the largest star-forming complex in the local group of galaxies. This 'enhanced color' picture is composed of three narrow-band-filter images obtained by Hubble on March 28, 2000. The red and blue light come from regions of hydrogen gas heated by nearby stars. The green light on the left comes from glowing oxygen. The energy to illuminate the green light is supplied by a powerful stellar wind, a stream of high-speed particles coming from a massive star just outside the image. The central white region is a combination of all three emissions and indicates a core of hot, massive stars in this star-formation region. Intense emission from these stars has carved a bowl-shaped cavity in surrounding gas. In the white region, the two bright areas (the 'eyes of the ghost') - named A1 (left) and A2 (right) -- are very hot, glowing 'blobs' of hydrogen and oxygen. The bubble in A1 is produced by the hot, intense radiation and powerful stellar wind from one massive star. A2 contains more dust and several hidden, massive stars. The massive stars in A1 and A2 must have formed within the last 10,000 years, since their natal gas shrouds are not yet disrupted by the powerful radiation of the newborn stars. The Space Telescope Science Institute is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract with the Goddard Space Flight Center, Greenbelt, Md. The

  18. Solar Wind Interaction with the Martian Upper Atmosphere at Early Mars/Extreme Solar Conditions

    Science.gov (United States)

    Dong, C.; Bougher, S. W.; Ma, Y.; Toth, G.; Lee, Y.; Nagy, A. F.; Tenishev, V.; Pawlowski, D. J.; Combi, M. R.

    2014-12-01

    The investigation of ion escape fluxes from Mars, resulting from the solar wind interaction with its upper atmosphere/ionosphere, is important due to its potential impact on the long-term evolution of Mars atmosphere (e.g., loss of water) over its history. In the present work, we adopt the 3-D Mars cold neutral atmosphere profiles (0 ~ 300 km) from the newly developed and validated Mars Global Ionosphere Thermosphere Model (M-GITM) and the 3-D hot oxygen profiles (100 km ~ 5 RM) from the exosphere Monte Carlo model Adaptive Mesh Particle Simulator (AMPS). We apply these 3-D model output fields into the 3-D BATS-R-US Mars multi-fluid MHD (MF-MHD) model (100 km ~ 20 RM) that can simulate the interplay between Mars upper atmosphere and solar wind by considering the dynamics of individual ion species. The multi-fluid MHD model solves separate continuity, momentum and energy equations for each ion species (H+, O+, O2+, CO2+). The M-GITM model together with the AMPS exosphere model take into account the effects of solar cycle and seasonal variations on both cold and hot neutral atmospheres. This feature allows us to investigate the corresponding effects on the Mars upper atmosphere ion escape by using a one-way coupling approach, i.e., both the M-GITM and AMPS model output fields are used as the input for the multi-fluid MHD model and the M-GITM is used as input into the AMPS exosphere model. In this study, we present M-GITM, AMPS, and MF-MHD calculations (1-way coupled) for 2.5 GYA conditions and/or extreme solar conditions for present day Mars (high solar wind velocities, high solar wind dynamic pressure, and high solar irradiance conditions, etc.). Present day extreme conditions may result in MF-MHD outputs that are similar to 2.5 GYA cases. The crustal field orientations are also considered in this study. By comparing estimates of past ion escape rates with the current ion loss rates to be returned by the MAVEN spacecraft (2013-2016), we can better constrain the

  19. The search for and analysis of direct samples of early Solar System aqueous fluids.

    Science.gov (United States)

    Zolensky, Michael E; Bodnar, Robert J; Yurimoto, Hisayoshi; Itoh, Shoichi; Fries, Marc; Steele, Andrew; Chan, Queenie H-S; Tsuchiyama, Akira; Kebukawa, Yoko; Ito, Motoo

    2017-05-28

    We describe the current state of the search for direct, surviving samples of early, inner Solar System fluids-fluid inclusions in meteorites. Meteoritic aqueous fluid inclusions are not rare, but they are very tiny and their characterization is at the state of the art for most analytical techniques. Meteoritic fluid inclusions offer us a unique opportunity to study early Solar System brines in the laboratory. Inclusion-by-inclusion analyses of the trapped fluids in carefully selected samples will, in the immediate future, provide us detailed information on the evolution of fluids as they interacted with anhydrous solid materials. Thus, real data can replace calculated fluid compositions in thermochemical calculations of the evolution of water and aqueous reactions in comets, asteroids, moons and the terrestrial planets.This article is part of the themed issue 'The origin, history and role of water in the evolution of the inner Solar System'. © 2017 The Author(s).

  20. Hierarchies of Models: Toward Understanding Planetary Nebulae

    Science.gov (United States)

    Knuth, Kevin H.; Hajian, Arsen R.; Clancy, Daniel (Technical Monitor)

    2003-01-01

    Stars like our sun (initial masses between 0.8 to 8 solar masses) end their lives as swollen red giants surrounded by cool extended atmospheres. The nuclear reactions in their cores create carbon, nitrogen and oxygen, which are transported by convection to the outer envelope of the stellar atmosphere. As the star finally collapses to become a white dwarf, this envelope is expelled from the star to form a planetary nebula (PN) rich in organic molecules. The physics, dynamics, and chemistry of these nebulae are poorly understood and have implications not only for our understanding of the stellar life cycle but also for organic astrochemistry and the creation of prebiotic molecules in interstellar space. We are working toward generating three-dimensional models of planetary nebulae (PNe), which include the size, orientation, shape, expansion rate and mass distribution of the nebula. Such a reconstruction of a PN is a challenging problem for several reasons. First, the data consist of images obtained over time from the Hubble Space Telescope (HST) and spectra obtained from Kitt Peak National Observatory (KPNO) and Cerro Tololo Inter-American Observatory (CTIO). These images are of course taken from a single viewpoint in space, which amounts to a very challenging tomographic reconstruction. Second, the fact that we have two disparate and orthogonal data types requires that we utilize a method that allows these data to be used together to obtain a solution. To address these first two challenges we employ Bayesian model estimation using a parameterized physical model that incorporates much prior information about the known physics of the PN. In our previous works we have found that the forward problem of the comprehensive model is extremely time consuming. To address this challenge, we explore the use of a set of hierarchical models, which allow us to estimate increasingly more detailed sets of model parameters. These hierarchical models of increasing complexity are akin

  1. Astrobiology and the Chemistry of the Early Solar System

    Science.gov (United States)

    Cook, Jamie Elsila

    2011-01-01

    The field of astrochemistry investigates the origin of the chemicals necessary for the formation of life. Astrochemists use remote observations, laboratory simulations, and analysis of extraterrestrial samples to understand the inventory of pre biotic chemicals present on the early Earth. Among the problems investigated by astrochemists is the origin of homo chirality in terrestrial life. Analysis of meteorites shows that they may have delivered an excess of L-amino acids to the Earth's surface, perhaps leading to homochirality.

  2. Trojans' Odyssey: Unveiling the early history of the Solar System

    Science.gov (United States)

    Lamy, Philippe; Vernazza, Pierre; Poncy, Joel; Martinot, Vincent; Hinglais, Emmanuel; Canalias, Elisabet; Bell, Jim; Cruikshank, Dale; Groussin, Olivier; Helbert, Joern; Marzari, Francesco; Morbidelli, Alessandro; Rosenblatt, Pascal; Sierks, Holger

    2012-04-01

    In our present understanding of the Solar System, small bodies (asteroids, Jupiter Trojans, comets and TNOs) are the most direct remnants of the original building blocks that formed the planets. Jupiter Trojan and Hilda asteroids are small primitive bodies located beyond the `snow line', around respectively the L4 and L5 Lagrange points of Jupiter at ˜5.2 AU (Trojans) and in the 2:3 mean-motion resonance with Jupiter near 3.9 AU (Hildas). They are at the crux of several outstanding and still conflicting issues regarding the formation and evolution of the Solar System. They hold the potential to unlock the answers to fundamental questions about planetary migration, the late heavy bombardment, the formation of the Jovian system, the origin and evolution of trans-neptunian objects, and the delivery of water and organics to the inner planets. The proposed Trojans' Odyssey mission is envisioned as a reconnaissance, multiple flyby mission aimed at visiting several objects, typically five Trojans and one Hilda. It will attempt exploring both large and small objects and sampling those with any known differences in photometric properties. The orbital strategy consists in a direct trajectory to one of the Trojan swarms. By carefully choosing the aphelion of the orbit (typically 5.3 AU), the trajectory will offer a long arc in the swarm thus maximizing the number of flybys. Initial gravity assists from Venus and Earth will help reducing the cruise time as well as the ΔV needed for injection thus offering enough capacity to navigate among Trojans. This solution further opens the unique possibility to flyby a Hilda asteroid when leaving the Trojan swarm. During the cruise phase, a Main Belt Asteroid could be targeted if requiring a modest ΔV. The specific science objectives of the mission will be best achieved with a payload that will perform high-resolution panchromatic and multispectral imaging, thermal-infrared imaging/ radiometry, near- and mid-infrared spectroscopy, and

  3. The Violent Early Solar System, as Told by Sample Geochronology

    Science.gov (United States)

    Cohen, Barbara

    2013-01-01

    One of the legacies of the samples collected by the Apollo and Luna missions is the link forged between radiometric ages of rocks and relative ages according to stratigraphic relationships and impact crater size-frequency distributions. Our current understanding of the history of the inner solar system is based on the relative chronology of individual planets, tied to the absolute geochronology of the Moon via these important samples. Sample ages have enabled us to infer that impact-melt breccias from Apollo 14 and 15 record the formation of the Imbrium Basin, those from the highland massifs at Apollo 17 record the age of Serenitatis, those from the KREEP-poor Apollo 16 site record the age of Nectaris, and materials from Luna 24 record the age of Crisium. Ejecta from smaller and younger craters Copernicus and Tycho were sampled at Apollo 12 and 17, respectively, and local craters such as Cone at Apollo 14, and North Ray and South Ray at Apollo 16 were also sampled and ages determined for those events. Much of what we understand about the lunar impact flux is based on these ages. Samples from these nearside locations reveal a preponderance of impact-disturbed or recrystallized ages between 3.75 and 3.95 billion years. Argon and lead loss (and correlated disturbances in the Rb-Sr system) have been attributed to metamorphism of the lunar crust by an enormous number of impacts in a brief pulse of time, called the Lunar Cataclysm or Late Heavy Bombardment. Subsequent high-precision geochronometric analyses of Apollo samples and lunar highlands meteorites show a wider range of ages, but very few older than 4 Ga. The paucity of ancient impact melt rocks has been interpreted to mean that either that most impact basins formed at this time, or that ejecta from the large, near-side, young basins dominates the Apollo samples.

  4. Short-lived radioactivity in the early Solar System: the Super-AGB star hypothesis

    OpenAIRE

    Lugaro, Maria; Doherty, Carolyn; Karakas, A. I.; Maddison, S. T.; Liffman, K.; Garc'ia-Hernández, D.A.; Siess, Lionel; Lattanzio, J. C.

    2012-01-01

    The composition of the most primitive solar system condensates, such as calcium-aluminum-rich inclusions (CAIs) and micron-sized corundum grains, show that short-lived radionuclides (SLR), e.g. 26Al, were present in the early solar system. Their abundances require a local or stellar origin, which, however, is far from being understood. We present for the first time the abundances of several SLR up to 60Fe predicted from stars with initial mass in the range approximately 7-11M⊙. These stars ev...

  5. Distances from Planetary Nebulae

    CERN Document Server

    Ciardullo, R

    2003-01-01

    The [O III] 5007 planetary nebula luminosity function (PNLF) occupies an important place on the extragalactic distance ladder. Since it is the only method that is applicable to all the large galaxies of the Local Supercluster, it is uniquely useful for cross-checking results and linking the Population I and Population II distance scales. We review the physics underlying the method, demonstrate its precision, and illustrate its value by comparing its distances to distances obtained from Cepheids and the Surface Brightness Fluctuation (SBF) method. We use the Cepheid and PNLF distances to 13 galaxies to show that the metallicity dependence of the PNLF cutoff is in excellent agreement with that predicted from theory, and that no additional systematic corrections are needed for either method. However, when we compare the Cepheid-calibrated PNLF distance scale with the Cepheid-calibrated SBF distance scale, we find a significant offset: although the relative distances of both methods are in excellent agreement, th...

  6. Young stars of low mass in the Gum nebula

    Science.gov (United States)

    Graham, J. A.; Heyer, Mark H.

    1989-01-01

    Observations are presented for four recently formed stars in the vicinity of the Gum nebula which are heavily obscured by surrounding dust and are associated with small reflection nebulae. HH46 is the only currently active star of the sample, and it is found to have a spectral type in the range of late G-early K, with superimposed emission lines of H-alpha, Ca II, Fe I, Fe II, and weak He I at near zero velocities. It is suggested that the observed scenario of low-mass stars in an older massive star environment may be analogous to the circumstances surrounding the birth of the sun.

  7. Molecular studies of Planetary Nebulae

    OpenAIRE

    Zhang, Yong

    2016-01-01

    Circumstellar envelopes (CEs) around evolved stars are an active site for the production of molecules. After evolving through the Asymptotic Giant Branch (AGB), proto-planetary nebula (PPN), to planetary nebula (PN) phases, CEs ultimately merge with the interstellar medium (ISM). The study of molecules in PNe, therefore, is essential to understanding the transition from stellar to interstellar materials. So far, over 20 molecular species have been discovered in PNe. The molecular composition ...

  8. New portrait of Omega Nebula's glistening watercolours

    Science.gov (United States)

    2009-07-01

    The Omega Nebula, sometimes called the Swan Nebula, is a dazzling stellar nursery located about 5500 light-years away towards the constellation of Sagittarius (the Archer). An active star-forming region of gas and dust about 15 light-years across, the nebula has recently spawned a cluster of massive, hot stars. The intense light and strong winds from these hulking infants have carved remarkable filigree structures in the gas and dust. When seen through a small telescope the nebula has a shape that reminds some observers of the final letter of the Greek alphabet, omega, while others see a swan with its distinctive long, curved neck. Yet other nicknames for this evocative cosmic landmark include the Horseshoe and the Lobster Nebula. Swiss astronomer Jean-Philippe Loys de Chéseaux discovered the nebula around 1745. The French comet hunter Charles Messier independently rediscovered it about twenty years later and included it as number 17 in his famous catalogue. In a small telescope, the Omega Nebula appears as an enigmatic ghostly bar of light set against the star fields of the Milky Way. Early observers were unsure whether this curiosity was really a cloud of gas or a remote cluster of stars too faint to be resolved. In 1866, William Huggins settled the debate when he confirmed the Omega Nebula to be a cloud of glowing gas, through the use of a new instrument, the astronomical spectrograph. In recent years, astronomers have discovered that the Omega Nebula is one of the youngest and most massive star-forming regions in the Milky Way. Active star-birth started a few million years ago and continues through today. The brightly shining gas shown in this picture is just a blister erupting from the side of a much larger dark cloud of molecular gas. The dust that is so prominent in this picture comes from the remains of massive hot stars that have ended their brief lives and ejected material back into space, as well as the cosmic detritus from which future suns form. The

  9. Analysis of Direct Samples of Early Solar System Aqueous Fluids

    Science.gov (United States)

    Zolensky, Michael E.; Bodnar, R J.; Fedele, L.; Yurimoto,H.; Itoh, S.; Fries, M.; Steele, A.

    2012-01-01

    Over the past three decades we have become increasingly aware of the fundamental importance of water, and aqueous alteration, on primitive solar-system bodies. Some carbonaceous and ordinary chondrites have been altered by interactions with liquid water within the first 10 million years after formation of their parent asteroids. Millimeter to centimeter-sized aggregates of purple halite containing aqueous fluid inclusions were found in the matrix of two freshly-fallen brecciated H chondrite falls, Monahans (1998, hereafter simply "Monahans") (H5) and Zag (H3-6) (Zolensky et al., 1999; Whitby et al., 2000; Bogard et al., 2001) In order to understand origin and evolution of the aqueous fluids inside these inclusions we much measure the actual fluid composition, and also learn the O and H isotopic composition of the water. It has taken a decade for laboratory analytical techniques to catch up to these particular nanomole-sized aqueous samples. We have recently been successful in (1) measuring the isotopic composition of H and O in the water in a few fluid inclusions from the Zag and Monahans halite, (2) mineralogical characterization of the solid mineral phases associated with the aqueous fluids within the halite, and (3) the first minor element analyses of the fluid itself. A Cameca ims-1270 equipped with a cryo-sample-stage of Hokkaido University was specially prepared for the O and H isotopic measurements. The cryo-sample-stage (Techno. I. S. Corp.) was cooled down to c.a. -190 C using liquid nitrogen at which the aqueous fluid in inclusions was frozen. We excavated the salt crystal surfaces to expose the frozen fluids using a 15 keV Cs+ beam and measured negative secondary ions. The secondary ions from deep craters of approximately 10 m in depth emitted stably but the intensities changed gradually during measurement cycles because of shifting states of charge compensation, resulting in rather poor reproducibility of multiple measurements of standard fluid

  10. /sup 182/Hf: a new stopwatch for the early solar system

    Energy Technology Data Exchange (ETDEWEB)

    Norman, E.B.; Schramm, D.N.

    1983-01-01

    It is now well established that live /sup 26/Al (t/sub 1/2/ = 7.2 x 10/sup 5/ yr) and /sup 107/Pd (t/sub 1/2/ = 6.5 x 10/sup 6/ yr) were present in the early solar system. Thus, the nucleosynthetic vent (supernova) responsible for the production of these nuclei must have occurred no more than a few million years prior to the formation of solid bodies. It is possible that this event also produced the /sup 129/I known to be present in the early solar system. However, the last event to contribute /sup 244/Pu to the solar system occurred approx. 10/sup 8/ yr prior to the time of solidification. This latter time scale is also consistent with the lack of evidence for a /sup 247/Cm chronometer. In this letter, we propose that /sup 182/Hf (t/sub 1/2/ = 9 x 10/sup 6/ yr) can resolve the question of whether heavy-element non-actinide nucleosynthesis occurred during the /sup 26/Al-producing event. The answer to this question will help to clarify the chronology of the formation of the solar system and will help to determine the astrophysical sites of heavy-element nucleosynthesis.

  11. Early scattering of the solar protoplanetary disk recorded in meteoritic chondrules.

    Science.gov (United States)

    Marrocchi, Yves; Chaussidon, Marc; Piani, Laurette; Libourel, Guy

    2016-07-01

    Meteoritic chondrules are submillimeter spherules representing the major constituent of nondifferentiated planetesimals formed in the solar protoplanetary disk. The link between the dynamics of the disk and the origin of chondrules remains enigmatic. Collisions between planetesimals formed at different heliocentric distances were frequent early in the evolution of the disk. We show that the presence, in some chondrules, of previously unrecognized magnetites of magmatic origin implies the formation of these chondrules under impact-generated oxidizing conditions. The three oxygen isotopes systematic of magmatic magnetites and silicates can only be explained by invoking an impact between silicate-rich and ice-rich planetesimals. This suggests that these peculiar chondrules are by-products of the early mixing in the disk of populations of planetesimals from the inner and outer solar system.

  12. RECONSTRUCTING THE SOLAR WIND FROM ITS EARLY HISTORY TO CURRENT EPOCH

    Energy Technology Data Exchange (ETDEWEB)

    Airapetian, Vladimir S.; Usmanov, Arcadi V., E-mail: vladimir.airapetian@nasa.gov, E-mail: avusmanov@gmail.com [NASA Goddard Space Flight Center, Greenbelt, MD (United States)

    2016-02-01

    Stellar winds from active solar-type stars can play a crucial role in removal of stellar angular momentum and erosion of planetary atmospheres. However, major wind properties except for mass-loss rates cannot be directly derived from observations. We employed a three-dimensional magnetohydrodynamic Alfvén wave driven solar wind model, ALF3D, to reconstruct the solar wind parameters including the mass-loss rate, terminal velocity, and wind temperature at 0.7, 2, and 4.65 Gyr. Our model treats the wind thermal electrons, protons, and pickup protons as separate fluids and incorporates turbulence transport, eddy viscosity, turbulent resistivity, and turbulent heating to properly describe proton and electron temperatures of the solar wind. To study the evolution of the solar wind, we specified three input model parameters, the plasma density, Alfvén wave amplitude, and the strength of the dipole magnetic field at the wind base for each of three solar wind evolution models that are consistent with observational constrains. Our model results show that the velocity of the paleo solar wind was twice as fast, ∼50 times denser and 2 times hotter at 1 AU in the Sun's early history at 0.7 Gyr. The theoretical calculations of mass-loss rate appear to be in agreement with the empirically derived values for stars of various ages. These results can provide realistic constraints for wind dynamic pressures on magnetospheres of (exo)planets around the young Sun and other active stars, which is crucial in realistic assessment of the Joule heating of their ionospheres and corresponding effects of atmospheric erosion.

  13. Reconstructing the Solar Wind from Its Early History to Current Epoch

    Science.gov (United States)

    Airapetian, Vladimir S.; Usmanov, Arcadi V.

    2016-02-01

    Stellar winds from active solar-type stars can play a crucial role in removal of stellar angular momentum and erosion of planetary atmospheres. However, major wind properties except for mass-loss rates cannot be directly derived from observations. We employed a three-dimensional magnetohydrodynamic Alfvén wave driven solar wind model, ALF3D, to reconstruct the solar wind parameters including the mass-loss rate, terminal velocity, and wind temperature at 0.7, 2, and 4.65 Gyr. Our model treats the wind thermal electrons, protons, and pickup protons as separate fluids and incorporates turbulence transport, eddy viscosity, turbulent resistivity, and turbulent heating to properly describe proton and electron temperatures of the solar wind. To study the evolution of the solar wind, we specified three input model parameters, the plasma density, Alfvén wave amplitude, and the strength of the dipole magnetic field at the wind base for each of three solar wind evolution models that are consistent with observational constrains. Our model results show that the velocity of the paleo solar wind was twice as fast, ∼50 times denser and 2 times hotter at 1 AU in the Sun's early history at 0.7 Gyr. The theoretical calculations of mass-loss rate appear to be in agreement with the empirically derived values for stars of various ages. These results can provide realistic constraints for wind dynamic pressures on magnetospheres of (exo)planets around the young Sun and other active stars, which is crucial in realistic assessment of the Joule heating of their ionospheres and corresponding effects of atmospheric erosion.

  14. A Self-Perpetuating Catalyst for the Production of Complex Organic Molecules in Protostellar Nebulae

    Science.gov (United States)

    Nuth, Joseph A.; Johnson, N. M.

    2010-01-01

    The formation of abundant carbonaceous material in meteorites is a long standing problem and an important factor in the debate on the potential for the origin of life in other stellar systems. Many mechanisms may contribute to the total organic content in protostellar nebulae, ranging from organics formed via ion-molecule and atom-molecule reactions in the cold dark clouds from which such nebulae collapse, to similar ion-molecule and atom-molecule reactions in the dark regions of the nebula far from the proto star, to gas phase reactions in sub-nebulae around growing giant planets and in the nebulae themselves. The Fischer-Tropsch-type (FTT) catalytic reduction of CO by hydrogen was once the preferred model for production of organic materials in the primitive solar nebula. The Haber-Bosch catalytic reduction of N2 by hydrogen was thought to produce the reduced nitrogen found in meteorites. However, the clean iron metal surfaces that catalyze these reactions are easily poisoned via reaction with any number of molecules, including the very same complex organics that they produce and both reactions work more efficiently in the hot regions of the nebula. We have demonstrated that many grain surfaces can catalyze both FTT and HB-type reactions, including amorphous iron and magnesium silicates, pure silica smokes as well as several minerals. Although none work as well as pure iron grains, and all produce a wide range of organic products rather than just pure methane, these materials are not truly catalysts.

  15. Monitoring the Orion Nebula Cluster

    Science.gov (United States)

    Reipurth, Bo

    The VYSOS (Variable Young Stars Optical Survey) project has at its disposal five small telescopes: a 5-inch and a 20-inch robotic optical imaging telescope in Hawaii funded by the NSF, and a 6-inch robotic optical imaging telescope, a 32-inch robotic infrared imaging telescope, and a 60-inch optical spectroscopic telescope in Chile, funded and operated from Germany. Through an agreement between the leaders of the two sites (B. Reipurth and R. Chini), it has been decided to devote a significant fraction of time on these facilities to a large Key Project, conducting a massive monitoring survey of the Orion Nebula Cluster. The vast data streams are being reduced through automated customized pipelines. The applicant seeks funding to employ a postdoc and an undergraduate assistant to work at the University of Hawaii and collaborate on the analysis of the data. Virtually all young stars are variable, with a wide range of amplitudes and characteristic timescales. This is mainly due to accretion shocks as material from circumstellar disks fall onto the stars along magnetic funnel flows, but also giant star spots, magnetic flares, occultations by orbiting dust condensations, and eclipses by companions can modulate the light from the nascent star. It is increasingly recognized that the rather static view of pre-main sequence evolution that has prevailed for many years is misleading, and that time-dependent phenomena may hold the key to an understanding of the way young stars grow and their circumstellar environments evolve. The VYSOS project is designed to bring sophisticated modern techniques to bear on the long neglected problem of variability in young solar type stars. To interpret the observations they will be compared to sophisticated MHD models of circumstellar disks around young stars. The Orion Nebula Cluster is the nearest rich region of star formation, and numerous, albeit heterogeneous, studies exist of the cluster members. The present study will provide the first

  16. The San Pedro M\\'artir Planetary Nebula Kinematic Catalogue: Extragalactic Planetary Nebulae

    CERN Document Server

    Richer, M G; Díaz-Méndez, E; Riesgo, H; Báez, S -H; García-Díaz, Ma -T; Meaburn, J; Clark, D M; Olvera, R M Calderón; Soto, G López; Rebolo, O Toledano

    2010-01-01

    We present kinematic data for 211 bright planetary nebulae in eleven Local Group galaxies: M31 (137 PNe), M32 (13), M33 (33), Fornax (1), Sagittarius (3), NGC 147 (2), NGC 185 (5), NGC 205 (9), NGC 6822 (5), Leo A (1), and Sextans A (1). The data were acquired at the Observatorio Astron\\'omico Nacional in the Sierra de San Pedro M\\'artir using the 2.1m telescope and the Manchester Echelle Spectrometer in the light of [\\ion{O}{3}]$\\lambda$5007 at a resolution of 11 km/s. A few objects were observed in H$\\alpha$. The internal kinematics of bright planetary nebulae do not depend strongly upon the metallicity or age of their progenitor stellar populations, though small systematic differences exist. The nebular kinematics and H$\\beta$ luminosity require that the nebular shells be accelerated during the early evolution of their central stars. Thus, kinematics provides an additional argument favoring similar stellar progenitors for bright planetary nebulae in all galaxies.

  17. The Orion Nebula: The Jewel in the Sword

    Science.gov (United States)

    2001-01-01

    -Res - JPEG: 2273 x 2784 pix - 976k] Caption : PR Photo 03d/01 shows a small section of the observational data (in one infrared spectral band only, here reproduced in B/W) on which PR Photo 03a/01 is based. The field is centred on one of the famous Orion silhouette disks (Orion 114-426) (it is located approximately halfway between the centre and the right edge of PR Photo 03c/01 ). The dusty disk itself is seen edge-on as a dark streak against the background emission of the Orion Nebula, while the bright fuzzy patches on either side betray the presence of the embedded parent star that illuminates tenuous collections of dust above its north and south poles to create these small reflection nebulae. Recent HST studies suggest that the very young Orion 114-426 disk - that is thirty times bigger than our present-day Solar System - may already be showing signs of forming its own proto-planetary system. Technical information about this photo is available below. It is even possible to see disks of dust and gas surrounding a few of the young stars, as silhouettes in projection against the bright background of the nebula. Many of these disks are very small and usually only seen on images obtained with the Hubble Space Telescope (HST) [2]. However, under the best seeing conditions on Paranal, the sharpness of VLT images at infrared wavelengths approaches that of the HST in this spectral band, revealing some of these disks, as shown in PR Photo 03d/01 . Indeed, the theoretical image sharpness of the 8.2-m VLT is more than three times better than that of the 2.4-m HST. Thus, the VLT will soon yield images of small regions with even higher resolution by means of the High-Resolution Near-Infrared Camera (CONICA) and the Nasmyth Adaptive Optics System (NAOS) that will compensate the smearing effect introduced by the turbulence in the atmosphere. Later on, extremely sharp images will be obtained when all four VLT telescopes are combined to form the Very Large Telescope Interferometer (VLTI

  18. Pulsar Wind Nebulae Modeling

    CERN Document Server

    Bucciantini, N

    2013-01-01

    Pulsar Wind Nebulae (PWNe) are ideal astrophysical laboratories where high energy relativistic phenomena can be investigated. They are close, well resolved in our observations, and the knowledge derived in their study has a strong impact in many other fields, from AGNs to GRBs. Yet there are still unresolved issues, that prevent us from a full clear understanding of these objects. The lucky combination of high resolution X-ray imaging and numerical codes to handle the outflow and dynamical properties of relativistic MHD, has opened a new avenue of investigation that has lead to interesting progresses in the last years. Despite all of this, we do not understand yet how particles are accelerated, and the functioning of the pulsar wind and pulsar magnetosphere, that power PWNe. I will review what is now commonly known as the MHD paradigm, and in particular I will focus on various approaches that have been and are currently used to model these systems. For each I will highlight its advantages, limitations, and de...

  19. Revised Diagnostic Diagrams for Planetary Nebulae

    CERN Document Server

    Riesgo, H

    2006-01-01

    Diagnostic diagrams of electron density - excitation for a sample of 613 planetary nebulae are presented. The present extensive sample allows the definition of new statistical limits for the distribution of planetary nebulae in the log [Ha/[SII

  20. Formation of planetesimals in the Solar Nebula

    Science.gov (United States)

    Hueso, R.; Guillot, T.

    2001-11-01

    We study the evolution of protoplanetary disks with gas and embedded particles using a classical alpha-disk model. Solid matter entrained in the gas is incorporated following the formalism of Stepinski and Valageas (A&A, 1996, 1997). Dust grains coagulate into larger particles until they eventually decouple from the gas. The coagulation process is modulated by the evaporation and condensation of dust in the disk. We simultaneously consider grains of ices and rock, which allows us to study the amount of different solid material available to form the different planets. In particular, we present consequences for the development of planetesimals in the Uranus and Neptune region. This is interesting in the light of interior models of these planets, which naturally tend to predict a low rock to ice ratio. We will also discuss the consequences of these results on the standard core-accretion formation scenario. Acknowledgements: This work has been supported by Programme National du Planetologie. R. Hueso acknowledges a post-doctoral fellowship from Gobierno Vasco.

  1. Further considerations on contracting solar nebula

    Science.gov (United States)

    Rawal, J. J.

    1986-01-01

    Kepler's third law of the planetary system is analyzed in terms of Prentice's (1978a) modern Laplacian theory and Rawal's (1984) Roche limit concept. Prentice has determined, based on laws of conservation of mass and angular momentum and the concept of supersonic turbulent convection, that the ratio of orbital radii of successively disposed gaseous rings is a constant of approximately 1.69. Rawal studied the relationship between the supersonic turbulent convection concept and Roche limit and established a limit of 1.442. It is concluded that Kepler's law determines the rotation period of the sun at the time of its formation at the present radius to be equal to 0.1216 d. The correlation between orbital periods of the radii and resonant structure is investigated.

  2. Solar and Calendrical Symbolism in the Early Medieval Finnish Church Murals

    Science.gov (United States)

    Ridderstad, Marianna

    2015-05-01

    The earliest church murals of the first stone churches in Finland were painted at the time when Christianity had only just become the official faith in the region and the old ethnic religion was still widely practiced. The 'pagan' motifs of these Early Medieval Finnish church murals reflect the complexity of the religious beliefs in this transition phase. The church actively transformed the festivals of the vernacular religion by giving Christian meanings to the symbols and rituals, as well as by replacing the ethnic deities with Christian figures. The solar symbolism and the calendrical motifs of the church murals are interpreted as imagery largely based on the Christianized remnants of the pre-Christian annual festivals. The earliest church murals thus provide important insight into the pre-Christian religious beliefs of late Iron Age Finland. Many of the motifs and symbols represented in the murals are related to the annual fertility cult and the solar goddess as one of its central figures.

  3. Progress in the Early Solar System Chronology: A Sketch of an Ever-Changing Landscape

    Science.gov (United States)

    Amelin, Yuri; Yin, Q.-Z.; Krot, A. N.; Bouvier, A.; Wadhwa, M.; Kleine, T.; Nyquist, L. E.

    2011-01-01

    The years since the Workshop on the Chronology of Meteorites and the Early Solar System, are marked with ongoing progress in cosmochronology. Rapid improvements in techniques, discovery of new meteorites unlike any previously known, and findings that what was deemed well established constants are actually variables, will be reflected in an updated review of the solar system chronology we are currently preparing. Along with updating the database of meteorite ages, it will involve development of a set of criteria for evaluation of accuracy and consistency of isotopic dates across the entire range of meteorite classes and isotope chronometer systems. Here we present some ideas on what we think is important in meteorite chronology, and invite the cosmochemistry community to discuss them.

  4. Early Solar System irradiation quantified by linked vanadium and beryllium isotope variations in meteorites

    Science.gov (United States)

    Sossi, Paolo A.; Moynier, Frédéric; Chaussidon, Marc; Villeneuve, Johan; Kato, Chizu; Gounelle, Matthieu

    2017-03-01

    X-ray emission in young stellar objects (YSOs) is orders of magnitude more intense than in main sequence stars1,2, suggestive of cosmic ray irradiation of surrounding accretion disks. Protoplanetary disk irradiation has been detected around YSOs by the Herschel Space Observatory3. In our Solar System, short-lived 10Be (with a half-life of 1.39 Myr)4, which cannot be produced by stellar nucleosynthesis, was discovered in the oldest Solar System solids, the calcium-aluminium-rich inclusions (CAIs)5. The high 10Be abundance, as well as the detection of other tracers6,7, suggest 10Be likely originates from cosmic ray irradiation caused by solar flares8-10. Nevertheless, the nature of these flares (gradual or impulsive), the target (gas or dust), and the duration and location of irradiation remain unknown. Here we use the vanadium isotopic composition, together with the initial 10Be abundance to quantify irradiation conditions in the early Solar System11. For the initial 10Be abundances recorded in most CAIs, 50V excesses of a few per mil (‰) relative to chondrites have been predicted8,9. We report 50V excesses in CAIs up to 4.4‰ that co-vary with 10Be abundance. Their co-variation dictates that excess 50V and 10Be were synthesized through irradiation of refractory dust. Modelling of the production rate of 50V and 10Be demonstrates that the dust was exposed to solar cosmic rays produced by gradual flares for less than 300 years at ≈0.1 au from the protosun.

  5. Herschel imaging and spectroscopy of the nebula around the luminous blue variable star WRAY 15-751

    CERN Document Server

    Vamvatira-Nakou, C; Royer, P; Naze, Y; Magain, P; Exter, K; Waelkens, C; Groenewegen, M A T

    2013-01-01

    We have obtained far-infrared Herschel PACS imaging and spectroscopic observations of the nebular environment of the luminous blue variable WRAY 15-751. These images clearly show that the main, dusty nebula is a shell of radius 0.5 pc and width 0.35 pc extending outside the H-alpha nebula. They also reveal a second, bigger and fainter dust nebula, observed for the first time. Both nebulae lie in an empty cavity, likely the remnant of the O-star wind bubble formed when the star was on the main sequence. The kinematic ages of the nebulae are about 20000 and 80000 years and each nebula contains about 0.05 Msun of dust. Modeling of the inner nebula indicates a Fe-rich dust. The far-infrared spectrum of the main nebula revealed forbidden emission lines coming from ionized and neutral gas. Our study shows that the main nebula consists of a shell of ionized gas surrounded by a thin photodissociation region illuminated by an "average" early-B star. The derived abundance ratios N/O=1.0+/-0.4 and C/O=0.4+/-0.2 indicate...

  6. Transformation of Graphitic and Amorphous Carbon Dust to Complex Organic Molecules in a Massive Carbon Cycle in Protostellar Nebulae

    Science.gov (United States)

    Nuth, Joseph A., III; Johnson, Natasha M.

    2012-01-01

    More than 95% of silicate minerals and other oxides found in meteorites were melted, or vaporized and recondensed in the Solar Nebula prior to their incorporation into meteorite parent bodies. Gravitational accretion energy and heating via radioactive decay further transformed oxide minerals accreted into planetesimals. In such an oxygen-rich environment the carbonaceous dust that fell into the nebula as an intimate mixture with oxide grains should have been almost completely converted to CO. While some pre-collapse, molecular-cloud carbonaceous dust does survive, much in the same manner as do pre-solar oxide grains, such materials constitute only a few percent of meteoritic carbon and are clearly distinguished by elevated D/H, N-15/N-16, C-13/C-12 ratios or noble gas patterns. Carbonaceous Dust in Meteorites: We argue that nearly all of the carbon in meteorites was synthesized in the Solar Nebula from CO and that this CO was generated by the reaction of carbonaceous dust with solid oxides, water or OH. It is probable that some fraction of carbonaceous dust that is newly synthesized in the Solar Nebula is also converted back into CO by additional thermal processing. CO processing might occur on grains in the outer nebula through irradiation of CO-containing ice coatings or in the inner nebula via Fischer-Tropsch type (FTT) reactions on grain surfaces. Large-scale transport of both gaseous reaction products and dust from the inner nebula out to regions where comets formed would spread newly formed carbonaceous materials throughout the solar nebula. Formation of Organic Carbon: Carbon dust in the ISM might easily be described as inorganic graphite or amorphous carbon, with relatively low structural abundances of H, N, O and S . Products of FTT reactions or organics produced via irradiation of icy grains contain abundant aromatic and aliphatic hydrocarbons. aldehydes, keytones, acids, amines and amides.. The net result of the massive nebular carbon cycle is to convert

  7. Volatile inventories in clathrate hydrates formed in the primordial nebula

    CERN Document Server

    Mousis, O; Picaud, S; Cordier, D

    2010-01-01

    Examination of ambient thermodynamic conditions suggest that clathrate hydrates could exist in the martian permafrost, on the surface and in the interior of Titan, as well as in other icy satellites. Clathrate hydrates probably formed in a significant fraction of planetesimals in the solar system. Thus, these crystalline solids may have been accreted in comets, in the forming giant planets and in their surrounding satellite systems. In this work, we use a statistical thermodynamic model to investigate the composition of clathrate hydrates that may have formed in the primordial nebula. In our approach, we consider the formation sequence of the different ices occurring during the cooling of the nebula, a reasonable idealization of the process by which volatiles are trapped in planetesimals. We then determine the fractional occupancies of guests in each clathrate hydrate formed at given temperature. The major ingredient of our model is the description of the guest-clathrate hydrate interaction by a spherically a...

  8. The Price-Concentration Relationship in Early Residential Solar Third-Party Markets

    Energy Technology Data Exchange (ETDEWEB)

    Pless, Jacquelyn [Univ. of Oxford (United Kingdom); Langheim, Ria [Center for Sustainable Energy, San Francisco, CA (United States); Machak, Christina [Center for Sustainable Energy, San Francisco, CA (United States); Hellow, Henar [Center for Sustainable Energy, San Francisco, CA (United States); Sigrin, Ben [National Renewable Energy Lab. (NREL), Golden, CO (United States)

    2017-01-01

    that firms charged higher prices in more competitive markets in our sample. The finding is robust across multiple definitions of firm concentration. There are at least two potential explanations for our findings. First, firms could be conducting entry deterrence strategies. It is possible that firms are acting in a non-competitive way and setting prices lower than they would be otherwise. Setting low prices that are below potential competitors' marginal costs could deter entrants and ensure a larger market share. Second, there could be a group of dominant firms (with a competitive fringe), and the dominant firms may occasionally engage in price wars. If this is true, prices should be lower in more concentrated markets during the price wars (Salinger, 1990). As the rooftop PV market continues to grow, market structure will remain a relevant policy issue in consideration of the potential for rooftop solar to contribute to de-carbonization efforts or other policy objectives. This paper adds to a growing emphasis on understanding supply-side factors in scaling up solar markets in the residential sector. Generally, solar markets have become more competitive over the same time period that solar technology costs decreased. While solar system hard costs have come down, our research suggests that total costs are more nuanced in early solar system TPO markets. Policymakers should consider these findings when designing markets, and have the data needed to make informed decisions.

  9. Solar XUV and ENA-driven water loss from early Venus' steam atmosphere

    Science.gov (United States)

    Lichtenegger, H. I. M.; Kislyakova, K. G.; Odert, P.; Erkaev, N. V.; Lammer, H.; Gröller, H.; Johnstone, C. P.; Elkins-Tanton, L.; Tu, L.; Güdel, M.; Holmström, M.

    2016-05-01

    We present a study on the influence of the upper atmosphere hydrodynamic escape of hydrogen, driven by the solar soft X-ray and extreme ultraviolet radiation (XUV), on an expected outgassed steam atmosphere of early Venus. By assuming that the young Sun was either a weak or moderately active young G star, we estimated the water loss from a hydrogen dominated thermosphere due to the absorption of the solar XUV flux and the precipitation of solar wind produced energetic hydrogen atoms (ENAs). The production of ENAs and their interaction with the hydrodynamic extended upper atmosphere, including collision-related feedback processes, have been calculated by means of Monte Carlo models. ENAs that collide in the upper atmosphere deposit their energy and heat the surrounding atmosphere mainly above the main XUV energy deposition layer. It is shown that precipitating ENAs modify the thermal structure of the upper atmosphere, but the enhancement of the thermal escape rates caused by these energetic hydrogen atoms is negligible. Our results also indicate that the majority of oxygen arising from dissociated H2O molecules is left behind during the first 100 Myr. It is thus suggested that the main part of the remaining oxygen has been absorbed by crustal oxidation.

  10. Financialization impedes climate change mitigation: Evidence from the early American solar industry.

    Science.gov (United States)

    Jerneck, Max

    2017-03-01

    The article investigates how financialization impedes climate change mitigation by examining its effects on the early history of one low-carbon industry, solar photovoltaics in the United States. The industry grew rapidly in the 1970s, as large financial conglomerates acquired independent firms. While providing needed financial support, conglomerates changed the focus from existing markets in consumer applications toward a future utility market that never materialized. Concentration of the industry also left it vulnerable to the corporate restructuring of the 1980s, when the conglomerates were dismantled and solar divisions were pared back or sold off to foreign firms. Both the move toward conglomeration, when corporations became managed as stock portfolios, and its subsequent reversal were the result of increased financial dominance over corporate governance. The American case is contrasted with the more successful case of Japan, where these changes to corporate governance did not occur. Insulated from shareholder pressure and financial turbulence, Japanese photovoltaics manufacturers continued to expand investment throughout the 1980s when their American rivals were cutting back. The study is informed by Joseph Schumpeter's theory of creative destruction and Hyman Minsky's theory of financialization, along with economic sociology. By highlighting the tenuous and conflicting relation between finance and production that shaped the early history of the photovoltaics industry, the article raises doubts about the prevailing approach to mitigate climate change through carbon pricing. Given the uncertainty of innovation and the ease of speculation, it will do little to spur low-carbon technology development without financial structures supporting patient capital.

  11. Herschel imaging of the dust in the Helix Nebula (NGC 7293)

    CERN Document Server

    Van de Steene, G C; Exter, K M; Barlow, M J; Cernicharo, J; Etxaluze, M; Gear, W K; Goicoechea, J R; Gomez, H L; Groenewegen, M A T; Hargrave, P C; Ivison, R J; Leeks, S J; Lim, T L; Matsuura, M; Olofsson, G; Polehampton, E T; Swinyard, B M; Ueta, T; Van Winckel, H; Waelkens, C; Wesson, R

    2014-01-01

    In our series of papers presenting the Herschel imaging of evolved planetary nebulae, we present images of the dust distribution in the Helix nebula (NGC 7293). Images at 70, 160, 250, 350, and 500 micron were obtained with the PACS and SPIRE instruments on board the Herschel satellite. The broadband maps show the dust distribution over the main Helix nebula to be clumpy and predominantly present in the barrel wall. We determined the spectral energy distribution of the main nebula in a consistent way using Herschel, IRAS, and Planck flux values. The emissivity index of 0.99 +/- 0.09, in combination with the carbon rich molecular chemistry of the nebula, indicates that the dust consists mainly of amorphous carbon. The dust excess emission from the central star disk is detected at 70 micron and the flux measurement agree with previous measurement. We present the temperature and dust column density maps. The total dust mass across the Helix nebula (without its halo) is determined to be 0.0035 solar mass at a dis...

  12. Star formation and chemical complexity in the Orion nebula: A new view with the IRAM and ALMA interferometers

    Science.gov (United States)

    Baudry, Alain; Brouillet, Nathalie; Despois, Didier

    2016-11-01

    The Orion nebula is one of the most observed celestial regions in the Milky Way. It is an active massive star-forming region, especially well studied in the millimeter and submillimeter domains that allow us to unveil the cool and obscured regions in which stars are being formed. After a brief introduction to the main properties of a radio telescope, we recall that the most sensitive radio interferometers, the IRAM mm array and, especially, the recently built ALMA millimeter/submillimeter array, offer an outstanding spatial resolution reaching the sub-arcsecond scale, or even about 10 milli-arcseconds for ALMA (about four times the Earth's orbit radius at the Orion distance). These interferometers can reveal the fine spatial details of the Orion clouds of gas and dust within which new stars and associated planetary systems are being formed. The high spectral resolution and sensitivity of both interferometers and the broad instantaneous bandwidth offered by ALMA allowed us to map the emission from a number of complex organic molecules, to estimate the molecular abundances, and to address some important aspects of the molecular complexity in Orion. Our observations do not lead to a unique molecular formation and excitation scheme, but the chemistry at work in the proto-stellar 'fragments' at the center of the Orion nebula can be compared with the chemistry prevailing in comets of the Solar system. We have underlined the possible links between the prebiotic molecules observed in space and the chemistry leading to the early terrestrial life.

  13. Molecular studies of Planetary Nebulae

    CERN Document Server

    Zhang, Yong

    2016-01-01

    Circumstellar envelopes (CEs) around evolved stars are an active site for the production of molecules. After evolving through the Asymptotic Giant Branch (AGB), proto-planetary nebula (PPN), to planetary nebula (PN) phases, CEs ultimately merge with the interstellar medium (ISM). The study of molecules in PNe, therefore, is essential to understanding the transition from stellar to interstellar materials. So far, over 20 molecular species have been discovered in PNe. The molecular composition of PNe is rather different from those of AGB and PPNe, suggesting that the molecules synthesized in PN progenitors have been heavily processed by strong ultraviolet radiation from the central star. Intriguingly, fullerenes and complex organic compounds having aromatic and aliphatic structures can be rapidly formed and largely survive during the PPN/PN evolution. The similar molecular compositions in PNe and diffuse clouds as well as the detection of C$_{60}^+$ in the ISM reinforce the view that the mass-loss from PNe can ...

  14. Observations of the filamentary nebula Simeiz 22

    Science.gov (United States)

    Lozinskaya, T. A.; Sitnik, T. G.; Toropova, M. S.; Klement'eva, A. Yu.

    1984-02-01

    Interference-filter photographs of the nebula Simeiz 22 (Sharpless 188) in the (S II), (N II), (O III) lines, taken with a contact image tube at the Cassegrain focus of the 125-cm Crimean reflector, have been processed by photographic equidensitometry, yielding detailed isophotes in each line. The nebula morphology differs in the three lines, showing the stratified emission typical of planetary nebulae. The origin of Simeiz 22 is discussed; indirect arguments point to mass loss by the central star.

