Bangs and meteors from the quiet comet 15P/Finlay

Czech Academy of Sciences Publication Activity Database

Ye, Q.Z.; Brown, P. G.; Bell, Ch.; Gao, X.; Mašek, Martin; Hui, M.T.

2015-01-01

Roč. 814, č. 1 (2015), s. 1-10, č. článku 79. ISSN 0004-637X R&D Projects: GA MŠk(CZ) LG13007 EU Projects: European Commission(XE) 283783 - GLORIA Institutional support: RVO:68378271 Keywords : comet s * 15P/Finlay * meteorites * meteors * meteoroids Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics OBOR OECD: Astronomy (including astrophysics,space science) Impact factor: 5.909, year: 2015

DYNAMICS OF DUST PARTICLES RELEASED FROM OORT CLOUD COMETS AND THEIR CONTRIBUTION TO RADAR METEORS

International Nuclear Information System (INIS)

Nesvorný, David; Vokrouhlický, David; Pokorný, Petr; Janches, Diego

2011-01-01

The Oort Cloud Comets (OCCs), exemplified by the Great Comet of 1997 (Hale-Bopp), are occasional visitors from the heatless periphery of the solar system. Previous works hypothesized that a great majority of OCCs must physically disrupt after one or two passages through the inner solar system, where strong thermal gradients can cause phase transitions or volatile pressure buildup. Here we study the fate of small debris particles produced by OCC disruptions to determine whether the imprints of a hypothetical population of OCC meteoroids can be found in the existing meteor radar data. We find that OCC particles with diameters D ∼ 1 mm have a very low Earth-impact probability. The intermediate particle sizes, D ∼ 100 μm, represent a sweet spot. About 1% of these particles orbitally evolve by Poynting-Robertson drag to reach orbits with semimajor axis a ∼ 1 AU. They are expected to produce meteors with radiants near the apex of Earth's orbital motion. We find that the model distributions of their impact speeds and orbits provide a good match to radar observations of apex meteors, except for the eccentricity distribution, which is more skewed toward e ∼ 1 in our model. Finally, we propose an explanation for the long-standing problem in meteor science related to the relative strength of apex and helion/antihelion sources. As we show in detail, the observed trend, with the apex meteors being more prominent in observations of highly sensitive radars, can be related to orbital dynamics of particles released on the long-period orbits.

Meteors, comets, and millennialism.

Science.gov (United States)

McBeath, A.

1999-12-01

An overview of meteoric and cometary activity between circa 250 BC and circa 1600 AD is discussed with especial regard to the inclusion of meteoric imagery in Christian religious texts. Evidence is presented to suggest meteorite images played a leading role in the creation of millennial fears among adherents of the early medieval Church in Europe, which fears still persist into modern times, but which may have their origins in Mesopotamia circa 2200 BC. An extended discussion of meteoric imagery in Christian writings is also presented.

Optical observations of the Phoenicid meteor shower in 2014 and activity of comet 289P/Blanpain in the early 20th century

Science.gov (United States)

Fujiwara, Yasunori; Nakamura, Takuji; Uehara, Satoshi; Sagayama, Toru; Toda, Hiroyuki

2017-08-01

Optical observations of the Phoenicid meteor shower were made in North Carolina, USA, with seven video cameras and two digital cameras over a period of about 5 hr between 22:30 UT on 2014 December 1 and 04:00 UT on December 2. Activity of the Phoenicids was confirmed during this period, including the predicted maximum around 00 h UT on December 2. The activity level was not high, considering that 29 Phoenicid meteors and 109 non-Phoenicid meteors were detected. A gentle peak in the activity was recognized between 01:00 UT and 03:00 UT on December 2. The compact radiant of the Phoenicids agreed well with what was predicted. A comparison of the observed and predicted peak times, radiant position, bright meteors' dominance, and radiants' spread revealed that the observed meteors originated from the dust trails formed by comet 289P/Blanpain at the perihelion passage in the early 20th century. This indicates that the parent body of the Phoenicids, comet 289P/Blanpain, was still active as a comet in the early 20th century and provided meteoroids, although its activity level was significantly weaker than that at the beginning of the 19th century.