  15. Chandra X-Ray Observatory Image of Crab Nebula

    Science.gov (United States)

    1999-01-01

    After barely 2 months in space, the Chandra X-Ray Observatory (CXO) took this sturning image of the Crab Nebula, the spectacular remains of a stellar explosion, revealing something never seen before, a brilliant ring around the nebula's heart. The image shows the central pulsar surrounded by tilted rings of high-energy particles that appear to have been flung outward over a distance of more than a light-year from the pulsar. Perpendicular to the rings, jet-like structures produced by high-energy particles blast away from the pulsar. Hubble Space Telescope images have shown moving knots and wisps around the neutron star, and previous x-ray images have shown the outer parts of the jet and hinted at the ring structure. With CXO's exceptional resolution, the jet can be traced all the way in to the neutron star, and the ring pattern clearly appears. The image was made with CXO's Advanced Charge-Coupled Device (CCD) Imaging Spectrometer (ACIS) and High Energy Transmission Grating. The Crab Nebula, easily the most intensively studied object beyond our solar system, has been observed using virtually every astronomical instrument that could see that part of the sky

  16. Unveiling the molecular environment of the ring nebula RCW 78

    CERN Document Server

    Cappa, C E; Martín, M C; Romero, G A

    2009-01-01

    We present a study of the ionized, neutral atomic, and molecular gas associated with the ring nebula RCW 78 around the WR star HD 117688 (= WR 55). We based our study on CO observations carried out with the SEST and NANTEN telescopes. We report the detection of molecular gas with velocities in the range -56 to -33 km/s. The CO emission is mainly connected to the western section, with a total molecular mass of 1.3 x 10^5 solar masses. The analysis of the HI gas distribution reveals the HI envelope of the molecular cloud, while the radio continuum emission shows a ring-like structure, which is the radio counterpart of the optical nebula. The gas distribution is compatible with the western section of RCW 78 having originated in the photodissociation and ionization of the molecular gas by HD 117688, and with the action of the stellar winds of the WR star. A number of infrared point sources classified as YSO candidates showed that stellar formation activity is present in the molecular gas linked to the nebula. The...

  17. The western Veil nebula (Image)

    Science.gov (United States)

    Glenny, M.

    2009-12-01

    The western Veil nebula in Cygnus. 15-part mosaic by Mike Glenny, Gloucestershire, taken over several months mostly in the autumn of 2008. 200mm LX90/f10 autoguided, Meade UHC filter, 0.3xFR/FF, Canon 20Da DSLR. Exposures each typically 10x360 secs at ISO1600, processed in Registax4, PixInsight (for flat field correction) & Photoshop CS.

  18. Gallery of Planetary Nebula Spectra

    CERN Document Server

    Kwitter, K B; Kwitter, Karen B.; Henry, Richard B.C.

    2006-01-01

    We present the Gallery of Planetary Nebula Spectra now available at http://oitwilliams.edu/nebulae. The website offers high-quality, moderate resolution (~7-10 A FWHM) spectra of 128 Galactic planetary nebulae from 3600-9600 A, obtained by Kwitter, Henry, and colleagues with the Goldcam spectrograph at the KPNO 2.1-m or with the RC spectrograph at the CTIO 1.5-m. The master PN table contains atlas data and an image link. A selected object's spectrum is displayed in a zoomable window; line identification templates are provided. In addition to the spectra themselves, the website also contains a brief discussion of PNe as astronomical objects and as contributors to our understanding of stellar evolution. We envision that this website, which concentrates a large amount of data in one place, will be of interest to a variety of users: researchers might need to check the spectrum of a particular object of interest; the non-specialist astronomer might simply be interested in perusing such a collection of spectra; and...

  19. Laser Induced Breakdown Spectroscopy of meteorites as a probe of the early solar system

    Energy Technology Data Exchange (ETDEWEB)

    Dell' Aglio, M., E-mail: marcella.dellaglio@ba.imip.cnr.it [CNR-IMIP, Via Amendola 122/D, 70126 Bari (Italy); De Giacomo, A. [CNR-IMIP, Via Amendola 122/D, 70126 Bari (Italy); Chemistry Department, University of Bari, Via Orabona 4, 70126 Bari (Italy); Gaudiuso, R.; De Pascale, O. [CNR-IMIP, Via Amendola 122/D, 70126 Bari (Italy); Longo, S. [Chemistry Department, University of Bari, Via Orabona 4, 70126 Bari (Italy); INAF-Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi 5, Firenze (Italy)

    2014-11-01

    This paper presents an evaluation of Laser Induced Breakdown Spectroscopy (LIBS) as a technique for gathering data relevant to Solar System geophysics. Two test cases were demonstrated: elemental analysis of chondrules in a chondrite meteorite, and space- resolved analysis of the interface between kamacite and taenite crystals in an octahedrite iron meteorite. In particular most major and minor elements (Fe, Mg, Si, Ti, Al, Cr, Mn, Ca, Fe, Ni, Co) in Sahara 98222 (chondrite) and its chondrules, as well as the profile of Ni content in Toluca (iron meteorite), were determined with the Calibration Free (CF) method. A special attention was devoted to exploring the possibilities offered by variants of the basic technique, such as the use of Fe I Boltzmann distribution as an intensity calibration method of the spectroscopic system, and the use of spatially resolved analysis. - Highlights: • LIBS of meteorites can supply data relevant to the early evolution of solar system. • CF-LIBS was applied to two different test cases. • Chemical identification of chondrules embedded in a chondrite meteorite • Experimental and theoretical profiles of Ni content in an iron meteorite.

  20. Short-lived radioactivity in the early Solar System: the Super-AGB star hypothesis

    CERN Document Server

    Lugaro, Maria; Karakas, Amanda I; Maddison, Sarah T; Liffman, Kurt; García-Hernández, D A; Siess, Lionel; Lattanzio, John C

    2012-01-01

    The composition of the most primitive Solar System condensates, such as calcium-aluminum-rich inclusions (CAI) and micron-sized corundum grains, show that short-lived radionuclides (SLR), e.g., 26Al, were present in the early Solar System. Their abundances require a local origin, which however is far from being understood. We present for the first time the abundances of several SLR up to 60Fe predicted from stars with initial mass in the range roughly 7-11 Msun. These stars evolve through core H, He, and C burning. After core C burning they go through a "Super"-asymptotic giant branch (Super-AGB) phase, with the H and He shells activated alternately, episodic thermal pulses in the He shell, a very hot temperature at the base of the convective envelope (~ 10^8 K), and strong stellar winds driving the H-rich envelope into the surrounding interstellar medium. The final remnants of the evolution of Super-AGB stars are mostly O-Ne white dwarfs. Our Super-AGB models produce 26Al/27Al yield ratios ~ 0.02 - 0.26. The...

  1. Early growth dynamical implications for the steerability of stratospheric solar radiation management via sulfur aerosol particles

    Science.gov (United States)

    Benduhn, François; Schallock, Jennifer; Lawrence, Mark G.

    2016-09-01

    Aerosol growth dynamics may have implications for the steerability of stratospheric solar radiation management via sulfur particles. This paper derives a set of critical initial growth conditions that are analyzed as a function of two key parameters: the initial concentration of the injected sulfuric acid and its dilution rate with the surrounding air. Based upon this analysis, early aerosol growth dynamical regimes may be defined and classified in terms of their likelihood to serve as candidates for the controlled generation of a radiatively effective aerosol. Our results indicate that the regime that fulfills all critical conditions would require that airplane turbines be used to provide sufficient turbulence. The regime's parameter space is narrow and related to steep gradients, thus pointing to potential fine tuning requirements. More research, development, and testing would be required to refine our findings and determine their global-scale implications.

  2. EVIDENCE FOR MULTIPLE SOURCES OF {sup 10}Be IN THE EARLY SOLAR SYSTEM

    Energy Technology Data Exchange (ETDEWEB)

    Wielandt, Daniel; Krot, Alexander N.; Bizzarro, Martin [Centre for Star and Planet Formation, Natural History Museum of Denmark, University of Copenhagen, Copenhagen DK-1350 (Denmark); Nagashima, Kazuhide; Huss, Gary R. [Hawai' i Institute of Geophysics and Planetology, University of Hawai' i at Manoa, HI 96822 (United States); Ivanova, Marina A. [Vernadsky Institute of Geochemistry and Analytical Chemistry, Moscow 119991 (Russian Federation)

    2012-04-01

    Beryllium-10 is a short-lived radionuclide (t{sub 1/2} = 1.4 Myr) uniquely synthesized by spallation reactions and inferred to have been present when the solar system's oldest solids (calcium-aluminum-rich inclusions, CAIs) formed. Yet, the astrophysical site of {sup 10}Be nucleosynthesis is uncertain. We report Li-Be-B isotope measurements of CAIs from CV chondrites, including CAIs that formed with the canonical {sup 26}Al/{sup 27}Al ratio of {approx}5 Multiplication-Sign 10{sup -5} (canonical CAIs) and CAIs with Fractionation and Unidentified Nuclear isotope effects (FUN-CAIs) characterized by {sup 26}Al/{sup 27}Al ratios much lower than the canonical value. Our measurements demonstrate the presence of four distinct fossil {sup 10}Be/{sup 9}Be isochrons, lower in the FUN-CAIs than in the canonical CAIs, and variable within these classes. Given that FUN-CAI precursors escaped evaporation-recondensation prior to evaporative melting, we suggest that the {sup 10}Be/{sup 9}Be ratio recorded by FUN-CAIs represents a baseline level present in presolar material inherited from the protosolar molecular cloud, generated via enhanced trapping of galactic cosmic rays. The higher and possibly variable apparent {sup 10}Be/{sup 9}Be ratios of canonical CAIs reflect additional spallogenesis, either in the gaseous CAI-forming reservoir, or in the inclusions themselves: this indicates at least two nucleosynthetic sources of {sup 10}Be in the early solar system. The most promising locale for {sup 10}Be synthesis is close to the proto-Sun during its early mass-accreting stages, as these are thought to coincide with periods of intense particle irradiation occurring on timescales significantly shorter than the formation interval of canonical CAIs.

  3. Financialization impedes climate change mitigation: Evidence from the early American solar industry

    Science.gov (United States)

    Jerneck, Max

    2017-01-01

    The article investigates how financialization impedes climate change mitigation by examining its effects on the early history of one low-carbon industry, solar photovoltaics in the United States. The industry grew rapidly in the 1970s, as large financial conglomerates acquired independent firms. While providing needed financial support, conglomerates changed the focus from existing markets in consumer applications toward a future utility market that never materialized. Concentration of the industry also left it vulnerable to the corporate restructuring of the 1980s, when the conglomerates were dismantled and solar divisions were pared back or sold off to foreign firms. Both the move toward conglomeration, when corporations became managed as stock portfolios, and its subsequent reversal were the result of increased financial dominance over corporate governance. The American case is contrasted with the more successful case of Japan, where these changes to corporate governance did not occur. Insulated from shareholder pressure and financial turbulence, Japanese photovoltaics manufacturers continued to expand investment throughout the 1980s when their American rivals were cutting back. The study is informed by Joseph Schumpeter’s theory of creative destruction and Hyman Minsky’s theory of financialization, along with economic sociology. By highlighting the tenuous and conflicting relation between finance and production that shaped the early history of the photovoltaics industry, the article raises doubts about the prevailing approach to mitigate climate change through carbon pricing. Given the uncertainty of innovation and the ease of speculation, it will do little to spur low-carbon technology development without financial structures supporting patient capital. PMID:28435862

  4. Young starless cores embedded in the magnetically dominated Pipe Nebula

    CERN Document Server

    Frau, Pau; Beltran, Maria T; Morata, Oscar; Masque, Josep Maria; Busquet, Gemma; Alves, Felipe O; Sanchez-Monge, Alvaro; Estalella, Robert; Franco, Gabriel A P

    2010-01-01

    The Pipe Nebula is a massive, nearby dark molecular cloud with a low star-formation efficiency which makes it a good laboratory to study the very early stages of the star formation process. The Pipe Nebula is largely filamentary, and appears to be threaded by a uniform magnetic field at scales of few parsecs, perpendicular to its main axis. The field is only locally perturbed in a few regions, such as the only active cluster forming core B59. The aim of this study is to investigate primordial conditions in low-mass pre-stellar cores and how they relate to the local magnetic field in the cloud. We used the IRAM 30-m telescope to carry out a continuum and molecular survey at 3 and 1 mm of early- and late-time molecules toward four selected starless cores inside the Pipe Nebula. We found that the dust continuum emission maps trace better the densest regions than previous 2MASS extinction maps, while 2MASS extinction maps trace better the diffuse gas. The properties of the cores derived from dust emission show av...

  5. Workshop on Pristine Highlands Rocks and the early History of the Moon

    Science.gov (United States)

    Longhi, J. (Editor); Ryder, G. (Editor)

    1983-01-01

    Oxide composition of the Moon, evidence for an initially totally molten Moon, geophysical contraints on lunar composition, random sampling of a layered intrusion, lunar highland rocks, early evolution of the Moon, mineralogy and petrology of the pristine rocks, relationship of the pristine nonmore rocks to the highlands soils and breccias, ferroan anorthositic norite, early lunar igneous history, compositional variation in ferroan anosthosites, a lunar magma ocean, deposits of lunar pristine rocks, lunar and planetary compositions and early fractionation in the solar nebula, Moon composition models, petrogenesis in a Moon with a chondritic refractory lithophile pattern, a terrestrial analog of lunar ilmenite bearing camulates, and the lunar magma ocean are summarized.

  6. Prediction of close binarity based on planetary nebula morphology

    CERN Document Server

    Miszalski, B; Jones, D; Santander-García, M; Rodríguez-Gil, P; Rubio-Díez, M M

    2010-01-01

    A thorough search of the OGLE-III microlensing project has more than doubled the total sample of PNe known to have close binary central stars. These discoveries have enabled close binary induced morphological trends to be revealed for the first time. Canonical bipolar nebulae, low-ionisation structures and polar outflows are all identified within the sample and are provisionally associated with binarity. We have embarked upon a large photometric monitoring program using the Flemish Mercator telescope to simultaneously test the predictive power of these morphological features and to find more close binaries. Early results are very positive with at least five binaries found so far. This suggests our method is an effective means to expedite the construction of a statistically significant sample of close binary shaped nebulae. Such an authoritative sample will be essential to quantify the degree to which close binary nuclei may shape PNe.

  7. Studies of volatiles and organic materials in early terrestrial and present-day outer solar system environments

    Science.gov (United States)

    Sagan, Carl; Thompson, W. Reid; Chyba, Christopher F.; Khare, B. N.

    1991-01-01

    A review and partial summary of projects within several areas of research generally involving the origin, distribution, chemistry, and spectral/dielectric properties of volatiles and organic materials in the outer solar system and early terrestrial environments are presented. The major topics covered include: (1) impact delivery of volatiles and organic compounds to the early terrestrial planets; (2) optical constants measurements; (3) spectral classification, chemical processes, and distribution of materials; and (4) radar properties of ice, hydrocarbons, and organic heteropolymers.

  8. Redox History of Early Solar System Planetismals Recorded in the D;Orbigny Angrite

    Energy Technology Data Exchange (ETDEWEB)

    King, P.L.; Sutton, S.R.; Spilde, M.N.; Wirick, S.; Lanzirotti, A.; Agee, C.B. (UNM); (UC); (BNL)

    2012-04-02

    Angrites are ancient basaltic meteorites ({approx}4.56 Ga) that preserve evidence of some of the solar system's earliest melting events. The volcanic-textured angrites such as D'Orbigny were rapidly crystallized and are relatively pristine; lacking shock, brecciation, and parent-body weathering textures. Thus, these angrites provide a unique 'window' into the petrogenesis of planetary bodies in the early solar system. Angrites may be formed by partial melting of CV chondrites under relatively oxidized sources compared to the eucrites, and therefore may document variations in fO{sub 2} conditions on carbonaceous chondrite parent bodies. Thus, understanding the intrinsic fO{sub 2} conditions of the angrites is needed to determine how different early Solar System basalts form, to model separation of the core, mantle and crust, and to understand magnetic fields on planetary bodies. The D'Orbigny angrite contains a range of textures: (a) crystalline texture containing interlocking crystals of fassaite (pyroxene) with Ti-rich rims, anorthite, and Mg-olivine with Fe-rich rims; (b) cavities with protruding needle-like pyroxene and anorthite dusted by Ca-(Mg)-carbonate; (c) mesostasis with kirschsteinite, ilmenite, troilite, phosphates (e.g., merrilite, whitlockite and Casilicophosphate), rhonite and minor glass; (d) glasses ({approx} angrite composition) in vesicles, as inclusions and as beads, and also cross-cutting crystal-rich portions of the rock; (e) vesicles (e.g., {approx}1.4 vol. %, 0.0219-87.7 mm{sup 3}). Analysis of the textures and Fe{sup 3+}/Fetotal of the cavity pyroxene suggests that the oxygen fugacity (fO{sub 2}) increased in the D'Orbigny angrite perhaps due to introduction of a gas phase. Here we examine the detailed fO{sub 2} history using micro-analyses that allow us to avoid inclusions that may cause spurious results. We present analyses of both S- and V- oxidation states to complement other work using Fe-oxidation state

  9. Extinct 129I in Halite from a Primitive Meteorite: Evidence for Evaporite Formation in the Early Solar System

    Science.gov (United States)

    Whitby, James; Burgess, Ray; Turner, Grenville; Gilmour, Jamie; Bridges, John

    2000-06-01

    Halite crystals from the Zag H3-6 chondrite contain essentially pure (monoisotopic) xenon-129 (129Xe) produced in the early history of the solar system by the decay of short-lived iodine-129 (129I) (half-life = 15.7 million years). Correlated release of 129Xe and 128Xe, produced artificially from 127I by neutron irradiation, corresponds to an initial (129I/127I) ratio of (1.35 +/- 0.05) × 10-4, close to the most primitive early solar system value. If the 129Xe was produced by in situ decay, then the halite formed from an aqueous fluid within 2 million years of the oldest known solar system minerals.

  10. A Low Abundance of 135Cs in the Early Solar System from Barium Isotopic Signatures of Volatile-depleted Meteorites

    Science.gov (United States)

    Brennecka, Gregory A.; Kleine, Thorsten

    2017-03-01

    Precise knowledge of the abundances of short-lived radionuclides at the start of the solar system leads to fundamental information about the stellar environment of solar system formation. Previous investigations of the short-lived {}135{Cs} \\to {}135{Ba} system (t 1/2 = 2.3 Ma) have resulted in a range of calculated initial amounts of 135Cs, with most estimates elevated to a level that requires extraneous input of material to the protoplanetary disk. Such an array of proposed 135Cs/133Cs initial solar system values has severely restricted the system’s use as both a possible chronometer and as an informant about supernovae input. However, if 135Cs was as abundant in the early solar system as previously proposed, the resulting deficits in its daughter product 135Ba would be easily detectable in volatile-depleted parent bodies (i.e., having sub-chondritic Cs/Ba) from the very early solar system. In this work, we show that angrites and eucrites, which were volatile-depleted within ∼1 million years of the start of the solar system, do not possess deficits in 135Ba compared to other planetary bodies. From this, we calculate an upper limit for the initial 135Cs/133Cs of 2.8 × 10‑6, well below previous estimates. This significantly lower initial 135Cs/133Cs ratio now suggests that all of the 135Cs present in the early solar system was inherited simply from galactic chemical evolution and no longer requires an addition from an external stellar source such as an asymptotic giant branch star or SN II, corroborating evidence from several other short-lived radionuclides.

  11. PLANETARY-SCALE STRONTIUM ISOTOPIC HETEROGENEITY AND THE AGE OF VOLATILE DEPLETION OF EARLY SOLAR SYSTEM MATERIALS

    Energy Technology Data Exchange (ETDEWEB)

    Moynier, Frederic; Podosek, Frank A. [Department of Earth and Planetary Science and McDonnell Center for Space Sciences, Washington University, St. Louis, MO 63130 (United States); Day, James M. D. [Geosciences Research Division, Scripps Institution of Oceanography, La Jolla, CA 92093-0244 (United States); Okui, Wataru; Yokoyama, Tetsuya [Department of Earth and Planetary Sciences, Tokyo Institute of Technology, Tokyo 152-8551 (Japan); Bouvier, Audrey [Department of Earth Sciences, University of Minnesota, Minneapolis, MN 55455-0231 (United States); Walker, Richard J., E-mail: moynier@levee.wustl.edu, E-mail: fap@levee.wustl.edu, E-mail: jmdday@ucsd.edu, E-mail: rjwalker@umd.edu, E-mail: okui.w.aa@m.titech.ac.jp, E-mail: tetsuya.yoko@geo.titech.ac.jp, E-mail: abouvier@umn.edu [Department of Geology, University of Maryland, College Park, MD 20742 (United States)

    2012-10-10

    Isotopic anomalies in planetary materials reflect both early solar nebular heterogeneity inherited from presolar stellar sources and processes that generated non-mass-dependent isotopic fractionations. The characterization of isotopic variations in heavy elements among early solar system materials yields important insight into the stellar environment and formation of the solar system, and about initial isotopic ratios relevant to long-term chronological applications. One such heavy element, strontium, is a central element in the geosciences due to wide application of the long-lived {sup 87}Rb-{sup 87}Sr radioactive as a chronometer. We show that the stable isotopes of Sr were heterogeneously distributed at both the mineral scale and the planetary scale in the early solar system, and also that the Sr isotopic heterogeneities correlate with mass-independent oxygen isotope variations, with only CI chondrites plotting outside of this correlation. The correlation implies that most solar system material formed by mixing of at least two isotopically distinct components: a CV-chondrite-like component and an O-chondrite-like component, and possibly a distinct CI-chondrite-like component. The heterogeneous distribution of Sr isotopes may indicate that variations in initial {sup 87}Sr/{sup 86}Sr of early solar system materials reflect isotopic heterogeneity instead of having chronological significance, as interpreted previously. For example, given the differences in {sup 84}Sr/{sup 86}Sr between calcium aluminum inclusions and eucrites ({epsilon}{sup 84}Sr > 2), the difference in age between these materials would be {approx}6 Ma shorter than previously interpreted, placing the Sr chronology in agreement with other long- and short-lived isotope systems, such as U-Pb and Mn-Cr.

  12. Organic and volatile elements in the solar system

    Directory of Open Access Journals (Sweden)

    Remusat L.

    2012-01-01

    Full Text Available Chondrites and comets have accreted primitive materials from the early solar system. Those materials include organics, water and other volatile components. The most primitive chondrites and comets have undergone few modifications on their respective parent bodies and can deliver to laboratories components that were present at the origin of the protosolar nebula. Here I present a review of the organic material and volatile components that have been studied in the most primitive chondrites, and the last data from the stardust mission about the cometary record. This paper focuses on materials that can be studied in laboratories, by mass spectrometry, ion probes or organic chemistry techniques.

  13. The Iron abundance in Galactic Planetary Nebulae

    CERN Document Server

    Delgado-Inglada, G; Mampaso, A; Viironen, K

    2008-01-01

    We constrain the iron abundance in a sample of 33 low-ionization Galactic planetary nebulae (PNe) using [Fe III] lines and correcting for the contribution of higher ionization states with ionization correction factors (ICFs) that take into account uncertainties in the atomic data. We find very low iron abundances in all the objects, suggesting that more than 90% of their iron atoms are condensed onto dust grains. This number is based on the solar iron abundance and implies a lower limit on the dust-to-gas mass ratio, due solely to iron, of M_dust/M_gas>1.3x10^{-3} for our sample. The depletion factors of different PNe cover about two orders of magnitude, probably reflecting differences in the formation, growth, or destruction of their dust grains. However, we do not find any systematic difference between the gaseous iron abundances calculated for C-rich and O-rich PNe, suggesting similar iron depletion efficiencies in both environments. The iron abundances of our sample PNe are similar to those derived follow...

  14. Using Planetary Nebulae to Teach Physics

    Science.gov (United States)

    Kwitter, Karen B.

    2011-05-01

    We have developed an interactive website, "Gallery of Planetary Nebula Spectra," (www.williams.edu/Astronomy/research/PN/nebulae/) that contains high-quality optical-to-near-infrared spectra, atlas information, and bibliographic references for more than 160 planetary nebulae that we have observed in the Milky Way Galaxy. To make the material more accessible to students, I have created three undergraduate-level exercises that explore physics-related aspects of planetary nebulae. "Emission Lines and Central Star Temperature” uses the presence or absence of emission lines from species with different ionization potentials to rank the temperatures of the exciting stars in a selection of nebulae. "Interstellar Reddening” uses the observed Balmer decrement in a sample of planetary nebulae at different Galactic latitudes to infer the distribution of interstellar dust in the Milky Way. Finally, "Determining the Gas Density in Planetary Nebulae,” which I will focus on here, uses the observed intensity ratio of the 6717 Å and 6731 Å emission lines from singly ionized sulfur to determine the electron density in the nebular gas. These exercises demonstrate that planetary nebula spectra are useful real-world examples illustrating a variety of physical principles, including the behavior of blackbodies, wavelength-dependent particle scattering, recombination-line ratios, atomic physics, and statistical mechanics.

  15. Planetary nebulae abundances and stellar evolution II

    NARCIS (Netherlands)

    Pottasch, S. R.; Bernard-Salas, J.

    2010-01-01

    Context. In recent years mid-and far infrared spectra of planetary nebulae have been analysed and lead to more accurate abundances. It may be expected that these better abundances lead to a better understanding of the evolution of these objects. Aims. The observed abundances in planetary nebulae are

  16. A Smoking Gun in the Carina Nebula

    Science.gov (United States)

    Hamaguchi, Kenji; Corcoran, Michael F.; Ezoe, Yuichiro; Townsley, Leisa; Broos, Patrick; Gruendl, Robert; Vaidya, Kaushar; White, Stephen M.; Petre, Rob; Chu, You-Hua

    2009-01-01

    The Carina Nebula is one of thc youngest, most active sites of massive star formation in our Galaxy. In this nebula, we have discovered a bright X-ray source that has persisted for approx.30 years. The soft X-ray spectrum. consistent with kT approx.130 eV blackbody radiation with mild extinction, and no counterpart in the near- and mid-infrared wavelengths indicate that it is a, approx. 10(exp 6)-year-old neutron star housed in the Carina Nebula. Current star formation theory does not suggest that the progenitor of the neutron star and massive stars in the Carina Nebula, in particular (eta)Car, are coeval. This result demonstrates that the Carina Nebula experienced at least two major episodes of massive star formation. The neutron star would be responsible for remnants of high energy activity seen in multiple wavelengths.

  17. Central Stars of Planetary Nebulae

    CERN Document Server

    Jones, David

    2016-01-01

    In this brief invited review, I will attempt to summarise some of the key areas of interest in the study of central stars of planetary nebulae which (probably) won't be covered by other speakers' proceedings. The main focus will, inevitably, be on the subject of multiplicity, with special emphasis on recent results regarding triple central star systems as well as wide binaries which avoid a common-envelope phase. Furthermore, in light of the upcoming release of Kepler's Campaign 11 data, I will discuss a few of the prospects from that data including the unique possibility to detect merger products.

  18. The Violent Early Solar System, as Told by Lunar Sample Geochronology

    Science.gov (United States)

    Cohen, B. A.

    2012-12-01

    the lunar surface was resurfaced; on Earth, this would scale to ~23,000 large impacts in a brief time. Impact ages in ordinary chondrites, HED meteorites, and the Martian meteorite ALH 84001 suggest that this early bombardment event affected the entire inner solar system. If true, the late heavy bombardment may have directly affected the evolution of life on Earth and our understanding of "habitable" planets. Lunar sample ages have also been used to drive large-scale dynamical modeling of solar system formation. These new models of planetary dynamics show a violent beginning to our solar system, where the late formation or outward migration of the gas giant planets destabilizes the Kuiper belt and main-belt asteroids, sending a cascade of impactors into the Moon and all the inner planets. The existence of an early bombardment has even been postulated in extrasolar planetary systems. Even after 40+ years of study, the provenance of returned lunar samples and ages of key events continue to be a focus of research and a topic of debate. One of the most important lessons learned from Apollo missions is that small samples yield a wealth of information and are gifts that keep on giving. The legacy of Apollo samples serves as a model and impetus for future sample return missions from the Moon, Mars, and asteroids.

  19. Properties and Spatial Distribution of Dust Emission in the Crab Nebula

    Science.gov (United States)

    Sonneborn, G.; Temim, T.; Dwek, E.; Arendt, R.; Gehrz, R.; Slane, P.

    2011-01-01

    The nature and quantity of dust produced in supernovae (SNe) is still poorly understood. Recent IR observations of freshly-formed dust in supernova remnants (SNRs) have yielded significantly lower dust masses than predicted by theoretical models and observations high-redshift galaxies. The Crab Nebula's pulsar wind is thought to be sweeping up freshly-formed SN dust along with the SN ejecta. The evidence for this dust was found in the form of an IR bump in the integrated spectrum of the Crab and in extinction against the synchrotron nebula that revealed the presence of dust in the filament cores. We present the first spatially-resolved emission spectra of dust in the Crab Nebula acquired with the Spitzer Space Telescope. The IR spectra are dominated by synchrotron emission and show forbidden line emission from both sides of the expanding nebula, including emission from [S III], [Si II], [Ne II], [Ne III], [Ne V], [Ar III], [Ar V], [Fe II], and [Ni II]. We extrapolated a synchrotron spectral data cube from the Spitzer 3.6 and 4.5 micron images, and subtracted this contribution from our 15-40 micron spectral data to produce a map of the residual continuum emission from dust. The emission appears to be concentrated along the ejecta filaments and is well described by astronomical silicates at an average temperature of 65 K. The estimated mass of dust in the Crab Nebula is 0.008 solar masses.

  20. The Search for Surviving Direct Samples of Early Solar System Water

    Science.gov (United States)

    Zolensky, Michael

    2016-01-01

    We have become increasingly aware of the fundamental importance of water, and aqueous alteration, on primitive solar-system bodies. All classes of astromaterials studied show some degree of interaction with aqueous fluids. Nevertheless, we are still lacking fundamental information such as the location and timing of the aqueous alteration and the detailed nature of the aqueous fluids. Halite crystals in two meteorite regolith breccias were found to contain aqueous fluid inclusions (brines) trapped approx. 4.5 BYBP. Heating/freezing studies of the aqueous fluid inclusions in these halites demonstrated that they were trapped near 25 C. The initial results of our O and H isotopic measurements on these brine inclusions can be explained by a simple model mixing asteroidal and cometary water. We have been analyzing solids and organics trapped alongside the brines in the halites by FTIR, C-XANES, SXRD and Raman, as clues to the origin of the water. The organics show thermal effects that span the entire range witnessed by organics in all chondrite types. Since we identified water-soluble aromatics, including partially halogenated methanol, in some of the halite, we suspected amino acids were also present, but have thus far found that levels of amino acids were undetectable (which is very interesting). We have also been locating aqueous fluid inclusions in other astromaterials, principally carbonates in CI and CM chondrites. Although we have advanced slowly towards detailed analysis of these ancient brines, since they require techniques right at or just beyond current analytical capabilities, their eventual full characterization will completely open the window onto the origin and activity of early solar system water.

  1. Early Solar System Alkali Fractionation Events Recorded by K-Ca Isotopes in the Yamato-74442 LL-Chondritic Breccia

    Science.gov (United States)

    Tatsunori, T.; Misawa, K.; Okano, O.; Shih, C.-Y.; Nyquist, L. E.; Simon, J. I.; Tappa, M. J.; Yoneda, S.

    2015-01-01

    Radiogenic ingrowth of Ca-40 due to decay of K-40 occurred early in the solar system history causing the Ca-40 abundance to vary within different early-former reservoirs. Marshall and DePaolo ] demonstrated that the K-40/Ca-40 decay system could be a useful radiogenic tracer for studies of terrestrial rocks. Shih et al. [3,4] determined 40K/40Ca ages of lunar granitic rock fragments and discussed the chemical characteristics of their source materials. Recently, Yokoyama et al. [5] showed the application of the K-40/Ca-40 chronometer for high K/Ca materials in ordinary chondrites (OCs). High-precision calcium isotopic data are needed to constrain mixing processes among early solar system materials and the time of planetesimal formation. To better constrain the solar system calcium isotopic compositions among astromaterials, we have determined the calcium isotopic compositions of OCs and an angrite. We further estimated a source K/Ca ratio for alkali-rich fragments in a chondritic breccia using the estimated solar system initial Ca-40/Ca-44.

  2. Two short mass-loss events that unveil the binary heart of Minkowski's Butterfly Nebula

    CERN Document Server

    Castro-Carrizo, A; Bujarrabal, V; Chesneau, O; Cox, P; Bachiller, R

    2012-01-01

    Studying the appearance and properties of bipolar winds is critical to understand the stellar evolution from the AGB to the planetary nebula (PN) phase. Many uncertainties exist regarding the presence and role of binary stellar systems, mainly due to the deficit of conclusive observational evidences. We investigate the extended equatorial distribution around the early bipolar planetary nebula M 2-9 ("Minkowski's Butterfly Nebula") to gather new information on the mechanism of the axial ejections. Interferometric millimeter observations of molecular emission provide the most comprehensive view of the equatorial mass distribution and kinematics in early PNe. Here we present subarcsecond angular-resolution observations of the 12CO J=2-1 line and continuum emission with the Plateau de Bure interferometer. The data reveal two ring-shaped and eccentric structures at the equatorial basis of the two coaxial optical lobes. The two rings were formed during short mass-loss episodes (~ 40 yr), separated by ~ 500 yr. Thei...

  3. Where Do Messy Planetary Nebulae Come From?

    Science.gov (United States)

    Kohler, Susanna

    2017-03-01

    If you examined images of planetary nebulae, you would find that many of them have an appearance that is too messy to be accounted for in the standard model of how planetary nebulae form. So what causes these structures?Examples of planetary nebulae that have a low probability of having beenshaped by a triple stellar system. They are mostly symmetric, with only slight departures (labeled) that can be explained by instabilities, interactions with the interstellar medium, etc. [Bear and Soker 2017]A Range of LooksAt the end of a stars lifetime, in the red-giant phase, strong stellar winds can expel the outer layers of the star. The hot, luminous core then radiates in ultraviolet, ionizing the gas of the ejected stellar layers and causing them to shine as a brightly colored planetary nebula for a few tens of thousands of years.Planetary nebulae come in a wide variety of morphologies. Some are approximately spherical, but others can be elliptical, bipolar, quadrupolar, or even more complex.Its been suggested that non-spherical planetary nebulae might be shaped by the presence of a second star in a binary system with the source of the nebula but even this scenario should still produce a structure with axial or mirror symmetry.A pair of scientists from Technion Israel Institute of Technology, Ealeal Bear and Noam Soker, argue that planetary nebulae with especially messy morphologies those without clear axial or point symmetries may have been shaped by an interacting triple stellar system instead.Examples of planetary nebulae that might have been shaped by a triple stellar system. They have some deviations from symmetry but also show signs of interacting with the interstellar medium. [Bear and Soker 2017]Departures from SymmetryTo examine this possibility more closely, Bear and Soker look at a sample of thousands planetary nebulae and qualitatively classify each of them into one of four categories, based on the degree to which they show signs of having been shaped by a

  4. Short-lived radioactive nuclides in meteorites and early solar system processes; Radioactivites eteintes a courtes periodes dans les meteorites et evolution precoce du systeme solaire

    Energy Technology Data Exchange (ETDEWEB)

    Chaussidon, M. [Centre de Recherches Petrographiques et Geochimiques, CRPG-CNRS, 54 - Vandoeuvre-les-Nancy (France); Gounelle, M. [Museum National d' Histoire Naturelle, Lab. d' Etude de la Matiere Extra-Terrestre (LEME), 75 - Paris (France)

    2007-11-15

    Now extinct, short-lived radioactive nuclides, such as {sup 7}Be (T{sub 1/2} = 53 days), {sup 10}Be (T{sub 1/2} = 1.5 Ma), {sup 26}Al (T{sub 1/2} = 0.74 Ma), {sup 36}Cl (T{sub 1/2} = 0.3 Ma), {sup 41}Ca (T{sub 1/2} = 0.1 Ma), {sup 53}Mn (T{sub 1/2} = 3.7 Ma) and {sup 60}Fe (T{sub 1/2} = 1.5 Ma), were present in the proto-solar nebula when the various components of meteorites formed. The presence of these radioactive isotopes requires a 'last-minute' origin, either nucleosynthesis in a massive star dying close in space and time to the nascent solar system or production by local irradiation of part of the proto-solar disk by high-energy solar cosmic rays. In this review, we list: (i) the different observations indicating the existence of multiple origins for short-lived radioactive nuclides, namely {sup 7}Be, {sup 10}Be and {sup 36}Cl for irradiation scenario and {sup 60}Fe for injection scenario; (ii) the constraints that exist on their distribution (homogeneous or heterogeneous) in the accretion disk; (iii) the constraints they brought on the timescales of nebular processes (from Ca-Al-rich inclusions to chondrules) and of the accretion and differentiation of planetesimals. (authors)

  5. A Broadband Emission Model of Magnetar Wind Nebulae

    Science.gov (United States)

    Tanaka, Shuta J.

    2016-08-01

    Angular momentum loss by the plasma wind is considered as a universal feature of isolated neutron stars including magnetars. The wind nebulae that are powered by magnetars allow us to compare the wind properties and the spin evolution of magnetars with those of rotation-powered pulsars (RPPs). In this paper, we construct a broadband emission model of magnetar wind nebulae (MWNe). This model is similar to past studies of young pulsar wind nebulae (PWNe) around RPPs, but is modified for the application to MWNe that have far less observational information than the young PWNe. We apply the model to the MWN around the youngest (˜1 kyr) magnetar, 1E 1547.0-5408, which has the largest spin-down power L spin among all the magnetars. However, the MWN is faint because of the low L spin of 1E 1547.0-5408 when compared to the young RPPs. Since most parameters are not well constrained by only an X-ray flux upper limit of the MWN, we adopt the model’s parameters from the young PWN Kes 75 around PSR J1846-0258, which is a peculiar RPP showing magnetar-like behaviors. The model predicts that γ-ray flux will be detected in a future TeV γ-ray observation by CTA (Cherenkov Telescope Array). The MWN spectrum does not allow us to test the hypothesis that 1E 1547.0-5408 had a period of milliseconds at its birth because the particles injected during the early phase of evolution suffered from severe adiabatic and synchrotron losses. Furthermore, both observational and theoretical studies of the wind nebulae around magnetars are required to constrain the wind and the spin-down properties of magnetars.

  6. Science on NIF Eagle Nebula

    Science.gov (United States)

    Kane, Jave; Martinez, David; Pound, Marc; Heeter, Robert; Casner, Alexis; Villette, Bruno; Mancini, Roberto

    2014-10-01

    For over fifteen years astronomers at the University of Maryland and scientists at LLNL have investigated the origin and dynamics of the famous Pillars of the Eagle Nebula and similar parsec-scale structures at the boundaries of HII regions in molecular hydrogen clouds. Eagle Nebula is one of the National Ignition Facility (NIF) Science programs, and has been awarded two days of NIF shots to study the cometary model of pillar formation. The NIF shots will feature a new long-duration x-ray source prototyped at the Omega EP laser, in which multiple hohlraums mimicking a cluster of stars are driven with UV light in series for 10 ns each to create a 30 ns output x-ray pulse. The drive generates deeply nonlinear hydrodynamics in the Eagle science package, which consists of a dense layered plastic and foam core embedded in lower-density background foam. The scaled Omega EP shots validated the multi-hohlraum concept, showing that earlier time hohlraums do not degrade later time hohlraums by preheat or by ejecting ablated plumes that deflect the later beams. The Omega EP shots illuminated three 2.8 mm long by 1.4 mm diameter Cu hohlraums with 4.3 kJ per hohlraum. At NIF each hohlraum will be 4 mm long by 3 mm in diameter and will be driven with 80-100 kJ. Prepared by LLNL under Contract DE-AC52-07NA27344.

  7. NIF Discovery Science Eagle Nebula

    Science.gov (United States)

    Kane, Jave; Martinez, David; Pound, Marc; Heeter, Robert; Huntington, Channing; Casner, Alexis; Villette, Bruno; Mancini, Roberto

    2016-10-01

    For almost 20 years a team of astronomers, theorists and experimentalists have investigated the creation of the famous Pillars of the Eagle Nebula and similar parsec-scale structures at the boundaries of HII regions in molecular hydrogen clouds, using a combination of astronomical observations, astrophysical simulations, and recently, scaled laboratory experiments. Eagle Nebula, one of the National Ignition Facility (NIF) Discovery Science programs, has completed four NIF shots to study the dense `shadowing' model of pillar formation, and been awarded more shots to study the `cometary' model. These experiments require a long-duration drive, 30 ns or longer, to generate deeply nonlinear ablative hydrodynamics. A novel x-ray source featuring multiple UV-driven hohlraums driven is used. The source directionally illuminates a science package, mimicking a cluster of stars. The first four NIF shots generated radiographs of shadowing-model pillars, and suggested that cometary structures can be generated. The velocity and column density profiles of the NIF shadowing and cometary pillars have been compared with observations of the Eagle Pillars made at millimeter observatories, and indicate cometary growth is key to matching observations. Supported in part by a Grant from the DOE OFES HEDLP program. Prepared by LLNL under Contract DE-AC52-07NA27344.

  8. Polarization in Pulsar Wind Nebulae

    CERN Document Server

    Volpi, D; Amato, E; Bucciantini, N

    2009-01-01

    The main goal of our present work is to provide, for the first time, a simple computational tool that can be used to compute the brightness, the spectral index, the polarization, the time variability and the spectrum of the non-thermal light (both synchrotron and inverse Compton, IC) associated with the plasma dynamics resulting from given relativistic magnetohydrodynamics (RMHD) simulations. The proposed method is quite general, and can be applied to any scheme for RMHD and to all non-thermal emitting sources, e.g. pulsar wind nebulae (PWNe), and in particular to the Crab Nebula (CN) as in the present proceeding. Here only the linear optical and X-ray polarization that characterizes the PWNe synchrotron emission is analyzed in order to infer information on the inner bulk flow structure, to provide a direct investigation of the magnetic field configuration, in particular the presence and the strength of a poloidal component, and to understand the origin of some emitting features, such as the knot, whose origi...

  9. Radio Properties of Pinwheel Nebulae

    CERN Document Server

    Monnier, J D; Tuthill, P G; Danchi, W C

    2002-01-01

    A small number of dusty Wolf-Rayet stars have been resolved into pinwheel nebulae, defined by their ``rotating'' spiral dust shells observed in the infrared. This morphology is naturally explained by dust formation associated with colliding winds in a binary system. In order to confirm and further explore this hypothesis, we have observed the known pinwheel nebulae (WR 104 and WR 98a) as well as the suspected binary WR 112 at multiple radio wavelengths with the Very Large Array to search for non-thermal radio emission from colliding winds. The spectrum of each target is nearly flat between 5 and 22 GHz, consistent with the presence of non-thermal emission that is reduced at low frequencies by free-free absorption. This emission must lie outside the radio ``photosphere,'' leading us to estimate a lower limit to the physical size of the non-thermal emitting region that is larger than expected from current theory. Based on a radio and infrared comparison to WR 104 and 98a, we conclude that WR 112 is a likely can...

  10. HUBBLE CAPTURES DYNAMICS OF CRAB NEBULA (color)

    Science.gov (United States)

    2002-01-01

    A new sequence of Hubble Space Telescope images of the remnant of a tremendous stellar explosion is giving astronomers a remarkable look at the dynamic relationship between the tiny Crab Pulsar and the vast nebula that it powers. This colorful photo shows a ground-based image of the entire Crab Nebula, the remnant of a supernova explosion witnessed over 900 years ago. The nebula, which is 10 light-years across, is located 7,000 light-years away in the constellation Taurus. The green, yellow and red filaments concentrated toward the edges of the nebula are remnants of the star that were ejected into space by the explosion. At the center of the Crab Nebula lies the Crab Pulsar -- the collapsed core of the exploded star. The Crab Pulsar is a rapidly rotating neutron star -- an object only about six miles across, but containing more mass than our Sun. As it rotates at a rate of 30 times per second the Crab Pulsar's powerful magnetic field sweeps around, accelerating particles, and whipping them out into the nebula at speeds close to that of light. The blue glow in the inner part of the nebula -- light emitted by energetic electrons as they spiral through the Crab's magnetic field -- is powered by the Crab Pulsar. Credit: Jeff Hester and Paul Scowen (Arizona State University), and NASA

  11. Processing NASA Earth Science Data on Nebula Cloud

    Science.gov (United States)

    Chen, Aijun; Pham, Long; Kempler, Steven

    2012-01-01

    Three applications were successfully migrated to Nebula, including S4PM, AIRS L1/L2 algorithms, and Giovanni MAPSS. Nebula has some advantages compared with local machines (e.g. performance, cost, scalability, bundling, etc.). Nebula still faces some challenges (e.g. stability, object storage, networking, etc.). Migrating applications to Nebula is feasible but time consuming. Lessons learned from our Nebula experience will benefit future Cloud Computing efforts at GES DISC.

  12. Early solar system. Stellar origin of the ¹⁸²Hf cosmochronometer and the presolar history of solar system matter.

    Science.gov (United States)

    Lugaro, Maria; Heger, Alexander; Osrin, Dean; Goriely, Stephane; Zuber, Kai; Karakas, Amanda I; Gibson, Brad K; Doherty, Carolyn L; Lattanzio, John C; Ott, Ulrich

    2014-08-08

    Among the short-lived radioactive nuclei inferred to be present in the early solar system via meteoritic analyses, there are several heavier than iron whose stellar origin has been poorly understood. In particular, the abundances inferred for (182)Hf (half-life = 8.9 million years) and (129)I (half-life = 15.7 million years) are in disagreement with each other if both nuclei are produced by the rapid neutron-capture process. Here, we demonstrate that contrary to previous assumption, the slow neutron-capture process in asymptotic giant branch stars produces (182)Hf. This has allowed us to date the last rapid and slow neutron-capture events that contaminated the solar system material at ~100 million years and ~30 million years, respectively, before the formation of the Sun.

  13. REDISTRIBUTION OF ALKALINE ELEMENTS IN ASSOCIATION WITH AQUEOUS ACTIVITY IN THE EARLY SOLAR SYSTEM

    Energy Technology Data Exchange (ETDEWEB)

    Hidaka, Hiroshi; Higuchi, Takuya [Department of Earth and Planetary Systems Science, Hiroshima University, Higashi-Hiroshima 739-8526 (Japan); Yoneda, Shigekazu, E-mail: hidaka@hiroshima-u.ac.jp, E-mail: s-yoneda@kahaku.go.jp [Department of Science and Engineering, National Museum of Nature and Science, Tsukuba 305-0005 (Japan)

    2015-12-10

    It is known that the Sayama meteorite (CM2) shows an extensive signature for aqueous alteration on the meteorite parent body, and that most of the primary minerals in the chondrules are replaced with phyllosilicates as the result of the aqueous alteration. In this paper, it is confirmed from the observation of two-dimensional Raman spectra that a part of olivine in a chondrule collected from the Sayama chondrite is serperntinized. Ion microprobe analysis of the chondrule showed that alkaline elements such as Rb and Cs are heterogeneously redistributed in the chondrule. The result of higher Rb and Cs contents in serpentinized phases in the chondrule rather than in other parts suggested the selective adsorption of alkaline elements into the serpentine in association with early aqueous activity on the meteorite parent body. Furthermore Ba isotopic analysis provided variations of {sup 135}Ba/{sup 138}Ba and {sup 137}Ba/{sup 138}Ba in the chondrule. This result was consistent with our previous isotopic data suggesting isotopic evidence for the existence of the presently extinct nuclide {sup 135}Cs in the Sayama meteorite, but the abundance of {sup 135}Cs in the solar system remains unclear because of large analytical uncertainties.

  14. Impactor flux and cratering on Ceres and Vesta: Implications for the early Solar System

    CERN Document Server

    de Elía, G C

    2011-01-01

    We study the impactor flux and cratering on Ceres and Vesta caused by the collisional and dynamical evolution of the asteroid Main Belt. We develop a statistical code based on a well-tested model for the simultaneous evolution of the Main Belt and NEA size distributions. This code includes catastrophic collisions and noncollisional removal processes such as the Yarkovsky effect and the orbital resonances. The model assumes that the dynamical depletion of the early Main Belt was very strong, and owing to that, most Main Belt comminution occurred when its dynamical structure was similar to the present one. Our results indicate that the number of D > 1 km Main Belt asteroids striking Ceres and Vesta over the Solar System history are approximately 4 600 and 1 100 respectively. The largest Main Belt asteroids expected to have impacted Ceres and Vesta had diameters of 71.7 km and 21.1 km. The number of D > 0.1 km craters on Ceres is \\sim 3.4 \\times 10^8 and 6.2 \\times 10^7 on Vesta. The number of craters with D > 1...

  15. The Asteroid Belt as a Relic From a Chaotic Early Solar System

    CERN Document Server

    Izidoro, Andre; Pierens, Arnaud; Morbidelli, Alessandro; Winter, Othon C; Nesvorny, David

    2016-01-01

    The orbital structure of the asteroid belt holds a record of the Solar System's dynamical history. The current belt only contains ${\\rm \\sim 10^{-3}}$ Earth masses yet the asteroids' orbits are dynamically excited, with a large spread in eccentricity and inclination. In the context of models of terrestrial planet formation, the belt may have been excited by Jupiter's orbital migration. The terrestrial planets can also be reproduced without invoking a migrating Jupiter; however, as it requires a severe mass deficit beyond Earth's orbit, this model systematically under-excites the asteroid belt. Here we show that the orbits of the asteroids may have been excited to their current state if Jupiter and Saturn's early orbits were chaotic. Stochastic variations in the gas giants' orbits cause resonances to continually jump across the main belt and excite the asteroids' orbits on a timescale of tens of millions of years. While hydrodynamical simulations show that the gas giants were likely in mean motion resonance at...