Constraints on Comet 332P/Ikeya-Murakami

Science.gov (United States)

Hui, Man-To; Ye, Quan-Zhi; Wiegert, Paul

2017-01-01

Encke-type comet 332P/Ikeya-Murakami is experiencing cascading fragmentation events during its 2016 apparition. It is likely the first splitting Encke-type comet ever observed. A nongravitational solution to the astrometry reveals a statistical detection of the radial and transverse nongravitational parameters, {A}1=(1.54+/- 0.39)× {10}-8 au day‑2 and {A}2=(7.19+/- 1.92)× {10}-9 au day‑2, respectively, which implies a nucleus erosion rate of (9.1+/- 1.7)‰ per orbital revolution. The mass-loss rate likely has to be supported by a much larger fraction of an active surface area than known cases of short-period comets; it may be relevant to the ongoing fragmentation. We failed to detect any serendipitous pre-discovery observations of the comet in archival data from major sky surveys, whereby we infer that 332P used to be largely inactive, and is perhaps among the few short-period comets that have been reactivated from weakly active or dormant states. We therefore constrain an upper limit to the nucleus size as 2.0 ± 0.2 km in radius. A search for small bodies in similar orbits to that of 332P reveals comet P/2010 B2 (WISE) to be the best candidate. From an empirical generalized Jupiter-family (Encke-type included) comet population model, we estimate the likelihood of a chance alignment of the 332P–P/2010 B2 pair to be 1 in 33, a small number indicative of a genetic linkage between the two comets on a statistical basis. The pair possibly originated from a common progenitor, which underwent a disintegration event well before the twentieth century.

Meteor Beliefs Project: Meteors in the Maori astronomical traditions of New Zealand

Science.gov (United States)

Britton, Tui R.; Hamacher, Duane W.

2014-02-01

We review the literature for perceptions of meteors in the Maori culture of Aotearoa or New Zealand. We examine representations of meteors in religion, story, and ceremony. We find that meteors are sometimes personified as gods or children, or are seen as omens of death and destruction. The stories we found highlight the broad perception of meteors found throughout the Maori culture, and note that some early scholars conflated the terms comet and meteor.

Observations of faint comets at McDonald Observatory: 1978-1980

Science.gov (United States)

Barker, E. S.; Cochran, A. L.; Rybski, P. M.

1981-01-01

Modern observational techniques, developed for spectroscopy and photometry of faint galaxies and quasars, successfully applied to faint comets on the 2.7 m telescope. The periodic comets Van Biesbrock, Ashbrook-Jackson, Schwassmann-Wachmann 1, Tempel 2, Encke, Forbes, Brooks 2, Stephan-Oterma and the new comets Bradfield (19791), Bowell (1980b), Chernis-Petrauskas (1980k) were observed. The comets ranged in magnitude from 10th to 20th magnitude. For comets fainter than 19th magnitude, reflectance spectra at 100A resolution and area photometry were obtained. On comets of 17th or 18th magnitude, spectrometric scans (6A resolution) of the nucleus or inner coma region. On those comets which are brighter than 16th magnitude spatial spectrophotometric (6A resolution) studies of the inner and extended comae were done. An extensive spatial study of the comae of P/Encke and P/Stephen-Oterma, correlated with heliocentric distance is taking place. The observing process used is described and examples of the results obtained to date are discussed.

Water production rates of recent comets (2016-2017) by SOHO/SWAN: 2P/Encke, 41P/Tuttle-Giacobini-Kresak, 45P/ Honda-Mrkos-Pajdusakova, and C/2015 ER61 (PanSTARRS)

Science.gov (United States)

Combi, Michael R.; Mäkinen, Terhi; Bertaux, Jean-Loup; Quémerais, Eric; Ferron, Stephane

2017-10-01

The all-sky hydrogen Lyman-alpha camera, SWAN (Solar Wind Anisotropies), on the SOlar and Heliospheric Observatory (SOHO) satellite makes observations of the hydrogen coma of comets. Most water molecules produced by comets are ultimately photodissociated into two H atoms and one O atom producing a huge atomic hydrogen coma that is routinely observed in the daily full-sky SWAN images in comets of sufficient brightness. Water production rates are calculated using our time-resolved model (Mäkinen & Combi, 2005, Icarus 177, 217), typically yielding about 1 observation every 2 days on the average for each comet over the brightest part of its apparition. Here we describe the progress in analysis of observations of comets observed in 2016 and 2017. These include comets 2P/Encke, 41P/Tuttle-Giacobini-Sresak, 45P/ Honda-Mrkos-Pajdusakova, and C/2015 ER61 (PanSTARRS). A status update on the entire SOHO/SWAN archive of water production rates in comets will also be given.SOHO is an international cooperative mission between ESA and NASA. Support from grants NNX15AJ81G from the NASA Solar System Observations Planetary Astronomy Program and a previous grant NNX13AQ66G from the NASA Planetary Mission Data Analysis Program are gratefully acknowledged, as is support from CNRS, CNES, and the Finnish Meteorological Institute (FMI).

DUST FROM COMET 209P/LINEAR DURING ITS 2014 RETURN: PARENT BODY OF A NEW METEOR SHOWER, THE MAY CAMELOPARDALIDS

Energy Technology Data Exchange (ETDEWEB)

Ishiguro, Masateru [Department of Physics and Astronomy, Seoul National University, Gwanak, Seoul 151-742 (Korea, Republic of); Kuroda, Daisuke [Okayama Astrophysical Observatory, National Astronomical Observatory of Japan, Asakuchi, Okayama 719-0232 (Japan); Hanayama, Hidekazu [Ishigakijima Astronomical Observatory, National Astronomical Observatory of Japan, Ishigaki, Okinawa 907-0024 (Japan); Takahashi, Jun; Takagi, Yuhei; Morihana, Kumiko; Honda, Satoshi; Arai, Akira [Nishi-Harima Astronomical Observatory, Center for Astronomy, University of Hyogo, Sayo, Hyogo 679-5313 (Japan); Hasegawa, Sunao; Sarugaku, Yuki [Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA), Sagamihara, Kanagawa 252-5210 (Japan); Watanabe, Makoto; Imai, Masataka; Goda, Shuhei [Department of Cosmosciences, Graduate School of Science, Hokkaido University, Sapporo 060-0810 (Japan); Akitaya, Hiroshi [Hiroshima Astrophysical Science Center, Hiroshima University, Higashihiroshima, Hiroshima 739-8526 (Japan); Sekiguchi, Kazuhiro [National Astronomical Observatory of Japan, National Institute of Natural Sciences, Mitaka, Tokyo 181-8588 (Japan); Oasa, Yumiko [Faculty of Education, Saitama University, Sakura, Saitama 338-8570 (Japan); Saito, Yoshihiko [Department of Physics, Tokyo Institute of Technology, Meguro-ku, Tokyo 152-8551 (Japan); Morokuma, Tomoki [Institute of Astronomy, Graduate School of Science, The University of Tokyo, Mitaka, Tokyo 181-0015 (Japan); Murata, Katsuhiro [Department of Astrophysics, Nagoya University, Chikusa-ku, Nagoya 464-8602 (Japan); Nogami, Daisaku [Department of Astronomy, Graduate School of Science, Kyoto University, Kyoto 606-8502 (Japan); and others

2015-01-10

We report a new observation of the Jupiter family comet 209P/LINEAR during its 2014 return. The comet is recognized as a dust source of a new meteor shower, the May Camelopardalids. 209P/LINEAR was apparently inactive at a heliocentric distance r{sub h} = 1.6 AU and showed weak activity at r{sub h} ≤ 1.4 AU. We found an active region of <0.001% of the entire nuclear surface during the comet's dormant phase. An edge-on image suggests that particles up to 1 cm in size (with an uncertainty of factor 3-5) were ejected following a differential power-law size distribution with index q = –3.25 ± 0.10. We derived a mass-loss rate of 2-10 kg s{sup –1} during the active phase and a total mass of ≈5 × 10{sup 7} kg during the 2014 return. The ejection terminal velocity of millimeter- to centimeter-sized particles was 1-4 m s{sup –1}, which is comparable to the escape velocity from the nucleus (1.4 m s{sup –1}). These results imply that such large meteoric particles marginally escaped from the highly dormant comet nucleus via the gas drag force only within a few months of the perihelion passage.

Meteor activity from 2001XQ on 2-3 December 2016?

Science.gov (United States)

Roggemans, Paul

2016-04-01

The minor shower 66 Draconid (541 SDD) which was discovered by the Croatian Meteor Network has a mean orbit based on 43 meteors, similar to the orbit of 2001 XD. The asteroid 2001 XD has an orbit typical for Jupiter family comets and therefore may be a dormant comet. The shower activity ranges from November 23 until December 21. All meteor observers are encouraged to pay attention to any possible meteors from this source, although no outburst or any anything spectacular has to be expected.