  16. Impact-induced shock and the formation of natural quasicrystals in the early solar system.

    Science.gov (United States)

    Hollister, Lincoln S; Bindi, Luca; Yao, Nan; Poirier, Gerald R; Andronicos, Christopher L; MacPherson, Glenn J; Lin, Chaney; Distler, Vadim V; Eddy, Michael P; Kostin, Alexander; Kryachko, Valery; Steinhardt, William M; Yudovskaya, Marina; Eiler, John M; Guan, Yunbin; Clarke, Jamil J; Steinhardt, Paul J

    2014-06-13

    The discovery of a natural quasicrystal, icosahedrite (Al63Cu24Fe13), accompanied by khatyrkite (CuAl2) and cupalite (CuAl) in the CV3 carbonaceous chondrite Khatyrka has posed a mystery as to what extraterrestrial processes led to the formation and preservation of these metal alloys. Here we present a range of evidence, including the discovery of high-pressure phases never observed before in a CV3 chondrite, indicating that an impact shock generated a heterogeneous distribution of pressures and temperatures in which some portions reached at least 5 GPa and 1,200 °C. The conditions were sufficient to melt Al-Cu-bearing minerals, which then rapidly solidified into icosahedrite and other Al-Cu metal phases. The meteorite also contains heretofore unobserved phases of iron-nickel and iron sulphide with substantial amounts of Al and Cu. The presence of these phases in Khatyrka provides further proof that the Al-Cu alloys are natural products of unusual processes that occurred in the early solar system.

  17. The Magnetic Field Effect on Planetary Nebulae

    Institute of Scientific and Technical Information of China (English)

    A. R. Khesali; K. Kokabi

    2006-01-01

    In our previous work on the 3-dimensional dynamical structure of planetary nebulae the effect of magnetic field was not considered. Recently Jordan et al. have directly detected magnetic fields in the central stars of some planetary nebulae. This discovery supports the hypothesis that the non-spherical shape of most planetary nebulae is caused by magnetic fields in AGB stars. In this study we focus on the role of initially weak toroidal magnetic fields embedded in a stellar wind in altering the shape of the PN. We found that magnetic pressure is probably influential on the observed shape of most PNe.

  18. Interstellar gas in the Gum Nebula

    Science.gov (United States)

    Wallerstein, G.; Jenkins, E. B.; Silk, J.

    1980-01-01

    A survey of the interstellar gas near the Gum Nebula by optical observation of 67 stars at Ca II, 42 stars at Na I, and 14 stars in the UV with the Copernicus satellite provided radial velocities and column densities for all resolved absorption components. Velocity dispersions for gas in the Gum Nebula are not significantly larger than in the general interstellar medium; the ionization structure is predominantly that of an H II region with moderately high ionization. Denser, more highly ionized clouds are concentrated toward the Gum Nebula; these clouds do not show the anomalously high ionization observed in the Vela remnant clouds.

  19. Heavy element abundances in planetary nebulae: A theorist's perspective

    CERN Document Server

    Karakas, Amanda I

    2009-01-01

    The determination of heavy element abundances from planetary nebula (PN) spectra provides an exciting opportunity to study the nucleosynthesis occurring in the progenitor asymptotic giant branch (AGB) star. We perform post-processing calculations on AGB models of a large range of mass and metallicity to obtain predictions for the production of neutron-capture elements up to the first s-process peak at strontium. We find that solar metallicity intermediate-mass AGB models provide a reasonable match to the heavy element composition of Type I PNe. Likewise, many of the Se and Kr enriched PNe are well fitted by lower mass models with solar or close-to-solar metallicities. However the most Kr-enriched objects, and the PN with sub-solar Se/O ratios are difficult to explain with AGB nucleosynthesis models. Furthermore, we compute s-process abundance predictions for low-mass AGB models of very low metallicity ([Fe/H] =-2.3) using both scaled solar and an alpha-enhanced initial composition. For these models, O is dred...

  20. First solar system solids to proto-planets: A Rapid growth in a few million years

    Science.gov (United States)

    Goswami, Jitendranath

    2016-07-01

    First solar system solids to proto-planets: A Rapid growth in a few million years J. N. Goswami Physical Research Laboratory Ahmedabad-380009, India Collapse of a dense molecular cloud led to the formation of the proto-Sun surrounded by a high temperature gaseous nebula. The nebula settled down to the mid-plane and formation of the first solar system solids, refractory oxides and silicates, such as Corundum, Perovskite, Melilite took place, that was followed by formation of more common silicate minerals. Laboratory studies of primitive meteorites support this scenario and also provide evidence for correlated presence of several now-extinct short-lived nuclides (e.g. 41Ca, 26Al, 60Fe) at the time of formation of the first solar system solids. Presence of 60Fe in early solar system solids suggests injection of freshly synthesized nuclides from a stellar source (a supernova) into the proto-solar cloud that also triggered its collapse and led to formation of our solar system. Presence of 41Ca (half-life: 0.1Ma) in early solar system solids suggest a time scale of less than a million years for the collapse of the proto-solar cloud and formation of proto-Sun and the first solar system solids. The gradual evolution of larger solar system objects, up to planetesimals (represented by the asteroids), took place at a rapid pace within a time scale of a few million years. Some of the asteroids retain their pristine nature (e.g. parent bodies of carbonaceous chondrite), while others, underwent melting and differentiation due to internal heating. Harold Urey proposed radioactive 26Al as a possible heat source that was confirmed by experiment only in 1999. Irons and stony iron meteorites are fragments from core regions of differentiated asteroids. Extensive computer simulation studies suggest that an explosive stellar event (e.g. supernova) can indeed trigger the collapse of the proto-solar cloud and also inject freshly synthesized short-lived nuclides into it within a relatively

  1. Reconstructing the Solar Wind From Its Early History To Current Epoch

    CERN Document Server

    Airapetian, Vladimir S

    2016-01-01

    Stellar winds from active solar type stars can play a crucial role in removal of stellar angular momentum and erosion of planetary atmospheres. However, major wind properties except for mass loss rates cannot be directly derived from observations. We employed a three dimensional magnetohydrodynamic Alfven wave driven solar wind model, ALF3D, to reconstruct the solar wind parameters including the mass loss rate, terminal velocity and wind temperature at 0.7, 2 and 4.65 Gyr. Our model treats the wind thermal electrons, protons and pickup protons as separate fluids and incorporates turbulence transport, eddy viscosity, turbulent resistivity, and turbulent heating to properly describe proton and electron temperatures of the solar wind. To study the evolution of the solar wind, we specified three input model parameters, the plasma density, Alfven wave amplitude and the strength of the dipole magnetic field at the wind base for each of three solar wind evolution models that are consistent with observational constra...

  2. James Dunlop's historical catalogue of southern nebulae and clusters

    Science.gov (United States)

    Cozens, Glen; Walsh, Andrew; Orchiston, Wayne

    2010-03-01

    In 1826 James Dunlop compiled the second ever catalogue of southern star clusters, nebulae and galaxies from Parramatta (NSW, Australia) using a 23-cm reflecting telescope. Initially acclaimed, the catalogue and author were later criticised and condemned by others - including Sir John Herschel and both the catalogue and author are now largely unknown. The criticism of the catalogue centred on the large number of fictitious or ‘missing’ objects, yet detailed analysis reveals the remarkable completeness of the catalogue, despite its inherent errors. We believe that James Dunlop was an important early Australian astronomer, and his catalogue should be esteemed as the southern equivalent of Messier's famous northern catalogue.

  3. The Eagle Nebula on NIF

    Science.gov (United States)

    Kane, Jave; Cooper, Amy; Remington, Bruce; Ryutov, Dmitri; Smalyuk, Vladimir; Pound, Marc

    2011-10-01

    In one of the eight Science on NIF campaigns, dynamics of molecular clouds such as the Eagle Nebula will be studied in scaled laboratory astrophysics experiments, focusing on new hydrodynamic stabilities of ablation fronts induced by strong directionality of a sustained radiation drive, and on the formation of cometary structures as a model for the famous Eagle Pillars. The NIF Radiation Transport Platform will be adapted to drive a foam target stood off several mm from the halfraum to simulate a molecular cloud illuminated by a distant O-type star, with the drive collimated by an aperture. Pulses of length 20-100 ns generating effective radiation temperatures of 100 eV are being sought. Design of the experiment, theory of the directional radiation instabilities, and supporting astrophysical modeling will be presented. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  4. The nature of the Napoleon's Hat nebula of SN 1987A

    Science.gov (United States)

    Wang, L.; Dyson, J. E.; Kahn, F. D.

    1993-03-01

    The interstellar and circumstellar environment of SN 1987A is modeled. The geometries of Napoleon's Hat nebula and the dark bay suggest that there is relative motion between the SN progenitor and the surrounding ISM. Most of the dark bay can be identified with the bubble produced by the fast blue supergiant (BSG) wind before the red supergiant (RSG) stage. The relative motion between the star and the ISM is the primary reason for the star being at the edge of this bubble. After the first BSG stage, the star evolves to the RSG stage; the wind velocity is now typically 10 km/s and the mass loss rate is around 10 exp -5 solar mass/yr. The star eventually breaks through the bubble produced in the early BSG stage and starts to interact directly with the ISM outside, thus producing Napoleon's Hat. The success of this model is convincing proof of the BSG-RSG-BSG evolutionary model for the SN 1987A progenitors, and shows that is has moved from the site where it was formed.

  5. Chandra X-ray observation of the young stellar cluster NGC 3293 in the Carina Nebula Complex

    Science.gov (United States)

    Preibisch, T.; Flaischlen, S.; Gaczkowski, B.; Townsley, L.; Broos, P.

    2017-09-01

    Context. NGC 3293 is a young stellar cluster at the northwestern periphery of the Carina Nebula Complex that has remained poorly explored until now. Aims: We characterize the stellar population of NGC 3293 in order to evaluate key parameters of the cluster population such as the age and the mass function, and to test claims of an abnormal IMF and a deficit of M ≤ 2.5 M⊙ stars. Methods: We performed a deep (70 ks) X-ray observation of NGC 3293 with Chandra and detected 1026 individual X-ray point sources. These X-ray data directly probe the low-mass (M ≤ 2 M⊙) stellar population by means of the strong X-ray emission of young low-mass stars. We identify counterparts for 74% of the X-ray sources in our deep near-infrared images. Results: Our data clearly show that NGC 3293 hosts a large population of ≈solar-mass stars, refuting claims of a lack of M ≤ 2.5 M⊙ stars. The analysis of the color magnitude diagram suggests an age of 8-10 Myr for the low-mass population of the cluster. There are at least 511 X-ray detected stars with color magnitude positions that are consistent with young stellar members within 7 arcmin of the cluster center. The number ratio of X-ray detected stars in the [1-2 ] M⊙ range versus the M ≥ 5 M⊙ stars (known from optical spectroscopy) is consistent with the expectation from a normal field initial mass function. Most of the early B-type stars and ≈20% of the later B-type stars are detected as X-ray sources. Conclusions: Our data shows that NGC 3293 is one of the most populous stellar clusters in the entire Carina Nebula Complex (very similar to Tr 16 and Tr 15; only Tr 14 is more populous). The cluster probably harbored several O-type stars, whose supernova explosions may have had an important impact on the early evolution of the Carina Nebula Complex. The Chandra data described in this paper have been obtained in the open time project with ObsID 16648 (PI: T. Preibisch) ivo://ADS/Sa.CXO#obs/16648.Tables 1-3 are only

  6. Nebulae and how to observe them

    CERN Document Server

    Coe, Steven

    2007-01-01

    This "Astronomers' Observing Guides" are designed for practical amateur astronomers who not only want to observe, but want to know the details of exactly what they are looking at. Nebulae are the places where the stars are born. For amateur astronomers, the many different kinds of nebulae vary from "easy" targets that can be seen with modest equipment under mediocre skies, to "challenging" objects that require experienced observers, large telescopes and excellent seeing. The concept of the book - and of the series - is to present an up-to-date detailed description and categorisation (part one); and then (part two) to consider how best to successfully observe and record the large range of astronomical objects that fall under the general heading of "nebulae". "Nebulae, and How to Observe Them" is a mine of information for all levels of amateur observers, from the beginner to the experienced.

  7. Observations of planetary nebulae in the Galactic Bulge

    CERN Document Server

    Cuisinier, F; Köppen, J; Acker, A; Stenholm, B

    2000-01-01

    High quality spectrophotometric observations of 30 Planetary Nebulae in the Galactic Bulge have been made. Accurate reddenings, plasma parameters, and abundances of He,O,N,S,Ar,Cl are derived. We find the abundances of O,S,Ar in the Planetary Nebulae in the Galactic Bulge to be comparable with the abundances of the Planetary Nebulae in the Disk, high abundances being maybe slightly more frequent in the Bulge. The distribution of the N/O ratio does not present in the Galactic Bulge Planetary Nebulae the extension to high values that it presents in the Disk Planetary Nebulae. We interpret this as a signature of the greater age of Bulge Planetary Nebulae. We thus find the Bulge Planetary Nebulae to be an old population, slightly more metal-rich than the Disk Planetary Nebulae. The population of the Bulge Planetary Nebulae shows hence the same characteristics than the Bulge stellar population.

  8. TeV Gamma Ray Emission from Nearby Pulsar Wind Nebulae with HAWC

    Science.gov (United States)

    Zhou, Hao; Salesa Greus, Francisco; López-Coto, Rubén; Benzvi, Segev; Casanova, Sabrina; HAWC Collaboration

    2017-01-01

    Pulsar wind nebulae are considered efficient electron/positron accelerators in our Galaxy. It has been suggested that particles accelerated by nearby pulsar wind nebulae, such as Geminga, would possibly account for the observed multi-GeV positron excess. The Geminga pulsar is one of the closest middle-aged pulsars and its pulsations were first discovered in X-rays. Milagro reported an extended TeV source spatially coincident with the Geminga pulsar, but IACT observations using standard analysis techniques have only provided upper limits. The High Altitude Water Cherenkov (HAWC) Observatory, located in central Mexico at 4100 m above sea level, is sensitive to gamma rays between 100 GeV and 100 TeV. With a field of view of 2 steradians, HAWC has a good sensitivity to extended sources such as pulsar wind nebulae. Early data collected with HAWC reveals an extended source coincident with the Geminga pulsar, similar to what Milagro has reported. We will present results of spectral and morphological analyses on extended TeV gamma-ray emission from Geminga and other nearby pulsar wind nebulae with HAWC data. The interpretation of whether positrons from nearby pulsar wind nebulae can explain the observed positron excess will be discussed as well.

  9. Discovery of Double Ring Nebulae Around Twin Wolf-Rayet Stars

    CERN Document Server

    Mauerhan, Jon; Morris, Pat; Van Dyk, Schuyler; Hoard, D W

    2010-01-01

    We have spectroscopically discovered a pair of twin, nitrogen-type, hydrogen-rich, Wolf-Rayet stars (WN8-9h) that are both surrounded by circular, mid-infrared-bright nebulae detected with the Spitzer Space Telescope and MIPS instrument. The emission is probably dominated by a thermal continuum from cool dust, but also may contain contributions from atomic line emission. There is no counterpart at shorter Spitzer/IRAC wavelengths, indicating a lack of emission from warm dust. The two nebulae are probably wind-swept stellar ejecta released by the central stars during a prior evolutionary phase. The nebulae partially overlap on the sky and we speculate on the possibility that they are in the early stage of a collision. Two other evolved massive stars have also been identified within the area subtended by the nebulae, including a carbon-type Wolf-Rayet star (WC8) and an O7-8 III-I star, the latter of which appears to be embedded in one of the larger WN8-9h nebulae. The derived distances to these stars imply that...

  10. Young Planetary Nebulae: Hubble Space Telescope Imaging and a New Morphological Classification System

    CERN Document Server

    Sahai, Raghvendra; Villar, Gregory G

    2011-01-01

    Using Hubble Space Telescope images of 119 young planetary nebulae, most of which have not previously been published, we have devised a comprehensive morphological classification system for these objects. This system generalizes a recently devised system for pre-planetary nebulae, which are the immediate progenitors of planetary nebulae (PNs). Unlike previous classification studies, we have focussed primarily on young PNs rather than all PNs, because the former best show the influences or symmetries imposed on them by the dominant physical processes operating at the first and primary stage of the shaping process. Older PNs develop instabilities, interact with the ambient interstellar medium, and are subject to the passage of photoionization fronts, all of which obscure the underlying symmetries and geometries imposed early on. Our classification system is designed to suffer minimal prejudice regarding the underlying physical causes of the different shapes and structures seen in our PN sample, however, in many...

  11. Early Solar System Bombardment: Exploring the Echos of Planetary Migration and Lost Ice Giants

    Science.gov (United States)

    Bottke, William

    2017-01-01

    Heavily cratered surfaces on the Moon, Mars, Mercury show the terrestrial planets were battered by an intense bombardment during their first billion years or more, but the timing, sources, and dynamical implications of these impacts are controversial. The Late Heavy Bombardment refers to impact events that occurred after stabilization of planetary lithospheres such that they could be preserved as craters. Lunar melt rocks and meteorite shock ages point toward a discrete episode of elevated impact flux between ~3.5 to ~4.2 Ga and a relative quiescence between ~4.0-4.2 to ~4.4 Ga. Evidence from Precambrian impact spherule layers suggest a long-lived tail of terrestrial impactors lasted to ~2.0-2.5 Ga.Dynamical models that include populations residual from primary accretion and destabilized by giant planet migration can potentially account for observations, although all have pros and cons. The most parsimonious solution to match constraints is a hybrid model with discrete early, post-accretion and later, planetary instability-driven impactor populations.For the latter, giant planet instability models can successfully reproduce the orbits of the giant planets, the origin/properties of Jupiter/Neptune Trojans, irregular satellites, the structure of the main asteroid and Kuiper belts, and the presence of comet-like bodies in the main belt, Hilda, and Trojan asteroid populations. The best solutions, however, postulate there were once five giant planets: Jupiter, Saturn, and three ice giants, one that was eventually ejected out of the Solar System by a Jupiter encounter. Intriguing evidence for this “lost” ice giant planet can be found in the orbital properties of bodies captured in the main asteroid belt.The applicability of giant planet instabilities to exoplanet systems seems likely, with the initial configuration of giant planet orbits a byproduct of their early migration and subsequent capture into mutual mean motion resonances. The question is how long can a

  12. An emerging chemical classifications of comets: implications for the early Solar System

    Science.gov (United States)

    Mumma, M. J.

    Cometary nuclei are messengers from the early solar system; they contain key information from the time when planets were forming, and even earlier - some contain material from the natal interstellar cloud. During the first 500 million years of Earth's existence, comets likely delivered vast quantities of pre-biotic organic material along with water for its oceans. The most easily modified forms of matter -the ices, low-temperature-refractory organics, and refractory minerals - hold special significance for understanding these processes. More than two dozen parent volatile species can be characterized directly from Earth-based observatories. Hyakutake and Hale-Bopp were the first bright comets to be studied with powerful new astronomical facilities. A wealth of new information on cometary organic composition was obtained, including the discovery of symmetric hydrocarbons (methane, ethane, acetylene) by infrared spectroscopy and the detection of six new parent volatiles at radio wavelengths. Since then, larger telescopes and even more powerful instruments have become available, permitting in-depth investigation of much fainter comets. With the powerful cross-dispersed cryogenic infrared echelle spectrometer (NIRSPEC, at the 10-m Keck-2 telescope), ten parent volatile species can be characterized in about two hours, eliminating many sources of systematic error. Six Oort cloud comets have been studied with it since 1999. The apparition of two bright comets in spring 2004 doubled the number of comets in which more than a dozen parent volatiles were quantified. The compositions of eleven Oort-cloud comets (including comet Halley and the deceased comet C/1999 S4 LINEAR) and two Jupiter-family comets (Encke, G-Z) will be compared and discussed in the context of chemical diversity in the giant-planets' nebular region. Implications for the delivery of water and pre-biotic organics to the early Earth will be mentioned. Mumma, M. J. et al. (2001), Ap. J. 546, 1183-1193. Mumma

  13. An early solar dynamo prediction: Cycle 23 is approximately cycle 22

    Science.gov (United States)

    Schatten, Kenneth H.; Pesnell, W. Dean

    1993-01-01

    In this paper, we briefly review the 'dynamo' and 'geomagnetic precursor' methods of long-term solar activity forecasting. These methods depend upon the most basic aspect of dynamo theory to predict future activity, future magnetic field arises directly from the magnification of pre-existing magnetic field. We then generalize the dynamo technique, allowing the method to be used at any phase of the solar cycle, through the development of the 'Solar Dynamo Amplitude' (SODA) index. This index is sensitive to the magnetic flux trapped within the Sun's convection zone but insensitive to the phase of the solar cycle. Since magnetic fields inside the Sun can become buoyant, one may think of the acronym SODA as describing the amount of buoyant flux. Using the present value of the SODA index, we estimate that the next cycle's smoothed peak activity will be about 210 +/- 30 solar flux units for the 10.7 cm radio flux and a sunspot number of 170 +/- 25. This suggests that solar cycle #23 will be large, comparable to cycle #22. The estimated peak is expected to occur near 1999.7 +/- 1 year. Since the current approach is novel (using data prior to solar minimum), these estimates may improve when the upcoming solar minimum is reached.

  14. Sulfur Isotopic Fractionation During Vacuum Ultraviolet Photolysis of SO2: Implication for Meteorites and Early Earth

    Science.gov (United States)

    Chakraborty, S.; Jackson, T. L.; Rude, B.; Ahmed, M.; Thiemens, M. H.

    2016-12-01

    Several sulfur bearing gas phase species existed in the solar nebula, including H2S, SO2, SiS, OCS, CS2, CS, NS and SO as a consequence of multiple available chemical valence states (S2- to S6+). Sulfur directly condensed into refractory phases in the solar nebula under reducing conditions. Mass independent (MI) sulfur isotopic compositions have been measured in chondrules and organics from chondritic meteorites. Large 33S excesses in sulfides from achondrite meteoritic groups have also been found suggesting that refractory sulfide minerals condensed from a nebular gas with an enhanced carbon to oxygen ratio. Photochemical reactions in the early solar nebula have been inferred to be a leading process in generating MI sulfur compositions. Previously, we have reported wavelength dependent mass-independent sulfur isotopic compositions (with a varying degree in D33S and D36S) in the product elemental sulfur during vacuum ultraviolet (VUV) photodissociation of H2S. Recently we performed photodissociation of SO2 experiments in the wavelength region 98 to 200 nm at low pressures (0.5 torr) using the VUV photons from the Advanced Light Source Synchrotron in a differentially pumped reaction chamber. To our knowledge, this is the first ever experiment to determine the isotopic fractionation in VUV photodissociation of SO2. At VUV energy region, SO2 is mostly predissociative. The measured sulfur isotopic compositions in the product elemental sulfur are MI and dependent on the wavelength. These new results support the previous finding from photodissociation of other di- and tri-atomic molecules (CO, N2, H2S) that predissociative photodissociation produces MI isotopic products and is a quantum mechanically driven selective phenomenon. These new results are useful because (i) they are important in interpreting meteoritic data and decipher sulfur chemistry in the early nebula which is indicative of the redox condition of the nebula (ii) SO2 photolysis in the atmosphere of early

  15. Evolutionary status of the Of?p star HD 148937 and of its surrounding nebula NGC 6164/5

    Science.gov (United States)

    Mahy, L.; Hutsemékers, D.; Nazé, Y.; Royer, P.; Lebouteiller, V.; Waelkens, C.

    2017-03-01

    Aims: The magnetic star HD 148937 is the only Galactic Of?p star surrounded by a nebula. The structure of this nebula is particularly complex and is composed, from the center out outwards, of a close bipolar ejecta nebula (NGC 6164/5), an ellipsoidal wind-blown shell, and a spherically symmetric Strömgren sphere. The exact formation process of this nebula and its precise relation to the star's evolution remain unknown. Methods: We analyzed infrared Spitzer IRS and far-infrared Herschel/PACS observations of the NGC 6164/5 nebula. The Herschel imaging allowed us to constrain the global morphology of the nebula. We also combined the infrared spectra with optical spectra of the central star to constrain its evolutionary status. We used these data to derive the abundances in the ejected material. To relate this information to the evolutionary status of the star, we also determined the fundamental parameters of HD 148937 using the CMFGEN atmosphere code. Results: The Hα image displays a bipolar or "8"-shaped ionized nebula, whilst the infrared images show dust to be more concentrated around the central object. We determine nebular abundance ratios of N/O = 1.06 close to the star, and N/O = 1.54 in the bright lobe constituting NGC 6164. Interestingly, the parts of the nebula located further from HD 148937 appear more enriched in stellar material than the part located closer to the star. Evolutionary tracks suggest that these ejecta have occured 1.2-1.3 and 0.6 Myr ago, respectively. In addition, we derive abundances of argon for the nebula compatible with the solar values and we find a depletion of neon and sulfur. The combined analyses of the known kinematics and of the new abundances of the nebula suggest either a helical morphology for the nebula, possibly linked to the magnetic geometry, or the occurrence of a binary merger. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important

  16. A LOWER INITIAL ABUNDANCE OF SHORT-LIVED {sup 41}Ca IN THE EARLY SOLAR SYSTEM AND ITS IMPLICATIONS FOR SOLAR SYSTEM FORMATION

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Ming-Chang [Institute of Astronomy and Astrophysics, Academia Sinica, Taipei, Taiwan (China); Chaussidon, Marc [Centre de Recherches Petrographiques et Geochimiques, CNRS, Nancy (France); Srinivasan, Gopalan [Center for Earth Science, Indian Institute of Science, Bangalore (India); McKeegan, Kevin D., E-mail: mcliu@asiaa.sinica.edu.tw [Department of Earth and Space Sciences, UCLA, Los Angeles, CA (United States)

    2012-12-20

    The short-lived radionuclide {sup 41}Ca plays an important role in constraining the immediate astrophysical environment and the formation timescale of the nascent solar system due to its extremely short half-life (0.1 Myr). Nearly 20 years ago, the initial ratio of {sup 41}Ca/{sup 40}Ca in the solar system was determined to be (1.41 {+-} 0.14) Multiplication-Sign 10{sup -8}, primarily based on two Ca-Al-rich Inclusions (CAIs) from the CV chondrite Efremovka. With an advanced analytical technique for isotopic measurements, we reanalyzed the potassium isotopic compositions of the two Efremovka CAIs and inferred the initial ratios of {sup 41}Ca/{sup 40}Ca to be (2.6 {+-} 0.9) Multiplication-Sign 10{sup -9} and (1.4 {+-} 0.6) Multiplication-Sign 10{sup -9} (2{sigma}), a factor of 7-10 lower than the previously inferred value. Considering possible thermal processing that led to lower {sup 26}Al/{sup 27}Al ratios in the two CAIs, we propose that the true solar system initial value of {sup 41}Ca/{sup 40}Ca should have been {approx}4.2 Multiplication-Sign 10{sup -9}. Synchronicity could have existed between {sup 26}Al and {sup 41}Ca, indicating a uniform distribution of the two radionuclides at the time of CAI formation. The new initial {sup 41}Ca abundance is 4-16 times lower than the calculated value for steady-state galactic nucleosynthesis. Therefore, {sup 41}Ca could have originated as part of molecular cloud materials with a free decay time of 0.2-0.4 Myr. Alternative possibilities, such as a last-minute input from a stellar source and early solar system irradiation, could not be definitively ruled out. This underscores the need for more data from diverse CAIs to determine the true astrophysical origin of {sup 41}Ca.

  17. Constraints on neon and argon isotopic fractionation in solar wind.

    Science.gov (United States)

    Meshik, Alex; Mabry, Jennifer; Hohenberg, Charles; Marrocchi, Yves; Pravdivtseva, Olga; Burnett, Donald; Olinger, Chad; Wiens, Roger; Reisenfeld, Dan; Allton, Judith; McNamara, Karen; Stansbery, Eileen; Jurewicz, Amy J G

    2007-10-19

    To evaluate the isotopic composition of the solar nebula from which the planets formed, the relation between isotopes measured in the solar wind and on the Sun's surface needs to be known. The Genesis Discovery mission returned independent samples of three types of solar wind produced by different solar processes that provide a check on possible isotopic variations, or fractionation, between the solar-wind and solar-surface material. At a high level of precision, we observed no significant inter-regime differences in 20Ne/22Ne or 36Ar/38Ar values. For 20Ne/22Ne, the difference between low- and high-speed wind components is 0.24 +/- 0.37%; for 36Ar/38Ar, it is 0.11 +/- 0.26%. Our measured 36Ar/38Ar ratio in the solar wind of 5.501 +/- 0.005 is 3.42 +/- 0.09% higher than that of the terrestrial atmosphere, which may reflect atmospheric losses early in Earth's history.

  18. Double Engine for a Nebula

    Science.gov (United States)

    2009-08-01

    ESO has just released a stunning new image of a field of stars towards the constellation of Carina (the Keel). This striking view is ablaze with a flurry of stars of all colours and brightnesses, some of which are seen against a backdrop of clouds of dust and gas. One unusual star in the middle, HD 87643, has been extensively studied with several ESO telescopes, including the Very Large Telescope Interferometer (VLTI). Surrounded by a complex, extended nebula that is the result of previous violent ejections, the star has been shown to have a companion. Interactions in this double system, surrounded by a dusty disc, may be the engine fuelling the star's remarkable nebula. The new image, showing a very rich field of stars towards the Carina arm of the Milky Way, is centred on the star HD 87643, a member of the exotic class of B[e] stars [1]. It is part of a set of observations that provide astronomers with the best ever picture of a B[e] star. The image was obtained with the Wide Field Imager (WFI) attached to the MPG/ESO 2.2-metre telescope at the 2400-metre-high La Silla Observatory in Chile. The image shows beautifully the extended nebula of gas and dust that reflects the light from the star. The central star's wind appears to have shaped the nebula, leaving bright, ragged tendrils of gas and dust. A careful investigation of these features seems to indicate that there are regular ejections of matter from the star every 15 to 50 years. A team of astronomers, led by Florentin Millour, has studied the star HD 87643 in great detail, using several of ESO's telescopes. Apart from the WFI, the team also used ESO's Very Large Telescope (VLT) at Paranal. At the VLT, the astronomers used the NACO adaptive optics instrument, allowing them to obtain an image of the star free from the blurring effect of the atmosphere. To probe the object further, the team then obtained an image with the Very Large Telescope Interferometer (VLTI). The sheer range of this set of observations

  19. RGS X-Ray Spectroscopy of the Crab Nebula

    Science.gov (United States)

    Kaastra, J. S.; de Vries, C. P.; Costantini, E.; den Herder, J. A.

    The Crab nebula and pulsar have been widely used as a calibration source for X-ray instruments. The in-flight effective area calibration of the Reflection Grating Spectrometers (RGS) of XMM-Newton depends upon the availability of reliable calibration sources. We analyse RGS observations of the Crab using different instrument configurations and spatial offsets, and make use of previous determinations of the continuum spectrum of the nebula plus pulsar. Due to the high spectral resolution of the RGS, we resolve the main absorption edges. We get an excellent fit to the Crab spectrum using this fixed continuum and the absorption spectrum determined by RGS. We get accurate column densities for the neutral atoms of H, N, O, Ne, Mg and Fe as well as a clear detection of Fe II and firm upper limits for other ions (O II, Mg II). We find solar-like abundances for N, O and Mg, and Fe (adding Fe I and Fe II), while Ne is overabundant. Finally, we show how we can determine the absolute flux of Crab with high accuracy by combining RGS and Chandra LETGS spectra of different sources.

  20. Gas absorption and dust extinction towards the Orion Nebula Cluster

    CERN Document Server

    Hasenberger, Birgit; Alves, Joao; Wolk, Scott; Meingast, Stefan; Getman, Konstantin; Pillitteri, Ignazio

    2016-01-01

    We characterise the relation between the gas and dust content of the interstellar medium towards young stellar objects in the Orion Nebula Cluster. X-ray observations provide estimates of the absorbing equivalent hydrogen column density N_H based on spectral fits. Near-infrared extinction values are calculated from intrinsic and observed colour magnitudes (J-H) and (H-K_s) as given by the VISTA Orion A survey. A linear fit of the correlation between column density and extinction values A_V yields an estimate of the N_H/A_V ratio. We investigate systematic uncertainties of the results by describing and (if possible) quantifying the influence of circumstellar material and the adopted extinction law, X-ray models, and elemental abundances on the N_H/A_V ratio. Assuming a Galactic extinction law with R_V=3.1 and solar abundances by Anders & Grevesse (1989), we deduce an N_H/A_V ratio of (1.39 +- 0.14) x 10^21 cm^-2 mag^-1 for Class III sources in the Orion Nebula Cluster where the given error does not include...

  1. Helium recombination spectra as temperature diagnostics for planetary nebulae

    CERN Document Server

    Zhang, Y; Liu, Y; Rubin, R H

    2005-01-01

    Electron temperatures derived from the \\ion{He}{1} recombination line ratios, designated $T_{\\rm e}$(\\ion{He}{1}), are presented for 48 planetary nebulae (PNe). We study the effect that temperature fluctuations inside nebulae have on the $T_{\\rm e}$(\\ion{He}{1}) value. We show that a comparison between $T_{\\rm e}$(\\ion{He}{1}) and the electron temperature derived from the Balmer jump of the \\ion{H}{1} recombination spectrum, designated $T_{\\rm e}$(\\ion{H}{1}), provides an opportunity to discriminate between the paradigms of a chemically homogeneous plasma with temperature and density variations, and a two-abundance nebular model with hydrogen-deficient material embedded in diffuse gas of a ``normal'' chemical composition (i.e. $\\sim$ solar), as the possible causes of the dichotomy between the abundances that are deduced from collisionally excited lines to those deduced from recombination lines. We find that $T_{\\rm e}$(\\ion{He}{1}) values are significantly lower than $T_{\\rm e}$(\\ion{H}{1}) values, with an av...

  2. Trojan Tour and Rendezvous (TTR): A New Frontiers Mission to Explore the Origin and Evolution of the Early Solar System

    Science.gov (United States)

    Bell, J. F., III; Olkin, C.; Castillo, J. C.

    2015-12-01

    The orbital properties, compositions, and physical properties of the diverse populations of small outer solar system bodies provide a forensic map of how our solar system formed and evolved. Perhaps the most potentially diagnostic, but least explored, of those populations are the Jupiter Trojan asteroids, which orbit at ~5 AU in the L4 and L5 Lagrange points of Jupiter. More than 6200 Jupiter Trojans are presently known, but these are predicted to be only a small fraction of the 500,000 to 1 million Trojans >1 km in size. The Trojans are hypothesized to be either former Kuiper Belt Objects (KBOs) that were scattered into the inner solar system by early giant planet migration and then trapped in the 1:1 Jupiter mean motion resonance, or bodies formed near 5 AU in a much more quiescent early solar system, and then trapped at L4 and L5. The 2011 Planetary Science Decadal Survey identified important questions about the origin and evolution of the solar system that can be addressed by studying of the Trojan asteroids, including: (a) How did the giant planets and their satellite systems accrete, and is there evidence that they migrated to new orbital positions? (b) What is the relationship between large and small KBOs? Is the small population derived by impact disruption of the large one? (c) What kinds of surface evolution, radiation chemistry, and surface-atmosphere interactions occur on distant icy primitive bodies? And (d) What are the sources of asteroid groups (Trojans and Centaurs) that remain to be explored by spacecraft? The Trojan Tour and Rendezvous (TTR) is a New Frontiers-class mission designed to answer these questions, and to test hypotheses for early giant planet migration and solar system evolution. Via close flybys of a large number of these objects,, and orbital characterization of at least one large Trojan, TTR will enable the first-time exploration of this population. Our primary mission goals are to characterize the overall surface geology

  3. Simulation of organic molecule formation in solar system environments-The Miller-Urey Experiment in Space project overview

    Science.gov (United States)

    Kotler, J. Michelle; Ehrenfruend, Pascale; Botta, Oliver; Blum, Jurgen; Schrapler, Rainer; van Dongen, Joost; Palmans, Anja; Sephton, Mark A.; Martins, Zita; Cleaves, Henderson J.; Ricco, Antonio

    The Miller-Urey Experiment in space (MUE) investigates the formation of potential prebiotic organic compounds in the early solar system environment. The MUE experiment will be sent to and retrieved from the International Space Station (ISS), where it will be performed inside the Microgravity Science Glovebox (MSG). The goal of this space experiment is to understand prebiotic reactions in microgravity by simulating environments of the early solar nebula. The dynamic environment of the solar nebula with the simultaneous presence of gas, particles, and energetic processes, including shock waves, lightning, and radiation may trigger a rich organic chemistry leading to organic molecules. These environments will be simulated in six fabricated vials containing various gas mixtures as well as solid particles. Two gas mixture compositions will be tested and subjected to continuous spark discharges for 48, 96, and 192 hours. Silicate particles will serve as surfaces on which thin water ice mantles can accrete. The particles will move repeatedly through a high-voltage spark discharge in microgravity, enabling chemical re-actions analogous to the original Miller-Urey experiment. The experiment will be performed at low temperatures (-5 C), slowing hydrolysis and improving chances of detection of interme-diates, initial products, and their distributions. Executing the Miller-Urey experiment in the space environment (microgravity) allows us to simulate conditions that could have prevailed in the energetic early solar nebula and provides insights into the chemical pathways that may occur in forming planetary systems. Analysis will be performed post-flight using chemical analytical methods. The anticipated results will provide information about chemical reaction pathways to form organic compounds in space environment, emphasizing abiotic chemical pathways and mechanisms that could have been crucial in the formation of biologically relevant compounds such as amino acids and

  4. Studies of Constraints from the Terrestrial Planets, Asteroid Belt and Giant Planet Obliquities on the Early Solar System Instability

    Science.gov (United States)

    Nesvorny, David

    The planetary instability has been invoked as a convenient way to explain several observables in the present Solar System. This theory, frequently referred to under a broad and somewhat ill-defined umbrella as the ‘Nice model’, postulates that at least one of the ice giants suffered scattering encounters with Jupiter and Saturn. This could explain several things, including the excitation of the proper eccentric mode in Jupiter's orbit, survival of the terrestrial planets during giant planet migration, and, if the instability was conveniently delayed, also the Late Heavy Bombardment of the Moon. These properties/events would be unexpected if the migration histories of the outer planets were ideally smooth (at least no comprehensive model has yet been fully developed to collectively explain them). Additional support for the planetary instability comes from the dynamical properties of the asteroid and Kuiper belts, Trojans, and planetary satellites. We created a large database of dynamical evolutions of the outer planets through and 100 Myr past the instability (Nesvorny and Morbidelli 2012. Many of these dynamical histories have been found to match constraints from the orbits of the outer planets themselves. We now propose to test these different scenarios using constraints from the terrestrial planets, asteroid belt and giant planet obliquities. As we explain in the proposal narrative, we will bring all these constraints together in an attempt to develop a comprehensive model of early Solar System's evolution. This will be a significant improvement over the past work, where different constraints were considered piecewise and in various approximations. Our work has the potential to generate support for the Nice-type instability, or to rule it out, which could help in sparking interest in developing better models. RELEVANCE The proposed research is fundamental to understanding the formation and early evolution of the Solar System. This is a central theme of NASA

  5. The Moon as a recorder of organic evolution in the early solar system: a lunar regolith analog study.

    Science.gov (United States)

    Matthewman, Richard; Court, Richard W; Crawford, Ian A; Jones, Adrian P; Joy, Katherine H; Sephton, Mark A

    2015-02-01

    The organic record of Earth older than ∼3.8 Ga has been effectively erased. Some insight is provided to us by meteorites as well as remote and direct observations of asteroids and comets left over from the formation of the Solar System. These primitive objects provide a record of early chemical evolution and a sample of material that has been delivered to Earth's surface throughout the past 4.5 billion years. Yet an effective chronicle of organic evolution on all Solar System objects, including that on planetary surfaces, is more difficult to find. Fortunately, early Earth would not have been the only recipient of organic matter-containing objects in the early Solar System. For example, a recently proposed model suggests the possibility that volatiles, including organic material, remain archived in buried paleoregolith deposits intercalated with lava flows on the Moon. Where asteroids and comets allow the study of processes before planet formation, the lunar record could extend that chronicle to early biological evolution on the planets. In this study, we use selected free and polymeric organic materials to assess the hypothesis that organic matter can survive the effects of heating in the lunar regolith by overlying lava flows. Results indicate that the presence of lunar regolith simulant appears to promote polymerization and, therefore, preservation of organic matter. Once polymerized, the mineral-hosted newly formed organic network is relatively protected from further thermal degradation. Our findings reveal the thermal conditions under which preservation of organic matter on the Moon is viable.

  6. Measurement of the 33S(\\alpha,p)36Cl cross section: Implications for production of 36Cl in the early Solar System

    OpenAIRE

    Bowers, Matthew; Kashiv, Yoav; Bauder, William; Beard, Mary; Collon, Philippe; Lu, Wenting; Ostdiek, Karen; Robertson, Daniel

    2013-01-01

    Short-lived radionuclides (SLRs) with lifetimes \\tau < 100 Ma are known to have been extant when the Solar System formed over 4.5 billion years ago. Identifying the sources of SLRs is important for understanding the timescales of Solar System formation and processes that occurred early in its history. Extinct 36Cl (t_1/2 = 0.301 Ma) is thought to have been produced by interaction of solar energetic particles (SEPs), emitted by the young Sun, with gas and dust in the nascent Solar System. Howe...

  7. The Chandra Planetary Nebula Survey (ChanPlaNS). II. X-ray Emission from Compact Planetary Nebulae

    CERN Document Server

    Freeman, M; Montez, R; Balick, B; Frew, D J; Jones, D; Miszalski, B; Sahai, R; Blackman, E; Chu, Y -H; De Marco, O; Frank, A; Guerrero, M A; Lopez, J A; Zijlstra, A; Bujarrabal, V; Corradi, R L M; Nordhaus, J; Parker, Q A; Sandin, C; Schönberner, D; Soker, N; Sokoloski, J L; Steffen, M; Toalá, J A; Ueta, T; Villaver, E

    2014-01-01

    We present results from the most recent set of observations obtained as part of the Chandra X-ray observatory Planetary Nebula Survey (ChanPlaNS), the first comprehensive X-ray survey of planetary nebulae (PNe) in the solar neighborhood (i.e., within ~1.5 kpc of the Sun). The survey is designed to place constraints on the frequency of appearance and range of X-ray spectral characteristics of X-ray-emitting PN central stars and the evolutionary timescales of wind-shock-heated bubbles within PNe. ChanPlaNS began with a combined Cycle 12 and archive Chandra survey of 35 PNe. ChanPlaNS continued via a Chandra Cycle 14 Large Program which targeted all (24) remaining known compact (R_neb ~1000 cm^-3), and rarely associated with PNe that show H_2 emission and/or pronounced butterfly structures. Hb 5 is one such exception of a PN with a butterfly structure that hosts diffuse X-ray emission. Additionally, of the five new diffuse X-ray detections, two host [WR]-type CSPNe, NGC 1501 and NGC 6369, supporting the hypothes...

  8. The Chandra planetary nebula survey (CHANPLANS). II. X-ray emission from compact planetary nebulae

    Energy Technology Data Exchange (ETDEWEB)

    Freeman, M.; Kastner, J. H. [Center for Imaging Science and Laboratory for Multiwavelength Astrophysics, Rochester Institute of Technology, 54 Lomb Memorial Drive, Rochester, NY 14623 (United States); Montez, R. Jr. [Department of Physics and Astronomy, Vanderbilt University, Nashville, TN (United States); Balick, B. [Department of Astronomy, University of Washington, Seattle, WA (United States); Frew, D. J.; De Marco, O.; Parker, Q. A. [Department of Physics and Astronomy and Macquarie Research Centre for Astronomy, Astrophysics and Astrophotonics, Macquarie University, Sydney, NSW 2109 (Australia); Jones, D. [Departamento de Física, Universidad de Atacama, Copayapu 485, Copiapó (Chile); Miszalski, B. [South African Astronomical Observatory, P.O. Box 9, Observatory, 7935 (South Africa); Sahai, R. [Jet Propulsion Laboratory, MS 183-900, California Institute of Technology, Pasadena, CA 91109 (United States); Blackman, E.; Frank, A. [Department of Physics and Astronomy, University of Rochester, Rochester, NY (United States); Chu, Y.-H. [Department of Astronomy, University of Illinois at Urbana-Champaign, Urbana, IL (United States); Guerrero, M. A. [Instituto de Astrofísica de Andalucía, IAA-CSIC, Glorieta de la Astronomía s/n, Granada, E-18008 (Spain); Lopez, J. A. [Instituto de Astronomía, Universidad Nacional Autonoma de Mexico, Campus Ensenada, Apdo. Postal 22860, Ensenada, B. C. (Mexico); Zijlstra, A. [School of Physics and Astronomy, University of Manchester, Manchester M13 9PL (United Kingdom); Bujarrabal, V. [Instituto de Astrofísica de Canarias, E-38200 La Laguna, Tenerife (Spain); Corradi, R. L. M. [Departamento de Astrofísica, Universidad de La Laguna, E-38206 La Laguna, Tenerife (Spain); Nordhaus, J. [NSF Astronomy and Astrophysics Fellow, Center for Computational Relativity and Gravitation, Rochester Institute of Technology, Rochester, NY 14623 (United States); and others

    2014-10-20

    We present results from the most recent set of observations obtained as part of the Chandra X-ray observatory Planetary Nebula Survey (CHANPLANS), the first comprehensive X-ray survey of planetary nebulae (PNe) in the solar neighborhood (i.e., within ∼1.5 kpc of the Sun). The survey is designed to place constraints on the frequency of appearance and range of X-ray spectral characteristics of X-ray-emitting PN central stars and the evolutionary timescales of wind-shock-heated bubbles within PNe. CHANPLANS began with a combined Cycle 12 and archive Chandra survey of 35 PNe. CHANPLANS continued via a Chandra Cycle 14 Large Program which targeted all (24) remaining known compact (R {sub neb} ≲ 0.4 pc), young PNe that lie within ∼1.5 kpc. Results from these Cycle 14 observations include first-time X-ray detections of hot bubbles within NGC 1501, 3918, 6153, and 6369, and point sources in HbDs 1, NGC 6337, and Sp 1. The addition of the Cycle 14 results brings the overall CHANPLANS diffuse X-ray detection rate to ∼27% and the point source detection rate to ∼36%. It has become clearer that diffuse X-ray emission is associated with young (≲ 5 × 10{sup 3} yr), and likewise compact (R {sub neb} ≲ 0.15 pc), PNe with closed structures and high central electron densities (n{sub e} ≳ 1000 cm{sup –3}), and is rarely associated with PNe that show H{sub 2} emission and/or pronounced butterfly structures. Hb 5 is one such exception of a PN with a butterfly structure that hosts diffuse X-ray emission. Additionally, two of the five new diffuse X-ray detections (NGC 1501 and NGC 6369) host [WR]-type central stars, supporting the hypothesis that PNe with central stars of [WR]-type are likely to display diffuse X-ray emission.

  9. Mass independent sulfur isotope signatures in CMs: Implications for sulfur chemistry in the early solar system

    Science.gov (United States)

    Labidi, J.; Farquhar, J.; Alexander, C. M. O.'D.; Eldridge, D. L.; Oduro, H.