The "silent world" of Comet 15P/Finlay

CERN Document Server

Beech, M; Jones, J

1999-01-01

Comet 15P/Finlay is unusual in that, contrary to ab initio expectations, it demonstrates no apparent linkage to any known meteor shower. Using data contained within the Electronic Atlas of Dynamical Evolutions of Short-Period Comets, the authors evaluate theoretical shower radiants for Comet 15P/Finlay, but find no evidence to link it to any meteoric anomalies in recorded antiquity. This result, however, must be tempered by the fact that any Comet 15P/Finlay- derived meteoroids will have a low, 16 km s/sup -1/, encounter velocity with Earth's atmosphere. Typically, therefore, one would expect mostly faint meteors to be produced during an encounter with a Comet 15P/Finlay-derived meteoroid stream. they have conducted a D- criterion survey of meteoroid orbits derived from three southern hemisphere meteor radar surveys conducted during the 1960s, and again they find no evidence for any Comet 15P/Finlay-related activity. Numerical calculations following the orbital evolution of hypothetical meteoroids ejected fro...

The Composition of the Y2K Meteor

Science.gov (United States)

Coulson, S. G.

During the Leonid meteor shower of November 1999 a very bright meteor train, subsequently called the Y2K meteor, was observed. Analysis of the trajectory of the meteor suggests that it was composed of two distinct materials. The bulk of the meteor was composed of a comet-like material, while a much smaller fraction was of a denser carbonaceous material. A simple model is used to analytically determine the mass of the meteor fragments.

The Inner Coma Physical Environments of Ecliptic Comets 45P/Honda-Mrkos-Pajdusakova, 2P/Encke, and 41P/Tuttle-Giacobini-Kresak Revealed Through Long-Slit Spectroscopy at NASA IRTF

Science.gov (United States)

Bonev, Boncho P.; DiSanti, Michael A.; Roth, Nathan; Dello Russo, Neil; Vervack, Ronald J.; Gibb, Erika L.; Villanueva, Geronimo Luis; Combi, Michael R.; Fougere, Nicolas; Kawakita, Hideyo; McKay, Adam J.; Saki, Mohammad; Cordiner, Martin; Protopapa, Silvia; de Val-Borro, Miguel

2017-10-01

Understanding the physical processes in the inner regions of cometary atmospheres is vital for interpretation of molecular cometary emission at all wavelengths. Furthermore, because ecliptic comets are continuously evaluated as space mission targets, understanding their coma environments is a central theme in both enhancing the science return of past missions (EPOXI, Rosetta) and in selecting future mission targets. With this motivation, we report long-slit high-resolution observations of H2O emission in the comae of three ecliptic comets observed in early 2017: 45P/Honda-Mrkos-Pajdusakova, 2P/Encke, and 41P/Tuttle-Giacobini-Kresak. Using the new crossed-dispersed spectrograph iSHELL at NASA IRTF, we detected a suite of water rovibrational emission lines from these comets and measured the spatial distributions of H2O rotational temperatures and molecular column densities. Both parameters are highly diagnostic of the physical environment in cometary comae, the competition between cooling and heating processes in these environments, and the presence (or lack thereof) of extended coma sources of gas-phase H2O. Comets 2P and 45P allowed a rare glimpse into coma physics at small (staff for their help with these challenging observations, most of which were done during daytime.

Meteors, meteorites and cosmic dust

International Nuclear Information System (INIS)

Lebedinets, V.N.

1987-01-01

The problem of meteorite origin and meteorite composition is discussed. Nowadays, most scientists suppose that the giant Oort cloud consisting of ice comet nuclei is the sourse of the meteor matter. A principle unity of the matter of meteorites falling to the Earth and cosmic dust is noted as well as that of meteorite bodies evaporating in the atmosphere and bearing meteors and bodies

Spectrophotometry of seventeen comets. II - The continuum

Science.gov (United States)

Newburn, R. L., Jr.; Spinrad, H.

1985-01-01

One-hundred-twenty IDS scans of the continua in 17 comets are analyzed to determine dust production rates and color as a function of heliocentric distance. Improved theory indicates that the dust loading of gas typically varies between 0.05 and 0.3 by mass (assuming a geometric albedo of 0.05 and oxygen expansion at 1 km/s) except during outbursts, when it rises much higher. P/Encke near perihelion falls much lower yet, to 0.004 or less. Dust loading is not always constant as a function of time in a given comet. Dust color is typically reddish, as has often been noted before.

Meteoroid Streams from Sunskirter Comet Breakup

Science.gov (United States)

Jenniskens, P. M.