    2017-01-01

    We have investigated the quadruple sulfur isotopic composition of inorganic sulfur-bearing phases from 13 carbonaceous chondrites of CM type. Our samples include 4 falls and 9 Antarctic finds. We extracted sulfur from sulfides, sulfates, and elemental sulfur (S0) from all samples. On average, we recover a bulk sulfur (S) content of 2.11 ± 0.39 wt.% S (1σ). The recovered sulfate, S0 and sulfide contents represent 25 ± 12%, 10 ± 7% and 65 ± 15% of the bulk S, respectively (all 1σ). There is no evidence for differences in the bulk S content between falls and finds, and there is no correlation between the S speciation and the extent of aqueous alteration. We report ranges of Δ33S and Δ36S values in CMs that are significantly larger than previously observed. The largest variations are exhibited by S0, with Δ33S values ranging between -0.104 ± 0.012‰ and +0.256 ± 0.018‰ (2σ). The Δ36S/33S ratios of S0 are on average -3.1 ± 1.0 (2σ). Two CMs show distinct Δ36S/33S ratios, of +1.3 ± 0.1 and +0.9 ± 0.1. We suggest that these mass independent S isotopic compositions record H2S photodissociation in the nebula. The varying Δ36S/Δ33S ratios are interpreted to reflect photodissociation that occurred at different UV wavelengths. The preservation of these isotopic features requires that the S-bearing phases were heterogeneously accreted to the CM parent body. Non-zero Δ33S values are also preserved in sulfide and sulfate, and are positively correlated with S0 values. This indicates a genetic relationship between the S-bearing phases: We argue that sulfates were produced by the direct oxidation of S0 (not sulfide) in the parent body. We describe two types of models that, although imperfect, can explain the major features of the CM S isotope compositions, and can be tested in future studies. Sulfide and S0 could both be condensates from the nebula, as the residue and product, respectively, of incomplete H2S photodissociation by UV light (wavelength H2S

  10. Spitzer Space Telescope Infrared Imaging and Spectroscopy of the Crab Nebula

    CERN Document Server

    Temim, T; Woodward, C E; Roellig, T L; Smith, N; Rudnick, L R; Polomski, E F; Davidson, K; Yuen, L; Onaka, T; Temim, Tea; Gehrz, Robert D.; Woodward, Charles E.; Roellig, Thomas L.; Smith, Nathan; Rudnick, Lawrence R.; Polomski, Elisha F.; Davidson, Kris; Yuen, Lunming; Onaka, Takashi

    2006-01-01

    We present 3.6, 4.5, 5.8, 8.0, 24, and 70 micron images of the Crab Nebula obtained with the Spitzer Space Telescope IRAC and MIPS cameras, Low- and High-resolution Spitzer IRS spectra of selected positions within the nebula, and a near-infrared ground-based image made in the light of [Fe II]1.644 micron. The 8.0 micron image, made with a bandpass that includes [Ar II]7.0 micron, resembles the general morphology of visible H-alpha and near-IR [Fe II] line emission, while the 3.6 and 4.5 micron images are dominated by continuum synchrotron emission. The 24 micron and 70 micron images show enhanced emission that may be due to line emission or the presence of a small amount of warm dust in the nebula on the order of less than 1% of a solar mass. The ratio of the 3.6 and 4.5 micron images reveals a spatial variation in the synchrotron power law index ranging from approximately 0.3 to 0.8 across the nebula. Combining this information with optical and X-ray synchrotron images, we derive a broadband spectrum that re...

  11. Aftermath of early Hit-and-Run collisions in the Inner Solar System

    Science.gov (United States)

    Sarid, Gal; Stewart, Sarah T.; Leinhardt, zoe M.

    2015-08-01

    Planet formation epoch, in the terrestrial planet region and the asteroid belt, was characterized by a vigorous dynamical environment that was conducive to giant impacts among planetary embryos and asteroidal parent bodies, leading to diverse outcomes. Among these the greatest potential for producing diverse end-members lies is the erosive Hit-and-Run regime (small mass ratios, off-axis oblique impacts and non-negligible ejected mass), which is also more probable in terms of the early dynamical encounter configuration in the inner solar system. This collision regime has been invoked to explain outstanding issues, such as planetary volatile loss records, origin of the Moon and mantle stripping from Mercury and some of the larger asteroids (Vesta, Psyche).We performed and analyzed a set of simulations of Hit-and-Run events, covering a large range of mass ratios (1-20), impact parameters (0.25-0.96, for near head-on to barely grazing) and impact velocities (~1.5-5 times the mutual escape velocity, as dependent on the mass ratio). We used an SPH code with tabulated EOS and a nominal simlated time >1 day, to track the collisional shock processing and the provenance of material components. of collision debris. Prior to impact runs, all bodies were allowed to initially settle to negligible particle velocities in isolation, within ~20 simulated hrs. The total number of particles involved in each of our collision simulations was between (1-3 x 105). Resulting configurations include stripped mantles, melting/vaporization of rock and/or iron cores and strong variations of asteroid parent bodies fromcanonical chondritic composition.In the context of large planetary formation simulations, velocity and impact angle distributions are necessary to asses impact probabilities. The mass distribution and interaction within planetary embryo and asteroid swarms depends both on gravitational dynamics and the applied fragmentation mechanism. We will present results pertaining to general

  12. Geminga's puzzling pulsar wind nebula

    CERN Document Server

    Posselt, B; Slane, P O; Romani, R; Bucciantini, N; Bykov, A M; Kargaltsev, O; Weisskopf, M C; Ng, C -Y

    2016-01-01

    We report on six new Chandra observations of the Geminga pulsar wind nebula (PWN). The PWN consists of three distinct elongated structures - two $\\approx 0.2 d_{250}$ pc long lateral tails and a segmented axial tail of $\\approx 0.05 d_{250}$ pc length, where $d_{250}=d/(250 {\\rm pc})$. The photon indices of the power law spectra of the lateral tails, $\\Gamma \\approx 1$, are significantly harder than those of the pulsar ($\\Gamma \\approx 1.5$) and the axial tail ($\\Gamma \\approx 1.6$). There is no significant diffuse X-ray emission between the lateral tails -- the ratio of the X-ray surface brightness between the south tail and this sky area is at least 12. The lateral tails apparently connect directly to the pulsar and show indication of moving footpoints. The axial tail comprises time-variable emission blobs. However, there is no evidence for constant or decelerated outward motion of these blobs. Different physical models are consistent with the observed morphology and spectra of the Geminga PWN. In one scena...

  13. Unveiling shocks in planetary nebulae

    CERN Document Server

    Guerrero, M A; Medina, J J; Luridiana, V; Miranda, L F; Riera, A; Velázquez, P F

    2013-01-01

    The propagation of a shock wave into a medium is expected to heat the material beyond the shock, producing noticeable effects in intensity line ratios such as [O III]/Halpha. To investigate the occurrence of shocks in planetary nebulae (PNe), we have used all narrowband [O III] and Halpha images of PNe available in the HST archive to build their [O III]/Halpha ratio maps and to search for regions where this ratio is enhanced. Regions with enhanced [O III]/Halpha emission ratio can be ascribed to two different types of morphological structures: bow-shock structures produced by fast collimated outflows and thin skins enveloping expanding nebular shells. Both collimated outflows and expanding shells are therefore confirmed to generate shocks in PNe. We also find regions with depressed values of the [O III]/Halpha ratio which are found mostly around density bounded PNe, where the local contribution of [N II] emission into the F656N Halpha filter cannot be neglected.

  14. The Crab Nebula flaring activity

    Directory of Open Access Journals (Sweden)

    G. Montani

    2014-12-01

    Full Text Available The discovery made by AGILE and Fermi of a short time scale flaring activity in the gamma-ray energy emission of the Crab Nebula is a puzzling and unexpected feature, challenging particle acceleration theory. In the present work we propose the shock-induced magnetic reconnection as a viable mechanism to explain the Crab flares. We postulate that the emitting region is located at ∼1015 cm from the central pulsar, well inside the termination shock, which is exactly the emitting region size as estimated by the overall duration of the phenomenon ∼1 day. We find that this location corresponds to the radial distance at which the shock-induced magnetic reconnection process is able to accelerate the electrons up to a Lorentz factor ∼109, as required by the spectral fit of the observed Crab flare spectrum. The main merit of the present analysis is to highlight the relation between the observational constraints to the flare emission and the radius at which the reconnection can trigger the required Lorentz factor. We also discuss different scenarios that can induce the reconnection. We conclude that the existence of a plasma instability affecting the wind itself as the Weibel instability is the privileged scenario in our framework.

  15. The Crab Nebula flaring activity

    Energy Technology Data Exchange (ETDEWEB)

    Montani, G., E-mail: giovanni.montani@frascati.enea.it [ENEA – C.R, UTFUS-MAG, via Enrico Fermi 45, I-00044 Frascati (RM) (Italy); Dipartimento di Fisica, Università di Roma “Sapienza”, p.le Aldo Moro 5, I-00185 Roma (Italy); Bernardini, M.G. [INAF – Osservatorio Astronomico di Brera, via Bianchi 46, I-23807 Merate (Italy)

    2014-12-12

    The discovery made by AGILE and Fermi of a short time scale flaring activity in the gamma-ray energy emission of the Crab Nebula is a puzzling and unexpected feature, challenging particle acceleration theory. In the present work we propose the shock-induced magnetic reconnection as a viable mechanism to explain the Crab flares. We postulate that the emitting region is located at ∼10{sup 15} cm from the central pulsar, well inside the termination shock, which is exactly the emitting region size as estimated by the overall duration of the phenomenon ∼1 day. We find that this location corresponds to the radial distance at which the shock-induced magnetic reconnection process is able to accelerate the electrons up to a Lorentz factor ∼10{sup 9}, as required by the spectral fit of the observed Crab flare spectrum. The main merit of the present analysis is to highlight the relation between the observational constraints to the flare emission and the radius at which the reconnection can trigger the required Lorentz factor. We also discuss different scenarios that can induce the reconnection. We conclude that the existence of a plasma instability affecting the wind itself as the Weibel instability is the privileged scenario in our framework.

  16. Accretion and early evolution of Earth

    DEFF Research Database (Denmark)

    Saji, Nikitha Susan

    -stage impacts had to play in determining the bulk composition as well as pace of the chemical dierentiation and internal dynamics of terrestrial planets - is preserved in the form of isotopic signatures in some of the oldest terrestrial and extraterrestrial samples available to us. A potential means to unravel...... this is by the application of Nd-isotope systematics as the coupled 146;147Sm - 143;142Nd decay system enables the study of chronology of planetary silicate mantles while the stable Nd-isotopes help track the origin and early transport of material. Deciphering this information, however, requires the analytical capability...... in solar system materials is found to be related to selective thermal processing of dust in the early nebula given the correlation observed for these eects with Fe-peak neutron-rich isotope anomalies, whose origin is attributed to distinct nucleosnythetic sites other than classical s-, r- or p...

  17. The reconnaissance and early-warning optical system design for dual field of space-based "solar blind ultraviolet"

    Science.gov (United States)

    Wang, Wen-cong; Jin, Dong-dong; Shao, Fei; Hu, Hui-jun; Shi, Yu-feng; Song, Juan; Zhang, Yu-tu; Yong, Liu

    2016-07-01

    With the development of modern technology, especially the development of information technology at high speed, the ultraviolet early warning system plays an increasingly important role. In the modern warfare, how to detect the threats earlier, prevent and reduce the attack of precision-guided missile has become a new challenge. Because the ultraviolet warning technology has high environmental adaptability, the low false alarm rate, small volume and other advantages, in the military field applications it has been developed rapidly. According to current application demands for solar blind ultraviolet detection and warning, this paper proposes a reconnaissance and early-warning optical system, which covers solar blind ultraviolet (250nm-280nm) and dual field. This structure takes advantage of a narrow field of view and long focal length optical system to achieve the target object detection, uses wide-field and short focal length optical system to achieve early warning of the target object. It makes use of an ultraviolet beam-splitter to achieve the separation of two optical systems. According to the detector and the corresponding application needs of two visual field of the optical system, the calculation and optical system design were completed. After the design, the MTF of the two optical system is more than 0.8@39lp/mm. A single pixel energy concentration is greater than 80%.

  18. Hydroxyl Emission in the Westbrook Nebula

    Science.gov (United States)

    Strack, Angelica; Araya, Esteban; Ghosh, Tapasi; Arce, Hector G.; Lebron, Mayra E.; Salter, Christopher J.; Minchin, Robert F.; Pihlstrom, Ylva; Kurtz, Stan; Hofner, Peter; Olmi, Luca

    2016-06-01

    CRL 618, also known as the Westbrook Nebula, is a carbon-rich pre-planetary nebula. Hydroxyl (OH) transitions are typically not detected in carbon-rich late-type stellar objects, however observations conducted with the 305m Arecibo Telescope in 2008 resulted in the detection of 4765 MHz OH emission in CRL 618. We present results of observations carried out a few months after the original detection that confirm the line. This is the first detection of 4765 MHz OH emission (most likely a maser) in a pre-planetary nebula. Follow up observations conducted in 2015 resulted in non-detection of the 4765 MHz OH transition. This behavior is consistent with the high level of variability of excited OH lines that have been detected toward a handful of other pre-planetary nebulae. Our work supports that excited OH masers are short-lived during the pre-planetary nebula phase. We also conducted a search for other OH transitions from 1612 MHz to 8611 MHz with the Arecibo Telescope; we report no other detections at rms levels of ~5 mJy.This work has made use of the computational facilities donated by Frank Rodeffer to the WIU Astrophysics Research Laboratory. We also acknowledge support from M. & C. Wong RISE scholarships and a grant from the WIU College of Arts and Sciences.

  19. Properties and geoeffectiveness of magnetic clouds in the rising, maximum and early declining phases of solar cycle 23

    Directory of Open Access Journals (Sweden)

    K. E. J. Huttunen

    2005-02-01

    Full Text Available The magnetic structure and geomagnetic response of 73 magnetic clouds (MC observed by the WIND and ACE satellites in solar cycle 23 are examined. The results have been compared with the surveys from the previous solar cycles. The preselected candidate MC events were investigated using the minimum variance analysis to determine if they have a flux-rope structure and to obtain the estimation for the axial orientation (θC, φC. Depending on the calculated inclination relative to the ecliptic we divided MCs into "bipolar" (θC<45° and "unipolar" (θC>45°. The number of observed MCs was largest in the early rising phase, although the halo CME rate was still low. It is likely that near solar maximum we did not identify all MCs at 1AU, as they were crossed far from the axis or they had interacted strongly with the ambient solar wind or with other CMEs. The occurrence rate of MCs at 1AU is also modified by the migration of the filament sites on the Sun towards the poles near solar maximum and by the deflection of CMEs towards the equator due to the fast solar wind flow from large polar coronal holes near solar minimum. In the rising phase nearly all bipolar MCs were associated with the rotation of the magnetic field from the south at the leading edge to the north at the trailing edge. The results for solar cycles 21-22 showed that the direction of the magnetic field in the leading portion of the MC starts to reverse at solar maximum. At solar maximum and in the declining phase (2000-2003 we observed several MCs with the rotation from the north to the south. We observed unipolar (i.e. highly inclined MCs frequently during the whole investigated period. For solar cycles 21-22 the majority of MCs identified in the rising phase were bipolar while in the declining phase most MCs were unipolar. The geomagnetic response of a given MC depends greatly on its magnetic structure and the orientation of the sheath

  20. The Radio Spectral Index of the Crab Nebula

    Science.gov (United States)

    1997-11-20

    We present the results of a new, comprehensive investigation of the radio spectral index of the Crab Nebula supernova remnant. New data at 74 MHz are...thermal material in the Crab Nebula’s filaments. Apart from some possible renewed acceleration occurring in the wisps, the dominant accelerator of relativistic electrons in the Crab Nebula is the pulsar itself.

  1. Planetary nebulae as kinematic tracers of galaxy stellar halos

    CERN Document Server

    Coccato, Lodovico

    2016-01-01

    The kinematic and dynamical properties of galaxy stellar halos are difficult to measure because of the faint surface brightness that characterizes these regions. Spiral galaxies can be probed using the radio HI emission; on the contrary, early-type galaxies contain less gas, therefore alternative kinematic tracers need to be used. Planetary nebulae (PNe) can be easily detected far out in the halo thanks to their bright emission lines. It is therefore possible to map the halo kinematics also in early-type galaxies, typically out to 5 effective radii or beyond. Thanks to the recent spectroscopic surveys targeting extra-galactic PNe, we can now rely on a few tens of galaxies where the kinematics of the stellar halos are measured. Here, I will review the main results obtained in this field in the last decades.

  2. Most Detailed Image of the Crab Nebula

    Science.gov (United States)

    2005-01-01

    This new Hubble image -- one among the largest ever produced with the Earth-orbiting observatory -- shows the most detailed view so far of the entire Crab Nebula ever made. The Crab is arguably the single most interesting object, as well as one of the most studied, in all of astronomy. The image is the largest image ever taken with Hubble's WFPC2 workhorse camera. The Crab Nebula is one of the most intricately structured and highly dynamical objects ever observed. The new Hubble image of the Crab was assembled from 24 individual exposures taken with the NASA/ESA Hubble Space Telescope and is the highest resolution image of the entire Crab Nebula ever made.

  3. Monitoring the Crab Nebula with LOFT

    Science.gov (United States)

    Wilson-Hodge, Colleen A.

    2012-01-01

    From 2008-2010, the Crab Nebula was found to decline by 7% in the 15-50 keV band, consistently in Fermi GBM, INTEGRAL IBIS, SPI, and JEMX, RXTE PCA, and Swift BAT. From 2001-2010, the 15-50 keV flux from the Crab Nebula typically varied by about 3.5% per year. Analysis of RXTE PCA data suggests possible spectral variations correlated with the flux variations. I will present estimates of the LOFT sensitivity to these variations. Prior to 2001 and since 2010, the observed flux variations have been much smaller. Monitoring the Crab with the LOFT WFM and LAD will provide precise measurements of flux variations in the Crab Nebula if it undergoes a similarly active episode.

  4. High energy neutrinos from pulsar wind nebulae

    Science.gov (United States)

    Di Palma, Irene

    2017-09-01

    Several Pulsar Wind Nebulae have been detected in the TeV band in the last decade.The TeV emission is typically interpreted in a purely leptonic scenario, but this usually requires that the magnetic field in the Nebula be much lower than the equipartition value and the assumption of an enhanced target radiation at IR frequencies. In this work we consider the possibility that, in addition to the relativistic electrons, also relativistic hadrons are present in these nebulae. Assuming that part of the emitted TeV photons are of hadronic origin, we compute the associated flux of ∼ 1 ‑ 100 TeV neutrinos. We use the IceCube non detection to put constraints on the fraction of TeV photons that might be contributed by hadrons and estimate the number of neutrino events that can be expected from these sources in IceCube, ANTARES and in KM3Net.

  5. Highlighting the history of Japanese radio astronomy. 4: early solar research in Osaka

    Science.gov (United States)

    Orchiston, Wayne; Nakamura, Tsuko; Ishiguro, Masato

    2016-12-01

    For about two years, from late 1949, Minoru Oda and Tatsuo Takakura carried out solar observations from Osaka, initially with a hand-made horn and later with a small parabolic antenna connected to a 3.3 GHz receiver, but they only published one short paper on this work. At about the same time, Ojio and others at Osaka City University presented the concept of a solar grating array at a meeting of the Japan Physical Society, but this was never built. In this paper, we provide brief biographical accounts of Oda and Takakura before examining their radio telescopes and the observations that they made. We also briefly discuss the proposed Japanese solar grating array.

  6. The net-zero building 'Solar 2002': Learning from an early example

    OpenAIRE

    Claes, Koen; Klein, Ralf; De Couvreur, Guido Henri; Versele, Alexis; Breesch, Hilde

    2010-01-01

    This paper describes the “Solar 2002" building in Berlaar (Belgium) that was constructed by the Flemish non-profit organization mondo vzw. The aim of this retro-fit of an existing single family dwelling was the creation of an example project, demonstrating the potential of solar energy for the energy needs of buildings in a moderate, rather cloudy climate. This has led to a “Net-Zero Energy" building, that finally supplies more energy to the grid, then it consumes on an annual basis. While t...

  7. Re-measurement of the 33S(α ,p )36Cl cross section for early solar system nuclide enrichment

    Science.gov (United States)

    Anderson, Tyler; Skulski, Michael; Clark, Adam; Nelson, Austin; Ostdiek, Karen; Collon, Philippe; Chmiel, Greg; Woodruff, Tom; Caffee, Marc

    2017-07-01

    Short-lived radionuclides (SLRs) with half-lives less than 100 Myr are known to have existed around the time of the formation of the solar system around 4.5 billion years ago. Understanding the production sources for SLRs is important for improving our understanding of processes taking place just after solar system formation as well as their timescales. Early solar system models rely heavily on calculations from nuclear theory due to a lack of experimental data for the nuclear reactions taking place. In 2013, Bowers et al. measured 36Cl production cross sections via the 33S(α ,p ) reaction and reported cross sections that were systematically higher than predicted by Hauser-Feshbach codes. Soon after, a paper by Peter Mohr highlighted the challenges the new data would pose to current nuclear theory if verified. The 33S(α ,p )36Cl reaction was re-measured at five energies between 0.78 MeV/nucleon and 1.52 MeV/nucleon, in the same range as measured by Bowers et al., and found systematically lower cross sections than originally reported, with the new results in good agreement with the Hauser-Feshbach code talys. Loss of Cl carrier in chemical extraction and errors in determination of reaction energy ranges are both possible explanations for artificially inflated cross sections measured in the previous work.

  8. Towards a Solution to the Early Faint Sun Paradox: A Lower Cosmic Ray Flux from a Stronger Solar Wind

    CERN Document Server

    Shaviv, N J

    2003-01-01

    The solar luminosity obtained in standard solar models should have gradually increased by about 30% over the past 4.5 billion years. Under the faint sun, Earth should have been frozen solid for most of its existence. Yet, running water is observed to have been present since very early in Earth's history. This enigma is known as the faint sun paradox. We show here that it can be significantly extenuated once we consider the cooling effect that cosmic rays are suspected to have on the global climate and that the younger sun must have had a stronger solar wind, such that it was more effective at stopping cosmic rays from reaching Earth. We therefore find that even modest greenhouse warming in sufficient to completely resolve the paradox. When coupled to the variable star formation rate in the Milky Way, we recover that the past Eon and the Eon between 2 and 3 Gyr before present should have had glaciations, while others not. As to the future, we find that without human intervention, the average global temperature...

  9. Ultraviolet studies of the Crab Nebula

    Science.gov (United States)

    Talavera, A.

    2017-03-01

    The Crab Nebula (Messier 1) is one of the most observed sources with the XMM-Newton space telescope of ESA. The Crab and its related pulsar are a calibration source for the on-board X-rays cameras. There are around 80 observations between 2000 and 2015. In this observations, the XMM-Newton Optical and UV Monitor (OM) has also been used. We present a preliminary study of the Crab using images obtained the OM UV filters at 291, 231 and 212 nm. Photometric data for the pulsar (PSR0531+21), created in the supernova event of AD 1054 origin of the nebula, are also presented

  10. Dust Extinction in Compact Planetary Nebulae

    OpenAIRE

    Lee, TH; Kwok, S.

    2005-01-01

    The effects of dust extinction on the departure from axisymmetry in the morphology of planetary nebulae (PNs) are investigated through a comparison of the radio free-free emission and hydrogen recombination line images. The dust extinction maps from five compact PNs are derived using high-resolution (̃0"1) Hα and radio maps of the HST and VLA. These extinction maps are then analyzed by an ellipsoidal shell ionization model including the effects of dust extinction to infer the nebulae's intrin...

  11. Stars and Nebulae in the Southern Crown

    Science.gov (United States)

    2000-10-01

    The R Coronae Australis complex of young stars and interstellar gas clouds is one of the nearest star-forming regions, at a distance of approx. 500 light-years from the Sun. It is seen in the southern constellation of that name (The "Southern Crown"). Images of this sky area were recently obtained with the Wide Field Imager (WFI) , a 67-million pixel digital camera that is installed at the 2.2-m MPG/ESO Telescope at ESO's La Silla Observatory. Some of these exposures have been combined into a magnificent colour image, here reproduced as PR Photo 25a/00 . The field shown measures about 4.7 x 4.7 light-years 2. It displays the central part of the complex, its brightest stars, and the nebulosity that they illuminate. The interstellar clouds that are associated with the complex are visible all across this field and also beyond its borders (on other exposures), due to the obscuring effect of the dust particles that "dim" the light of stars behind these clouds. This effect is particularly noticeable in the lower left corner where very few stars are seen. R Coronae Australis , the bright star from which the entire complex is named, is located at the center of the field and illuminates the reddish nebula around it. The bright star in the lower part, illuminating a somewhat bluer nebula, is known as TY Coronae Australis . The brightness of these two stars and several others in the same field is variable. They belong to the so-called "T Tauri" class , a type that is quite common in star-forming regions. T Tauri stars are in the early stages of stellar evolution and display various observable characteristics of this phase, e.g. emission at visible and infrared wavelengths due to the accretion of matter left over from their formation, as well as X-ray emission. The nebulosity seen in this picture is mostly due to reflection of the stellar light by small dust particles. The stars in the R Coronae Australis complex do not emit sufficient ultraviolet light to ionize a substantial

  12. The Fe/Ni ratio in ionized nebulae: clues on dust depletion patterns

    CERN Document Server

    Delgado-Inglada, Gloria; García-Rojas, Jorge; Rodríguez, Mónica; Esteban, César

    2015-01-01

    We perform a homogeneous analysis of the Fe/Ni abundance ratio in eight Galactic planetary nebulae (PNe) and three Galactic H II regions that include the Orion nebula, where we study four nebular zones and one shocked region. We use [Fe ii], [Fe iii], and [Ni iii] lines, and ionization correction factors (ICFs) that account for the unobserved ions. We derive an ICF for nickel from an extensive grid of photoionization models. We compare our results with those derived by other authors for 16 neutral clouds in the solar neighbourhood with available Fe/Ni ratios in the literature. We find an excellent agreement between the ionized nebulae and the diffuse clouds, with both types of regions showing a clear correlation between the Fe/Ni ratios and the iron and nickel depletion factors. The trend shows that the objects with a relatively low depletion have near solar Fe/Ni ratios whereas at higher depletions the Fe/Ni ratio increases with the depletion. Our results confirm that, compared to iron atoms, nickel ones are...

  13. The Integral Field View of the Orion Nebula

    Directory of Open Access Journals (Sweden)

    Adal Mesa-Delgado

    2014-01-01

    Full Text Available This paper reviews the major advances achieved in the Orion Nebula through the use of integral field spectroscopy (IFS. Since the early work of Vasconcelos and collaborators in 2005, this technique has facilitated the investigation of global properties of the nebula and its morphology, providing new clues to better constrain its 3D structure. IFS has led to the discovery of shock-heated zones at the leading working surfaces of prominent Herbig-Haro objects as well as the first attempt to determine the chemical composition of Orion protoplanetary disks, also known as proplyds. The analysis of these morphologies using IFS has given us new insights into the abundance discrepancy problem, a long-standing and unresolved issue that casts doubt on the reliability of current methods used for the determination of metallicities in the universe from the analysis of H II regions. Results imply that high-density clumps and high-velocity flows may play an active role in the production of such discrepancies. Future investigations based on the large-scale IFS mosaic of Orion will be very valuable for exploring how the integrated effect of small-scale structures may have impact at larger scales in the framework of star-forming regions.

  14. The Integral Field View of the Orion Nebula

    CERN Document Server

    Mesa-Delgado, Adal

    2013-01-01

    This paper reviews the major advances achieved in the Orion Nebula through the use of integral field spectroscopy (IFS). Since the early work of Vasconcelos and collaborators in 2005, the capability of this technique has allowed to investigate the global properties of the nebula and its internal morphologies, providing new clues to constrain a better picture of its 3D structure. This spectroscopic technique has permitted the discovery of shock-heated zones at the leading working surfaces of prominent Herbig-Haro objects as well as the first attempt to determine the chemical composition of Orion protoplanetary disks, also known as proplyds. The analysis of these morphologies using IFS has given us new insights into the abundance discrepancy problem, a long-standing and unresolved issue that threatens the reliability of our current methods of determining metallicities in the Universe from the analysis of HII regions. Results imply that high-density clumps and high-velocity flows may play an active role in the p...

  15. Origin and Early Evolution of Comet Nuclei Workshop honouring Johannes Geiss on the occasion of his 80th birthday

    CERN Document Server

    Balsiger, H; Huebner, W; Owen, T; Schulz, R

    2008-01-01

    Comet nuclei are the most primitive bodies in the solar system. They have been created far away from the early Sun and it is supposed that their material has been altered the least since their formation. This volume presents the results of a scientific workshop on comet nuclei and is written by experts working on interstellar clouds, star-forming regions, the solar nebula, and comets. The articles formulate the current understanding and interconnectivity of the various source regions of comet nuclei and their associated compositions and orbital characteristics. This includes a discussion on the transport of materials into the Kuiper belt and Oort cloud regions of the solar system. The distinction between direct measurements of cometary material properties and properties derived from indirect means are emphasized with the aim to guide future investigations. This book serves as a guide for researchers and graduate students working in the field of planetology and solar system exploration. It should also help to ...

  16. Laboratory drop towers for the experimental simulation of dust-aggregate collisions in the early solar system.

    Science.gov (United States)

    Blum, Jürgen; Beitz, Eike; Bukhari, Mohtashim; Gundlach, Bastian; Hagemann, Jan-Hendrik; Heißelmann, Daniel; Kothe, Stefan; Schräpler, Rainer; von Borstel, Ingo; Weidling, René

    2014-06-05

    For the purpose of investigating the evolution of dust aggregates in the early Solar System, we developed two vacuum drop towers in which fragile dust aggregates with sizes up to ~10 cm and porosities up to 70% can be collided. One of the drop towers is primarily used for very low impact speeds down to below 0.01 m/sec and makes use of a double release mechanism. Collisions are recorded in stereo-view by two high-speed cameras, which fall along the glass vacuum tube in the center-of-mass frame of the two dust aggregates. The other free-fall tower makes use of an electromagnetic accelerator that is capable of gently accelerating dust aggregates to up to 5 m/sec. In combination with the release of another dust aggregate to free fall, collision speeds up to ~10 m/sec can be achieved. Here, two fixed high-speed cameras record the collision events. In both drop towers, the dust aggregates are in free fall during the collision so that they are weightless and match the conditions in the early Solar System.

  17. An Early Diagnostics of the Geoeffectiveness of Solar Eruptions from Photospheric Magnetic Flux Observations: The Transition from SOHO to SDO

    Science.gov (United States)

    Chertok, I. M.; Grechnev, V. V.; Abunin, A. A.

    2017-04-01

    In our previous articles (Chertok et al. in Solar Phys. 282, 175, 2013; Chertok et al. in Solar Phys. 290, 627, 2015), we presented a preliminary tool for the early diagnostics of the geoeffectiveness of solar eruptions based on the estimate of the total unsigned line-of-sight photospheric magnetic flux in accompanying extreme ultraviolet (EUV) arcades and dimmings. This tool was based on the analysis of eruptions observed during 1996 - 2005 with the Extreme-ultraviolet Imaging Telescope (EIT) and the Michelson Doppler Imager (MDI) onboard the Solar and Heliospheric Observatory (SOHO). Empirical relationships were obtained to estimate the probable importance of upcoming space weather disturbances caused by an eruption, which just occurred, without data on the associated coronal mass ejections. In particular, it was possible to estimate the intensity of a non-recurrent geomagnetic storm (GMS) and Forbush decrease (FD), as well as their onset and peak times. After 2010 - 2011, data on solar eruptions are obtained with the Atmospheric Imaging Assembly (AIA) and the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO). We use relatively short intervals of overlapping EIT-AIA and MDI-HMI detailed observations, and additionally, a number of large eruptions over the next five years with the 12-hour cadence EIT images to adapt the SOHO diagnostic tool to SDO data. We show that the adopted brightness thresholds select practically the same areas of arcades and dimmings from the EIT 195 Å and AIA 193 Å image, with a cross-calibration factor of 3.6 - 5.8 (5.0 - 8.2) for the AIA exposure time of 2.0 s (2.9 s). We also find that for the same photospheric areas, the MDI line-of-sight magnetic flux systematically exceeds the HMI flux by a factor of 1.4. Based on these results, the empirical diagnostic relationships obtained from SOHO data are adjusted to SDO instruments. Examples of a post-diagnostics based on SDO data are presented. As before, the

  18. The Chandra Planetary Nebulae Survey (ChanPlaNS): III. X-ray Emission from the Central Stars of Planetary Nebulae

    CERN Document Server

    Montez, R; Balick, B; Behar, E; Blackman, E; Bujarrabal, V; Chu, Y -H; Corradi, R L M; De Marco, O; Frank, A; Freeman, M; Frew, D J; Guerrero, M A; Jones, D; Lopez, J A; Miszalski, B; Nordhaus, J; Parker, Q A; Sahai, R; Sandin, C; Schonberner, D; Soker, N; Sokoloski, J L; Steffen, M; Toalá, J A; Ueta, T; Villaver, E; Zijlstra, A

    2014-01-01

    We present X-ray spectral analysis of 20 point-like X-ray sources detected in Chandra Planetary Nebula Survey (ChanPlaNS) observations of 59 planetary nebulae (PNe) in the solar neighborhood. Most of these 20 detections are associated with luminous central stars within relatively young, compact nebulae. The vast majority of these point-like X-ray-emitting sources at PN cores display relatively "hard" ($\\geq0.5$~keV) X-ray emission components that are unlikely to be due to photospheric emission from the hot central stars (CSPN). Instead, we demonstrate that these sources are well modeled by optically-thin thermal plasmas. From the plasma properties, we identify two classes of CSPN X-ray emission: (1) high-temperature plasmas with X-ray luminosities, $L_{\\rm X}$, that appear uncorrelated with the CSPN bolometric luminosity, $L_{\\rm bol}$; and (2) lower-temperature plasmas with $L_{\\rm X}/L_{\\rm bol}\\sim10^{-7}$. We suggest these two classes correspond to the physical processes of magnetically active binary comp...

  19. THE CHANDRA PLANETARY NEBULA SURVEY (ChanPlaNS). III. X-RAY EMISSION FROM THE CENTRAL STARS OF PLANETARY NEBULAE

    Energy Technology Data Exchange (ETDEWEB)

    Montez, R. Jr. [Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37212 (United States); Kastner, J. H.; Freeman, M. [Center for Imaging Science and Laboratory for Multiwavelength Astrophysics, Rochester Institute of Technology, Rochester, NY 14623 (United States); and others

    2015-02-10

    We present X-ray spectral analysis of 20 point-like X-ray sources detected in Chandra Planetary Nebula Survey observations of 59 planetary nebulae (PNe) in the solar neighborhood. Most of these 20 detections are associated with luminous central stars within relatively young, compact nebulae. The vast majority of these point-like X-ray-emitting sources at PN cores display relatively ''hard'' (≥0.5 keV) X-ray emission components that are unlikely to be due to photospheric emission from the hot central stars (CSPN). Instead, we demonstrate that these sources are well modeled by optically thin thermal plasmas. From the plasma properties, we identify two classes of CSPN X-ray emission: (1) high-temperature plasmas with X-ray luminosities, L {sub X}, that appear uncorrelated with the CSPN bolometric luminosity, L {sub bol} and (2) lower-temperature plasmas with L {sub X}/L {sub bol} ∼ 10{sup –7}. We suggest these two classes correspond to the physical processes of magnetically active binary companions and self-shocking stellar winds, respectively. In many cases this conclusion is supported by corroborative multiwavelength evidence for the wind and binary properties of the PN central stars. By thus honing in on the origins of X-ray emission from PN central stars, we enhance the ability of CSPN X-ray sources to constrain models of PN shaping that invoke wind interactions and binarity.

  20. Galaxy evolution. Quasar quartet embedded in giant nebula reveals rare massive structure in distant universe.

    Science.gov (United States)

    Hennawi, Joseph F; Prochaska, J Xavier; Cantalupo, Sebastiano; Arrigoni-Battaia, Fabrizio

    2015-05-15

    All galaxies once passed through a hyperluminous quasar phase powered by accretion onto a supermassive black hole. But because these episodes are brief, quasars are rare objects typically separated by cosmological distances. In a survey for Lyman-α emission at redshift z ≈ 2, we discovered a physical association of four quasars embedded in a giant nebula. Located within a substantial overdensity of galaxies, this system is probably the progenitor of a massive galaxy cluster. The chance probability of finding a quadruple quasar is estimated to be ∼10(-7), implying a physical connection between Lyman-α nebulae and the locations of rare protoclusters. Our findings imply that the most massive structures in the distant universe have a tremendous supply (≃10(11) solar masses) of cool dense (volume density ≃ 1 cm(-3)) gas, which is in conflict with current cosmological simulations. Copyright © 2015, American Association for the Advancement of Science.

  1. Quasar Quartet Embedded in Giant Nebula Reveals Rare Massive Structure in Distant Universe

    CERN Document Server

    Hennawi, Joseph F; Cantalupo, Sebastiano; Arrigoni-Battaia, Fabrizio

    2015-01-01

    All galaxies once passed through a hyperluminous quasar phase powered by accretion onto a supermassive black hole. But because these episodes are brief, quasars are rare objects typically separated by cosmological distances. In a survey for Lyman-alpha emission at redshift z ~ 2, we discovered a physical association of four quasars embedded in a giant nebula. Located within a substantial overdensity of galaxies, this system is probably the progenitor of a massive galaxy cluster. The chance probability of finding a quadruple quasar is estimated to be ~10^-7, implying a physical connection between Lyman-alpha nebulae and the locations of rare protoclusters. Our findings imply that the most massive structures in the distant universe have a tremendous supply (~ 10^11 solar masses) of cool dense (volume density ~1 cm^-3) gas, which is in conflict with current cosmological simulations.

  2. Chandra X-ray Spectroscopy of Kes75, its Young Pulsar, and its Synchrotron Nebula

    CERN Document Server

    Collins, B F; Helfand, D J

    2001-01-01

    We have observed the young Galactic supernova remnant Kes 75 with the Chandra X-ray Observatory. This object is one of an increasing number of examples of a shell-type remnant with a central extended radio core harboring a pulsar. Here we present a preliminary spatially resolved spectroscopic analysis of the Kes~75 system. We find that the spectrum of the pulsar is significantly harder than that of the wind nebula, and both of these components can be isolated from the diffuse thermal emission that seems to follow the same distribution as the extended radio shell. When we characterize the thermal emission with a model of an under-ionized plasma and non-solar elemental abundances, we require a significant diffuse high energy component, which we model as a power-law with a photon index similar to that of the synchrotron nebula.

  3. INTERNAL PROPER MOTIONS IN THE ESKIMO NEBULA

    Energy Technology Data Exchange (ETDEWEB)

    García-Díaz, Ma. T.; Gutiérrez, L.; Steffen, W.; López, J. A. [Instituto de Astronomía, Universidad Nacional Autónoma de México, Km 103 Carretera Tijuana-Ensenada, 22860 Ensenada, B.C. (Mexico); Beckman, J., E-mail: tere@astro.unam.mx, E-mail: leonel@astro.unam.mx, E-mail: wsteffen@astro.unam.mx, E-mail: jal@astro.unam.mx, E-mail: jeb@iac.es [Instituto de Astrofísica de Canarias, La Laguna, Tenerife (Spain)

    2015-01-10

    We present measurements of internal proper motions at more than 500 positions of NGC 2392, the Eskimo Nebula, based on images acquired with WFPC2 on board the Hubble Space Telescope at two epochs separated by 7.695 yr. Comparisons of the two observations clearly show the expansion of the nebula. We measured the amplitude and direction of the motion of local structures in the nebula by determining their relative shift during that interval. In order to assess the potential uncertainties in the determination of proper motions in this object, in general, the measurements were performed using two different methods, used previously in the literature. We compare the results from the two methods, and to perform the scientific analysis of the results we choose one, the cross-correlation method, because it is more reliable. We go on to perform a ''criss-cross'' mapping analysis on the proper motion vectors, which helps in the interpretation of the velocity pattern. By combining our results of the proper motions with radial velocity measurements obtained from high resolution spectroscopic observations, and employing an existing 3D model, we estimate the distance to the nebula to be 1.3 kpc.

  4. Abundances of planetary nebula NGC2392

    NARCIS (Netherlands)

    Pottasch, S. R.; Bernard-Salas, J.; Roellig, T. L.

    The spectra of the planetary nebula NGC2392 is reanalysed using spectral measurements made in the mid-infrared with the Spitzer Space Telescope. The aim is to determine the chemical composition of this object. We also make use of IUE and ground based spectra. Abundances determined from the

  5. Argon and neon in Galactic nebulae

    Science.gov (United States)

    Simpson, Janet P.; Bregman, Jesse D.; Dinerstein, H. L.; Lester, Dan F.; Rank, David M.; Witteborn, F. C.; Wooden, D. H.

    1995-01-01

    KAO observations of the 6.98 micron line of (Ar II), and KAO and ground-based observations of the 8.99 micron line of (Ar III) and the 12.8 micron line of (Ne II) are presented for a number of Galactic H II regions and planetary nebulae.

  6. Presolar grains from meteorites: Remnants from the early times of the solar system

    CERN Document Server

    Lodders, K; Lodders, Katharina; Amari, Sachiko

    2005-01-01

    This review provides an introduction to presolar grains - preserved stardust from the interstellar molecular cloud from which our solar system formed - found in primitive meteorites. We describe the search for the presolar components, the currently known presolar mineral populations, and the chemical and isotopic characteristics of the grains and dust-forming stars to identify the grains' most probable stellar sources. Keywords: presolar grains, interstellar dust, asymptotic giant branch (AGB) stars, novae, supernovae, nucleosynthesis, isotopic ratios, meteorites

  7. GALLEX solar neutrino observations. The results from GALLEX I and early results from GALLEX II

    Science.gov (United States)

    Anselmann, P.; Hampel, W.; Heusser, G.; Kiko, J.; Kirsten, T.; Laubenstein, M.; Pernicka, E.; Pezzoni, S.; Plaga, R.; Rönn, U.; Sann, M.; Schlosser, C.; Wink, R.; Wojcik, M.; Ammon, R. V.; Ebert, K. H.; Fritsch, T.; Hellriegel, K.; Henrich, E.; Stieglitz, L.; Weyrich, F.; Balata, M.; Ferrari, N.; Lalla, H.; Bellotti, E.; Cattadori, C.; Cremonesi, O.; Fiorini, E.; Zanotti, L.; Altmann, M.; Feilitzsch, F. V.; Mößbauer, R.; Schanda, U.; Berthomieu, G.; Schatzman, E.; Carmi, I.; Dostrovsky, I.; Bacci, C.; Belli, P.; Bernabei, R.; D'Angelo, S.; Paoluzi, L.; Charbit, S.; Cribier, M.; Dupont, G.; Gosset, L.; Rich, J.; Spiro, M.; Stolarczyk, T.; Tao, C.; Vignaud, D.; Hahn, R. L.; Hartmann, F. X.; Rowley, J. K.; Stoenner, R. W.; Weneser, J.

    1993-09-01

    The first period (GALLEX I) of data taking in the GALLEX solar neutrino experiment has been completed. From 14 May 1991 to 29 April 1992, the experiment observed the solar neutrino flux using neutrino capture by 71Ga to form 71Ge. Counting ended on 2 November 1992. The final result from the 15 runs of this periodpis (81+/-17 [stat.]+/-9 [syst.]) SNU (1σ). The first 6 runs of GALLEX II recorded the neutrino signal from 19 August 1992 to 3 February 1993. The preliminary result for this period is (97+/-23 [stat.]+/-7 [syst.]) SNU (1σ). With counting data considered until 29 April 1993, the joint result for all 21 runs is (87+/-14 [stat.]+/-7 [syst.]) SNU (1σ). The present neutrino recording period GALLEX II is continuing with one solar exposure every four weeks. This work has been supported by the Office of High Energy and Nuclear Physics of the US Department of Energy, United States.

  8. On the possible wind nebula of magnetar Swift J1834.9-0846: a magnetism-powered synchrotron nebula

    CERN Document Server

    Tong, H

    2016-01-01

    Recently, the magnetar Swift J1834.9$-$0846 is reported to have a possible wind nebula. It is shown that both the magnetar and its wind nebula are understandable in the wind braking scenario. The magnetar's rotational energy loss rate is not enough. The required particle luminosity should be about $10^{36} \\,\\rm erg \\,s^{-1}$ to $10^{38} \\,\\rm erg \\,s^{-1}$. It is obtained in three different approaches: considering wind braking of Swift J1834.9$-$0846; the spectral and spatial observations of the wind nebula; and an empirical upper bound on wind nebula X-ray luminosity. The nebula magnetic field is be about $10^{-4} \\,\\rm G$. The possible wind nebula of Swift J1834.9$-$0846 should be a magnetar wind nebula. It is powered by the magnetic energy release of the magnetar.

  9. On the possible wind nebula of magnetar Swift J1834.9–0846: a magnetism-powered synchrotron nebula

    Science.gov (United States)

    Tong, Hao

    2016-09-01

    Recently, the magnetar Swift J1834.9–0846 has been reported to have a possible wind nebula. It is shown that both the magnetar and its wind nebula are understandable in the wind braking scenario. The magnetar's rotational energy loss rate is not enough to power the particle luminosity. The required particle luminosity should be about 1036 erg s‑1 to 1038 erg s‑1. It is obtained in three different approaches: considering wind braking of Swift J1834.9–0846 the spectral and spatial observations of the wind nebula; and an empirical upper bound on wind nebula X-ray luminosity. The nebula magnetic field is about 10‑4 G. The possible wind nebula of Swift J1834.9–0846 should be a magnetar wind nebula. It is powered by the magnetic energy released from the magnetar.

  10. The formation of organic molecules in solar system environments: The Miller-Urey Experiment in Space preflight overview

    Science.gov (United States)

    Kotler, J.; Ehrenfreund, P.; Martins, Z.; Ricco, A.; Blum, J.; Schraepler, R.; van Dongen, J.; Palmans, A.; Sephton, M.; Cleaves, H. J.

    2011-12-01

    The Miller-Urey Experiment in space (MUE) will investigate the formation of prebiotic organic compounds in the early solar system environment when it is sent to, and later retrieved from, the International Space Station in 2012. The dynamic environment of the solar nebula with the simultaneous presence of gas, particles, and energetic processes, including shock waves, electrical discharges, and radiation may trigger a rich organic chemistry leading to organic molecules. Two gas mixture compositions (CH4, NH3, H2 and N2, H2, CO) will be tested and subjected to continuous spark discharges for 48, 96, and 192 hours. Silicate particles will serve as surfaces on which thin water ice mantles can accrete. The experiment will be performed at low temperatures (-5 °C), slowing hydrolysis and improving chances of detection of initial products, intermediates and their abundances. Conducting the Miller-Urey experiment in the space environment (microgravity) allows us to simulate conditions that could have prevailed in the low gravity, energetic early solar nebula and provides insights into the chemical pathways that may occur as planetary systems form.

  11. Dusty globules in the Crab Nebula

    Science.gov (United States)

    Grenman, T.; Gahm, G. F.; Elfgren, E.

    2017-03-01

    Context. Dust grains are widespread in the Crab Nebula. A number of small, dusty globules, are visible as dark spots against the background of continuous synchrotron emission in optical images. Aims: Our aim is to catalogue such dusty globules and investigate their properties. Methods: From existing broad-band images obtained with the Hubble Space Telescope, we located 92 globules, for which we derived positions, dimensions, orientations, extinctions, masses, proper motions, and their distributions. Results: The globules have mean radii ranging from 400 to 2000 AU and are not resolved in current infrared images of the nebula. The extinction law for dust grains in these globules matches a normal interstellar extinction law. Derived masses of dust range from 1 to 60 × 10-6M⊙, and the total mass contained in globules constitute a fraction of approximately 2% or less of the total dust content of the nebula. The globules are spread over the outer part of the nebula, and a fraction of them coincide in position with emission filaments, where we find elongated globules that are aligned with these filaments. Only 10% of the globules are coincident in position with the numerous H2-emitting knots found in previous studies. All globules move outwards from the centre with transversal velocities of 60 to 1600 km s-1, along with the general expansion of the remnant. We discuss various hypotheses for the formation of globules in the Crab Nebula. Based on observations collected with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute.

  12. STATISTICAL STUDY OF THE EARLY SOLAR SYSTEM'S INSTABILITY WITH FOUR, FIVE, AND SIX GIANT PLANETS

    Energy Technology Data Exchange (ETDEWEB)

    Nesvorny, David [Department of Space Studies, Southwest Research Institute, Boulder, CO 80302 (United States); Morbidelli, Alessandro [Departement Cassiopee, University of Nice, CNRS, Observatoire de la Cote d' Azur, F-06304 Nice (France)

    2012-10-01

    Several properties of the solar system, including the wide radial spacing and orbital eccentricities of giant planets, can be explained if the early solar system evolved through a dynamical instability followed by migration of planets in the planetesimal disk. Here we report the results of a statistical study, in which we performed nearly 10{sup 4} numerical simulations of planetary instability starting from hundreds of different initial conditions. We found that the dynamical evolution is typically too violent, if Jupiter and Saturn start in the 3:2 resonance, leading to ejection of at least one ice giant from the solar system. Planet ejection can be avoided if the mass of the transplanetary disk of planetesimals was large (M{sub disk} {approx}> 50 M{sub Earth}), but we found that a massive disk would lead to excessive dynamical damping (e.g., final e{sub 55} {approx}< 0.01 compared to present e{sub 55} = 0.044, where e{sub 55} is the amplitude of the fifth eccentric mode in the Jupiter's orbit), and to smooth migration that violates constraints from the survival of the terrestrial planets. Better results were obtained when the solar system was assumed to have five giant planets initially, and one ice giant, with mass comparable to that of Uranus and Neptune, was ejected into interstellar space by Jupiter. The best results were obtained when the ejected planet was placed into the external 3:2 or 4:3 resonance with Saturn and M{sub disk} {approx_equal} 20 M{sub Earth}. The range of possible outcomes is rather broad in this case, indicating that the present solar system is neither a typical nor expected result for a given initial state, and occurs, in best cases, with only a {approx_equal}5% probability (as defined by the success criteria described in the main text). The case with six giant planets shows interesting dynamics but does offer significant advantages relative to the five-planet case.

  13. Physics and chemistry of the solar system

    CERN Document Server

    Lewis, John S

    2013-01-01

    Physics and Chemistry of the Solar System is a broad survey of the Solar System. The book discusses the general properties and environment of our planetary system, including the astronomical perspective, the general description of the solar system and of the sun and the solar nebula). The text also describes the solar system beyond mars, including the major planets; pluto and the icy satellites of the outer planets; the comets and meteors; and the meteorites and asteroids. The inner solar system, including the airless rocky bodies; mars, venus, and earth; and planets and life about other stars

  14. Gaia-ESO Survey: Global properties of clusters Trumpler 14 and 16 in the Carina nebula ⋆⋆

    Science.gov (United States)

    Damiani, F.; Klutsch, A.; Jeffries, R. D.; Randich, S.; Prisinzano, L.; Maíz Apellániz, J.; Micela, G.; Kalari, V.; Frasca, A.; Zwitter, T.; Bonito, R.; Gilmore, G.; Flaccomio, E.; Francois, P.; Koposov, S.; Lanzafame, A. C.; Sacco, G. G.; Bayo, A.; Carraro, G.; Casey, A. R.; Alfaro, E. J.; Costado, M. T.; Donati, P.; Franciosini, E.; Hourihane, A.; Jofré, P.; Lardo, C.; Lewis, J.; Magrini, L.; Monaco, L.; Morbidelli, L.; Worley, C. C.; Vink, J. S.; Zaggia, S.

    2017-07-01

    Aims: We present the first extensive spectroscopic study of the global population in star clusters Trumpler 16, Trumpler 14, and Collinder 232 in the Carina nebula, using data from the Gaia-ESO Survey, down to solar-mass stars. Methods: In addition to the standard homogeneous survey data reduction, a special processing was applied here because of the bright nebulosity surrounding Carina stars. Results: We find about 400 good candidate members ranging from OB types down to slightly subsolar masses. About 100 heavily reddened early-type Carina members found here were previously unrecognized or poorly classified, including two candidate O stars and several candidate Herbig Ae/Be stars. Their large brightness makes them useful tracers of the obscured Carina population. The spectroscopically derived temperatures for nearly 300 low-mass members enables the inference of individual extinction values and the study of the relative placement of stars along the line of sight. Conclusions: We find a complex spatial structure with definite clustering of low-mass members around the most massive stars and spatially variable extinction. By combining the new data with existing X-ray data, we obtain a more complete picture of the three-dimensional spatial structure of the Carina clusters and of their connection to bright and dark nebulosity and UV sources. The identification of tens of background giants also enables us to determine the total optical depth of the Carina nebula along many sightlines. We are also able to put constraints on the star formation history of the region with Trumpler 14 stars found to be systematically younger than stars in other subclusters. We find a large percentage of fast-rotating stars among Carina solar-mass members, which provide new constraints on the rotational evolution of pre-main-sequence stars in this mass range. Based on observations collected with the FLAMES spectrograph at VLT/UT2 telescope (Paranal Observatory, ESO, Chile), for the Gaia

  15. Dynamics of the Galactic Bulge using Planetary Nebulae

    CERN Document Server

    Beaulieu, S F; Kálnay, A J; Saha, P; Zhao, H S; Beaulieu, Sylvie F.; Freeman, Kenneth C.; Kalnajs, Agris J.; Saha, Prasenjit; Zhao, HongSheng

    2000-01-01

    Evidence for a bar at the center of the Milky Way triggered a renewed enthusiasm for dynamical modelling of the Galactic bar-bulge. Our goal is to compare the kinematics of a sample of tracers, planetary nebulae, widely distributed over the bulge with the corresponding kinematics for a range of models of the inner Galaxy. Three of these models are N-body barred systems arising from the instabilities of a stellar disk (Sellwood, Fux and Kalnajs), and one is a Schwarzschild system constructed to represent the 3D distribution of the COBE/DIRBE near-IR light and then evolved as an N-body system for a few dynamical times (Zhao). For the comparison of our data with the models, we use a new technique developed by Saha (1998). The procedure finds the parameters of each model, i.e. the solar galactocentric distance R_o in model units, the orientation angle phi, the velocity scale (in km/s per model unit), and the solar tangential velocity which best fit the data.

  16. CO Isotopes in Planetary Nebulae

    OpenAIRE

    Balser, Dana S.; McMullin, Joseph P.; Wilson, T. L.

    2002-01-01

    Standard stellar evolution theory is inconsistent with the observed isotopic carbon ratio, 12C/13C, in evolved stars. This theory is also inconsistent with the 3He/H abundance ratios observed in Galactic HII regions, when combined with chemical evolution theory. These discrepancies have been attributed to an extra, non-standard mixing which further processes material during the RGB and should lower both the 12C/13C and 3He/H abundance ratios for stars with masses < 2 solar masses. Measurement...

  17. A Consolidated Online Database of Galactic Planetary Nebulae

    CERN Document Server

    Miszalski, B; Ochsenbein, F; Parker, Q A

    2011-01-01

    Since the unifying Strasbourg-ESO Catalogue of Galactic Planetary Nebulae (SECGPN) a large number of new discoveries have been made thanks to improved surveys and discovery techniques. The increasingly heterogeneous published population of Galactic PNe, that we have determined totals < 2850 PNe, is becoming more difficult to study on the whole without a centralised repository. We introduce a consolidated and interactive online database with object classifications that reflect the latest multi-wavelength data and the most recent results. The extensible database, hosted by the Centre de Donnees astronomique de Strasbourg (CDS), will contain a wealth of observed data for large, well-defined samples of PNe including coordinates, multi-wavelength images, spectroscopy, line intensities, radial velocities and central star information. It is anticipated that the database will be publicly released early 2012.

  18. Early Giant Planet Migration in the Solar System: Geochemical and Cosmochemical Implications for Terrestrial Planet Formation

    Science.gov (United States)

    O'Brien, David P.; Walsh, K. J.; Morbidelli, A.; Raymond, S. N.; Mandell, A. M.; Bond, J. C.

    2010-10-01

    A new terrestrial planet formation model (Walsh et al., this meeting) explores the effects of a two-stage, inward-then-outward migration of Jupiter and Saturn, as found in numerous hydrodynamical simulations of giant planet formation (Masset & Snellgrove 2001, Morbidelli & Crida 2007, Pierens & Nelson 2008). Walsh et al. show that the inward migration of Jupiter truncates the disk of planetesimals and embryos in the terrestrial planet region. Subsequent accretion in that region then forms a realistic system of terrestrial planets, in particular giving a low-mass Mars, which has been difficult to reproduce in simulations with a self-consistent set of initial conditions (see, eg. Raymond et al. 2009). Additionally, the outward migration of the giant planets populates the asteroid belt with distinct populations of bodies, with the inner belt filled by bodies originating inside of 3 AU, and the outer belt filled with bodies originating from beyond the giant planets. From a geochemical and cosmochemical point of view, this scenario differs significantly from the "standard model" in which essentially all of the material in the inner Solar System initially formed there. Specifically, the assumption that the current radial distribution of material in the inner Solar System is reflective of the primordial distribution of material in that region is no longer necessary. This is important for understanding the chemical and isotopic diversity of the inner Solar System as inferred from studies of the terrestrial planets, asteroids, and meteorites, as well as for understanding the origin of Earth's water. We will discuss the geochemical and cosmochemical implications of this model in relation to available constraints, as well as to previous models of terrestrial planet formation. Masset & Snellgrove (2001), MNRAS 320, L55. Morbidelli & Crida (2007), Icarus 191, 158. Pierens & Nelson (2008), A&A 482, 333. Raymond et al. (2009), Icarus 203, 644.

  19. Uranium isotope compositions of the basaltic angrite meteorites and the chronological implications for the early Solar System.

    Science.gov (United States)

    Brennecka, Gregory A; Wadhwa, Meenakshi

    2012-06-12

    Events occurring within the first 10 million years of the Solar System's approximately 4.5 billion-year history, such as formation of the first solids, accretion, and differentiation of protoplanetary bodies, have determined the evolutionary course of our Solar System and the planetary bodies within it. The application of high-resolution chronometers based on short-lived radionuclides is critical to our understanding of the temporal sequence of these critical events. However, to map the relative ages from such chronometers onto the absolute time scale, they must be "anchored" to absolute ages of appropriate meteoritic materials using the high-precision lead-lead (Pb-Pb) chronometer. Previously reported Pb-Pb dates of the basaltic angrite meteorites, some of which have been used extensively as time anchors, assumed a constant (238)U/(235)U ratio (= 137.88). In this work, we report measurements of (238)U/(235)U ratios in several angrites that are distinct from the previously assumed value, resulting in corrections to the Pb-Pb ages of ≥ 1 million years. There is no resolvable variation in the (238)U/(235)U ratio among the angrite bulk samples or mineral separates, suggesting homogeneity in the U isotopic composition of the angrite parent body. Based on these measurements, we recalculated the Pb-Pb age for the commonly used anchor, the D'Orbigny angrite, to be 4563.37 ± 0.25 Ma. An adjustment to the Pb-Pb age of a time anchor (such as D'Orbigny) requires a corresponding correction to the "model ages" of all materials dated using that anchor and a short-lived chronometer. This, in turn, has consequences for accurately defining the absolute timeline of early Solar System events.

  20. Towards a Measurement of the Half-Life of {sup 60}Fe for Stellar and Early Solar System Models

    Energy Technology Data Exchange (ETDEWEB)

    Ostdiek, K.; Anderson, T.; Bauder, W.; Bowers, M.; Collon, P.; Dressler, R.; Greene, J.; Kutschera, W.; Lu, W.; Paul, M.

    2015-10-15

    Radioisotopes, produced in stars and ejected into the Interstellar Medium, are important for constraining stellar and early Solar System (ESS) models. In particular, the half-life of the radioisotope, Fe-60, can have an impact on calculations for the timing for ESS events, the distance to nearby Supernovae, and the brightness of individual, non-steady-state Fe gamma ray sources in the Galaxy. A half-life measurement has been undertaken at the University of Notre Dame and measurements of the Fe-60/Fe-56 concentration of our samples using Accelerator Mass Spectrometry has begun. This result will be coupled with an activity measurement of the isomeric decay in Co-60, which is the decay product of Fe. Preliminary half-life estimates of (2.53 +/- 0.24) x 10(6) years seem to confirm the recent measurement by Rugel et al. (2009). (C) 2015 Elsevier B.V. All rights reserved.

  1. Towards a measurement of the half-life of {sup 60}Fe for stellar and early Solar System models

    Energy Technology Data Exchange (ETDEWEB)

    Ostdiek, K.; Anderson, T. [University of Notre Dame, Notre Dame, IN 46556 (United States); Bauder, W. [University of Notre Dame, Notre Dame, IN 46556 (United States); Argonne National Laboratory, 9700 South Cass Avenue, Lemont, IL 60439 (United States); Bowers, M.; Collon, P. [University of Notre Dame, Notre Dame, IN 46556 (United States); Dressler, R. [Paul Scherrer Institute – Laboratory for Radiochemistry and Environmental Chemistry, 5232 Villigen (Switzerland); Greene, J. [Argonne National Laboratory, 9700 South Cass Avenue, Lemont, IL 60439 (United States); Kutschera, W. [Vienna Environmental Research Accelerator Laboratory, Waehringer Strasse 17, 1090 Vienna (Austria); Lu, W. [University of Notre Dame, Notre Dame, IN 46556 (United States); Paul, M. [Racah Institute of Physics, Hebrew University, Jerusalem 91904 (Israel); Robertson, D. [University of Notre Dame, Notre Dame, IN 46556 (United States); Schumann, D. [Paul Scherrer Institute – Laboratory for Radiochemistry and Environmental Chemistry, 5232 Villigen (Switzerland); Skulski, M. [University of Notre Dame, Notre Dame, IN 46556 (United States); Wallner, A. [The Australian National University, Canberra, ACT 0200 (Australia)

    2015-10-15

    Radioisotopes, produced in stars and ejected into the Interstellar Medium, are important for constraining stellar and early Solar System (ESS) models. In particular, the half-life of the radioisotope, {sup 60}Fe, can have an impact on calculations for the timing for ESS events, the distance to nearby Supernovae, and the brightness of individual, non-steady-state {sup 60}Fe gamma ray sources in the Galaxy. A half-life measurement has been undertaken at the University of Notre Dame and measurements of the {sup 60}Fe/{sup 56}Fe concentration of our samples using Accelerator Mass Spectrometry has begun. This result will be coupled with an activity measurement of the isomeric decay in {sup 60}Co, which is the decay product of {sup 60}Fe. Preliminary half-life estimates of (2.53 ± 0.24) × 10{sup 6} years seem to confirm the recent measurement by Rugel et al. (2009).

  2. Early Evaluation of the Corona at the 2016 March 9 Total Solar Eclipse

    Science.gov (United States)

    Pasachoff, Jay M.; Seaton, Daniel B.; Sterling, Alphonse C.

    2016-05-01

    We observed the corona on 2016 March 9 with a variety of assets on the ground and in space. The umbra of the total eclipse swept across Indonesia and into the Pacific, with totality at our Indonesian observation sites lasting 2 min 45 s at Ternate in the Spice Islands (Malukus) and 2 min 10 at Belitung. We compare our ground-based results with the coronal configurations observed with PROBA2/SWAP and Hinode XRT. One of our scientific goals is to follow the coronal configuration over the solar-activity cycle, with the sunspot number now half its maximum of either its 2012 or 2014 peak. We are evaluating temporal changes by comparing eclipse observations made at several ground-based sites along the path, with the longest span being 75 min from Belitung to the Woleia atoll in mid-Pacific, 1:25 UTC to 2:40 UTC; we are evaluating whether the airborne observations made at 3:35 UTC on March 8 (across the International Dateline) are of suitable quality to provide further comparison at high spatial resolution. We also compare our images with the near-simultaneous coronal observations made with SOHO/LASCO, SDO/AIA, STEREO-A/SECCHI, and the Mauna Loa Solar Observatory's K-cor coronagraph. ACS received support for image analysis from the Hinode project.

  3. Assemblage of Presolar Materials and Early Solar System Condensates in Chondritic Porous Interplanetary Dust Particles

    Science.gov (United States)

    Nguyen, A. N.; Nakamura-Messenger, K.; Messenger, S.; Keller, L. P.; Kloeck, W.

    2015-01-01

    Anhydrous chondritic porous inter-planetary dust particles (CP IDPs) contain an assortment of highly primitive solar system components, molecular cloud matter, and presolar grains. These IDPs have largely escaped parent body processing that has affected meteorites, advocating cometary origins. Though the stardust abundance in CP IDPs is generally greater than in primitive meteorites, it can vary widely among individual CP IDPs. The average abundance of silicate stardust among isotopically primitive IDPs is approx. 375 ppm while some have extreme abundances up to approx. 1.5%. H and N isotopic anomalies are common in CP IDPs and the carrier of these anomalies has been traced to organic matter that has experienced chemical reactions in cold molecular clouds or the outer protosolar disk. Significant variations in these anomalies may reflect different degrees of nebular processing. Refractory inclusions are commonly observed in carbonaceous chondrites. These inclusions are among the first solar system condensates and display 16O-rich isotopic compositions. Refractory grains have also been observed in the comet 81P/Wild-2 samples re-turned from the Stardust Mission and in CP IDPs, but they occur with much less frequency. Here we conduct coordinated mineralogical and isotopic analyses of CP IDPs that were characterized for their bulk chemistry by to study the distribution of primitive components and the degree of nebular alteration incurred.

  4. 'Peony Nebula' Star Settles for Silver Medal

    Science.gov (United States)

    2008-01-01

    [figure removed for brevity, see original site] [figure removed for brevity, see original site] Poster Version Movie If our galaxy, the Milky Way, were to host its own version of the Olympics, the title for the brightest known star would go to a massive star called Eta Carina. However, a new runner-up now the second-brightest star in our galaxy has been discovered in the galaxy's dusty and frenzied interior. This image from NASA's Spitzer Space Telescope shows the new silver medalist, circled in the inset above, in the central region of our Milky Way. Dubbed the 'Peony nebula' star, this blazing ball of gas shines with the equivalent light of 3.2 million suns. The reigning champ, Eta Carina, produces the equivalent of 4.7 million suns worth of light though astronomers say these estimates are uncertain, and it's possible that the Peony nebula star could be even brighter than Eta Carina. If the Peony star is so bright, why doesn't it stand out more in this view? The answer is dust. This star is located in a very dusty region jam packed with stars. In fact, there could be other super bright stars still hidden deep in the stellar crowd. Spitzer's infrared eyes allowed it to pierce the dust and assess the Peony nebula star's true brightness. Likewise, infrared data from the European Southern Observatory's New Technology Telescope in Chile were integral in calculating the Peony nebula star's luminosity. The Peony nebula, which surrounds the Peony nebular star, is the reddish cloud of dust in and around the white circle. The movie begins by showing a stretch of the dusty and frenzied central region of our Milky Way galaxy. It then zooms in to reveal the 'Peony nebula' star the new second-brightest star in the Milky Way, discovered in part by NASA's Spitzer Space Telescope. This is a three-color composite showing infrared observations from two Spitzer instruments. Blue represents 3.6-micron light and green shows light of 8 microns, both captured by Spitzer's infrared array

  5. Thermal to Nonthermal Energy Partition at the Early Rise Phase of Solar Flares

    CERN Document Server

    Altyntsev, Alexander A; Lesovoi, Sergey V; Meshalkina, Natalia S

    2012-01-01

    In some flares the thermal component appears much earlier than the nonthermal component in X-ray range. Using sensitive microwave observations we revisit this finding made by Battaglia et al. (2009) based on RHESSI data analysis. We have found that nonthermal microwave emission produced by accelerated electrons with energy of at least several hundred keV, appears as early as the thermal soft X-ray emission indicative that the electron acceleration takes place at the very early flare phase. The non-detection of the hard X-rays at that early stage of the flares is, thus, an artifact of a limited RHESSI sensitivity. In all considered events, the microwave emission intensity increases at the early flare phase. We found that either thermal or nonthermal gyrosynchrotron emission can dominate the low-frequency part of the microwave spectrum below the spectral peak occurring at 3-10 GHz. In contrast, the high-frequency optically thin part of the spectrum is always formed by the nonthermal, accelerated electron compon...

  6. Vesta and Ceres: crossing the history of the Solar System

    CERN Document Server

    Coradini, Angioletta; Federico, Costanzo; Magni, Gianfranco

    2011-01-01

    The evolution of the Solar System can be schematically divided into three different phases: the Solar Nebula, the Primordial Solar System and the Modern Solar System. These three periods were characterized by very different conditions, both from the point of view of the physical conditions and from that of the processes there were acting through them. Across the Solar Nebula phase, planetesimals and planetary embryos were forming and differentiating due to the decay of short-lived radionuclides. At the same time, giant planets formed their cores and accreted the nebular gas to reach their present masses. After the gas dispersal, the Primordial Solar System began its evolution. In the inner Solar System, planetary embryos formed the terrestrial planets and, in combination with the gravitational perturbations of the giant planets, depleted the residual population of planetesimals. In the outer Solar System, giant planets underwent a violent, chaotic phase of orbital rearrangement which caused the Late Heavy Bom...

  7. Shooting stars: Our guide to the early solar system`s formation

    Energy Technology Data Exchange (ETDEWEB)

    O`Reilly, J.

    1995-11-01

    Plagioclase grains were studied from the Allende meteorite, sample 916, to determine a chronology of events that occurred within the first ten million years of the solar system`s formation. Radiometric dating of the {sup 26}-Al-{sup 26}Mg system was accomplished on the ion microprobe mass spectromer. The excess {sup 26}-Mg in core plagioclase grains of calcium-aluminum rich inclusions (CAIs) provided a time of original condensation for {sup 26}-Al of {approximately}4.55 million years ago, a hundred million years prior to the formation of the planets. This data has been found to correlate with other excess {sup 26}-Mg samples. Measurements of plagioclase in the CAI`s periphery dated 1.52 million years later, suggesting an interesting history of collision and melting.

  8. Laser Induced Breakdown Spectroscopy of meteorites as a probe of the early solar system

    Science.gov (United States)

    Dell'Aglio, M.; De Giacomo, A.; Gaudiuso, R.; De Pascale, O.; Longo, S.

    2014-11-01

    This paper presents an evaluation of Laser Induced Breakdown Spectroscopy (LIBS) as a technique for gathering data relevant to Solar System geophysics. Two test cases were demonstrated: elemental analysis of chondrules in a chondrite meteorite, and space- resolved analysis of the interface between kamacite and taenite crystals in an octahedrite iron meteorite. In particular most major and minor elements (Fe, Mg, Si, Ti, Al, Cr, Mn, Ca, Fe, Ni, Co) in Sahara 98222 (chondrite) and its chondrules, as well as the profile of Ni content in Toluca (iron meteorite), were determined with the Calibration Free (CF) method. A special attention was devoted to exploring the possibilities offered by variants of the basic technique, such as the use of Fe I Boltzmann distribution as an intensity calibration method of the spectroscopic system, and the use of spatially resolved analysis.

  9. The Violent Early Solar System, as Told by Lunar Sample Geochronology

    Science.gov (United States)

    Cohen, Barbara

    2012-01-01

    One of the legacies of the samples collected by the Apollo and Luna missions is the link forged between radiometric ages of rocks and relative ages according to stratigraphic relationships and impact crater size-frequency distributions. Our current understanding of the history of the inner solar system is based on the relative chronology of individual planets, tied to the absolute geochronology of the Moon via these important samples. Samples from these nearside locations reveal a preponderance of impact-disturbed or recrystallized ages between 3.75 and 3.95 billion years. Argon and lead loss (and correlated disturbances in the Rb-Sr system) have been attributed to metamorphism of the lunar crust by an enormous number of impacts in a brief pulse of time, called the Lunar Cataclysm or Late Heavy Bombardment. Subsequent high-precision geochronometric analyses of Apollo samples and lunar highlands meteorites show a wider range of ages, but very few older than 4 Ga. The paucity of ancient impact melt rocks has been interpreted to mean that either that most impact basins formed at this time, or that ejecta from the large, near-side, young basins dominates the Apollo samples. Selenochronology is getting more complicated: new results question meaning of sample ages, crater counts, crater production functions, and the solar system itself. Improved geological mapping of lunar geologic units and boundaries using multiple remote sensing datasets. High-resolution image-based crater counting of discrete geologic units and relating them to location. Improved understanding of the regolith thickness and its global variation (GRAIL). Tying the sampling of impact-melt rocks to the lunar impact flux. Using improved techniques (magnetic fields, diffusion studies, isotopic analysis) on existing samples. New sample return from benchmark craters, particularly SPA, which appears in 2013 Decadal Survey.

  10. FACT. Energy spectrum of the Crab Nebula

    Energy Technology Data Exchange (ETDEWEB)

    Temme, Fabian; Einecke, Sabrina; Buss, Jens [TU Dortmund, Experimental Physics 5, Otto-Hahn-Str.4, 44221 Dortmund (Germany); Collaboration: FACT-Collaboration

    2016-07-01

    The First G-APD Cherenkov Telescope is the first Imaging Air Cherenkov Telescope which uses silicon photon detectors (G-APDs aka SiPM) as photo sensors. With more than four years of operation, FACT proved an application of SiPMs is suitable for the field of ground-based gamma-ray astronomy. Due to the stable flux at TeV energies, the Crab Nebula is handled as a ''standard candle'' in Cherenkov astronomy. The analysis of its energy spectrum and comparison with other experiments, allows to evaluate the performance of FACT. A modern analysis chain, based on data stream handling and multivariate analysis methods was developed in close cooperation with the department of computer science at the TU Dortmund. In this talk, this analysis chain and its application are presented. Further to this, results, including the energy spectrum of the Crab Nebula, measured with FACT, are shown.

  11. Star Formation in the Eagle Nebula

    CERN Document Server

    Oliveira, Joana M

    2008-01-01

    M16 (the Eagle Nebula) is a striking star forming region, with a complex morphology of gas and dust sculpted by the massive stars in NGC 6611. Detailed studies of the famous ``elephant trunks'' dramatically increased our understanding of the massive star feedback into the parent molecular cloud. A rich young stellar population (2 - 3 Myr) has been identified, from massive O-stars down to substellar masses. Deep into the remnant molecular material, embedded protostars, Herbig-Haro objects and maser sources bear evidence of ongoing star formation in the nebula, possibly triggered by the massive cluster members. M 16 is a excellent template for the study of star formation under the hostile environment created by massive O-stars. This review aims at providing an observational overview not only of the young stellar population but also of the gas remnant of the star formation process.

  12. The nebulae around LBVs: a multiwavelength approach

    CERN Document Server

    Umana, Grazia; Trigilio, Corrado; Leto, Paolo; Hora, Joseph L; Fazio, Giovanni

    2010-01-01

    We present first results of our study of a sample of Galactic LBV, aimed to contribute to a better understanding of the LBV phenomenon, by recovering the mass-loss history of the central object from the analysis of its associated nebula. Mass-loss properties have been derived by a synergistic use of different techniques, at different wavelengths, to obtain high-resolution, multi-wavelength maps, tracing the different emitting components coexisting in the stellar ejecta: the ionized/neutral gas and the dust. Evidence for asymmetric mass-loss and observational evidence of possible mutual interaction between gas and dust components have been observed by the comparison of mid-IR (Spitzer/IRAC, VLT/VISIR) and radio (VLA) images of the nebulae, while important information on the gas and dust composition have been derived from Spitzer/IRS spectra.

  13. Ring Nebulae: Tracers of the CNO Nucleosynthesis

    CERN Document Server

    Mesa-Delgado, A; García-Rojas, J

    2015-01-01

    Preliminary results are presented from spectroscopic data in the optical range of the Galactic ring nebulae NGC 6888, G2:4+1:4, RCW 58 and Sh2-308. Deep observations with long exposure times were carried out at the 6.5m Clay Telescope and at the 10.4m Gran Telescopio Canarias. In NGC 6888, recombination lines of C II, O II and N II are detected with signal-to-noise ratios higher than 8. The chemical content of NGC 6888 is discussed within the chemical enrichment predicted by evolution models of massive stars. For all nebulae, a forthcoming work will content in-depth details about observations, analysis and final results (Esteban et al. 2015, in prep.).

  14. The theory of pulsar winds and nebulae

    CERN Document Server

    Kirk, J G; Petri, J

    2007-01-01

    We review current theoretical ideas on pulsar winds and their surrounding nebulae. Relativistic MHD models of the wind of the aligned rotator, and of the striped wind, together with models of magnetic dissipation are discussed. It is shown that the observational signature of this dissipation is likely to be point-like, rather than extended, and that pulsed emission may be produced. The possible pulse shapes and polarisation properties are described. Particle acceleration at the termination shock of the wind is discussed, and it is argued that two distinct mechanisms must be operating, with the first-order Fermi mechanism producing the high-energy electrons (above 1 TeV) and either magnetic annihilation or resonant absorption of ion cyclotron waves responsible for the 100 MeV to 1 TeV electrons. Finally, MHD models of the morphology of the nebula are discussed and compared with observation.

  15. Discovery of New Faint Northern Galactic Planetary Nebulae

    CERN Document Server

    Acker, Agnes; Outters, Nicolas; Miszalski, Brent; Sabin, Laurence; Le Du, Pascal; Alves, Filipe

    2012-01-01

    We present the discovery of 6 nebular objects made by amateur astronomers. Four of these discoveries are clearly planetary nebulae (PNe), one is a possible PN, and another is a likely H II region. The bipolar nebula Ou4 presents the largest angular extent ever found : over one degree on the sky! We consider various scenarios that could explain such a nebula. Ou4 could be one of the nearest PNe known, though its possible PN nature will need confirmation.

  16. Observations of the thin filamentary nebula Simeiz 22

    Energy Technology Data Exchange (ETDEWEB)

    Lozinskaya, T.A.; Sitnik, T.G.; Toropova, M.S.; Klement' eva, A.Yu. (Moskovskij Gosudarstvennyj Univ. (USSR) Gosudarstvennyj Astronomicheskij Inst. ' ' GAISh' ' )

    1984-02-01

    The (N 2), (S 2) and (0 3) image-converter photographs of the rebula Simeiz 22 made through interfererce filters in the Cassegrain focus of the 125-cm reflector are presented. Detailed isophote systems in every line are obtained by photographic eguidepsitometry methods. Our narrow-bandrass photographs show variations in the nebula morphology, including the emission stratification typical of planetary nebulae. The origin of the nebula is discussed; some indirect arguments showing mass loss by the central star are presented.

  17. Outflows, Dusty Cores, and a Burst of Star Formation in the North America and Pelican Nebulae

    CERN Document Server

    Bally, John; Probst, Ron; Reipurth, Bo; Shirley, Yancy L; Stringfellow, Guy S

    2014-01-01

    We present observations of near-infrared 2.12 micro-meter molecular hydrogen outflows emerging from 1.1 mm dust continuum clumps in the North America and Pelican Nebula (NAP) complex selected from the Bolocam Galactic Plane Survey (BGPS). Hundreds of individual shocks powered by over 50 outflows from young stars are identified, indicating that the dusty molecular clumps surrounding the NGC 7000 / IC 5070 / W80 HII region are among the most active sites of on-going star formation in the Solar vicinity. A spectacular X-shaped outflow, MHO 3400, emerges from a young star system embedded in a dense clump more than a parsec from the ionization front associated with the Pelican Nebula (IC 5070). Suspected to be a binary, the source drives a pair of outflows with orientations differing by 80 degrees. Each flow exhibits S-shaped symmetry and multiple shocks indicating a pulsed and precessing jet. The `Gulf of Mexico' located south of the North America Nebula (NGC 7000), contains a dense cluster of molecular hydrogen ...

  18. IC 4663: The first unambiguous [WN] Wolf-Rayet central star of a planetary nebula

    CERN Document Server

    Miszalski, B; De Marco, O; Köppen, J; Moffat, A F J; Acker, A; Hillwig, T C

    2012-01-01

    We report on the serendipitous discovery of the first central star of a planetary nebula (PN) that mimics the helium- and nitrogen-rich WN sequence of massive Wolf-Rayet (WR) stars. The central star of IC 4663 (PN G346.2-08.2) is dominated by broad He II and N V emission lines which correspond to a [WN3] spectral type. Unlike previous [WN] candidates, the surrounding nebula is unambiguously a PN. At an assumed distance of 3.5 kpc, corresponding to a stellar luminosity of 4000 Lsun, the V=16.9 mag central star remains 4-6 mag fainter than the average luminosity of massive WN3 stars even out to an improbable d=8 kpc. The nebula is typical of PNe with an elliptical morphology, a newly discovered Asymptotic Giant Branch (AGB) halo, a relatively low expansion velocity (v_exp=30 km/s) and a highly ionised spectrum with an approximately Solar chemical abundance pattern. The [WN3] star is hot enough to show Ne VII emission (T_*=140+/-20 kK) and exhibits a fast wind (v_infty=1900 km/s), which at d=3.5 kpc would yield ...

  19. Planetary systems and real planetary nebulae from planets destruction near white dwarfs

    CERN Document Server

    Bear, Ealeal

    2015-01-01

    We suggest that tidal destruction of Earth-like and icy planets near a white dwarf (WD) might lead to the formation of one or more low-mass planets in tight orbits around the WD. More massive planets contain hydrogen which will start burning on the surface of the WD and inflate an envelope, part of which be ejected to form a nebula. This nebula will be ionized and be observed as a planetary nebulae. The formation of the WD planetary system starts with a tidal break-up of icy or lower mass planets to planetesimals near their tidal radius of about 1Rsun. Internal stress forces keep the planetesimal from tidal break-up when their radius is less than about 100km. We suggest that the planetesimals then bind together to form new sub-Earth-like planets around the WD at a few solar radii. More massive planets that contain hydrogen will supply the WD with fresh nuclear fuel to reincarnate its stellar-giant phase. Some of the hydrogen will be inflated in a large envelope that will cause the planetesimal formed from the...

  20. Multiband observations of the Crab Nebula

    Science.gov (United States)

    Krassilchtchikov, A. M.; Bykov, A. M.; Castelletti, G. M.; Dubner, G. M.; Kargaltsev, O. Yu; Pavlov, G. G.

    2017-01-01

    Results of simultaneous imaging of the Crab Nebula in the radio (JVLA), optical (HST), and X-ray (Chandra) bands are presented. The images show a variety of small-scale structures, including wisps mainly located to the north-west of the pulsar and knots forming a ring-like structure associated with the termination shock of the pulsar wind. The locations of the structures in different bands do not coincide with each other.

  1. Pulsating Radio Sources near the Crab Nebula.

    Science.gov (United States)

    Staelin, D H; Reifenstein, E C

    1968-12-27

    Two new pulsating radio sources, designated NP 0527 and NP 0532, were found near the Crab Nebula and could be coincident with it. Both sources are sporadic, and no periodicities are evident. The pulse dispersions indicate that 1.58 +/- 0.03 and 1.74 +/- 0.02 x 10(20) electrons per square centimeter lie in the direction of NP 0527 and NP 0532, respectively.

  2. Planetary nebulae in the Small Magellanic Cloud

    Science.gov (United States)

    Ventura, P.; Stanghellini, L.; Di Criscienzo, M.; García-Hernández, D. A.; Dell'Agli, F.

    2016-08-01

    We analyse the planetary nebulae (PNe) population of the Small Magellanic Cloud (SMC), based on evolutionary models of stars with metallicities in the range 10-3 ≤ Z ≤ 4 × 10-3 and mass 0.9 M⊙ Magellanic Cloud is explained on the basis of the diverse star formation history and age-metallicity relation of the two galaxies. The implications of this study for some still highly debated points regarding the AGB evolution are also commented.

  3. High scale anisotropies in planetary nebulae

    Energy Technology Data Exchange (ETDEWEB)

    Pascoli, G.

    1986-06-01

    We present a new classification of Planetary Nebulae (PN) grounded on their characteristic symmetries: bipolarity, ring shape, spiral structure, etc... The different anisotropic models (rotation of nucleus, binary progenitor intranebular magnetic field, nebular rotation, etc...) which have been lately proposed, are analysed and their explanatory power is tested with certain morphological criterious. The comparison with the other classifications (Acker, 1980; Kaler, 1978; Peimbert, 1978) reveals that the morphology has been insufficiently discussed in these latters.

  4. A METHOD TO CONSTRAIN THE SIZE OF THE PROTOSOLAR NEBULA

    Energy Technology Data Exchange (ETDEWEB)

    Kretke, K. A.; Levison, H. F.; Buie, M. W. [Southwest Research Institute, Department of Space Studies, 1050 Walnut Street, Suite 400, Boulder, CO 80302 (United States); Morbidelli, A., E-mail: kretke@boulder.swri.edu [Observatoire de la Cote d' Azur, BP 4229, 06304 Nice Cedex 4 (France)

    2012-04-15

    Observations indicate that the gaseous circumstellar disks around young stars vary significantly in size, ranging from tens to thousands of AU. Models of planet formation depend critically upon the properties of these primordial disks, yet in general it is impossible to connect an existing planetary system with an observed disk. We present a method by which we can constrain the size of our own protosolar nebula using the properties of the small body reservoirs in the solar system. In standard planet formation theory, after Jupiter and Saturn formed they scattered a significant number of remnant planetesimals into highly eccentric orbits. In this paper, we show that if there had been a massive, extended protoplanetary disk at that time, then the disk would have excited Kozai oscillations in some of the scattered objects, driving them into high-inclination (i {approx}> 50 Degree-Sign ), low-eccentricity orbits (q {approx}> 30 AU). The dissipation of the gaseous disk would strand a subset of objects in these high-inclination orbits; orbits that are stable on Gyr timescales. To date, surveys have not detected any Kuiper-belt objects with orbits consistent with this dynamical mechanism. Using these non-detections by the Deep Ecliptic Survey and the Palomar Distant Solar System Survey we are able to rule out an extended gaseous protoplanetary disk (R{sub D} {approx}> 80 AU) in our solar system at the time of Jupiter's formation. Future deep all sky surveys such as the Large Synoptic Survey Telescope will allow us to further constrain the size of the protoplanetary disk.

  5. Kinematics, turbulence and evolution of planetary nebulae

    CERN Document Server

    Gesicki, K; Zijlstra, A A; Gesicki, Krzysztof; Acker, Agnes; Zijlstra, Albert A.

    2003-01-01

    This paper discusses the location of a sample of planetary nebulae on the HR diagram. We determine the internal velocity fields of 14 planetary nebulae from high-resolution echelle spectroscopy, with the help of photoionization models. The mass averaged velocity is shown to be a robust, simple parameter describing the outflow. The expansion velocity and radius are used to define the dynamical age; together with the stellar temperature, this gives a measurement of the luminosity and core mass of the central star. The same technique is applied to other planetary nebulae with previously measured expansion velocities, giving a total sample of 73 objects. The objects cluster closely around the Schoenberner track of 0.61 M_sun, with a very narrow distribution of core masses. The masses are higher than found for local white dwarfs. The luminosities determined in this way tend to be higher by a factor of a few than those derived from the nebular luminosities. The discrepancy is highest for the hottest (most evolved) ...

  6. The evolution of planetary nebulae VII. Modelling planetary nebulae of distant stellar systems

    CERN Document Server

    Schönberner, D; Sandin, C; Steffen, M

    2010-01-01

    By means of hydrodynamical models we do the first investigations of how the properties of planetary nebulae are affected by their metal content and what can be learned from spatially unresolved spectrograms of planetary nebulae in distant stellar systems. We computed a new series of 1D radiation-hydrodynamics planetary nebulae model sequences with central stars of 0.595 M_sun surrounded by initial envelope structures that differ only by their metal content. At selected phases along the evolutionary path, the hydrodynamic terms were switched off, allowing the models to relax for fixed radial structure and radiation field into their equilibrium state with respect to energy and ionisation. The analyses of the line spectra emitted from both the dynamical and static models enabled us to systematically study the influence of hydrodynamics as a function of metallicity and evolution. We also recomputed selected sequences already used in previous publications, but now with different metal abundances. These sequences w...

  7. A deep kinematic survey of planetary nebulae in the Andromeda Galaxy using the Planetary Nebula Spectrograph

    CERN Document Server

    Merrett, H R; Bridges, T J; Capaccioli, M; Carter, D; Coccato, L; Douglas, N G; Evans, N W; Freeman, K C; Gerhard, O; Halliday, C; Kuijken, K; Merrifield, M R; Napolitano, N R; Romanowsky, A J; Wilkinson, M I

    2006-01-01

    We present a catalogue of positions, magnitudes and velocities for 3300 emission-line objects found by the Planetary Nebula Spectrograph in a survey of the Andromeda Galaxy, M31. Of these objects, 2615 are found likely to be planetary nebulae (PNe) associated with M31. The survey area covers the whole of M31's disk out to a radius of 1.5 degrees. Beyond this radius, observations have been made along the major and minor axes, and the Northern Spur and Southern Stream regions. The calibrated data have been checked for internal consistency and compared with other catalogues. With the exception of the very central, high surface brightness region of M31, this survey is complete to a magnitude limit of m_5007~23.75, 3.5 magnitudes into the planetary nebula luminosity function.

  8. Early

    Directory of Open Access Journals (Sweden)

    Kamel Abd Elaziz Mohamed

    2014-04-01

    Conclusion: Early PDT is recommended for patients who require prolonged tracheal intubation in the ICU as outcomes like the duration of mechanical ventilation length of ICU stay and hospital stay were significantly shorter in early tracheostomy.

  9. Extreme early solar system chemical fractionation recorded by alkali-rich clasts contained in ordinary chondrite breccias

    Science.gov (United States)

    Yokoyama, Tatsunori; Misawa, Keiji; Okano, Osamu; Shih, Chi-Yu; Nyquist, Laurence E.; Simon, Justin I.; Tappa, Michael J.; Yoneda, Shigekazu

    2017-01-01

    New K-Ca and Rb-Sr isotopic analyses have been performed on alkali-rich igneous rock fragments in the Yamato (Y)-74442 and Bhola LL-chondritic breccias to better understand the extent and timing of alkali enrichments in the early solar system. The Y-74442 fragments yield a K-Ca age of 4.41 ± 0.28 Ga for λ(40K) = 0.5543 Ga-1 with an initial 40Ca/44Ca ratio of 47.1618 ± 0.0032. Studying the same fragments with the Rb-Sr isotope system yields an age of 4.420 ± 0.031 Ga for λ(87Rb) = 0.01402 Ga-1 with an initial ratio of 87Sr/86Sr = 0.7203 ± 0.0044. An igneous rock fragment contained in Bhola shows a similar alkali fractionation pattern to those of Y-74442 fragments but does not plot on the K-Ca or Rb-Sr isochron of the Y-74442 fragments. Calcium isotopic compositions of whole-rock samples of angrite and chondrites are primordial, indistinguishable from mantle-derived terrestrial rocks, and here considered to represent the initial composition of bulk silicate Earth. The initial ε40Ca value determined for the source of the alkali clasts in Y-74442 that is ∼0.5 ε-units higher than the solar system value implies an early alkali enrichment. Multi-isotopic studies on these alkali-rich fragments reveal that the source material of Y-74442 fragments had elemental ratios of K/Ca = 0.43 ± 0.18, Rb/Sr = 3.45 ± 0.66 and K/Rb ∼ 170, that may have formed from mixtures of an alkali-rich component (possibly an alkali-enriched gaseous reservoir produced by fractionation of early nebular condensates) and chondritic components that were flash-heated during an impact event on the LL-chondrite parent body ∼4.42 Ga ago. Further enrichments of potassium and rubidium relative to calcium and strontium as well as a mutual alkali-fractionation (K/Rb ∼ 50 and heavier alkali-enrichment) would have likely occurred during subsequent cooling and differentiation of this melt. Alkali fragments in Bhola might have undergone similar solid-vapor fractionation processes to those of Y

  10. [An early warning method of cucumber downy mildew in solar greenhouse based on canopy temperature and humidity modeling].

    Science.gov (United States)

    Wang, Hui; Li, Mei-lan; Xu, Jian-ping; Chen, Mei-xiang; Li, Wen-yong; Li, Ming

    2015-10-01

    The greenhouse environmental parameters can be used to establish greenhouse nirco-climate model, which can combine with disease model for early warning, with aim of ecological controlling diseases to reduce pesticide usage, and protecting greenhouse ecological environment to ensure the agricultural product quality safety. Greenhouse canopy leaf temperature and air relative humidity, models were established using energy balance and moisture balance principle inside the greenhouse. The leaf temperature model considered radiation heat transfer between the greenhouse crops, wall, soil and cover, plus the heat exchange caused by indoor net radiation and crop transpiration. Furthermore, the water dynamic balance in the greenhouse including leaf transpiration, soil evaporation, cover and leaf water vapor condensation, was considered to develop a relative humidity model. The primary infection and latent period warning models for cucumber downy mildew (Pseudoperonospora cubensis) were validated using the results of the leaf temperature and relative humidity model, and then the estimated disease occurrence date of cucumber downy mildew was compared with actual disease occurrence date of field observation. Finally, the results were verified by the measured temperature and humidity data of September and October, 2014. The results showed that the root mean square deviations (RMSDs) of the measured and estimated leaf temperature were 0.016 and 0.024 °C, and the RMSDs of the measured and estimated air relative humidity were 0.15% and 0.13%, respectively. Combining the result of estimated temperature and humidity models, a cucumber disease early warning system was established to forecast the date of disease occurrence, which met with the real date. Thus, this work could provide the micro-environment data for the early warning system of cucumber diseases in solar greenhouses.

  11. Outflows, dusty cores, and a burst of star formation in the North America and Pelican nebulae

    Energy Technology Data Exchange (ETDEWEB)

    Bally, John [Department of Astrophysical and Planetary Sciences, University of Colorado, UCB 389, Boulder, CO 80309 (United States); Ginsburg, Adam [European Southern Observatory, Karl-Schwarzschild-Str. 2, D-85748 Garching bei Munchen (Germany); Probst, Ron [National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85719 (United States); Reipurth, Bo [Institute for Astronomy and NASA Astrobiology Institute, University of Hawaii at Manoa, 640 North A' ohoku Place, Hilo, HI 96720 (United States); Shirley, Yancy L. [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Stringfellow, Guy S., E-mail: John.Bally@colorado.edu, E-mail: aginsburg@eso.org, E-mail: probst@noao.edu, E-mail: reipurth@ifa.hawaii.edu, E-mail: yshirley@as.arizona.edu, E-mail: Guy.Stringfellow@colorado.edu [Center for Astrophysics and Space Astronomy, University of Colorado, UCB 389, Boulder, CO 80309 (United States)

    2014-12-01

    We present observations of near-infrared 2.12 μm molecular hydrogen outflows emerging from 1.1 mm dust continuum clumps in the North America and Pelican Nebula (NAP) complex selected from the Bolocam Galactic Plane Survey (BGPS). Hundreds of individual shocks powered by over 50 outflows from young stars are identified, indicating that the dusty molecular clumps surrounding the NGC 7000/IC 5070/W80 H II region are among the most active sites of ongoing star formation in the solar vicinity. A spectacular X-shaped outflow, MHO 3400, emerges from a young star system embedded in a dense clump more than a parsec from the ionization front associated with the Pelican Nebula (IC 5070). Suspected to be a binary, the source drives a pair of outflows with orientations differing by 80°. Each flow exhibits S-shaped symmetry and multiple shocks indicating a pulsed and precessing jet. The 'Gulf of Mexico', located south of the North America Nebula (NGC 7000), contains a dense cluster of molecular hydrogen objects (MHOs), Herbig-Haro (HH) objects, and over 300 young stellar objects (YSOs), indicating a recent burst of star formation. The largest outflow detected thus far in the North America and Pelican Nebula complex, the 1.6 parsec long MHO 3417 flow, emerges from a 500 M {sub ☉} BGPS clump and may be powered by a forming massive star. Several prominent outflows such as MHO 3427 appear to be powered by highly embedded YSOs only visible at λ > 70 μm. An 'activity index' formed by dividing the number of shocks by the mass of the cloud containing their source stars is used to estimate the relative evolutionary states of Bolocam clumps. Outflows can be used as indicators of the evolutionary state of clumps detected in millimeter and submillimeter dust continuum surveys.

  12. Mining the HST Survey of the Orion Nebula Cluster

    Science.gov (United States)

    Robberto, Massimo; Da Rio, Nicola

    2013-07-01

    The Hubble Space Telescope (HST) Treasury Program on the Orion Nebula Cluster has used 104 orbits of HST time to image the Great Orion Nebula region with the Advanced Camera for Surveys (ACS), the Wide-Field/Planetary Camera 2 (WFPC2) and the Near Infrared Camera and Multi Object Spectrograph (NICMOS) instrument in 11 filters ranging from the U-band to the H-band equivalent of HST. The program has been intended to perform the definitive study of the stellar component of the ONC at visible wavelengths, addressing key questions like the cluster IMF, age spread, mass accretion, binarity and circumstellar disk evolution. The scanning pattern allowed to cover a contiguous field of approximately 600 square arcmin with both ACS and WFPC2 reaching a photometric depth AB(F435W)=25.8 and AB(F775W)=25.2 with 0.2 magnitudes of photometric error. The paper Robberto et al. (2013, ApJSS 207, 10) describes the observations, data reduction and data products, including images, source catalogs and tools for quick look preview. In particular, source catalogs provide ACS photometry for 3399 stars, most of them detected at multiple epochs, WFPC2 photometry for 1643 stars, 1021 of them detected in the U-band, and NICMOS JH photometry for 2117 stars. The paper also summarize the early science results already published. The final set of images and the photometric catalogs are now publicly available through the archive as High Level Science Products at the STScI Multimission Archive hosted by the Space Telescope Science Institute. Here is a graphic description of how to access the data.

  13. AMMONIA IN THE EARLY SOLAR SYSTEM: AN ACCOUNT FROM CARBONACEOUS METEORITES

    Energy Technology Data Exchange (ETDEWEB)

    Pizzarello, S. [Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ 85287-1604 (United States); Williams, L. B., E-mail: pizzar@asu.edu [School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287-1404 (United States)

    2012-04-20

    This study presents a survey of abundance distribution and isotopic composition of the ammonia found incorporated in the kerogen-like insoluble material of selected carbonaceous chondrite meteorites; the ammonia was released upon hydrothermal treatment at 300 Degree-Sign C and 100 MPa. With the exception of Allende, a metamorphosed and highly altered stone, all the insoluble organic materials (IOM) of the meteorites analyzed released significant amounts of ammonia, which varied from over 4 {mu}g mg{sup -1} for the Orgueil IOM to 0.5 {mu}g mg{sup -1} for that of Tagish Lake; the IOM of the pristine Antarctica find GRA95229 remains the most rich in freeable ammonia with 10 {mu}g mg{sup -1}. While the amounts of IOM bound ammonia do not appear to vary between meteorites with a recognizable trend, a possible consequence of long terrestrial exposure of some of the stones, we found that the {delta}{sup 15}N composition of the ammonia-carrying materials is clearly distinctive of meteorite types and may reflect a preservation of the original {sup 15}N distribution of pre- and proto-solar materials.

  14. Corundum-Hibonite Inclusions and the Environments of High Temperature Processing in the Early Solar System

    Science.gov (United States)

    Needham, A. W.; Messenger, S.

    2013-01-01

    Calcium, Aluminum-rich inclusions (CAIs) are composed of the suite of minerals predicted to be the first to condense from a cooling gas of solar composition [1]. Yet, the first phase to condense, corundum, is rare in CAIs, having mostly reacted to form hibonite followed by other phases at lower temperatures. Many CAIs show evidence of complex post-formational histories, including condensation, evaporation, and melting [e.g. 2, 3]. However, the nature of these thermal events and the nebular environments in which they took place are poorly constrained. Some corundum and corundum-hibonite grains appear to have survived or avoided these complex CAI reprocessing events. Such ultra-refractory CAIs may provide a clearer record of the O isotopic composition of the Sun and the evolution of the O isotopic composition of the planet-forming region [4-6]. Here we present in situ O and Mg isotopic analyses of two corundum/hibonite inclusions that record differing formation histories.

  15. Raster Scanning the Crab Nebula to Produce an Extended VHE Calibration Source

    CERN Document Server

    Bird, Ralph

    2015-01-01

    The Crab Nebula has long been the standard reference point source for very-high-energy (VHE, E $>$100 GeV) gamma-ray observatories such as VERITAS. It has enabled testing and improvement of analysis methods, validation of techniques, and has served as a calibration source. No comparable extended source is known with a high, constant flux and well understood morphology. In order to artificially generate such a source, VERITAS has performed raster scans across the Crab Nebula. By displacing the source within the field-of-view in a known pattern, it is possible to generate an extended calibration source for verification of extended source analysis techniques. The method as well as early results of this novel technique are presented.

  16. Measurement of the 33S(\\alpha,p)36Cl cross section: Implications for production of 36Cl in the early Solar System

    CERN Document Server

    Bowers, Matthew; Bauder, William; Beard, Mary; Collon, Philippe; Lu, Wenting; Ostdiek, Karen; Robertson, Daniel

    2013-01-01

    Short-lived radionuclides (SLRs) with lifetimes \\tau < 100 Ma are known to have been extant when the Solar System formed over 4.5 billion years ago. Identifying the sources of SLRs is important for understanding the timescales of Solar System formation and processes that occurred early in its history. Extinct 36Cl (t_1/2 = 0.301 Ma) is thought to have been produced by interaction of solar energetic particles (SEPs), emitted by the young Sun, with gas and dust in the nascent Solar System. However, models that calculate SLR production in the early Solar System (ESS) lack experimental data for the 36Cl production reactions. We present here the first measurement of the cross section of one of the main 36Cl production reactions, 33S(\\alpha,p)36Cl, in the energy range 0.70 - 2.42 MeV/A. The cross section measurement was performed by bombarding a target and collecting the recoiled 36Cl atoms produced in the reaction, chemically processing the samples, and measuring the 36Cl/Cl ratio of the activated samples with ...

  17. Polarisation properties of OH emission in planetary nebulae

    CERN Document Server

    Gomez, Jose F; Green, James A; Miranda, Luis F; Suarez, Olga; Bendjoya, Philippe

    2016-01-01

    We present the interferometric, full-polarisation observations of the four ground-state transitions of OH, toward five confirmed and one candidate OH-emitting planetary nebulae (OHPNe). OHPNe are believed to be very young PNe, and information on their magnetic fields (provided by their polarisation) could be key to understand the early evolution of PNe. We detect significant circular and linear polarisation in four and two objects, respectively. Possible Zeeman pairs are seen in JaSt 23 and IRAS 17393-2727, resulting in estimates of magnetic field strengths between 0.8 and 24 mG. We also report the new detection of OH emission at 1720 MHz toward Vy 2-2, making it the third known PN with this type of emission. We suggest that younger PNe have spectra dominated by narrow maser features and higher degrees of polarisation. Shock-excited emission at 1720 MHz seems to be more common in PNe than in early evolutionary phases, and could be related to equatorial ejections during the early PN phase.

  18. Paleomagnetism. Solar nebula magnetic fields recorded in the Semarkona meteorite.

    Science.gov (United States)

    Fu, Roger R; Weiss, Benjamin P; Lima, Eduardo A; Harrison, Richard J; Bai, Xue-Ning; Desch, Steven J; Ebel, Denton S; Suavet, Clément; Wang, Huapei; Glenn, David; Le Sage, David; Kasama, Takeshi; Walsworth, Ronald L; Kuan, Aaron T

    2014-11-28

    Magnetic fields are proposed to have played a critical role in some of the most enigmatic processes of planetary formation by mediating the rapid accretion of disk material onto the central star and the formation of the first solids. However, there have been no experimental constraints on the intensity of these fields. Here we show that dusty olivine-bearing chondrules from the Semarkona meteorite were magnetized in a nebular field of 54 ± 21 microteslas. This intensity supports chondrule formation by nebular shocks or planetesimal collisions rather than by electric currents, the x-wind, or other mechanisms near the Sun. This implies that background magnetic fields in the terrestrial planet-forming region were likely 5 to 54 microteslas, which is sufficient to account for measured rates of mass and angular momentum transport in protoplanetary disks.

  19. Solar nebula magnetic fields recorded in the Semarkona meteorite

    DEFF Research Database (Denmark)

    Fu, Roger R.; Weiss, Benjamin P.; Lima, Eduardo A.

    2014-01-01

    on the intensity of these fields. Here we show that dusty olivine-bearing chondrules from the Semarkona meteorite were magnetized in a nebular field of 54 ± 21 microteslas. This intensity supports chondrule formation by nebular shocks or planetesimal collisions rather than by electric currents, the x-wind...

  20. Are cosmic rays effective for ionization of the solar nebula?

    Science.gov (United States)

    Dolginov, A. Z.; Stepinski, T. F.

    1993-01-01

    In this paper, we argue that the effectiveness of cosmic rays to ionize the bulk of the nebular gas may be further impaired by the influence of the magnetic field on the propagation of cosmic rays. When cosmic rays enter the nebular disk they ionize the gas and make the dynamo generation of magnetic fields possible. However, once magnetic fields are embedded in the nebular gas, the upcoming cosmic rays can no longer penetrate directly into the nebular disk because they start to interact with the magnetic field and lose their energy before propagating significantly toward the midplane. That, in turn, undercuts the ionization source within the bulk of the gas stopping the dynamo action. Nebular dynamo models ignored this back reaction of magnetic fields on cosmic rays. We calculate this back reaction effect, but for the sake of mathematical simplicity, we ignore the effect of magnetic field weakening due to diminishing ionization by cosmic rays.

  1. Herschel Planetary Nebula Survey (HerPlaNS). First detection of OH+ in planetary nebulae

    NARCIS (Netherlands)

    Aleman, I.; Ueta, T.; Ladjal, D.; Exter, K.M.; Kastner, J.H.; Montez, R.; Tielens, A.G.G.M.; Chu, Y.-H.; Izumiura, H.; McDonald, I.; Sahai, R.; Siódmiak, N.; Szczerba, R.; Hoof, van P. A. M.; Villaver, E.; Vlemmings, W.; Wittkowski, M.; Zijlstra, A.A.

    2014-01-01

    We report the first detections of OH+emission in planetary nebulae (PNe). As part of an imaging and spectroscopy survey of 11 PNe in the far-IR using the PACS and SPIRE instruments aboard the HerschelSpace Observatory, we performed a line survey in these PNe over the entire spectral range between 51

  2. Enhanced gamma-ray activity from the Crab nebula

    Science.gov (United States)

    Buehler, R.; Ciprini, S.

    2016-01-01

    Preliminary LAT analysis indicates enhanced gamma-ray activity from the Crab nebula. The daily-averaged gamma-ray emission (E > 100 MeV) from the direction of the Crab Nebula has surpassed 4.0 x 10^-6 ph cm^-2 s^-1 five times in the last 12 days.

  3. X-ray Pulsar in the Crab Nebula.

    Science.gov (United States)

    Fritz, G; Henry, R C; Meekins, J F; Chubb, T A; Friedman, H

    1969-05-09

    X-ray pulsations have been observed in the Crab Nebula at a frequency closely matching the radio and optical pulsations. About 5 percent of the total x-ray power of the nebula appears in the pulsed component. The x-ray pulsations have the form of a main pulse and an interpulse separated by about 12 milliseconds.

  4. Abundances in planetary nebulae : Me 2-1

    NARCIS (Netherlands)

    Surendiranath, R; Pottasch, [No Value; Garcia-Lario, P

    ISO and IUE spectra of the round planetary nebula Me 2-1 are combined with Visual spectra taken from the literature to obtain for the first time a complete extinction-corrected spectrum. With this, the physico-chemical characteristics of the nebula and its central star are determined by various

  5. A 15N-poor isotopic composition for the solar system as shown by Genesis solar wind samples.

    Science.gov (United States)

    Marty, B; Chaussidon, M; Wiens, R C; Jurewicz, A J G; Burnett, D S

    2011-06-24

    The Genesis mission sampled solar wind ions to document the elemental and isotopic compositions of the Sun and, by inference, of the protosolar nebula. Nitrogen was a key target element because the extent and origin of its isotopic variations in solar system materials remain unknown. Isotopic analysis of a Genesis Solar Wind Concentrator target material shows that implanted solar wind nitrogen has a (15)N/(14)N ratio of 2.18 ± 0.02 × 10(-3) (that is, ≈40% poorer in (15)N relative to terrestrial atmosphere). The (15)N/(14)N ratio of the protosolar nebula was 2.27 ± 0.03 × 10(-3), which is the lowest (15)N/(14)N ratio known for solar system objects. This result demonstrates the extreme nitrogen isotopic heterogeneity of the nascent solar system and accounts for the (15)N-depleted components observed in solar system reservoirs.

  6. Extreme Particle Acceleration via Magnetic Reconnection in the Crab Nebula

    Science.gov (United States)

    Cerutti, Benoit; Uzdensky, D. A.; Begelman, M. C.

    2012-01-01

    The discovery by Agile and Fermi of intense day-long synchrotron gamma-ray flares above 100 MeV in the Crab Nebula challenges classical models of pulsar wind nebulae and particle acceleration. We argue that the flares are powered by magnetic reconnection in the nebula. Using relativistic test-particle simulations, we show that particles are naturally focused into a thin fan beam, deep inside the reconnection layer where the magnetic field is small. The particles then suffer less from synchrotron losses and pile up at the maximum energy given by the electric potential drop in the layer. Applying this model to the Crab Nebula, we find that the emerging synchrotron emission spectrum above 100 MeV is consistent with the September 2010 flare observations. No detectable emission is expected at other wavelengths. This scenario provides a viable explanation for the Crab Nebula gamma-ray flares.

  7. Solution to the Sigma-Problem of Pulsar Wind Nebulae

    CERN Document Server

    Porth, Oliver; Keppens, Rony

    2012-01-01

    We present first results of three dimensional relativistic magnetohydrodynamical simulations of Pulsar Wind Nebulae. They show that the kink instability and magnetic dissipation inside these nebulae may be the key processes allowing to reconcile their observations with the theory of pulsar winds. In particular, the size of the termination shock, obtained in the simulations, agrees very well with the observations even for Poynting-dominated pulsar winds. Due to magnetic dissipation the total pressure in the simulated nebulae is particle-dominated and more or less uniform. While in the main body of the simulated nebulae the magnetic field becomes rather randomized, close to the termination shock, it is dominated by the regular toroidal field freshly injected by the pulsar wind. This field is responsible for driving polar outflows and may explain the high polarization observed in pulsar wind nebulae.

  8. Ices Under Conditions of Planetary Nebulae

    Science.gov (United States)

    Yeghikyan, A. G.

    2017-07-01

    A large number of molecules are observed in planetary nebulae, both simple, the most common (H2, CO and OH), and more complex (H2O, SiO, HCN, HNC, HCO+), and even the polycyclic aromatic hydrocarbons and fullerenes containing a few dozen and more atoms. The water molecules are observed, as a rule, in the young objects, in the gas phase (water "fountains" and related water masers) and solid phase (emission of crystalline ice particles), and, regardless of the C/O ratio, water and carbon-containing molecules may be linked to the same object. On the other hand, the results of calculations by the well known Cloudy computer program given in this paper for stationery models, show that the abundance of water ice in planetary nebulae, other conditions being equal, is dependent on the ionization rate of hydrogen, which depends in turn on the flux of energetic particles (protons and alpha particles) in the range of MeV energies and higher. The possibility of the increased flux of such particles in planetary nebulae under conditions of the standard interacting stellar winds scenario is discussed, when the flux may locally exceed by 1-3 orders of magnitude that of caused by galactic cosmic rays. Calculated water ice column densities reach values up to 1018-1019 cm-2 at the usual average ISM H2 ionisation rate of 10-16s -1 and sharply decrease for the thousands times larger rates. Known observed results of NGC 6302 show for the column density of crystalline ice about 1019cm-2 close to the calculated one.

  9. Determination of rare earth and refractory trace element abundances in early solar system objects by ion microprobe

    Indian Academy of Sciences (India)

    S Sahijpal; K K Marhas; J N Goswami

    2003-12-01

    Experimental and analytical procedures devised for measurement of rare earth element (REE) abundances using a secondary ion mass spectrometer (ion microprobe) are described. This approach is more versatile than the conventional techniques such as neutron activation analysis and isotope dilution mass spectrometry by virtue of its high spatial resolution that allows determination of REE abundances in small domains (10-20 micron) within individual mineral phases. The ion microprobe measurements are performed at a low mass-resolving power adopting the energy-filltering technique (Zinner and Crozaz 1986) for removal and suppression of unresolved complex molecular interferences in the REE masses of interest. Synthetic standards are used for determining various instrument specific parameters needed in the data deconvolution procedure adopted for obtaining REE abundances. Results obtained from analysis of standards show that our ion microprobe may be used for determining REE abundances down to ppm range with uncertainties of ∼10 to 15%. Abundances of rare earth and several other refractory trace elements in a set of early solar system objects isolated from two primitive carbonaceous chondrites were determined using the procedures devised by us. The results suggest that some of these objects could be high temperature nebular condensates, while others are products of melting and recrystallization of precursor nebular solids in a high temperature environment.

  10. Heat, Aromatic Units, and Iron-Rich Phyllosilicates: A Mechanism for Making Macromolecules in the Early Solar System.

    Science.gov (United States)

    Watson, Jonathan S; Sephton, Mark A

    2015-10-01

    The major organic component in carbonaceous chondrites is a highly aromatic macromolecular material. Aromatic organic matter and phyllosilicates are colocated in these meteorites, and it is possible that the physical association represents a synthetic chemical relationship. To explore the potential reactions that could take place to produce the aromatic macromolecular material, we heated various simple aromatic units in the presence of montmorillonite with different exchanged cations. The majority of cation-exchanged montmorillonites tested, sodium-, aluminum-, iron-, nickel-, and cobalt-rich montmorillonites, do not produce polymerization products. By contrast, Fe(3+) cation-exchanged montmorillonite readily facilitates addition reactions between aromatic hydrocarbons. A feasible mechanism for the process is oxidative coupling, which involves a corresponding reduction of the Fe(3+) cation to its Fe(2+) counterpart. A similar reduction process for the other metal cations does not take place, highlighting the importance of iron. This simple process is one feasible mechanism for the construction of aromatic macromolecules such as those found in carbonaceous chondrites. The search for a relationship between Fe(3+)-rich phyllosilicates and aromatic organic structures (particularly dimers, trimers, and more polymerized forms) in carbonaceous chondrites would represent an effective test for constraining the role of clay catalysis in the early Solar System.

  11. {sup 57}Fe Moessbauer Spectroscopy Studies of Meteorites: Implications for Weathering Rates, Meteorite Flux, and Early Solar System Processes

    Energy Technology Data Exchange (ETDEWEB)

    Bland, P. A. [Open University, Planetary Science Research Institute (United Kingdom); Berry, F. J. [Open University, Department of Chemistry (United Kingdom); Jull, A. J. T. [University of Arizona, NSF Accelerator Facility for Radioisotope Analyses (United States); Smith, T. B. [Open University, Department of Physics and Astronomy (United Kingdom); Bevan, A. W. R. [Western Australian Museum, Department of Earth and Planetary Sciences (Australia); Cadogan, J. M. [University of New South Wales, School of Physics (Australia); Sexton, A. S.; Franchi, L. A.; Pillinger, C. T. [Open University, Planetary Science Research Institute (United Kingdom)

    2002-09-15

    Ordinary chondrite finds, terrestrial age dated using {sup 14}C analyses, from different meteorite accumulation sites, have been examined by Moessbauer spectroscopy to quantitatively determine terrestrial oxidation. We observe differences in weathering rates between sites, and also between different chondrite groups. A comparison of weathering over time, and its effect in 'eroding' meteorites, together with the number and mass distribution of meteorites in each region, enables us to derive estimates of the number of meteorite falls over a given mass per year. Studies of how the oxygen isotopic composition of samples varies with weathering indicate that incipient alteration may occur without a pronounced isotopic effect, possibly due to weathering of silicates to topotactically oriented smectite confined spaces where the water volume is limited. This finding has profound implications for the use of oxygen isotopes as a tool in understanding water-rock interaction. It also may reconcile previously contradictory data regarding the nebular or asteroidal location of pre-terrestrial aqueous alteration. Finally, Moessbauer spectroscopy is also found to be a useful tool in determining mineral abundance in carbonaceous chondrites, where a fine-grained matrix makes traditional approaches inapplicable. Again, the results have implications for the modification of chondritic materials in the early solar system.

  12. Element Masses in the Crab Nebula

    Science.gov (United States)

    Sibley, Adam R.; Katz, Andrea M.; Satterfield, Timothy J.; Vanderveer, Steven J.; MacAlpine, Gordon M.

    2016-10-01

    Using our previously published element abundance or mass-fraction distributions in the Crab Nebula, we derived actual mass distributions and estimates for overall nebular masses of hydrogen, helium, carbon, nitrogen, oxygen and sulfur. As with the previous work, computations were carried out for photoionization models involving constant hydrogen density and also constant nuclear density. In addition, employing new flux measurements for [Ni ii] λ7378, along with combined photoionization models and analytic computations, a nickel abundance distribution was mapped and a nebular stable nickel mass estimate was derived.

  13. DA495 - an aging pulsar wind nebula

    CERN Document Server

    Kothes, R; Reich, W; Safi-Harb, S; Arzoumanian, Z

    2008-01-01

    We present a radio continuum study of the pulsar wind nebula (PWN) DA 495 (G65.7+1.2), including images of total intensity and linear polarization from 408 to 10550 MHz based on the Canadian Galactic Plane Survey and observations with the Effelsberg 100-m Radio Telescope. Removal of flux density contributions from a superimposed \\ion{H}{2} region and from compact extragalactic sources reveals a break in the spectrum of DA 495 at 1.3 GHz, with a spectral index ${\\alpha}={-0.45 \\pm 0.20}$ below the break and ${\\alpha}={-0.87 \\pm 0.10}$ above it (${S}_\

  14. Kinematic Distance of Galactic Planetary Nebulae

    CERN Document Server

    Yang, A Y; Zhu, H; Leahy, D A; Wu, D

    2016-01-01

    We construct \\HI~absorption spectra for 18 planetary nebulae (PNe) and their background sources using the data from the International Galactic Plane Survey. We estimate the kinematic distances of these PNe, among which 15 objects' kinematic distances are obtained for the first time. The distance uncertainties of 13 PNe range from 10% to 50%, which is a significant improvement with uncertainties of a factor two or three smaller than most of previous distance measurements. We confirm that PN G030.2-00.1 is not a PN because of its large distance found here.

  15. The Present and Future of Planetary Nebula Research. A White Paper by the IAU Planetary Nebula Working Group

    CERN Document Server

    Kwitter, K B; Peña, M; Stanghellini, L; Corradi, R L M; DeMarco, O; Fang, X; Henry, R B C; Karakas, A I; Liu, X -W; López, J A; Manchado, A; Parker, Q A

    2014-01-01

    We present a summary of current research on planetary nebulae and their central stars, and related subjects such as atomic processes in ionized nebulae, AGB and post-AGB evolution. Future advances are discussed that will be essential to substantial improvements in our knowledge in the field.

  16. High-resolution spectroscopy of central stars of planetary nebulae - LSS 1362

    Science.gov (United States)

    Heber, U.; Werner, K.; Drilling, J. S.

    1988-01-01

    High resolution spectra of the hot sdO star LSS 1362, a central star of a planetary nebula, are analyzed by means of model atmosphere techniques. Improved NLTE model atmospheres based on the newly developed 'accelerated lambda iteration' method are used. The very high effective temperature (100000 K) derived previously from the UV energy distribution is confirmed. The surface gravity (log g = 5.3) and a normal helium abundance are derived. A mass of 0.65 solar mass and a luminosity of 10 exp 3.9 solar luminosities result from a comparison with evolutionary tracks. The distance is 1.1 kpc and the nebula has a diameter of about 0.25 pc to 0.5 pc. Weak photospheric emission lines of He II, CIV, Nv, and O v are detected. These lines are slightly blue-shifted with respect to the absorption line spectrum which is regarded as evidence for an atmospheric velocity field. It is conjectured that the observed broadening of the metal lines (25 km/s) may be caused by the velocity field rather than by rotation.

  17. Planetary Nebula Abundances and Morphology: Probing the Chemical Evolution of the Milky Way

    CERN Document Server

    Stanghellini, L; Cunha, K; Manchado, A; Villaver, E

    2006-01-01

    This paper presents a homogeneous study of abundances in a sample of 79 northern galactic planetary nebulae whose morphological classes have been uniformly determined. Ionic abundances and plasma diagnostics were derived from selected optical line strengths in the literature, and elemental abundances were estimated with the Ionization Correction Factor developed by Kingsbourgh & Barlow (1994). We compare the elemental abundances to the final yields obtained from stellar evolution models of low-and intermediate-mass stars, and we confirm that most Bipolar planetary nebulae have high nitrogen and helium abundance, and are the likely progeny of stars with main-sequence mass larger than 3 solar masses. We derive =0.27, and discuss the implication of such a high ratio in connection with the solar neon abundance. We determine the galactic gradients of oxygen and neon, and found Delta log (O/H)/Delta R=-0.01 dex/kpc$ and Delta log (Ne/H)/Delta R=-0.01 dex/kpc. These flat PN gradients do not reconcile with galact...

  18. K 1-6: an asymmetric planetary nebula with a binary central star

    CERN Document Server

    Frew, David J; Fitzgerald, Michael; Parker, Quentin; Danaia, Lena; McKinnon, David; Guerrero, Martín A; Hedberg, John; Hollow, Robert; An, Yvonne; Bor, Shu Han; Colman, Isabel; Graham-White, Claire; Li, Qing Wen; Mai, Juliette; Papadakis, Katerina; Picone-Murray, Julia; Hoang, Melanie Vo; Yean, Vivian

    2010-01-01

    We present new imaging data and archival multiwavelength observations of the little studied emission nebula K 1-6 and its central star. Narrow-band images in H-alpha (+ [NII]) and [OIII] taken with the Faulkes Telescope North reveal a stratified, asymmetric, elliptical nebula surrounding a central star which has the colours of a late G- or early K-type subgiant or giant. GALEX ultraviolet images reveal a very hot subdwarf or white dwarf coincident in position with this star. The cooler, optically dominant star is strongly variable with a period of 21.312 +/- 0.008 days, and is possibly a high amplitude member of the RS CVn class, although an FK Com classification is also possible. Archival ROSAT data provide good evidence that the cool star has an active corona. We conclude that K 1-6 is most likely an old bona fide planetary nebula at a distance of ~1.0 kpc, interacting with the interstellar medium, and containing a binary or ternary central star. The observations and data analyses reported in this paper wer...

  19. The Eagle Nebula Science on NIF experiment

    Science.gov (United States)

    Kane, Jave; Heeter, Robert; Martinez, David; Pound, Marc; Remington, Bruce; Ryutov, Dmitri; Smalyuk, Vladimir

    2012-10-01

    The Eagle Nebula NIF experiment was one of nine selected for laser time through the Science on NIF program. The goal of this scale laboratory experiment is to study the dynamic evolution of distinctive structures in star forming regions of astrophysical molecular clouds such as the Pillars of the Eagle Nebula. That evolution is driven by photoionizing radiation from nearby stars. A critical aspect of the radiation is its very directional nature at the photoionization front. The long duration of the drive and its directionality can generate new classes of instabilities and dynamic flows at the front that may be responsible for the shapes of Pillars and other structures. The experiment will leverage and modify the existing NIF Radiation Transport platform, replacing the target at the back end of the halfraum with a collimating aperture, and extending the existing 20 ns drive to longer times, using a combination of gas fill and other new design features. The apertured, quasi-collimated drive will be used to drive a target placed 2 mm away from the aperture. The astrophysical background and the status of the experimental design will be presented.

  20. Detecting Abundance Variations in Planetary Nebulae

    Science.gov (United States)

    Monteiro, H.; Santos, P. M.; Falceta-Gonçalves, D.

    2014-04-01

    Empirical methods of investigating chemical abundances are still widely used as a primary tool to study planetary nebulae (PNe) as well as HII regions. In this work we investigate the capacity of the empirical abundance determination methods to recover pre-defined parameters and abundance variations in a realistically modeled planetary nebula. To perform the test we use a threedimensional density structure obtained from a hydrodynamical simulation which is fed through a threedimensional photoionization code. The density structure is an asymetrical and inhomogeneous elongated closed shell. The input parameters used, such as, ionizing source, density, and chemical abundances are typical values of type I PNe. The model emissivities are then projected in the line of sight and emission line maps are generated, which are used to obtain the temperature and density diagnostics. The diagnostics and line emission maps are then used to obtain spatially resolved maps of the abundances. In this work we use the method described above to investigate abundances for two distinct orientations of the density structure. Our results show that for typical signal to noise ratios obtained from long-slit spectroscopy, only large abundance variations can be determined with good precision.

  1. HUBBLE CAPTURES DYNAMICS OF CRAB NEBULA

    Science.gov (United States)

    2002-01-01

    A new sequence of Hubble Space Telescope images of the remnant of a tremendous stellar explosion is giving astronomers a remarkable look at the dynamic relationship between the tiny Crab Pulsar and the vast nebula that it powers. This picture shows a Hubble Space Telescope image of the inner parts of the Crab. The pulsar itself is visible as the left of the pair of stars near the center of the frame. Surrounding the pulsar is a complex of sharp knots and wisp-like features. This image is one of a sequence of Hubble images taken over the course of several months. This sequence shows that the inner part of the Crab Nebula is far more dynamic than previously understood. The Crab literally 'changes it stripes' every few days as these wisps stream away from the pulsar at half the speed of light. The Hubble Space Telescope photo was taken Nov. 5, 1995 by the Wide Field and Planetary Camera 2 at a wavelength of around 550 nanometers, in the middle of the visible part of the electromagnetic spectrum. Credit: Jeff Hester and Paul Scowen (Arizona State University), and NASA

  2. FITTING PHOTOIONIZATION MODELS TO PLANETARY NEBULAE

    Directory of Open Access Journals (Sweden)

    J. Bohigas

    2009-01-01

    Full Text Available Good to excellent photoionization models based on the Cloudy code were obtained for 13 out of 19 spectra of planetary nebulae. The two most important assumptions are that the photoionizing continuum is a Rauch model star, with gravity set by the condition that the stellar mass must be 1 M , and density is constant and determined from the observed [S II]6717/6731 ratio. The temperature and luminosity of the central star, the inner radius of the nebula and the abundance of carbon are treated as free parameters in each model run, destined to obtain the best possible t to the relative intensities of He II 4686, [O III]5007 and [N II]6584. Observed and modeled nebular temperatures derived from [N II] (6548+6584 /5755 agree within 10%, but models usually underestimate temperatures found from [O III] (4959+5007 /4363, more so when the slit does not cover the in-depth extent of the ionized region. Helium, nitrogen, oxygen, neon, sulfur and argon model abundances are uncertain at the 15%, 15%, 10%, 7%, 30% and 7% level. It is shown that neon abundance in PNe has been consistently overestimated, and an alternative ionization correction factor is recommended.

  3. Dark nebulae, dark lanes, and dust belts

    CERN Document Server

    Cooke, Antony

    2012-01-01

    As probably the only book of its type, this work is aimed at the observer who wants to spend time with something less conventional than the usual fare. Because we usually see objects in space by means of illumination of one kind or another, it has become routine to see them only in these terms. However, part of almost everything that we see is the defining dimension of dark shading, or even the complete obscuration of entire regions in space. Thus this book is focused on everything dark in space: those dark voids in the stellar fabric that mystified astronomers of old; the dark lanes reported in many star clusters; the magical dust belts or dusty regions that have given so many galaxies their identities; the great swirling 'folds' that we associate with bright nebulae; the small dark feature detectable even in some planetary nebulae; and more. Many observers pay scant attention to dark objects and details. Perhaps they are insufficiently aware of them or of the viewing potential they hold, but also it may be...

  4. High Velocity Features in the Orion Nebula

    CERN Document Server

    O'Dell, C R

    2008-01-01

    We have used widely spaced in time Hubble Space Telescope images to determine tangential velocities of features associated with outflows from young stars. These observations were supplemented by groundbased telescope spectroscopy and from the resultant radial velocities, space velocities were determined for many outflows. Numerous new moving features were found and grouped into known and newly assigned Herbig Haro objects. It was found that stellar outflow is highly discontinuous, as frequently is the case, with long-term gaps of a few hundred years and that these outflow periods are marked by staccato bursts over periods of about ten years. Although this has been observed in other regions, the Orion Nebula Cluster presents the richest display of this property. Most of the large scale Herbig Haro objects in the brightest part of the Orion Nebula appear to originate from a small region northeast of the strong Orion-S radio and infrared sources. With the possible exception of HH 203, we are not able to identify...

  5. THE CHANDRA X-RAY SURVEY OF PLANETARY NEBULAE (CHANPLANS): PROBING BINARITY, MAGNETIC FIELDS, AND WIND COLLISIONS

    Energy Technology Data Exchange (ETDEWEB)

    Kastner, J. H.; Montez, R. Jr.; Rapson, V. [Center for Imaging Science and Laboratory for Multiwavelength Astrophysics, Rochester Institute of Technology, 54 Lomb Memorial Drive, Rochester, NY 14623 (United States); Balick, B. [Department of Astronomy, University of Washington, Seattle, WA (United States); Frew, D. J.; De Marco, O.; Parker, Q. A. [Department of Physics and Astronomy and Macquarie Research Centre for Astronomy, Astrophysics and Astrophotonics, Macquarie University, Sydney, NSW 2109 (Australia); Miszalski, B. [South African Astronomical Observatory, P.O. Box 9, Observatory, 7935 (South Africa); Sahai, R. [Jet Propulsion Laboratory, California Institute of Technology, MS 183-900, Pasadena, CA 91109 (United States); Blackman, E.; Frank, A. [Department of Physics and Astronomy, University of Rochester, Rochester, NY (United States); Chu, Y.-H. [Department of Astronomy, University of Illinois, Champagne-Urbana, IL (United States); Guerrero, M. A. [Instituto de Astrofisica de Astronomia, Glorieta de la Astronomia s/n, Granada 18008 (Spain); Lopez, J. A. [Instituto de Astronomia, Universidad Nacional Autonoma de Mexico, Campus Ensenada, Apdo. Postal 22860, Ensenada, B. C. (Mexico); Zijlstra, A. [School of Physics and Astronomy, University of Manchester, Manchester M13 9PL (United Kingdom); Behar, E. [Department of Physics, Technion (Israel); Bujarrabal, V. [Observatorio Astronomico Nacional, Apartado 112, E-28803, Alcala de Henares (Spain); Corradi, R. L. M. [Instituto de Astrofisica de Canarias, E-38200 La Laguna, Tenerife (Spain); Nordhaus, J. [Center for Computational Relativity and Gravitation, Rochester Institute of Technology, Rochester, NY 14623 (United States); Sandin, C., E-mail: jhk@cis.rit.edu, E-mail: soker@physics.technion.ac.il, E-mail: eva.villaver@uam.es [Leibniz Institute for Astrophysics Potsdam (AIP), An der Sternwarte 16, D-14482 Potsdam (Germany); and others

    2012-08-15

    We present an overview of the initial results from the Chandra Planetary Nebula Survey (CHANPLANS), the first systematic (volume-limited) Chandra X-Ray Observatory survey of planetary nebulae (PNe) in the solar neighborhood. The first phase of CHANPLANS targeted 21 mostly high-excitation PNe within {approx}1.5 kpc of Earth, yielding four detections of diffuse X-ray emission and nine detections of X-ray-luminous point sources at the central stars (CSPNe) of these objects. Combining these results with those obtained from Chandra archival data for all (14) other PNe within {approx}1.5 kpc that have been observed to date, we find an overall X-ray detection rate of {approx}70% for the 35 sample objects. Roughly 50% of the PNe observed by Chandra harbor X-ray-luminous CSPNe, while soft, diffuse X-ray emission tracing shocks-in most cases, 'hot bubbles'-formed by energetic wind collisions is detected in {approx}30%; five objects display both diffuse and point-like emission components. The presence (or absence) of X-ray sources appears correlated with PN density structure, in that molecule-poor, elliptical nebulae are more likely to display X-ray emission (either point-like or diffuse) than molecule-rich, bipolar, or Ring-like nebulae. All but one of the point-like CSPNe X-ray sources display X-ray spectra that are harder than expected from hot ({approx}100 kK) central stars emitting as simple blackbodies; the lone apparent exception is the central star of the Dumbbell nebula, NGC 6853. These hard X-ray excesses may suggest a high frequency of binary companions to CSPNe. Other potential explanations include self-shocking winds or PN mass fallback. Most PNe detected as diffuse X-ray sources are elliptical nebulae that display a nested shell/halo structure and bright ansae; the diffuse X-ray emission regions are confined within inner, sharp-rimmed shells. All sample PNe that display diffuse X-ray emission have inner shell dynamical ages {approx}< 5 Multiplication

  6. Origin of the p-process radionuclides 92Nb and 146Sm in the early solar system and inferences on the birth of the Sun.

    Science.gov (United States)

    Lugaro, Maria; Pignatari, Marco; Ott, Ulrich; Zuber, Kai; Travaglio, Claudia; Gyürky, György; Fülöp, Zsolt

    2016-01-26

    The abundances of (92)Nb and (146)Sm in the early solar system are determined from meteoritic analysis, and their stellar production is attributed to the p process. We investigate if their origin from thermonuclear supernovae deriving from the explosion of white dwarfs with mass above the Chandrasekhar limit is in agreement with the abundance of (53)Mn, another radionuclide present in the early solar system and produced in the same events. A consistent solution for (92)Nb and (53)Mn cannot be found within the current uncertainties and requires the (92)Nb/(92)Mo ratio in the early solar system to be at least 50% lower than the current nominal value, which is outside its present error bars. A different solution is to invoke another production site for (92)Nb, which we find in the α-rich freezeout during core-collapse supernovae from massive stars. Whichever scenario we consider, we find that a relatively long time interval of at least ∼ 10 My must have elapsed from when the star-forming region where the Sun was born was isolated from the interstellar medium and the birth of the Sun. This is in agreement with results obtained from radionuclides heavier than iron produced by neutron captures and lends further support to the idea that the Sun was born in a massive star-forming region together with many thousands of stellar siblings.

  7. Origin of the p-process radionuclides 92Nb and 146Sm in the early Solar System and inferences on the birth of the Sun

    CERN Document Server

    Lugaro, Maria; Ott, Ulrich; Zuber, Kai; Travaglio, Claudia; Gyurky, Gyorgy; Fulop, Zsolt

    2016-01-01

    The abundances of 92Nb and 146Sm in the early Solar System are determined from meteoritic analysis and their stellar production is attributed to the p process. We investigate if their origin from thermonuclear supernovae deriving from the explosion of white dwarfs with mass above the Chandrasekhar limit is in agreement with the abundance of 53Mn, another radionuclide present in the early Solar System and produced in the same events. A consistent solution for 92Nb and 53Mn cannot be found within the current uncertainties and requires that the 92Nb/92Mo ratio in the early Solar System is at least 50% lower than the current nominal value, which is outside its present error bars. A different solution is to invoke another production site for 92Nb, which we find in the alpha-rich freezeout during core-collapse supernovae from massive stars. Whichever scenario we consider, we find that a relatively long time interval of at least ~10 Myr must have elapsed from when the star-forming region where the Sun was born was i...

  8. Hubble Space Telescope observations of Orion Nebula, Helix Nebula, and NGC 6822

    Science.gov (United States)

    Spitzer, Lyman; Fitzpatrick, Ed

    1999-01-01

    This grant covered the major part of the work of the Principal Investigator and his collaborators as a Guaranteed Time Observer on the Hubble Space Telescope. The work done naturally divided itself into two portions the first being study of nebular objects and the second investigation of the interstellar medium between stars. The latter investigation was pursued through a contract with Princeton University, with Professor Lyman Spitzer as the supervising astronomer, assisted by Dr. Ed Fitzpatrick. Following the abrupt death of Professor Spitzer, his responsibilities were shifted to Dr. Fitzpatrick. When Dr. Fitzpatrick relocated to Villanova University the concluding work on that portion of this grant was concluded under a direct service arrangement. This program has been highly successful and the resulting publications in scientific journals are listed below. To the scientist, this is the bottom line, so that I shall simply try to describe the general nature of what was accomplished. There were three nebular programs conducted, one on the Orion Nebula, the second on the Helix Nebula, and the third on NGC 6822. The largest program was that on the Orion Nebula. This involved both HST observations and supporting groundbased observations obtained with a variety of instruments, including the Coude Feed Telescope at the Kitt Peak National observatory in Arizona, the Cerro Tololo observatory in Chile, and the Keck Observatory on Mauna Kea, Hawaii. Moreover, considerable theoretical modeling was done and all of the data analysis was performed at the Rice University in Houston, except for the PI's period of sabbatical leave (6-96 through 7-97) when he was based at the Max Planck Institute for Astronomy in Heidelberg, Germany. The Orion Nebula program was the most productive part, resulting in numerous papers, but more important in the discovery of a new class of objects, for which we coined the name "proplyds". The proplyds are protoplanetary disks surrounding very young

  9. Forming Planets in the Hostile Carina Nebula

    Science.gov (United States)

    Kohler, Susanna

    2016-07-01

    Can protoplanetary disks form and be maintained around low-mass stars in the harsh environment of a highly active, star-forming nebula? A recent study examines the Carina nebula to answer this question.Crowded ClustersStars are often born in clusters that contain both massive and low-mass stars. The most massive stars in these clusters emit far-ultraviolet and extreme-ultraviolet light that irradiates the region around them, turning the surrounding area into a hostile environment for potential planet formation.Planet formation from protoplanetary disks typically requires timescales of at least 12 million years. Could the harsh radiation from massive stars destroy the protoplanetary disks around low-mass stars by photoevaporation before planets even have a chance to form?Artists impression of a protoplanetary disk. Such disks can be photoevaporated by harsh ultraviolet light from nearby massive stars, causing the disk to be destroyed before planets have a chance to form within them. [ESO/L. Calada]Turning ALMA Toward CarinaA perfect case study for exploring hostile environments is the Carina nebula, located about 7500 lightyears away and home to nearly 100 O-type stars as well as tens of thousands of lower-mass young stars. The Carina population is ~14 Myr old: old enough to form planets within protoplanetary disks, but also old enough that photoevaporation could already have wreaked havoc on those disks.Due to the dense stellar populations in Carinas clusters, this is a difficult region to explore, but the Atacama Large Millimeter-submillimeter Array (ALMA) is up to the task. In a recent study, a team of scientists led by Adal Mesa-Delgado (Pontifical Catholic University of Chile) made use of ALMAs high spatial resolution to image four regions spaced throughout Carina, searching for protoplanetary disks.Detections and Non-DetectionsTwo evaporating gas globules in the Carina nebula, 104-593 and 105-600, that each contain a protoplanetary disk. The top panels are

  10. The planetary nebula Abell 48 and its [WN4] nucleus

    CERN Document Server

    Frew, David J; Parker, Q A; Stupar, M; Wachter, S; DePew, K; Danehkar, A; Fitzgerald, M F

    2013-01-01

    We have conducted a detailed multi-wavelength study of the peculiar planetary nebula Abell 48 and its central star. We present evidence for a new classification of the nucleus as a helium-rich, hydrogen-deficient star of type [WN4], one of only two currently known examples of its type. The evidence for either a massive WN or a low-mass [WN] interpretation is critically examined, and we firmly conclude that Abell 48 is a planetary nebula around an evolved low-mass star, rather than a Population I ejecta nebula. Importantly, the surrounding nebula has a morphology typical of planetary nebulae, and is not enriched in nitrogen, and thus not the 'peeled atmosphere' of a massive star. We estimate a distance of 1.6 kpc and a reddening, E(B-V) = 1.90 mag, the latter value clearly showing the nebula lies on the near side of the Galactic bar, and therefore cannot be a massive WN star. The planetary nebula has an ionized mass (0.3 M_sun) and electron density (740 cm^-3) typical of somewhat evolved objects. The observed ...

  11. Comets as Messengers from the Early Solar System - Emerging Insights on Delivery of Water, Nitriles, and Organics to Earth

    Science.gov (United States)

    Mumma, Michael J.; Charnley, Steven B.

    2012-01-01

    The question of exogenous delivery of water and organics to Earth and other young planets is of critical importance for understanding the origin of Earth's volatiles, and for assessing the possible existence of exo-planets similar to Earth. Viewed from a cosmic perspective, Earth is a dry planet, yet its oceans are enriched in deuterium by a large factor relative to nebular hydrogen and analogous isotopic enrichments in atmospheric nitrogen and noble gases are also seen. Why is this so? What are the implications for Mars? For icy Worlds in our Planetary System? For the existence of Earth-like exoplanets? An exogenous (vs. outgassed) origin for Earth's atmosphere is implied, and intense debate on the relative contributions of comets and asteroids continues - renewed by fresh models for dynamical transport in the protoplanetary disk, by revelations on the nature and diversity of volatile and rocky material within comets, and by the discovery of ocean-like water in a comet from the Kuiper Belt (cf., Mumma & Charnley 2011). Assessing the creation of conditions favorable to the emergence and sustenance of life depends critically on knowledge of the nature of the impacting bodies. Active comets have long been grouped according to their orbital properties, and this has proven useful for identifying the reservoir from which a given comet emerged (OC, KB) (Levison 1996). However, it is now clear that icy bodies were scattered into each reservoir from a range of nebular distances, and the comet populations in today's reservoirs thus share origins that are (in part) common. Comets from the Oort Cloud and Kuiper Disk reservoirs should have diverse composition, resulting from strong gradients in temperature and chemistry in the proto-planetary disk, coupled with dynamical models of early radial transport and mixing with later dispersion of the final cometary nuclei into the long-term storage reservoirs. The inclusion of material from the natal interstellar cloud is probable

  12. Diffusive fractionation of carbon isotopes in γ-Fe: Experiment, models and implications for early solar system processes

    Science.gov (United States)

    Mueller, Thomas; Watson, E. Bruce; Trail, Dustin; Wiedenbeck, Michael; Van Orman, James; Hauri, Erik H.

    2014-02-01

    Carbon is an abundant element of planets and meteorites whose isotopes provide unique insights into both organic and inorganic geochemical processes. The identities of carbonaceous phases and their textural and isotopic characters shed light on dynamical processes in modern Earth systems and the evolution of the early solar system. In meteorites and their parent bodies, reduced carbon is often associated with Fe-Ni alloys, so knowledge of the mechanisms that fractionate C isotopes in such phases is crucial for deciphering the isotopic record of planetary materials. Here we present the results of a diffusion-couple experiment in which cylinders of polycrystalline Fe containing 11,500 and 150 μg/g of C were juxtaposed at 1273 K and 1.5 GPa for a duration of 36 min. Diffusion profiles of total C concentration and 13C/12C were measured by secondary ion mass spectrometry (SIMS). The elemental diffusivity extracted from the data is ˜3.0 × 10-11 m2 s-1, where 13C/12C was observed to change significantly along the diffusion profile, reflecting a higher diffusivity of 12C relative to 13C. The maximum isotopic fractionation along the diffusion profile is ˜30-40‰. The relative diffusivities (D) of the carbon isotopes can be related to their masses (M) by D/D=(C/M)β; the exponent β calculated from our data has a value of 0.225 ± 0.025. Similarly high β values for diffusion of other elements in metals have been taken as an indication of interstitial diffusion, so our results are consistent with C diffusion in Fe by an interstitial mechanism. The high β-value reported here means that significant fractionation of carbon isotopes in nature may arise via diffusion in Fe(-Ni) metal, which is an abundant component of planetary interiors and meteorites.

  13. X-ray Emission from the Guitar Nebula

    CERN Document Server

    Romani, R W; Yadigaroglu, I A; Romani, Roger W.; Cordes, James M.

    1997-01-01

    We have detected weak soft X-ray emission from the Pulsar Wind Nebula trailing the high velocity star PSR 2224+65 (the `Guitar Nebula'). This X-ray flux gives evidence of \\gamma~10^7 eV particles in the pulsar wind and constrains the properties of the post-shock flow. The X-ray emission is most easily understood if the shocked pulsar wind is partly confined in the nebula and if magnetic fields in this zone can grow to near equipartition values.

  14. The abundances of neon, sulfur, and argon in planetary nebulae

    Science.gov (United States)

    Beck, S. C.; Lacy, J. H.; Townes, C. H.; Aller, L. H.; Geballe, T. R.; Baas, F.

    1981-01-01

    New infrared observations of Ne II, Ar III, and S IV are used in optical observations of other ionization states of the considered elements to evaluate the abundances of neon, argon, and sulfur in 18 planetary nebulae. Attention is also given to one or more of the infrared lines in 18 other nebulae. It is pointed out that S IV was detected in approximately 90% of the observed objects, while Ar III was found in about 80%, and Ne II in roughly one-third. It is noted that optical observations typically include only a limited region of the nebula, while the infrared measurements frequently involve integration over the entire nebular image.

  15. The bimodal initial mass function in the Orion Nebula Cloud

    CERN Document Server

    Drass, H; Chini, R; Bayo, A; Hackstein, M; Hoffmeister, V; Godoy, N; Vogt, N

    2016-01-01

    Due to its youth, proximity and richness the Orion Nebula Cloud (ONC) is an ideal testbed to obtain a comprehensive view on the Initial Mass Function (IMF) down to the planetary mass regime. Using the HAWK-I camera at the VLT, we have obtained an unprecedented deep and wide near-infrared JHK mosaic of the ONC (90% completeness at K~19.0mag, 22'x28). Applying the most recent isochrones and accounting for the contamination of background stars and galaxies, we find that ONC's IMF is bimodal with distinct peaks at about 0.25 and 0.025 M_sun separated by a pronounced dip at the hydrogen burning limit (0.08 M_sun), with a depth of about a factor 2-3 below the log-normal distribution. Apart from ~920 low-mass stars (M 0.005 M_sun, hence about ten times more substellar candidates than known before. The substellar IMF peak at 0.025 M_sun could be caused by BDs and IPMOs which have been ejected from multiple systems during the early star-formation process or from circumstellar disks.

  16. Cherenkov Telescopes Results on Pulsar Wind Nebulae and Pulsars

    Science.gov (United States)

    Wilhelmi, Emma De Oña

    The last few years have seen a revolution in very high γ-ray astronomy (VHE; E>100 GeV) driven largely by a new generation of Cherenkov telescopes. These new facilities, namely H.E.S.S. (High Energy Stereoscopic System), MAGIC (Major Atmospheric Gamma Imaging Cherenkov Telescope) and its upgrade MAGIC 2, VERITAS (Very Energetic Radiation Imaging Telescope Array System) and CANGAROO (Collaboration of Australia and Nippon for a Gamma Ray Observatory in the Outback) were designed to increase the flux sensitivity in the energy regime of hundreds of GeV, expanding the observed energy range from 50 to multi-TeV, and fostered as a result a period of rapid growth in our understanding of the Non-ThermalUniverse. As a result of this fast development the number of pulsar wind nebulae (PWNe) detected has increased from a few in the early 90's to more than two dozen of firm candidates nowadays. Also, the low energy threshold achieved allows to investigate the pulsed spectra of the high energy pulsars powering PWNe. A review of the most relevant VHE results concerning pulsars and their relativistic winds is discussed here in the context of Cherenkov telescopes.

  17. BRIGHT Lights, BIG City: Massive Galaxies, Giant Ly-A Nebulae, and Proto-Clusters

    Energy Technology Data Exchange (ETDEWEB)

    van Breugel, W; Reuland, M; de Vries, W; Stanford, A; Dey, A; Kurk, J; Venemans, B; Rottgering, H; Miley, G; De Breuck, C; Dopita, M; Sutherland, R; Bland-Hawthorn, J

    2002-08-01

    High redshift radio galaxies are great cosmological tools for pinpointing the most massive objects in the early Universe: massive forming galaxies, active super-massive black holes and proto-clusters. They report on deep narrow-band imaging and spectroscopic observations of several z > 2 radio galaxy fields to investigate the nature of giant Ly-{alpha} nebulae centered on the galaxies and to search for over-dense regions around them. They discuss the possible implications for our understanding of the formation and evolution of massive galaxies and galaxy clusters.

  18. ISO Spectroscopy of Proto-Planetary Nebulae

    Science.gov (United States)

    Hrivnak, Bruce J.

    2000-01-01

    The goal of this program was to determine the chemical properties of the dust shells around protoplanetary nebulae (PPNs) through a study of their short-wavelength (6-45 micron) infrared spectra. PPNs are evolved stars in transition from the asymptotic giant branch to the planetary nebula stages. Spectral features in the 10 to 20 gm region indicate the chemical nature (oxygen- or carbon-rich), and the strengths of the features relate to the physical properties of the shells. A few bright carbon-rich PPNs have been observed to show PAH features and an unidentified 21 micron emission feature. We used the Infrared Space Observatory (ISO) to observe a sample of IRAS sources that have the expected properties of PPNs and for which we have accurate positions. Some of these have optical counterparts (proposal SWSPPN01) and some do not (SWSPPN02). We had previously observed these from the ground with near-infrared photometry and, for those with visible counterparts, visible photometry and spectroscopy, which we have combined with these new ISO data in the interpretation of the spectra. We have completed a study of the unidentified emission feature at 21 micron in eight sources. We find the shape of the feature to be the same in all of the sources, with no evidence of any substructure. The ratio of the emission peak to continuum ranges from 0.13 to 1.30. We have completed a study of seven PPNs and two other carbon-rich objects for which we had obtained ISO 2-45 micron observations. The unidentified emission features at 21 and 30 micron were detected in six sources, including four new detections of the 30 micron feature. This previously unresolved 30 micron feature was resolved and found to consist of a broad feature peaking at 27.2 micron (the "30 micron" feature) and a narrower feature peaking at 25.5 micron (the "26 micron" feature). This new 26 micron feature is detected in eight sources and is particularly strong in IRAS Z02229+6208 and 16594-4656. The unidentified

  19. Atlas of monochromatic images of planetary nebulae

    CERN Document Server

    Weidmann, W A; Valdarenas, R R Vena; Ahumada, J A; Volpe, M G; Mudrik, A

    2016-01-01

    We present an atlas of more than one hundred original images of planetary nebulae (PNe). These images were taken in a narrow-band filter centred on the nebular emission of the [N II] during several observing campaigns using two moderate-aperture telescopes, at the Complejo Astron\\'omico El Leoncito (CASLEO), and the Estaci\\'on Astrof\\'isica de Bosque Alegre (EABA), both in Argentina. The data provided by this atlas represent one of the most extensive image surveys of PNe in [N II]. We compare the new images with those available in the literature, and briefly describe all cases in which our [N II] images reveal new and interesting structures.

  20. High Energy Processes in Pulsar Wind Nebulae

    CERN Document Server

    Bednarek, W

    2006-01-01

    Young pulsars produce relativistic winds which interact with matter ejected during the supernova explosion and the surrounding interstellar gas. Particles are accelerated to very high energies somewhere in the pulsar winds or at the shocks produced in collisions of the winds with the surrounding medium. As a result of interactions of relativistic leptons with the magnetic field and low energy radiation (of synchrotron origin, thermal, or microwave background), the non-thermal radiation is produced with the lowest possible energies up to $\\sim$100 TeV. The high energy (TeV) gamma-ray emission has been originally observed from the Crab Nebula and recently from several other objects. Recent observations by the HESS Cherenkov telescopes allow to study for the first time morphology of the sources of high energy emission, showing unexpected spectral features. They might be also interpreted as due to acceleration of hadrons. However, theory of particle acceleration in the PWNe and models for production of radiation ...

  1. ISO Spectroscopy of Proto-Planetary Nebulae

    Science.gov (United States)

    Hrivnak, Bruce J.

    2000-01-01

    The goal of this program was to determine the chemical properties of the dust shells around protoplanetary nebulae (PPNs) through a study of their short-wavelength (6-45 micron) infrared spectra. PPNs are evolved stars in transition from the asymptotic giant branch to the planetary nebula stages. Spectral features in the 10 to 20 gm region indicate the chemical nature (oxygen- or carbon-rich), and the strengths of the features relate to the physical properties of the shells. A few bright carbon-rich PPNs have been observed to show PAH features and an unidentified 21 micron emission feature. We used the Infrared Space Observatory (ISO) to observe a sample of IRAS sources that have the expected properties of PPNs and for which we have accurate positions. Some of these have optical counterparts (proposal SWSPPN01) and some do not (SWSPPN02). We had previously observed these from the ground with near-infrared photometry and, for those with visible counterparts, visible photometry and spectroscopy, which we have combined with these new ISO data in the interpretation of the spectra. We have completed a study of the unidentified emission feature at 21 micron in eight sources. We find the shape of the feature to be the same in all of the sources, with no evidence of any substructure. The ratio of the emission peak to continuum ranges from 0.13 to 1.30. We have completed a study of seven PPNs and two other carbon-rich objects for which we had obtained ISO 2-45 micron observations. The unidentified emission features at 21 and 30 micron were detected in six sources, including four new detections of the 30 micron feature. This previously unresolved 30 micron feature was resolved and found to consist of a broad feature peaking at 27.2 micron (the "30 micron" feature) and a narrower feature peaking at 25.5 micron (the "26 micron" feature). This new 26 micron feature is detected in eight sources and is particularly strong in IRAS Z02229+6208 and 16594-4656. The unidentified

  2. HESS Observations of Pulsar Wind Nebulae

    CERN Document Server

    De Jager, O C

    2006-01-01

    The high resolution capabilities of the High Energy Stereoscopic System (HESS) introduced a new era in Gamma-Ray Astronomy, and opens a new window on pulsar wind nebula (PWN) research. A rotationally induced jet (associated with PSR B1509-58) is resolved for the first time in gamma-rays, allowing us to trace the particle transport directly, without having the complicating effect of spatially varying field distributions on the synchrotron emissivity. For PWN older or more extended than Crab (i.e. those with lower field strengths), HESS also reveals the properties of electrons contributing to the EUV/soft X-ray synchrotron bands, whereas EUV/soft X-rays suffer from severe interstellar absorption effects. Finally, HESS morphological studies of evovled PWN also allow us to directly measure the effects of assymetric reverse shock interactions due to SNR forward shock expansion into the inhomogeneous interstellar medium.

  3. Proposed nomenclature for Extragalactic Planetary Nebulae

    CERN Document Server

    Parker, Q A; Parker, Quentin A

    2004-01-01

    The ability to identify and distinguish between the wide variety of celestial objects benefits from application of a systematic and logical nomenclature. This often includes value-added information within the naming convention which can aid in placing the object positionally either via an RA/DEC or l,b concatenation. All new nomenclatures should be created following IAU guidelines. However as the number density of specific object types on the sky increases, as in the case of PN in external galaxies, a useful positional identifier becomes problematic. This brief but timely paper attempts to progress the debate on this vexing issue for the case of extragalactic planetary nebulae (EPN). There is a clear need to rationalise the current ad-hoc system now that many thousands of Extragalactic PN are being discovered.

  4. Planetary Nebula Surveys: Past, Present and Future

    CERN Document Server

    Parker, Quentin A

    2010-01-01

    In this review we cover the detection, identification and astrophysical importance of planetary nebulae (PN). The legacy of the historic Perek & Kohoutek and Acker et al. catalogues is briefly covered before highlighting the more recent but significant progress in PN discoveries in our Galaxy and the Magellanic Clouds. We place particular emphasis on the major MASH and the IPHAS catalogues, which, over the last decade alone, have essentially doubled Galactic and LMC PN numbers. We then discuss the increasing role and importance that multi-wavelength data is playing in both the detection of candidate PN and the elimination of PN mimics that have seriously biased previous PN compilations. The prospects for future surveys and current efforts and prospects for PN detections in external galaxies are briefly discussed due to their value both as cosmic distance indicators and as kinematical probes of galaxies and dark matter properties.

  5. Investigating potential planetary nebula/cluster pairs

    CERN Document Server

    Bidin, Christian Moni; Bonatto, Charles; Mauro, Francesco; Turner, David; Geisler, Doug; Chene, Andres-Nicolas; Gormaz-Matamala, Alex C; Borissova, Jura; Kurtev, Radostin G; Minniti, Dante; Carraro, Giovanni; Gieren, Wolfgang

    2013-01-01

    Fundamental parameters characterizing the end-state of intermediate-mass stars may be constrained by discovering planetary nebulae (PNe) in open clusters (OCs). Cluster membership may be exploited to establish the distance, luminosity, age, and physical size for PNe, and the intrinsic luminosity and mass of its central star. Four potential PN-OC associations were investigated, to assess the cluster membership for the PNe. Radial velocities were measured from intermediate-resolution optical spectra, complemented with previous estimates in the literature. When the radial velocity study supported the PN/OC association, we analyzed if other parameters (e.g., age, distance, reddening, central star brightness) were consistent with this conclusion. Our measurements imply that the PNe VBe3 and HeFa1 are not members of the OCs NGC5999 and NGC6067, respectively, and likely belong to the background bulge population. Conversely, consistent radial velocities indicate that NGC2452/NGC2453 could be associated, but our resul...

  6. Exploiting the HASH Planetary Nebula Research Platform

    CERN Document Server

    Parker, Quentin A; Frew, David J

    2016-01-01

    The HASH (Hong Kong/ AAO/ Strasbourg/ H{\\alpha}) planetary nebula research platform is a unique data repository with a graphical interface and SQL capability that offers the community powerful, new ways to undertake Galactic PN studies. HASH currently contains multi-wavelength images, spectra, positions, sizes, morphologies and other data whenever available for 2401 true, 447 likely, and 692 possible Galactic PNe, for a total of 3540 objects. An additional 620 Galactic post-AGB stars, pre-PNe, and PPN candidates are included. All objects were classified and evaluated following the precepts and procedures established and developed by our group over the last 15 years. The complete database contains over 6,700 Galactic objects including the many mimics and related phenomena previously mistaken or confused with PNe. Curation and updating currently occurs on a weekly basis to keep the repository as up to date as possible until the official release of HASH v1 planned in the near future.

  7. Watching Young Planetary Nebulae Grow: The Movie

    Science.gov (United States)

    Balick, Bruce

    2009-07-01

    The development of magneto-hydro gas dynamical models is the key to the understanding of both the physics {processes} and astronomy {initial conditions} of astrophysical nebulae of all sorts. The models are reaching their highest degree of accuracy when applied to and compared against pre Planetary Nebulae {pPNe} thanks to the simplicity, relative lack of extinction, and the detail of the imaging and kinematic data that have bcome available for these objects. The primary barrier to progress is inadequate kinematic data of pPNe against which the predictions models can be tested. Unlike PNe, pPNe do not emit emission lines for detailed Doppler measurements. Therefore it is essential to find another way to monitor the morphological evolution. Only HST can uncover the dynamics of the growth patterns by subtracting multi-epoch images spanning a decade or more. We have selected four pPNe with highly collimated outflows in different evolutionary stages for which high-quality first-epoch images were obtained from 1996 to 2002. All of them display regularly shaped thin rims, sharp edges, and symmetric pairs of knots or bowshocks that are ideal for our purposes. We will closely mimic many of the earlier exposures using ACS and to monitor changes in structures. The morphology and its evolution will be compared to 3-D MHD models with adaptive grids in order to build a far clearer picture of the nuclear geometry which shaped the outflows and constrained their propagation to the present. We shall also obtain R, J, and H images for use with a 3-D dust radiative transfer code LELUYA to model the dust distribution deep into the nuclear zones.

  8. The Spectroscopic Properties of Bright Extragalactic Planetary Nebulae

    CERN Document Server

    Richer, M G

    2006-01-01

    The properties of bright extragalactic planetary nebulae are reviewed based upon the results of low and high resolution spectroscopy. It is argued that bright extragalactic planetary nebulae from galaxies (or subsystems) with and without star formation have different distributions of central star temperature and ionization structure. As regards the chemical compositions, oxygen and neon are generally found to be unchanged as a result of the evolution of the stellar progenitors. Nitrogen enrichment may occur as a result of the evolution of the progenitors of bright planetary nebulae in all stellar populations, though this enrichment may be (more) random in old stellar populations. Helium abundances appear to be influenced by the chemical evolution of the host galaxy, with planetary nebulae in dwarf spheroidals having systematically elevated abundances. Neither the age nor the metallicity of the progenitor stellar population has a strong effect upon the kinematics observed for nebular shells. Both the range of ...

  9. Star Formation in the Orion Nebula I: Stellar Content

    CERN Document Server

    Muench, August; Hillenbrand, Lynne; Preibisch, Thomas

    2008-01-01

    The Orion Nebula is one of the most frequently observed nearby (<1 kiloparsec) star forming regions and, consequently, the subject of a large bibliography of observations and interpretation. The summary in this chapter is bounded spatially by the blister HII region, with sources beyond the central nebula that are part of the same dynamical clustering covered in other chapters in this book. Herein are discussed panchromatic observations of the massive OB stars, the general T Tauri population, the sub-stellar sources and variable stars within the Orion Nebula. First, a brief history of 400 years of observation of the Nebula is presented. As this history is marked clearly by revelations provided in each age of new technology, recent ultra-deep X-ray surveys and high resolution multi-epoch monitoring of massive binary systems and radio stars receive special attention in this review. Topics discussed include the kinematics, multiplicity, mass distribution, rotation, and circumstellar characteristics of the pre-...

  10. Chemical composition of planetary nebulae : Including ISO results

    NARCIS (Netherlands)

    Pottasch, [No Value; Beintema, DA; Salas, JB; Feibelman, WA; Henney, WJ; Franco, J; Martos, M; Pena, M

    2002-01-01

    The method of determining abundances using Infrared Space Observatory spectra is discussed. The results for seven planetary nebula are given. Using these data, a preliminary discussion of their evolution is given.

  11. A PROTOSOLAR NEBULA ORIGIN FOR THE ICES AGGLOMERATED BY COMET 67P/CHURYUMOV–GERASIMENKO

    Energy Technology Data Exchange (ETDEWEB)

    Mousis, O.; Vernazza, P. [Aix Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326, F-13388 Marseille (France); Lunine, J. I. [Center For Radiophysics And Space Research, Space Sciences Building Cornell University, Ithaca, NY 14853 (United States); Luspay-Kuti, A.; Hässig, M.; Waite, J. H. [Department of Space Research, Southwest Research Institute, 6220 Culebra Road, San Antonio, TX 78228 (United States); Guillot, T. [Laboratoire J.-L. Lagrange, Université de Nice-Sophia Antipolis, CNRS, Observatoire de la Côte d’Azur, BP 4229, F-06304 Nice (France); Marty, B. [CRPG-CNRS, Nancy-Université, 15 rue Notre Dame des Pauvres, F-54501 Vandoeuvre-lès-Nancy (France); Ali-Dib, M. [Université de Franche-Comté, Institut UTINAM, CNRS/INSU, UMR 6213, Besançon Cedex (France); Wurz, P.; Altwegg, K.; Bieler, A.; Rubin, M., E-mail: olivier.mousis@lam.fr [Physikalisches Institut, University of Bern, Sidlerstrasse 5, CH-3012 Bern (Switzerland)

    2016-03-10

    The nature of the icy material accreted by comets during their formation in the outer regions of the protosolar nebula (PSN) is a major open question in planetary science. Some scenarios of comet formation predict that these bodies agglomerated from crystalline ices condensed in the PSN. Concurrently, alternative scenarios suggest that comets accreted amorphous ice originating from the interstellar cloud or from the very distant regions of the PSN. On the basis of existing laboratory and modeling data, we find that the N{sub 2}/CO and Ar/CO ratios measured in the coma of the Jupiter-family comet 67P/Churyumov–Gerasimenko by the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis instrument on board the European Space Agency’s Rosetta spacecraft match those predicted for gases trapped in clathrates. If these measurements are representative of the bulk N{sub 2}/CO and Ar/CO ratios in 67P/Churyumov–Gerasimenko, it implies that the ices accreted by the comet formed in the nebula and do not originate from the interstellar medium, supporting the idea that the building blocks of outer solar system bodies have been formed from clathrates and possibly from pure crystalline ices. Moreover, because 67P/Churyumov–Gerasimenko is impoverished in Ar and N{sub 2}, the volatile enrichments observed in Jupiter’s atmosphere cannot be explained solely via the accretion of building blocks with similar compositions and require an additional delivery source. A potential source may be the accretion of gas from the nebula that has been progressively enriched in heavy elements due to photoevaporation.

  12. Evaluation of Anorthite Glass Standards for High Precision SIMS Al-Mg Dating of Early Solar System Materials

    Science.gov (United States)

    Kita, N.; Fournelle, J.; Mendybaev, R.; Knight, K.; Davis, A. M.; Richter, F. M.; Ushikubo, T.

    2009-12-01

    The decay of extinct nuclide 26Al to daughter nuclide 26Mg (half life of 7.3×105y) is considered to be a useful chronometer for the early solar system. The initial 26Al/26Al ratio of the solar system is estimated to be ~5×10-5 from the analyses of Ca, Al-rich refractory inclusions (CAIs) in primitive meteorites by the linear regression of multiple data on 26Al/26Mg vs. 26Mg/26Mg isochron diagram. Anorthite grains in CAIs show high 26Al/26Mg ratios (~400) with an excess of 26Mg/26Mg ratios as high as 100‰. By using the WiscSIMS IMS-1280, the Mg isotope ratio of anorthite can be obtained with a precision of better than 1‰, from which we can resolve time differences of only 10 ky among formation of individual CAIs. In order to obtain highly precise 26Al-26Mg isochrons, it is important to determine an accurate SIMS relative sensitivity factor (RSF) of 26Al/26Mg ratios from the analyses of plagioclase standard. However, uncertainties of Mg concentration in plagioclase standards are typically ~10% due to low concentrations of MgO (≤0.1wt.%) in naturally occurring plagioclase crystals. In order to obtain accurate initial 26Al/26Al ratios of CAIs, anorthite glass standards were prepared at the University of Chicago with MgO contents of 0.1%, 0.5% and 1.0 wt.% by melting Mg-, Ca-, Al-, and Si-oxides at 1620°C in N2 for 22 to 35 hours. Major and minor element concentrations (including MgO) of the glasses were analyzed precisely by EPMA (Cameca SX51 at University of Wisconsin). Operating conditions were 15 kV, 10 nA, 10 μm wide beam; for Mg, both peak and background were measured for 30 seconds each, and differential PHA was used. A synthetic akermanite standard was used, and a blank correction (0.01 wt% Mg) in Probe for EPMA software was applied. By obtaining ~30 EPMA point analyses for esch glass, MgO concentrations in these glasses were determined with precision of 1-3%. The homogeneity of Mg concentrations in the individual glass were examined by using SIMS and

  13. GIANT Hα NEBULA SURROUNDING THE STARBURST MERGER NGC 6240

    Energy Technology Data Exchange (ETDEWEB)

    Yoshida, Michitoshi [Hiroshima Astrophysical Science Center, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8526 (Japan); Yagi, Masafumi; Komiyama, Yutaka; Kashikawa, Nobunari [Optical and Infrared Astronomy Division, National Astronomical Observatory, Mitaka, Tokyo 181-8588 (Japan); Ohyama, Youichi [Institute of Astronomy and Astrophysics, Academia Sinica, 11F of Astronomy-Mathematics Building, AS/NTU No.1, Sec. 4, Roosevelt Road, Taipei 10617, Taiwan, R.O.C. (China); Tanaka, Hisashi [Department of Physical Science, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8526 (Japan); Okamura, Sadanori, E-mail: yoshidam@hiroshima-u.ac.jp [Department of Advanced Sciences, Faculty of Science and Engineering, Hosei University, Koganei, Tokyo 184-8584 (Japan)

    2016-03-20

    We revealed the detailed structure of a vastly extended Hα-emitting nebula (“Hα nebula”) surrounding the starburst/merging galaxy NGC 6240 by deep narrow-band imaging observations with the Subaru Suprime-Cam. The extent of the nebula is ∼90 kpc in diameter and the total Hα luminosity amounts to L{sub Hα} ≈ 1.6 × 10{sup 42} erg s{sup −1}. The volume filling factor and the mass of the warm ionized gas are ∼10{sup −4}–10{sup −5} and ∼5 × 10{sup 8} M{sub ⊙}, respectively. The nebula has a complicated structure, which includes numerous filaments, loops, bubbles, and knots. We found that there is a tight spatial correlation between the Hα nebula and the extended soft-X-ray-emitting gas, both in large and small scales. The overall morphology of the nebula is dominated by filamentary structures radially extending from the center of the galaxy. A large-scale bipolar bubble extends along the minor axis of the main stellar disk. The morphology strongly suggests that the nebula was formed by intense outflows—superwinds—driven by starbursts. We also found three bright knots embedded in a looped filament of ionized gas that show head-tail morphologies in both emission-line and continuum, suggesting close interactions between the outflows and star-forming regions. Based on the morphology and surface brightness distribution of the Hα nebula, we propose the scenario that three major episodes of starburst/superwind activities, which were initiated ∼10{sup 2} Myr ago, formed the extended ionized gas nebula of NGC 6240.

  14. The Boomerang Nebula - The Coldest Region of the Universe

    Science.gov (United States)

    Sahai, Raghvendra; Nyman, Lars-Ake

    1997-01-01

    In this letter, we report such observations of the Boomerang Nebula which show it to be a unique object, consisiting of an ultra-cold and extremely massive molecular envolope, expanding at very high speed. The extreeme physical characteristics of the Boomerang Nebula reported here have never been seen before in any AGB or post-AGB object, and should spur new theoretical and obesrvational efforts to understand the nature of the mass-loss processes occurring during later stellar evolution.

  15. Collimated Outflows in the Stingray Nebula (He 3-1357)

    Science.gov (United States)

    Bobrowsky, M.; Sahu, K. C.; Parthasarathy, M.; Garcia-Lario, P.

    1997-12-01

    Observations over the past four decades have revealed significant changes in the spectrum of the Stingray Nebula (He 3-1357). Here we present HST images and spectra showing the most recent developments. In 1950, Henize saw only Hα in emission; but more recent observations by Parthasarathy et al. in 1992 showed strong forbidden lines consistent with a young planetary nebula. The spherically aberrated 1992 HST images, in which Bobrowsky first optically resolved the nebula, showed a compact nebula surrounding the central star. Nebular gas appeared most strongly concentrated in an ellipse with its major axis subtending 1.('') 6 from NE to SW. If this ellipse is actually a circular ring viewed obliquely, then our line of sight is inclined from the symmetry axis by 56deg . Above and below the ring of gas are two bubbles containing lower-density gas. At the tip of each bubble, there is a hole where the gas inside the bubbles has broken through and is now escaping. While images of focused jets have been obtained previously (Borkowski et al.), this is the first case where the nebular structure responsible for the focusing of an outflow can be clearly seen. The windblown appearance of the nebula is consistent with the blueshifted Si IV (1394-1403 Angstroms) and Al III (1855-1863 Angstroms) doublets observed by Parthasarathy et al. that indicated the presence of a strong stellar wind. The N V (1239-1243 Angstroms) to C IV (1548-1551 Angstroms) ratio has increased in recent years, consistent with a young nebula becoming increasingly ionized. Our new spectra reveal additional developments that show the real-time development of this young nebula. Finally, the new HST Planetary Camera images of the nebula show detailed structure indicating a much more complex object than previously known, including the presence of a companion star 0.('') from the central star.

  16. Orientation of Galactic Bulge Planetary Nebulae toward the Galactic Center

    CERN Document Server

    Danehkar, A

    2014-01-01

    We have used the Wide Field Spectrograph on the Australian National University 2.3-m telescope to perform the integral field spectroscopy for a sample of the Galactic planetary nebulae. The spatially resolved velocity distributions of the H$\\alpha$ emission line were used to determine the kinematic features and nebular orientations. Our findings show that some bulge planetary nebulae toward the Galactic center have a particular orientation.

  17. Stars and Planetary Nebulae in the Galactic Bulge

    CERN Document Server

    Cuisinier, F; Acker, A; Maciel, W J

    2000-01-01

    We compare the populations of Red Giant stars and Planetary Nebulae in the Galactic Bulge, in the light of recent determinations of their abundances patterns. We find both populations to be compatible. From the planetary nebulae, we find evidences that the Bulge did not form stars recently. The whole abundances pattern remains however puzzling, some elements favoring a quick evolution of the Galactic Bulge (Mg and Ti), and others a much slower one (He, O, Si, S, Ar and Ca).

  18. Featured Image: A Detailed Look at the Crab Nebula

    Science.gov (United States)

    Kohler, Susanna

    2017-07-01

    Planning on watching fireworks tomorrow? Heres an astronomical firework to help you start the celebrations! A new study has stunningly detailed the Crab Nebula (click for a closer look), a nebula 6,500 light-years away thought to have been formedby a supernova explosion and the subsequent ultrarelativistic wind emitted by the pulsar at its heart. Led by Gloria Dubner (University of Buenos Aires), the authors of this study obtained new observations of the Crab Nebula from five different telescopes. They compiled these observations to compare the details of the nebulas structure across different wavelengths, which allowedthem to learnabout the sources of various features within the nebula. In the images above, thetop left shows the 3 GHz data from the Very Large Array (radio). Moving clockise, the radio data (shown in red) is composited with: infrared data from Spitzer Space Telescope, optical continuum from Hubble Space Telescope, 500-nm optical datafrom Hubble, and ultraviolet data from XMM-Newton. The final two images are of the nebula center, and they are composites of the radio imagewith X-ray data from Chandra and near-infrared data from Hubble. To read more about what Dubner and collaborators learned (and to see more spectacular images!), check out the paper below.CitationG. Dubner et al 2017 ApJ 840 82. doi:10.3847/1538-4357/aa6983

  19. The bipolar structure of the LBV nebula around HR Carinae

    CERN Document Server

    Weis, K; Bomans, D J; Chu, Y H; Joner, M D

    1997-01-01

    HR Carinae is one of the few Luminous Blue Variables (LBVs) in the Galaxy. It has a nebula that appears bipolar. We have obtained imaging and high-dispersion, long-slit echelle data of the HR Car nebula, and confirmed that it is a bipolar nebula. Its polar axis lies along the position angle of 125 +- 5 degree; each lobe has, at a distance of 5 kpc a diameter of about 0.65 pc and a line-of-sight expansion velocity of 75-150 km/sec. Beside the expanding bipolar lobes, a number of [NII]-bright knots are detected. These knots have lower expansion velocities than the lobes and are detected only within the projected boundary of the lobes. These knots are most likely nitrogen-enriched material ejected by HR Car. On a larger scale, a funnel-shaped nebula is detected at 2.5" northwest of HR Car. The axis of the funnel is roughly aligned with the polar axis of the HR Car nebula, suggesting that HR Car may be responsible for the ionization and shaping of this nebula. Future observations of kinematics and abundances are ...

  20. Discovery of a Circumstellar Disk in the Lagoon Nebula

    Science.gov (United States)

    1997-04-01

    photos as tear-drop shaped, bright-rimmed areas with the cusps of the ionised regions aligned towards the exciting star. Such a region is also a very compact source of radio emission. Clearly, the harsh environment in which these disks reside does not favour planet formation. These findings were facilitated by the fact that, at a distance of `only' 1500 lightyears (about 450 parsec), the Orion Nebula is the closest site of high-mass star formation. Furthermore, many circumstellar disks around stars in this nebula are seen in silhouette against a bright and uniform background and are therefore comparatively easy to detect. The Lagoon Nebula In principle, similar phenomena should occur in any giant molecular cloud that gives rise to the birth of massive stars. However, the detection of such disks in other clouds would be very difficult, first of all because of their much larger distance. The Lagoon Nebula (M8) is located four times further away than the Orion Nebula and it is also a site of recent high-mass star formation. Its brightest part constitutes a conspicuous region of ionised hydrogen gas (an `HII-region') dubbed `The Hourglass' because of the resemblance. The gas in this area is ionised by the action of the nearby, hot star Herschel 36 (Her 36) . High-resolution radio maps show that the emission from the ionised gas peaks at 2.7 arcsec southeast of Her 36. An early explanation was that this emission is due to an unseen, massive star that is deeply embedded in the gas and dust and which is causing an ultra-compact HII-region (UCHR), catalogued as G5.97-1.17 according to its galactic coordinates. High-resolution images from ESO During a detailed investigation of such ultra-compact HII regions, Bringfried Stecklum and his colleagues found that, unlike ordinary UCHRs, this particular object is visible on optical images obtained with the HST Wide-Field Planetary Camera (HST-WFPC). This means that, contrary to the others, it is not deeply embedded in the nebula - its

  1. BD-22deg3467, a DAO-type Star Exciting the Nebula Abell 35

    Science.gov (United States)

    Ziegler, M.; Rauch, T.; Werner, K.; Koppen, J.; Kruk, J. W.

    2013-01-01

    Spectral analyses of hot, compact stars with non-local thermodynamical equilibrium (NLTE) model-atmosphere techniques allow the precise determination of photospheric parameters such as the effective temperature (T(sub eff)), the surface gravity (log g), and the chemical composition. The derived photospheric metal abundances are crucial constraints for stellar evolutionary theory. Aims. Previous spectral analyses of the exciting star of the nebula A35, BD-22deg3467, were based on He+C+N+O+Si+Fe models only. For our analysis, we use state-of-the-art fully metal-line blanketed NLTE model atmospheres that consider opacities of 23 elements from hydrogen to nickel. We aim to identify all observed lines in the ultraviolet (UV) spectrum of BD-22deg3467 and to determine the abundances of the respective species precisely. Methods. For the analysis of high-resolution and high signal-to-noise ratio (S/N) far-ultraviolet (FUSE) and UV (HST/STIS) observations, we combined stellar-atmosphere models and interstellar line-absorption models to fully reproduce the entire observed UV spectrum. Results. The best agreement with the UV observation of BD-22deg3467 is achieved at T(sub eff) = 80 +/- 10 kK and log g = 7.2 +/- 0.3. While T(sub eff) of previous analyses is verified, log g is significantly lower. We re-analyzed lines of silicon and iron (1/100 and about solar abundances, respectively) and for the first time in this star identified argon, chromium, manganese, cobalt, and nickel and determined abundances of 12, 70, 35, 150, and 5 times solar, respectively. Our results partially agree with predictions of diffusion models for DA-type white dwarfs. A combination of photospheric and interstellar line-absorption models reproduces more than 90% of the observed absorption features. The stellar mass is M approx. 0.48 Solar Mass. Conclusions. BD.22.3467 may not have been massive enough to ascend the asymptotic giant branch and may have evolved directly from the extended horizontal branch

  2. The Orion Nebula: Still Full of Surprises

    Science.gov (United States)

    2011-01-01

    This ethereal-looking image of the Orion Nebula was captured using the Wide Field Imager on the MPG/ESO 2.2-metre telescope at the La Silla Observatory, Chile. This nebula is much more than just a pretty face, offering astronomers a close-up view of a massive star-forming region to help advance our understanding of stellar birth and evolution. The data used for this image were selected by Igor Chekalin (Russia), who participated in ESO's Hidden Treasures 2010 astrophotography competition. Igor's composition of the Orion Nebula was the seventh highest ranked entry in the competition, although another of Igor's images was the eventual overall winner. The Orion Nebula, also known as Messier 42, is one of the most easily recognisable and best-studied celestial objects. It is a huge complex of gas and dust where massive stars are forming and is the closest such region to the Earth. The glowing gas is so bright that it can be seen with the unaided eye and is a fascinating sight through a telescope. Despite its familiarity and closeness there is still much to learn about this stellar nursery. It was only in 2007, for instance, that the nebula was shown to be closer to us than previously thought: 1350 light-years, rather than about 1500 light-years. Astronomers have used the Wide Field Imager on the MPG/ESO 2.2-metre telescope at ESO's La Silla Observatory in Chile to observe the stars within Messier 42. They found that the faint red dwarfs in the star cluster associated with the glowing gas radiate much more light than had previously been thought, giving us further insights into this famous object and the stars that it hosts. The data collected for this science project, with no original intention to make a colour image, have now been reused to create the richly detailed picture of Messier 42 shown here. The image is a composite of several exposures taken through a total of five different filters. Light that passed through a red filter as well as light from a filter that

  3. S-process enrichment in the planetary nebula NGC 3918. Results from deep echelle spectrophotometry

    CERN Document Server

    García-Rojas, J; Luridiana, V; Sterling, N C; Morisset, C; Delgado-Inglada, G; Cipriano, L Toribio San

    2015-01-01

    (Abridged) The chemical content of the planetary nebula NGC 3918 is investigated through deep, high-resolution UVES at VLT spectrophotometric data. We identify and measure more than 750 emission lines, making ours one of the deepest spectra ever taken for a planetary nebula. Among these lines we detect very faint lines of several neutron-capture elements (Se, Kr, Rb, and Xe), which enable us to compute their chemical abundances with unprecedented accuracy, thus constraining the efficiency of the s-process and convective dredge-up in the progenitor star of NGC 3918. We find that Kr is strongly enriched in NGC 3918 and that Se is less enriched than Kr, in agreement with the results of previous papers and with predicted s-process nucleosynthesis. We also find that Xe is not as enriched by the s-process in NGC 3918 as is Kr and, therefore, that neutron exposure is typical of modestly sub-solar metallicity AGB stars. A clear correlation is found when representing [Kr/O] vs. log(C/O) for NGC 3918 and other objects ...

  4. A measurement of the gamma-ray spectrum from the Crab Nebula

    Science.gov (United States)

    Lizarazo, Juan Fernando

    CACTUS is a ground-based Air Cherenkov Telescope located at the Solar 2 facility in the Southern California Mojave desert. It uses an array of 168 heliostats and a camera with 80 photomultiplier tubes to detect Cherenkov radiation produced by air showers. CACTUS incorporates fast electronics together with novel techniques of time projection imaging and pattern triggering, thus improving upon the first generation sampling ACTs. Multiplexing of PMTS and heliostats allow us to collect up to 300 independent samples of a Cherenkov light front-wave. With the capability of detecting gamma rays with energies from 50 GeV up, CACTUS is poised to provide insight into very exciting new physics. In particular, measuring the Crab nebula spectrum in the energy range between 20 to 200 GeV, will allow us to define an appropriate model for the Inverse Compton lump, together with constraints on model parameters. A full analysis of the data set collected during the winter of 2005 provided us with a Crab nebula spectrum that starts under 100 GeV and goes up to a few TeV. Implications of this will be talked about.

  5. The Chandra X-ray Survey of Planetary Nebulae (ChanPlaNS): Probing Binarity, Magnetic Fields, and Wind Collisions

    CERN Document Server

    Kastner, J H; Balick, B; Frew, D J; Miszalski, B; Sahai, R; Blackman, E; Chu, Y -H; De Marco, O; Frank, A; Guerrero, M A; Lopez, J A; Rapson, V; Zijlstra, A; Behar, E; Bujarrabal, V; Corradi, R L M; Nordhaus, J; Parker, Q; Sandin, C; Schönberner, D; Soker, N; Sokoloski, J L; Steffen, M; Ueta, T; Villaver, E

    2012-01-01

    We present an overview of the initial results from the Chandra Planetary Nebula Survey (ChanPlaNS), the first systematic (volume-limited) Chandra X-ray Observatory survey of planetary nebulae (PNe) in the solar neighborhood. The first phase of ChanPlaNS targeted 21 mostly high-excitation PNe within ~1.5 kpc of Earth, yielding 3 detections of diffuse X-ray emission and 9 detections of X-ray-luminous point sources at the central stars (CSPNe) of these objects. Combining these results with those obtained from Chandra archival data for all (14) other PNe within ~1.5 kpc that have been observed to date, we find an overall X-ray detection rate of 68%. Roughly 50% of the PNe observed by Chandra harbor X-ray-luminous CSPNe, while soft, diffuse X-ray emission tracing shocks formed by energetic wind collisions is detected in ~30%; five objects display both diffuse and point-like emission components. The presence of X-ray sources appears correlated with PN density structure, in that molecule-poor, elliptical nebulae are...

  6. Magnetic Flux of EUV Arcade and Dimming Regions as a Relevant Parameter for Early Diagnostics of Solar Eruptions - Sources of Non-Recurrent Geomagnetic Storms and Forbush Decreases

    CERN Document Server

    Chertok, I M; Belov, A V; Abunin, A A

    2012-01-01

    This study aims at the early diagnostics of geoeffectiveness of coronal mass ejections (CMEs) from quantitative parameters of the accompanying EUV dimming and arcade events. We study events of the 23th solar cycle, in which major non-recurrent geomagnetic storms (GMS) with Dst <-100 nT are sufficiently reliably identified with their solar sources in the central part of the disk. Using the SOHO/EIT 195 A images and MDI magnetograms, we select significant dimming and arcade areas and calculate summarized unsigned magnetic fluxes in these regions at the photospheric level. The high relevance of this eruption parameter is displayed by its pronounced correlation with the Forbush decrease (FD) magnitude, which, unlike GMSs, does not depend on the sign of the Bz component but is determined by global characteristics of ICMEs. Correlations with the same magnetic flux in the solar source region are found for the GMS intensity (at the first step, without taking into account factors determining the Bz component near t...

  7. Visual Binaries in the Orion Nebula Cluster

    CERN Document Server

    Reipurth, Bo; Connelley, Michael S; Bally, John

    2007-01-01

    We have carried out a major survey for visual binaries towards the Orion Nebula Cluster using HST images obtained with an H-alpha filter. Among 781 likely ONC members more than 60" from theta-1 Ori C, we find 78 multiple systems (75 binaries and 3 triples), of which 55 are new discoveries, in the range from 0.1" to 1.5". About 9 binaries are likely line-of-sight associations. We find a binary fraction of 8.8%+-1.1% within the limited separation range from 67.5 to 675 AU. The field binary fraction in the same range is a factor 1.5 higher. Within the range 150 AU to 675 AU we find that T Tauri associations have a factor 2.2 more binaries than the ONC. The binary separation distribution function of the ONC shows unusual structure, with a sudden steep decrease in the number of binaries as the separation increases beyond 0.5", corresponding to 225 AU. We have measured the ratio of binaries wider than 0.5" to binaries closer than 0.5" as a function of distance from the Trapezium, and find that this ratio is signifi...

  8. The inner knot of the Crab nebula

    CERN Document Server

    Lyutikov, Maxim; Porth, Oliver

    2015-01-01

    We model the inner knot of the Crab Nebula as a synchrotron emission coming from the non-spherical MHD termination shock of relativistic pulsar wind. The post-shock flow is mildly relativistic; as a result the Doppler-beaming has a strong impact on the shock appearance. The model can reproduce the knot location, size, elongation, brightness distribution, luminosity and polarization provided the effective magnetization of the section of the pulsar wind producing the knot is low, $\\sigma \\leq 1$. In the striped wind model, this implies that the striped zone is rather wide, with the magnetic inclination angle of the Crab pulsar $\\ge 45^\\circ$; this agrees with the previous model-dependent estimate based on the gamma-ray emission of the pulsar. We conclude that the tiny knot is indeed a bright spot on the surface of a quasi-stationary magnetic relativistic shock and that this shock is a site of efficient particle acceleration. On the other hand, the deduced low magnetization of the knot plasma implies that this i...

  9. The inner knot of the Crab nebula

    Science.gov (United States)

    Lyutikov, Maxim; Komissarov, Serguei S.; Porth, Oliver

    2016-02-01

    We model the inner knot of the Crab nebula as a synchrotron emission coming from the non-spherical MHD termination shock of relativistic pulsar wind. The post-shock flow is mildly relativistic; as a result the Doppler beaming has a strong impact on the shock appearance. The model can reproduce the knot location, size, elongation, brightness distribution, luminosity and polarization provided the effective magnetization of the section of the pulsar wind producing the knot is low, σ ≤ 1. In the striped wind model, this implies that the striped zone is rather wide, with the magnetic inclination angle of the Crab pulsar ≥45°; this agrees with the previous model-dependent estimate based on the gamma-ray emission of the pulsar. We conclude that the tiny knot is indeed a bright spot on the surface of a quasi-stationary magnetic relativistic shock and that this shock is a site of efficient particle acceleration. On the other hand, the deduced low magnetization of the knot plasma implies that this is an unlikely site for the Crab's gamma-ray flares, if they are related to the fast relativistic magnetic reconnection events.

  10. Kn 26, a New Quadrupolar Planetary Nebula

    CERN Document Server

    Guerrero, Martin A; Ramos-Larios, Gerardo; Vazquez, Roberto

    2013-01-01

    Once classified as an emission line source, the planetary nebula (PN) nature of the source Kn 26 has been only recently recognized in digital sky surveys. To investigate the spectral properties and spatio-kinematical structure of Kn 26, we have obtained high spatial-resolution optical and near-IR narrow-band images, high-dispersion long-slit echelle spectra, and intermediate-resolution spectroscopic observations. The new data reveal an hourglass morphology typical of bipolar PNe. A detailed analysis of its morphology and kinematics discloses the presence of a second pair of bipolar lobes, making Kn 26 a new member of the subclass of quadrupolar PNe. The time-lap between the ejection of the two pairs of bipolar lobes is much smaller than their dynamical ages, implying a rapid change of the preferential direction of the central engine. The chemical composition of Kn 26 is particularly unusual among PNe, with a low N/O ratio (as of type II PNe) and a high helium abundance (as of type I PNe), although not atypica...

  11. Scaled Eagle Nebula Experiments on NIF

    Energy Technology Data Exchange (ETDEWEB)

    Pound, Marc

    2017-03-28

    We performed scaled laboratory experiments at the National Ignition Facility laser to assess models for the creation of pillar structures in star-forming clouds of molecular hydrogen, in particular the famous Pillars of the Eagle Nebula. Because pillars typically point towards nearby bright ultraviolet stars, sustained directional illumination appears to be critical to pillar formation. The experiments mock up illumination from a cluster of ultraviolet-emitting stars, using a novel long duration (30--60 ns), directional, laser-driven x-ray source consisting of multiple radiation cavities illuminated in series. Our pillar models are assessed using the morphology of the Eagle Pillars observed with the Hubble Space Telescope, and measurements of column density and velocity in Eagle Pillar II obtained at the BIMA and CARMA millimeter wave facilities. In the first experiments we assess a shielding model for pillar formation. The experimental data suggest that a shielding pillar can match the observed morphology of Eagle Pillar II, and the observed Pillar II column density and velocity, if augmented by late time cometary growth.

  12. H2 Temperatures in the Crab Nebula

    CERN Document Server

    Loh, E D; Ferland, G J; Curtis, Z K; Richardson, C T; Fabian, A C; Salomé, P

    2011-01-01

    We used K-band spectra to measure the H2 excitation temperatures in six molecular knots associated with the filaments in the Crab Nebula. The temperatures are quite high - in the range T ~ 2000-3000K, just below the H2 dissociation temperature. This is the temperature range over which the H2 1-0 S(1) line at 2.121\\mum has its maximum emissivity per unit mass, so there may be many additional H2 cores with lower temperatures that are too faint to detect. We also measured the electron density in adjacent ionized gas, which on the assumption of gas pressure balance indicates densities in the molecular region n_mol ~ 20,000 H baryons cm-3, although this really is just a lower limit since the H2 gas may be confined by other means. The excited region may be just a thin skin on a much more extensive blob of molecular gas that does not have the correct temperature and density to be as easily detectable. At the opposite extreme, the observed knots could consist of a fine mist of molecular gas in which we are detecting ...

  13. Embedded Star Formation in the Eagle Nebula

    CERN Document Server

    Thompson, R I; Hester, J J; Thompson, Rodger I.; Smith, Bradford A.

    2002-01-01

    M16=NGC 6611, the Eagle Nebula, is a well studied region of star formation and the source of a widely recognized Hubble Space Telescope (HST) image. High spatial resolution infrared observations with the Near Infrared Camera and Multi-Object Spectrometer (NICMOS) on HST reveal the detailed morphology of two embedded star formation regions that are heavily obscured at optical wavelengths. It is striking that only limited portions of the visually obscured areas are opaque at 2.2 microns. Although the optical images imply substantial columns of material, the infrared images show only isolated clumps of dense gas and dust. Rather than being an active factory of star production, only a few regions are capable of sustaining current star formation. Most of the volume in the columns may be molecular gas and dust, protected by capstones of dense dust. Two active regions of star formation are located at the tips of the optical northern and central large ``elephant trunk'' features shown in the WFPC2 images. They are em...

  14. The chemistry of compact planetary nebulae

    CERN Document Server

    Josselin, E

    2003-01-01

    We report high-sensitivity millimetre observations of several molecular species (13CO, HCN, HNC, CN, HCO+ and N2H+) in a sample of compact planetary nebulae. Some species such as HCO+ and CN are particularly abundant compared to envelopes around AGB stars or even interstellar clouds. We have estimated the following average values for the column densities ratios: CN/HCN~2.6, HCO+/HCN~0.5, and HNC/HCN~0.4. Thus, the chemical composition of the molecular envelopes in these compact PNe appears somewhat intermediate between the composition of proto-PNe (such as CRL 2688 or CRL 618) and well evolved PNe (such as the Ring, M4--9, or the Helix). From observations of the CO isotopomers, we have estimated that the 12C/13C ratio is in the range 10 ~< 12C/13C ~< 40. These values are below those expected from standard asymptotic giant branch models and suggest non-standard mixing processes. The observed molecular abundances are compared to very recent modelling work, and we conclude that the observations are well ex...

  15. Modelling of asymmetric nebulae. II. Line profiles

    CERN Document Server

    Morisset, C

    2006-01-01

    We present a tool, VELNEB_3D, which can be applied to the results of 3D photoionization codes to generate emission line profiles, position-velocity maps and 3D maps in any emission line by assuming an arbitrary velocity field. We give a few examples, based on our pseudo-3D photoionization code NEBU_3D (Morisset, Stasinska and Pena, 2005) which show the potentiality and usefulness of our tool. One example shows how complex line profiles can be obtained even with a simple expansion law if the nebula is bipolar and the slit slightly off-center. Another example shows different ways to produce line profiles that could be attributed to a turbulent velocity field while there is no turbulence in the model. A third example shows how, in certain circumstances, it is possible to discriminate between two very different geometrical structures -- here a face-on blister and its ``spherical impostor'' -- when using appropriate high resolution spectra. Finally, we show how our tool is able to generate 3D maps, similar to the ...

  16. Planetary Nebulae and How to Observe Them

    CERN Document Server

    Griffiths, Martin

    2012-01-01

    Astronomers' Observing Guides provide up-to-date information for amateur astronomers who want to know all about what is it they are observing. This is the basis of the first part of the book. The second part details observing techniques for practical astronomers, working with a range of different instruments. Planetary Nebulae and How to Observe Them is intended for amateur astronomers who want to concentrate on one of the most beautiful classes of astronomical objects in the sky. This book will help the observer to see these celestial phenomena using telescopes of various apertures. As a Sun-like star reaches the end of its life, its hydrogen fuel starts to run out. It collapses until helium nuclei begin nuclear fusion, whereupon the star begins to pulsate, each pulsation throwing off a layer of the star's atmosphere. Eventually the atmosphere has all been ejected as an expanding cloud of gas, the star's core is exposed and ultraviolet photons cause the shell of gas to glow brilliantly - that's planetary ...

  17. Planetary Nebulae in the Small Magellanic Cloud

    CERN Document Server

    Ventura, P; Di Criscienzo, M; García-Hernández, D A; Dell'Agli, F

    2016-01-01

    We analyse the planetary nebulae (PNe) population of the Small Magellanic Cloud (SMC), based on evolutionary models of stars with metallicities in the range $10^{-3} \\leq Z \\leq 4\\times 10^{-3}$ and mass $0.9 M\\odot < M < 8M\\odot$, evolved through the asymptotic giant branch (AGB) phase. The models used account for dust formation in the circumstellar envelope. To characterise the PNe sample of the SMC, we compare the observed abundances of the various species with the final chemical composition of the AGB models: this study allows us to identify the progenitors of the PNe observed, in terms of mass and chemical composition. According to our interpretation, most of the PNe descend from low-mass ($M < 2 M\\odot$) stars, which become carbon rich, after experiencing repeated third dredge-up episodes, during the AGB phase. A fraction of the PNe showing the signature of advanced CNO processing are interpreted as the progeny of massive AGB stars, with mass above $\\sim 6 M\\odot$, undergoing strong hot bottom ...

  18. Radio Planetary Nebulae in the Magellanic Clouds

    CERN Document Server

    Filipović, M D; Reid, W A; Payne, J L; Parker, Q A; Crawford, E J; Bojičić, I S; De Horta, A Y; Hughes, A; Dickel, J; Stootman, F

    2009-01-01

    We report the extragalactic radio-continuum detection of 15 planetary nebulae (PNe) in the Magellanic Clouds (MCs) from recent Australia Telescope Compact Array+Parkes mosaic surveys. These detections were supplemented by new and high resolution radio, optical and IR observations which helped to resolve the true nature of the objects. Four of the PNe are located in the Small Magellanic Cloud (SMC) and 11 are located in the Large Magellanic Cloud (LMC). Based on Galactic PNe the expected radio flux densities at the distance of the LMC/SMC are up to ~2.5 mJy and ~2.0 mJy at 1.4 GHz, respectively. We find that one of our new radio PNe in the SMC has a flux density of 5.1 mJy at 1.4 GHz, several times higher than expected. We suggest that the most luminous radio PN in the SMC (N S68) may represent the upper limit to radio peak luminosity because it is ~3 times more luminous than NGC 7027, the most luminous known Galactic PN. We note that the optical diameters of these 15 MCs PNe vary from very small (~0.08 pc or ...

  19. Adventures in Modern Time Series Analysis: From the Sun to the Crab Nebula and Beyond

    Science.gov (United States)

    Scargle, Jeffrey

    2014-01-01

    With the generation of long, precise, and finely sampled time series the Age of Digital Astronomy is uncovering and elucidating energetic dynamical processes throughout the Universe. Fulfilling these opportunities requires data effective analysis techniques rapidly and automatically implementing advanced concepts. The Time Series Explorer, under development in collaboration with Tom Loredo, provides tools ranging from simple but optimal histograms to time and frequency domain analysis for arbitrary data modes with any time sampling. Much of this development owes its existence to Joe Bredekamp and the encouragement he provided over several decades. Sample results for solar chromospheric activity, gamma-ray activity in the Crab Nebula, active galactic nuclei and gamma-ray bursts will be displayed.

  20. Resolving the electron temperature discrepancies in HII Regions and Planetary Nebulae: kappa-distributed electrons

    CERN Document Server

    Nicholls, David C; Sutherland, Ralph S

    2012-01-01

    The measurement of electron temperatures and metallicities in H ii regions and Planetary Nebulae (PNe) has-for several decades-presented a problem: results obtained using different techniques disagree. What it worse, they disagree consistently. There have been numerous attempts to explain these discrepancies, but none has provided a satisfactory solution to the problem. In this paper, we explore the possibility that electrons in H ii regions and PNe depart from a Maxwell-Boltzmann equilibrium energy distribution. We adopt a "kappa-distribution" for the electron energies. Such distributions are widely found in Solar System plasmas, where they can be directly measured. This simple assumption is able to explain the temperature and metallicity discrepancies in H ii regions and PNe arising from the different measurement techniques. We find that the energy distribution does not need to depart dramatically from an equilibrium distribution. From an examination of data from Hii regions and PNe it appears that kappa ~ ...

  1. Planetary Nebulae in Face-On Spiral Galaxies. I. Planetary Nebula Photometry and Distances

    CERN Document Server

    Herrmann, Kimberly A; Feldmeier, John J; Vinciguerra, Matt

    2008-01-01

    As the first step to determine disk mass-to-light ratios for normal spiral galaxies, we present the results of an imaging survey for planetary nebulae (PNe) in six nearby, face-on systems: IC 342, M74 (NGC 628), M83 (NGC 5236), M94 (NGC 4736), NGC 5068, and NGC 6946. Using Blanco/Mosaic II and WIYN/OPTIC, we identify 165, 153, 241, 150, 19, and 71 PN candidates, respectively, and use the Planetary Nebula Luminosity Function (PNLF) to obtain distances. For M74 and NGC 5068, our distances of 8.6 +/- 0.3 Mpc and 5.4 +0.2/-0.4 Mpc are the first reliable estimates to these objects; for IC 342 (3.5 +/- 0.3 Mpc), M83 (4.8 +/- 0.1 Mpc), M94 (4.4 +0.1/-0.2 Mpc), and NGC 6946 (6.1 +/- 0.6 Mpc) our values agree well with those in the literature. In the larger systems, we find no evidence for any systematic change in the PNLF with galactic position, though we do see minor field-to-field variations in the luminosity function. In most cases, these changes do not affect the measurement of distance, but in one case the fluct...

  2. Herschel Planetary Nebula Survey (HerPlaNS) - First Detection of OH+ in Planetary Nebulae

    CERN Document Server

    Aleman, I; Ladjal, D; Exter, K M; Kastner, J H; Montez, R; Tielens, A G G M; Chu, Y H; Izumiura, H; McDonald, I; Sahai, R; Siodmiak, N; Szczerba, R; van Hoof, P A M; Villaver, E; Vlemmings, W; Wittkowski, M; Zijlstra, A A

    2014-01-01

    We report the first detections of OH+ emission in planetary nebulae (PNe). As part of an imaging and spectroscopy survey of 11 PNe in the far-IR using the PACS and SPIRE instruments aboard the Herschel Space Observatory, we performed a line survey in these PNe over the entire spectral range between 51 and 672$\\mu$m to look for new detections. OH+ rotational emission lines at 152.99, 290.20, 308.48, and 329.77$\\mu$m were detected in the spectra of three planetary nebulae: NGC 6445, NGC 6720, and NGC 6781. Excitation temperatures and column densities derived from these lines are in the range of 27 to 47 K and 2 x $10$^{10}$ to 4 x $10$^{11}$ cm$^{-2}$, respectively. In PNe, the OH+ rotational line emission appears to be produced in the photodissociation region (PDR) in these objects. The emission of OH+ is observed only in PNe with hot central stars (Teff > 100000 K), suggesting that high-energy photons may play a role in the OH+ formation and its line excitation in these objects, as it seems to be the case for...

  3. Deformation-aided segregation of Fe-S liquid from olivine under deep Earth conditions: Implications for core formation in the early solar system

    Science.gov (United States)

    Berg, Madeleine T. L.; Bromiley, Geoffrey D.; Butler, Ian B.; Frost, Mungo; Bradley, Robert; Carr, James; Le Godec, Yann; Montési, Laurent G. J.; Zhu, Wenlu; Miller, Kevin; Perrillat, Jean-Philippe; Mariani, Elisabetta; Tatham, Daniel; Redfern, Simon A. T.

    2017-02-01

    The planets and larger rocky bodies of the inner solar system are differentiated, and consist of metallic, iron-rich cores surrounded by thick shells of silicate. Core formation in these bodies, i.e. the segregation of metal from silicate, was a key process in the early solar system, and one which left a lasting geochemical signature. It is commonly assumed that extensive silicate melting and formation of deep magma oceans was required to initiate core formation, due to the inability of iron-rich melts to segregate from a solid silicate matrix. Here we assess the role of deformation in aiding segregation of core-forming melts from solid silicate under conditions of planetary deep interiors. Low-strain rate, high-pressure/temperature deformation experiments and high-resolution 2-D and 3-D textural analysis demonstrate that deformation fundamentally alters iron-rich melt geometry, promoting wetting of silicate grain boundaries and formation of extensive micron to sub-micron width Fe-rich melt bands. Deformation-aided Fe-S melt networks noted here contrast those observed in higher finite strain experiments conducted at lower pressure, and may reveal either an alternative mechanism for melt segregation at higher pressures, or an early stage process of melt segregation. Results suggest, however, that core-mantle chemical equilibration cannot be assumed in models of planetary formation, and that instead, the chemistry of rocky planets may record a complex, multi-stage process of core formation.

  4. The dust content of planetary nebulae a reappraisal

    CERN Document Server

    Stasinska, G

    1999-01-01

    We have performed a statistical analysis using broad band IRAS data on about 500 planetary nebulae with the aim of characterizing their dust content. Our approach is different from previous studies in that it uses an extensive grid of photoionization models to test the methods for deriving the dust temperature, the dust-to-gas mass ratio and the average grain size. In addition, we use only distance independent diagrams. With our models, we show the effect of contamination by atomic lines in the broad band IRAS fluxes during planetary nebula evolution. We find that planetary nebulae with very different dust-to-gas mass ratios exist, so that the dust content is a primordial parameter for the interpretation of far infrared data of planetary nebulae. In contrast with previous studies, we find no evidence for a decrease in the dust-to-gas mass ratio as the planetary nebulae evolve. We also show that the decrease in grain size advocated by Natta and Panagia (1981, ApJ 248,189) and Lenzuni et al. (1989, ApJ 345, 306...

  5. The discovery of a highly polarized bipolar nebula

    Science.gov (United States)

    Wolstencroft, Ramon D.; Scarrott, S. M.; Menzies, J.

    1989-01-01

    During a search for the optical counterparts of IRAS sources whose flux peaks at 25 microns, a small faint bipolar nebula was discovered in Monoceros at the position of IRAS 07131-0147. The CCD images display the object's considerable structure. The central star seems relatively free of closeby nebulosity: the two lobes have a bow-tie structure with those parts nearest to the star consisting of series of small knots. The outer parts of the lobes seem to be made up of filaments streaming away from knots. On the basis of its optical spectrum, the central star was classified as a M5-6 giant. In the IRAS color classification scheme of Van der Veen and Habing (1988), the central star is VIb which indicates that there are distinct hot and cold components of circumstellar dust and that the mass loss process may have temporarily abated. Therefore, it is proposed that the object is in the post main sequence stage of evolution and is a protoplanetary nebulae. Young protoplanetary nebulae have totally obscured central stars illuminating reflective lobes whereas older ones such as M2-9 have lobes seen in emission from gas ionized by the central hot star which is clearly visible. Since the central object of IRAS07131-0147 is a relatively unobscured late type star and the lobes are seen only by reflection, it is suggested that this nebula is a protoplanetary nebula in an evolutionary stage intermediate between that of CRL2688 and M2-9.

  6. Bow-shock Pulsar Wind Nebulae Passing Through Density Discontinuities

    CERN Document Server

    Yoon, Doosoo

    2016-01-01

    Bow-shock pulsar wind nebulae are a subset of pulsar wind nebulae that form when the pulsar has high velocity due to the natal kick during the supernova explosion. The interaction between the relativistic wind from the fast-moving pulsar and the interstellar medium produces a bow-shock and a trail, which are detectable in H$_{\\alpha}$ emission. Among such bow-shock pulsar wind nebulae, the Guitar Nebula stands out for its peculiar morphology, which consists of a prominent bow-shock head and a series of bubbles further behind. We present a scenario in which multiple bubbles can be produced when the pulsar encounters a series of density discontinuities in the ISM. We tested the scenario using 2-D and 3-D hydrodynamic simulations. The shape of the guitar nebula can be reproduced if the pulsar traversed a region of declining low density. We also show that if a pulsar encounters an inclined density discontinuity, it produces an asymmetric bow-shock head, consistent with observations of the bow-shock of the millise...

  7. Chandra Confirmation of a Pulsar Wind Nebula in DA 495

    Science.gov (United States)

    Arzoumanian, Z.; Safi-Harb, S.; Landecker, T.L.; Kothes, R.; Camilo, F.

    2008-01-01

    As part of a multiwavelength study of the unusual radio supernova remnant DA 495, we present observations made with the Chandra X-ray Observatory. Imaging and spectroscopic analysis confirms the previously detected X-ray source at the heart of the annular radio nebula, establishing the radiative properties of two key emission components: a soft unresolved source with a blackbody temperature of 1 MK consistent with a neutron star, surrounded by a nontherma1 nebula 40" in diameter exhibiting a power-law spectrum with photon index Gamma = 1.63, typical of a pulsar wind nebula. Morphologically, the nebula appears to be slightly extended along a direction, in projection on the sky, previously demonstrated to be of significance in radio and ASCA observations; we argue that this represents the orientation of the pulsar spin axis. At smaller scales, a narrow X-ray feature is seen extending out 5" from the point source, but energetic arguments suggest that it is not the resolved termination shock of the pulsar wind against the ambient medium. Finally, we argue based on synchrotron lifetimes in the nebular magnetic field that DA 495 represents the first example of a pulsar wind nebula in which electromagnetic flux makes up a significant part, together with particle flux, of the neutron star's wind.

  8. Submillimeter and Far-Infrared Observations of the Carina Nebula

    Science.gov (United States)

    Oberst, Thomas E.; Parshley, S. C.; Nikola, T.; Stacey, G. J.; Loehr, A.; Lane, A. P.; Stark, A. A.; Kamenetzky, J.

    2011-05-01

    We present the results of a 250 arcmin2 mapping of the 205 μm [NII] fine-structure emission over the northern Carina Nebula, including the Car I and Car II HII regions. Spectra were obtained using the South Pole Imaging Fabry-Perot Interferometer (SPIFI) at the Antarctic Submillimeter Telescope and Remote Observatory (AST/RO) at South Pole. We supplement the 205 μm data with new reductions of far-IR fine-structure spectra from the Infrared Space Observatory (ISO) in 63 μm [OI], 122 μm [NII], 146 μm [OI], and 158 μm [CII]. Morphological comparisons are made with optical, radio continuum and CO maps. The 122 [NII] / 205 [NII] line ratio is used to probe the density of the low-ionization gas, and the 158 [C II] / 205 [NII] line ratio is used to probe the fraction of C+ arising from photodissociation regions (PDRs). From the [OI] and [CII] data, we construct a PDR model of Carina following Kaufman et al. (1999). When the PDR properties are compared with other sources, Carina is found to be more akin to 30 Doradus than Galactic star-forming regions such as the Orion Bar, M17, or W49; this is consistent with the view of Carina as a more evolved region, where much of the parent molecular cloud has been ionized or swept away. These data constitute the first ever ground-based detection of the 205 μm [NII] line, and only the third detection overall since those of the COBE FIRAS and the KAO in the early 1990s.

  9. A minimum mass nebula for M dwarfs

    Science.gov (United States)

    Gaidos, E.

    2017-09-01

    Recently revealed differences in planets around M dwarf versus solar-type stars could arise from differences in their primordial discs and surveys of T Tauri stars find a correlation between stellar mass and disc mass. 'Minimum' discs have been reconstructed for the Solar system and solar-type stars and here this exercise is performed for M dwarfs using Kepler-detected planets. Distribution of planet mass between current orbits produces a disc with total mass of ≈0.009 M⊙ and a power-law profile with index α = 2.2. Disc reconstruction from the output of a forward model of planet formation indicates that the effect of detection bias on disc profile is slight and that the observed scatter in planet masses and semimajor axes are consistent with a universal disc profile. This nominal M dwarf disc is more centrally concentrated than those inferred around the solar-type stars observed by Kepler, and the mass surface density beyond 0.02 au is sufficient for in situ accretion of planets as single embryos. The mass of refractory solids within 0.5 au is 5.6 M⊕ compared to 4 M⊕ for solar-type stars in contrast with the trend with total disc mass. The total solid beyond 0.5 au is sufficient for the core of at least one giant planet.

  10. A new Planetary Nebula in the outer reaches of the Galaxy

    DEFF Research Database (Denmark)

    Viironen, K.; Mampaso, A.; L. M. Corradi, R.;

    2011-01-01

    of a new planetary nebula towards the Anticentre direction, IPHASX J052531.19+281945.1 (PNG 178.1-04.0), is presented. The planetary nebula was discovered from the IPHAS survey. Long-slit follow-up spectroscopy was carried out to confirm its planetary nebula nature and to calculate its physical...

  11. Pulsar Wind Nebulae as Cosmic Pevatrons: A Current Sheet's Tale

    CERN Document Server

    Arons, Jonathan

    2012-01-01

    I outline, from a theoretical and somewhat personal perspective, significant features of Pulsar Wind Nebulae as Cosmic Accelerators. I discuss recent studies of Pulsar Wind Nebulae (PWNe). I pay special attention to the recently discovered gamma ray flares in the Crab Nebula's emission, focusing on the possibility, raised by the observations, that the accelerating electric field exceeds the magnetic field, suggesting that reconnection in the persistent current layer (a current sheet) plays a significant role in the behavior of this well studied Pevatron. I address the present status of the termination shock model for the particle accelerator that converts the wind flow energy to the observed non thermal particle spectra, concluding that it has a number of major difficulties related to the transverse magnetic geometry of the shock wave. I discuss recent work on the inferred pair outflow rates, which are in excess of those predicted by existing theories of pair creation, and use those results to point out that ...

  12. A disc in the heart of the Ant nebula

    CERN Document Server

    Lykou, Foteini; Lagadec, Eric; Zijlstra, Albert

    2007-01-01

    We present the discovery of a silicate disc at the centre of the planetary nebula Mz3 (the Ant). The nebula was observed with MIDI on the Very Large Telescope Interferometer (VLTI). The visibilities obtained at different orientations clearly indicate the presence of a dusty, nearly edge-on disc in the heart of the nebula. An amorphous silicate absorption feature is clearly seen in our mid-IR spectrum and visibility curves. We used radiative transfer Monte Carlo simulations to constrain the geometrical and physical parameters of the disc. We derive an inner radius of 9 AU (~6mas assuming D=1.4kpc). This disc is perpendicular to, but a factor of 10^{3} smaller than the optical bipolar outflow.

  13. EVOLUTION OF THE CRAB NEBULA IN A LOW ENERGY SUPERNOVA

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Haifeng; Chevalier, Roger A., E-mail: hy4px@virginia.edu, E-mail: rac5x@virginia.edu [Department of Astronomy, University of Virginia, P.O. Box 400325, Charlottesville, VA 22904 (United States)

    2015-06-20

    The nature of the supernova leading to the Crab Nebula has long been controversial because of the low energy that is present in the observed nebula. One possibility is that there is significant energy in extended fast material around the Crab but searches for such material have not led to detections. An electron capture supernova model can plausibly account for the low energy and the observed abundances in the Crab. Here, we examine the evolution of the Crab pulsar wind nebula inside a freely expanding supernova and find that the observed properties are most consistent with a low energy event. Both the velocity and radius of the shell material, and the amount of gas swept up by the pulsar wind point to a low explosion energy (∼10{sup 50} erg). We do not favor a model in which circumstellar interaction powers the supernova luminosity near maximum light because the required mass would limit the freely expanding ejecta.

  14. Newest insights from MHD numerical modeling of Pulsar Wind Nebulae

    Science.gov (United States)

    Olmi, B.; Del Zanna, L.; Amato, E.; Bucciantini, N.; Bandiera, R.

    2016-06-01

    Numerical MHD models are considered very successful in accounting for many of the observed properties of Pulsar Wind Nebulae (PWNe), especially those concerning the high energy emission morphology and the inner nebula dynamics. Although PWNe are known to be among the most powerful accelerators in nature, producing particles up to PeV energies, the mechanisms responsible of such an efficient acceleration are still a deep mystery. Indeed, these processes take place in one of the most hostile environment for particle acceleration: the relativistic and highly magnetized termination shock of the pulsar wind. The newest results from numerical simulations of the Crab Nebula, the PWN prototype, will be presented, with special attention to the problem of particle acceleration. In particular it will be shown how a multi-wavelengths analysis of the wisps properties can be used to constrain the particle acceleration mechanisms working at the Crab's termination shock, by identifying the particle acceleration site at the shock front.

  15. Evolution of the Crab nebula in a low energy supernova

    CERN Document Server

    Yang, Haifeng

    2015-01-01

    The nature of the supernova leading to the Crab Nebula has long been controversial because of the low energy that is present in the observed nebula. One possibility is that there is significant energy in extended fast material around the Crab but searches for such material have not led to detections. An electron capture supernova model can plausibly account for the low energy and the observed abundances in the Crab. Here, we examine the evolution of the Crab pulsar wind nebula inside a freely expanding supernova and find that the observed properties are most consistent with a low energy event. Both the velocity and radius of the shell material, and the amount of gas swept up by the pulsar wind point to a low explosion energy ($\\sim 10^{50}$ ergs). We do not favor a model in which circumstellar interaction powers the supernova luminosity near maximum light because the required mass would limit the freely expanding ejecta.

  16. The surprising Crab pulsar and its nebula: a review.

    Science.gov (United States)

    Bühler, R; Blandford, R

    2014-06-01

    The Crab nebula and its pulsar (referred to together as 'the Crab') have historically played a central role in astrophysics. True to this legacy, several unique discoveries have been made recently. The Crab was found to emit gamma-ray pulsations up to energies of 400 GeV, beyond what was previously expected from pulsars. Strong gamma-ray flares, of durations of a few days, were discovered from within the nebula, while the source was previously expected to be stable in flux on these time scales. Here we review these intriguing and suggestive developments. In this context we give an overview of the observational properties of the Crab and our current understanding of pulsars and their nebulae.

  17. Mass-loading of bow shock pulsar wind nebulae

    CERN Document Server

    Morlino, G; Vorster, M

    2016-01-01

    We investigate the dynamics of bow shock nebulae created by pulsars moving supersonically through a partially ionized interstellar medium. A fraction of interstellar neutral hydrogen atoms penetrating into the tail region of a pulsar wind will undergo photo-ionization due to the UV light emitted by the nebula, with the resulting mass loading dramatically changing the flow dynamics of the light leptonic pulsar wind. Using a quasi 1-D hydrodynamic model of relativistic flow we find that if a relatively small density of neutral hydrogen, as low as $10^{-4}$ cm$^{-3}$, penetrate inside the pulsar wind, this is sufficient to strongly affect the tail flow. Mass loading leads to the fast expansion of the pulsar wind tail, making the tail flow intrinsically non-stationary. The shapes predicted for the bow shock nebulae compare well with observations, both in H$\\alpha$ and X-rays.

  18. An atlas of synthetic line profiles of planetary nebulae

    CERN Document Server

    Morisset, C

    2008-01-01

    We have constructed a grid of photoionization models of spherical, elliptical and bipolar planetary nebulae. Assuming different velocity fields, we have computed line profiles corresponding to different orientations, slit sizes and positions. The atlas is meant both for didactic purposes and for the interpretation of data on real nebulae. As an application, we have shown that line profiles are often degenerate, and that recovering the geometry and velocity field from observations requires lines from ions with different masses and different ionization potentials. We have also shown that the empirical way to measure mass-weighted expansion velocities from observed line widths is reasonably accurate if considering the HWHM. For distant nebulae, entirely covered by the slit, the unknown geometry and orientation do not alter the measured velocities statistically. The atlas is freely accessible from internet. The Cloudy_3D suite and the associated VISNEB tool are available on request.

  19. Revised Predictions of Neutrino Fluxes from Pulsar Wind Nebulae

    Science.gov (United States)

    Di Palma, Irene; Guetta, Dafne; Amato, Elena

    2017-02-01

    Several pulsar wind nebulae (PWN) have been detected in the TeV band in the last decade. TeV emission is typically interpreted in a purely leptonic scenario, but this often requires that the magnetic field in the nebula be much lower than the equipartition value, as well as the assumption of an enhanced density of target radiation at IR frequencies. In this work, we consider the possibility that, in addition to the relativistic electrons and positrons, relativistic hadrons are also present in these nebulae. Assuming that some of the emitted TeV photons are of hadronic origin, we compute the associated flux of ∼ 1{--}100 TeV neutrinos. We use IceCube non-detection to put constraints on the fraction of TeV photons that might be contributed by hadrons and estimate the number of neutrino events that can be expected from these sources in ANTARES and KM3Net.

  20. Facilitating NASA Earth Science Data Processing Using Nebula Cloud Computing

    Science.gov (United States)

    Chen, A.; Pham, L.; Kempler, S.; Theobald, M.; Esfandiari, A.; Campino, J.; Vollmer, B.; Lynnes, C.

    2011-12-01

    Cloud Computing technology has been used to offer high-performance and low-cost computing and storage resources for both scientific problems and business services. Several cloud computing services have been implemented in the commercial arena, e.g. Amazon's EC2 & S3, Microsoft's Azure, and Google App Engine. There are also some research and application programs being launched in academia and governments to utilize Cloud Computing. NASA launched the Nebula Cloud Computing platform in 2008, which is an Infrastructure as a Service (IaaS) to deliver on-demand distributed virtual computers. Nebula users can receive required computing resources as a fully outsourced service. NASA Goddard Earth Science Data and Information Service Center (GES DISC) migrated several GES DISC's applications to the Nebula as a proof of concept, including: a) The Simple, Scalable, Script-based Science Processor for Measurements (S4PM) for processing scientific data; b) the Atmospheric Infrared Sounder (AIRS) data process workflow for processing AIRS raw data; and c) the GES-DISC Interactive Online Visualization ANd aNalysis Infrastructure (GIOVANNI) for online access to, analysis, and visualization of Earth science data. This work aims to evaluate the practicability and adaptability of the Nebula. The initial work focused on the AIRS data process workflow to evaluate the Nebula. The AIRS data process workflow consists of a series of algorithms being used to process raw AIRS level 0 data and output AIRS level 2 geophysical retrievals. Migrating the entire workflow to the Nebula platform is challenging, but practicable. After installing several supporting libraries and the processing code itself, the workflow is able to process AIRS data in a similar fashion to its current (non-cloud) configuration. We compared the performance of processing 2 days of AIRS level 0 data through level 2 using a Nebula virtual computer and a local Linux computer. The result shows that Nebula has significantly

  1. Gamma-rays from pulsar wind nebulae in starburst galaxies

    Science.gov (United States)

    Mannheim, Karl; Elsässer, Dominik; Tibolla, Omar

    2012-07-01

    Recently, gamma-ray emission at TeV energies has been detected from the starburst galaxies NGC253 (Acero et al., 2009) [1] and M82 (Acciari et al., 2009) [2]. It has been claimed that pion production due to cosmic rays accelerated in supernova remnants interacting with the interstellar gas is responsible for the observed gamma rays. Here, we show that the gamma-ray pulsar wind nebulae left behind by the supernovae contribute to the TeV luminosity in a major way. A single pulsar wind nebula produces about ten times the total luminosity of the Sun at energies above 1 TeV during a lifetime of 105 years. A large number of 3 × 104 pulsar wind nebulae expected in a typical starburst galaxy at a distance of 4 Mpc can readily produce the observed TeV gamma rays.

  2. Mass-loading of bow shock pulsar wind nebulae

    CERN Document Server

    Morlino, G; Vorster, M J

    2015-01-01

    We investigate the dynamics of bow shock nebulae created by pulsars moving supersonically through a partially ionized interstellar. A fraction of interstellar neutrals penetrating into the tail region of a pulsar wind will undergo photo-ionization due to the UV light emitted by the nebula, with the resulting mass loading dramatically changing the flow dynamics of the light leptonic pulsar wind. Using a quasi 1-D hydrodynamic model of both non-relativistic and relativistic flow, and focusing on scales much larger than the stand-off distance, we find that a relatively small density of neutrals, as low as $n_{\\rm ISM}=10^{-4}\\,\\text{cm}^{-3}$, is sufficient to strongly affect the tail flow. Mass loading leads to the fast expansion of the pulsar wind tail, making the tail flow intrinsically non-stationary. The shapes predicted for the bow shock nebulae compare well with observations, both in H$\\alpha$ and X-rays.

  3. Featured Image: A Search for Stellar Bow Shock Nebulae

    Science.gov (United States)

    Kohler, Susanna

    2017-02-01

    These dynamic infrared images (click for the full view!) reveal what are known as bow shock nebulae nebulae that form at the interface between the interstellar medium and the stellar wind from a high-speed star zipping through the galaxy (the arrows show the direction of motion of the star). When the relative speed between the two is supersonic, an arc-shaped bow shock forms ahead of the star, like the six prototypical ones pictured here. A team of scientists led by Henry Kobulnicky (University of Wyoming) has recently searched through survey data from the Spitzer Space Telescope and the Wide Field Infrared Explorer (WISE) to build a catalog of more than 700 such bow-shock nebula candidates, the vast majority of which are new discoveries. To find out more about their sample, check out the paper below!CitationHenry A. Kobulnicky et al 2016 ApJS 227 18. doi:10.3847/0067-0049/227/2/18

  4. Mass and motion of globulettes in the Rosette Nebula

    Science.gov (United States)

    Gahm, G. F.; Persson, C. M.; Mäkelä, M. M.; Haikala, L. K.

    2013-07-01

    Context. Tiny molecular clumps are abundant in many H ii regions surrounding newborn stellar clusters. In optical images these so-called globulettes appear as dark patches against the background of bright nebulosity. The majority of the globulettes were found to be of planetary mass in a previous optical investigation, while the largest objects may contain more than half a solar mass. Aims: We aim to clarify the physical nature of globulettes by deriving densities and masses, and to determine their velocities as a function of position over the nebula. This information will provide clues to the question of origins, evolution, and fate of globulettes. The Rosette Nebula is relatively rich in globulettes, and we selected a sample of well-confined objects of different sizes for the present investigation. Methods: Radio observations were made of molecular line emission from 16 globulettes combined with near-infrared (NIR) broad-band JHKs and narrow-band Paschen β and H2 imaging. Ten objects, for which we collected information from several transitions in 12CO and 13CO, were modelled using a spherically symmetric model. Results: Practically all globulettes were detected in our CO survey. The observed 12CO (3-2) and (2-1) line temperatures range from 0.6 K to 6 K, the 13CO being a third of this. As a rule, the lines are narrow, ~1.0 km s-1. The best fit to observed line ratios and intensities was obtained by assuming a model composed of a cool and dense centre and warm and dense surface layer. This model provides estimates of maximum and minimum mass; the average masses range from about 50 to 500 Jupiter masses, which is similar to earlier estimates based on extinction measures. The selected globulettes are dense, nH ~ 104 cm-3, with very thin layers of fluorescent H2 emission, showing that the gas is in molecular form just below the surface. The NIR data show that several globulettes are very opaque and contain dense cores. No infrared-excess stars in the fields are

  5. SIMS analyses of Mg, Cr, and Ni isotopes in primitive meteorites and short-lived radionuclides in the early solar system

    Energy Technology Data Exchange (ETDEWEB)

    Guan, Y.; Huss, G.R.; Leshin, L.A

    2004-06-15

    SIMS analyses of {sup 26}Al-{sup 26}Mg, {sup 60}Fe-{sup 60}Ni, and {sup 53}Mn-{sup 53}Cr systems in unequilibrated enstatite chondrites provide evidence for the former existence of {sup 26}Al, {sup 60}Fe, and {sup 53}Mn in this highly reduced meteorite group, suggesting the widespread of these short-lived radionuclides in the early solar system. Calcium-aluminum-rich inclusions and Al-rich chondrules in enstatite chondrites show {sup 26}Al-{sup 26}Mg characteristics similar to their counterparts in other types of chondrites. Assuming its homogenous distribution, fine-scale {sup 26}Al relative chronology can be obtained for different components in meteorites. Well-defined isochrons yield initial {sup 60}Fe/{sup 56}Fe ratios of (0.3-1)x10{sup -6} in sulfides from enstatite chondrites. The former presence of {sup 60}Fe suggests a stellar source and its possible high abundance points to a supernova origin. {sup 26}Al and {sup 60}Fe could be important heat sources for the early planetary processes. The large variations of initial {sup 60}Fe/{sup 56}Fe and {sup 53}Mn/{sup 55}Mn ratios and the discordance between {sup 60}Fe-{sup 60}Ni and {sup 53}Mn-{sup 53}Cr systems observed in sulfides indicate later disturbance of the two isotopic systems, and therefore, bear no strict chronological significance. SIMS isotopic analysis can be utilized to attain important information about the early evolution of the solar system.

  6. Geminga’s Puzzling Pulsar Wind Nebula

    Science.gov (United States)

    Posselt, B.; Pavlov, G. G.; Slane, P. O.; Romani, R.; Bucciantini, N.; Bykov, A. M.; Kargaltsev, O.; Weisskopf, M. C.; Ng, C.-Y.

    2017-01-01

    We report on six new Chandra observations of the Geminga pulsar wind nebula (PWN). The PWN consists of three distinct elongated structures—two ≈ 0.2{d}250 pc long lateral tails and a segmented axial tail of ≈ 0.05{d}250 pc length, where {d}250=d/(250 {pc}). The photon indices of the power-law spectra of the lateral tails, {{Γ }}≈ 1, are significantly harder than those of the pulsar ({{Γ }}≈ 1.5) and the axial tail ({{Γ }}≈ 1.6). There is no significant diffuse X-ray emission between the lateral tails—the ratio of the X-ray surface brightness between the south tail and this sky area is at least 12. The lateral tails apparently connect directly to the pulsar and show indications of moving footpoints. The axial tail comprises time-variable emission blobs. However, there is no evidence for constant or decelerated outward motion of these blobs. Different physical models are consistent with the observed morphology and spectra of the Geminga PWN. In one scenario, the lateral tails could represent an azimuthally asymmetric shell whose hard emission is caused by the Fermi acceleration mechanism of colliding winds. In another scenario, the lateral tails could be luminous, bent polar outflows, while the blobs in the axial tail could represent a crushed torus. In a resemblance to planetary magnetotails, the blobs of the axial tail might also represent short-lived plasmoids, which are formed by magnetic field reconnection in the relativistic plasma of the pulsar wind tail.

  7. An Interactive Gallery of Planetary Nebula Spectra

    Science.gov (United States)

    Kwitter, K. B.; Henry, R. B. C.

    2002-12-01

    We have created a website containing high-quality moderate-resolution spectra of 88 planetary nebulae (PNe) from 3600 to 9600 Å, obtained at KPNO and CTIO. Spectra are displayed in a zoomable window, and there are templates available that show wavelength and ion identifications. In addition to the spectra themselves, the website also contains a brief discussion of PNe as astronomical objects and as contributors to our understanding of stellar evolution, and a table with atlas information for each object along with a link to an image. This table can be re-ordered by object name, galactic or equatorial coordinates, distance from the sun, the galactic center, or the galactic plane. We envision that this website, which concentrates a large amount of data in one place, will be of interest to a variety of users. PN researchers might need to check the spectrum of a particular object of interest; the non-specialist astronomer might simply be interested in perusing such a collection of spectra; and finally, teachers of introductory astronomy can use this database to illustrate basic principles of atomic physics and radiation. To encourage such use, we have written two simple exercises at a basic level to introduce beginning astronomy students to the wealth of information that PN spectra contain. We are grateful to Adam Wang of the Williams College OIT and to his summer student teams who worked on various apects of the implementation of this website. This work has been supported by NSF grant AST-9819123 and by Williams College and the University of Oklahoma.

  8. s-process Enrichment in the Planetary Nebula NGC 3918

    CERN Document Server

    García-Rojas, J; Luridiana, V; Sterling, N C; Morisset, C

    2014-01-01

    We present deep, high-resolution (R~40000) UVES at VLT spectrophotometric data of the planetary nebula NGC 3918. This is one of the deepest spectra ever taken of a planetary nebula. We have identified and measured more than 700 emission lines and, in particular, we have detected very faint lines of several neutron-capture elements (s-process elements: Kr, Xe and Rb) that enable us to compute their chemical abundances with unprecedented accuracy, thus constraining the efficiency of the s-process and convective dredge-up.

  9. Planetary nebulae in 2014: A review of research

    CERN Document Server

    Zijlstra, Albert

    2015-01-01

    Planetary nebulae had a double anniversary in 2014, 250 year since their discovery and 150 year since the correct spectroscopic identification. This paper gives an overview of planetary nebula research published in 2014. Topics include surveys, central stars, abundances, morphologies, magnetic fields, stellar population and galactic dynamics. An important continuing controversy is the discrepancy between recombination-line and forbidden-line abundances. A new controversy is the relation between symbiotic stars and [WC] stars. PN of the year is undoubtedly CRL 618, with papers on its binary symbiotic/[WC] nucleus, rapid stellar evolution, expanding jets and magnetic fields.

  10. Observing by hand sketching the nebulae in the nineteenth century

    CERN Document Server

    Nasim, Omar W

    2014-01-01

    Today we are all familiar with the iconic pictures of the nebulae produced by the Hubble Space Telescope's digital cameras. But there was a time, before the successful application of photography to the heavens, in which scientists had to rely on handmade drawings of these mysterious phenomena.           Observing by Hand sheds entirely new light on the ways in which the production and reception of handdrawn images of the nebulae in the nineteenth century contributed to astronomical observation. Omar W. Nasim investigates hundreds of unpublished observing books and paper records from six ninete

  11. An Analysis of Spectra in the Red Rectangle Nebula

    Indian Academy of Sciences (India)

    Frédéric Zagury

    2005-12-01

    This paper presents an analysis of a series of spectra in the Red Rectangle nebula. Only the reddest part of the spectra can safely be attributed to light from the nebula, and indicates Rayleigh scattering by the gas, in conformity with the large angles of scattering involved and the proximity of the star. In the blue, light from HD 44179, refracted or scattered in the atmosphere, dominates the spectra. This paper questions the reliability of ground-based broad-band spectra of extended objects in the blue.

  12. Facilitating NASA Earth Science Data Processing Using Nebula Cloud Computing

    Science.gov (United States)

    Pham, Long; Chen, Aijun; Kempler, Steven; Lynnes, Christopher; Theobald, Michael; Asghar, Esfandiari; Campino, Jane; Vollmer, Bruce

    2011-01-01

    Cloud Computing has been implemented in several commercial arenas. The NASA Nebula Cloud Computing platform is an Infrastructure as a Service (IaaS) built in 2008 at NASA Ames Research Center and 2010 at GSFC. Nebula is an open source Cloud platform intended to: a) Make NASA realize significant cost savings through efficient resource utilization, reduced energy consumption, and reduced labor costs. b) Provide an easier way for NASA scientists and researchers to efficiently explore and share large and complex data sets. c) Allow customers to provision, manage, and decommission computing capabilities on an as-needed bases

  13. Final Summary of Research Report to the National Aeronautics and Space Administration Origins of Solar Systems Program

    Science.gov (United States)

    O'D. Alexander, Conel

    2003-01-01

    The chondrites are aggregates of components (e.g. chondrules, chondrule rims and matrix) that formed in the nebula but, at present, there is no consensus on how any of these components formed or whether their formation produced or post dated the chemical fractionations between the chondrites. Chondrites are, at present, the most primitive Solar System objects available for laboratory study and the conditions under which their principle components formed would provide the most direct constraints for models of nebula formation and evolution. The conditions under which chondrules formed is of particular importance because, if their relative abundance in chondrites approximates that in the nebula, they are the products of one of the most energetic and pervasive processes that operated in the early Solar System. The goal of this proposal was to combine theoretical modeling with a comprehensive study of the elemental and isotopic compositions of the major components in unequilibrated ordinary chondrites (UOCs), with the aim of determining the conditions in the nebula at the time of their formation. The isotopes of volatile and moderately volatile elements should be particularly revealing of conditions during chondrule formation, as evaporation under most conditions would lead to isotopic mass fractionation. Modeling of chondrule and matrix formation requires the development of a kinetic model of evaporation and condensation, and calibration of this model against experiments. Cosmic spherules present an opportunity to test our evaporation models under flash heating conditions that would be difficult to simulate experimentally. However, there is surprisingly little known about the isotopic compositions of silicate cosmic spherules, and a number of questions need to be addressed. Is the range of compositions they exhibit due to evaporation? If they are, are the relative volatilities consistent with the models/experiments and are the isotopic fractionations consistent with

  14. SALT reveals the barium central star of the planetary nebula Hen 2-39

    CERN Document Server

    Miszalski, B; Jones, D; Karakas, A I; Köppen, J; Tyndall, A A; Mohamed, S S; Rodríguez-Gil, P; Santander-García, M

    2013-01-01

    Classical barium stars are binary systems which consist of a late-type giant enriched in carbon and slow neutron capture (s-process) elements and an evolved white dwarf (WD) that is invisible at optical wavelengths. The youngest observed barium stars are surrounded by planetary nebulae (PNe), ejected soon after the wind accretion of polluted material when the WD was in its preceeding asymptotic giant branch (AGB) phase. Such systems are rare but powerful laboratories for studying AGB nucleosynthesis as we can measure the chemical abundances of both the polluted star and the nebula ejected by the polluter. Here we present evidence for a barium star in the PN Hen 2-39. The polluted giant is very similar to that found in WeBo 1. It is a cool (Teff=4250 +/- 150 K) giant enhanced in carbon ([C/H]=0.42 +/- 0.02 dex) and barium ([Ba/Fe]=1.50 +/- 0.25 dex). A spectral type of C-R3 C_24 nominally places Hen 2-39 amongst the peculiar early R-type carbon stars, however the barium enhancement and likely binary status mea...

  15. X-Ray Emission by A Shocked Fast Wind from the Central Stars of Planetary Nebulae

    CERN Document Server

    Akashi, M; Behar, E; Akashi, Muhammad; Soker, Noam; Behar, Ehud

    2005-01-01

    We calculate the X-ray emission from the shocked fast wind blown by the central stars of planetary nebulae (PNs) and compare with observations. Using spherically symmetric self similar solutions with radiative cooling, we calculate the flow structure and X-ray temperature for a fast wind slamming into a previously ejected slow wind. We find that the observed X-ray emission of six PNs can be accounted for by shocked wind segments that were expelled during the early PN phase, if the fast wind speed is moderate, ~400-600 km/sec, and the mass loss rate is a few times 10^{-7} Mo/year. We find, as proposed previously, that the morphology of the X-ray emission is in the form of a narrow ring inner to the optical bright part of the nebula. The bipolar X-ray morphology of several observed PNs, which indicates an important role of jets rather than a spherical fast wind, cannot be explained by the flow studied here.

  16. Pulsational variability in proto-planetary nebulae and other post-AGB objects

    Science.gov (United States)

    Hrivnak, Bruce J.

    2016-07-01

    Light and velocity curves of several classes of pulsating stars have been successfully modeled to determine physical properties of the stars. In this observational study, we review briefly the pulsational variability of the main classes of post-AGB stars. Our attention is focused in particular on proto-planetary nebulae (PPNe), those in the short-lived phase from AGB stars to the planetary nebulae. New light curves and period analyses have been used to determine the following general properties of the PPNe variability: (a) periods range from 35 to 160 days for those of F—G spectral types, with much shorter periods (day) found for those of early-B spectral type; (b) there is a correlation between the pulsation period, maximum amplitude, and temperature of the star, with cooler stars pulsating with longer periods and larger amplitudes; (c) similar correlations are found for carbon-rich, oxygen-rich, and lower-metalicity PPNe; and (d) multiple periods are found for all of them, with P2/P1 = 1.0±0.1. New models are needed to exploit these results.

  17. Extended Red Objects and Stellar Wind Bow Shocks in the Carina Nebula

    CERN Document Server

    Sexton, Remington O; Smith, Nathan; Babler, Brian L; Meade, Marilyn R; Rudolph, Alexander L

    2014-01-01

    We report the results of infrared photometry on 39 extended red objects (EROs) in the Carina Nebula, observed with the Spitzer Space Telescope. Most EROs are identified by bright, extended 8.0 um emission, which ranges from 10'' to 40'' in size, but our sample also includes 4 EROs identified by extended 24 um emission. Of particular interest are nine EROs associated with late O or early B-type stars and characterized by arc-shaped morphology, suggesting dusty, stellar-wind bow shocks. These objects are preferentially oriented towards the central regions of the Carina Nebula, suggesting that these bow shocks are generally produced by the interactions of OB winds with the bulk expansion of the H II region rather than high proper motion. We identify preferred regions of mid-infrared color space occupied by our bow shock candidates, which also contain bow shock candidates in M17 and RCW 49 but are well-separated from polycyclic aromatic hydrocarbon emission or circumstellar discs. Color cuts identify an additiona...

  18. A multiwavelength study of the Stingray Nebula; properties of the nebula, central star, and dust

    Science.gov (United States)

    Otsuka, Masaaki; Parthasarathy, Mudumba; Tajitsu, Akito; Hubrig, Swetlana

    2016-07-01

    We performed a detail chemical abundance analysis and photo-ionization modeling of the Stingray Nebula (Hen3-1357, Parthasarathy et al. 1993[1]) to more characterize this PN. We calculated nine elemental abundances using collisionally excited lines (CELs) and recombination lines (RLs). The RL C/O ratio indicates that this PN is O-rich, which is supported by the detection of the broad amorphous silicate features at 9 and 18 μm By photo-ionization modeling, we investigated properties of the central star and derived the gas and dust masses. The nebular elemental abundances, the core-mass of the central star, and the gas mass are in agreement with the AGB model for the initially 1.5 M ⊙ stars with the Z = 0.008.

  19. Luminosities and masses for three central stars of planetary nebulae in the Magellanic Clouds from ultraviolet spectroscopy with the IUE

    Science.gov (United States)

    Stecher, T. P.; Savedoff, M. P.; Maran, S. P.; Gull, T. R.; Aller, L. H.

    1982-01-01

    Physical parameters of the central stars of the planetary nebulae (PN) P40, N2, and N5 are determined from UV observations by the IUE spacecraft and emission line-data. The observations took place on May 23 and 26, 1981. Derived properties, such as the H-beta, color excess, nebular hydrogen emission, helium emission, and stellar continuum emission, the stellar radius, surface gravity, Zanstra temperature, luminosity, absolute bolometric magnitude, apparent visual magnitude, mass, and Zanstra parameter for the three PN central stars are presented. All the masses were over one solar mass, suggesting a specific PN nuclei mass. The finding was corroborated by all luminosities exceeding the Eddington luminosity for a 0.6 solar mass star, which has previously been calculated for the white dwarf core of a PN.

  20. Nuclear field shift effect as a possible cause of Te isotopic anomalies in the early solar system —An alternative explanation of Fehr et al. (2006 and 2009)

    Science.gov (United States)

    Moynier, F.; Fujii, T.; Albarède, F.

    2009-12-01

    We explore the possibility that Te isotopic anomalies measured in Ca-Al-rich inclusions (Fehr et al. 2009) and in leachates of carbonaceous chondrites (Fehr et al. 2006) may be due to mass-independent effects controlled by nuclear field shift rather than to nucleosynthetic processes. Fehr et al.’s spectrum of mass-independent anomalies of Te isotopes shows a smooth correlation with mass number and nuclear charge distribution. Ratios of even to odd isotopes, as the 125Te/126Te ratio used by these authors for normalization are particularly prone to nuclear field shift effects. We show that the alternative normalization of isotopic ratios to 130Te/126Te strongly reduces the trend of isotopic fractionation with mass number, leaving only 125Te as truly anomalous. For both normalizations (125Te/126Te and 130Te/126Te), Fehr et al.’s results fit the theory of Bigeleisen (1996), which suggests that the nuclear field shift effect can potentially account for the observed Te isotope abundances, as an alternative to nucleosynthetic processes. We propose that these mass-independent effects may be acquired during accretion of sulfides from the solar nebula.