2012-12-01

In its first year of operations, the CAMS project (Cameras for Allsky Meteor Surveillance) has measured 47,000 meteoroid orbits at Earth, including some that pass the Sun as close as 0.008 AU. The population density increases significantly above perihelion distance q = 0.037 AU. Meteoroid streams are known with q about 0.1 AU. The Sun has a profound effect on comets that pass at 0.04-0.16 AU distance, called the sunskirter comets. SOHO and STEREO see families of small comets called the Marsden and Kracht groups. Sunlight is efficiently scattered by small 10-m sized fragments, making those fragments visible even when far from Earth. These comet groups are associated with meteor showers on Earth, in particular the Daytime Arietids and Delta Aquariids. All are related to 96P/Machholz, a highly inclined short-period (5.2 year) Jupiter family comet that comes to within 0.12 AU from the Sun, the smallest perihelion distance known among numbered comets. The proximity of the Sun speeds up the disintegration process, providing us a unique window on this important decay mechanism of Jupiter family comets and creating meteoroid streams. These are not the only sunskirting comets, however. In this presentation, we will present CAMS observations of the complete low-q meteoroid population at Earth and review their association with known parent bodies.

Periodic Comet Machholz and its idiosyncrasies

International Nuclear Information System (INIS)

Sekanina, Z.

1990-01-01

The dynamics and physical characteristics of Comet P/Machholz are analyzed. The discovery of the comet (Machholz, 1986) is discussed, including the observational conditions and the theory that the comet is inactive over extensive periods of time. Consideration is given to observations of the two tails of Comet P/Machholz (Emerson, 1986), the brightness variations and light curve of the comet, and nuclear photometry of the comet (Green, 1987). It is suggested that the increase in activity beginning one day after perihelion was triggered by a discrete source within 15 deg of the rotation pole that became sunlit after perihelion. Also, the possibility that Comet P/Machholz is associated with a meteor stream is examined. 45 refs

Dynamical Model for the Zodiacal Cloud and Sporadic Meteors

Science.gov (United States)

Nesvorný, David; Janches, Diego; Vokrouhlický, David; Pokorný, Petr; Bottke, William F.; Jenniskens, Peter

2011-12-01

The solar system is dusty, and would become dustier over time as asteroids collide and comets disintegrate, except that small debris particles in interplanetary space do not last long. They can be ejected from the solar system by Jupiter, thermally destroyed near the Sun, or physically disrupted by collisions. Also, some are swept by the Earth (and other planets), producing meteors. Here we develop a dynamical model for the solar system meteoroids and use it to explain meteor radar observations. We find that the Jupiter Family Comets (JFCs) are the main source of the prominent concentrations of meteors arriving at the Earth from the helion and antihelion directions. To match the radiant and orbit distributions, as measured by the Canadian Meteor Orbit Radar (CMOR) and Advanced Meteor Orbit Radar (AMOR), our model implies that comets, and JFCs in particular, must frequently disintegrate when reaching orbits with low perihelion distance. Also, the collisional lifetimes of millimeter particles may be longer (gsim 105 yr at 1 AU) than postulated in the standard collisional models (~104 yr at 1 AU), perhaps because these chondrule-sized meteoroids are stronger than thought before. Using observations of the Infrared Astronomical Satellite to calibrate the model, we find that the total cross section and mass of small meteoroids in the inner solar system are (1.7-3.5) × 1011 km2 and ~4 × 1019 g, respectively, in a good agreement with previous studies. The mass input required to keep the zodiacal cloud in a steady state is estimated to be ~104-105 kg s-1. The input is up to ~10 times larger than found previously, mainly because particles released closer to the Sun have shorter collisional lifetimes and need to be supplied at a faster rate. The total mass accreted by the Earth in particles between diameters D = 5 μm and 1 cm is found to be ~15,000 tons yr-1 (factor of two uncertainty), which is a large share of the accretion flux measured by the Long Term Duration

Encke-Beta Predictor for Orion Burn Targeting and Guidance

Science.gov (United States)

Robinson, Shane; Scarritt, Sara; Goodman, John L.

2016-01-01

The state vector prediction algorithm selected for Orion on-board targeting and guidance is known as the Encke-Beta method. Encke-Beta uses a universal anomaly (beta) as the independent variable, valid for circular, elliptical, parabolic, and hyperbolic orbits. The variable, related to the change in eccentric anomaly, results in integration steps that cover smaller arcs of the trajectory at or near perigee, when velocity is higher. Some burns in the EM-1 and EM-2 mission plans are much longer than burns executed with the Apollo and Space Shuttle vehicles. Burn length, as well as hyperbolic trajectories, has driven the use of the Encke-Beta numerical predictor by the predictor/corrector guidance algorithm in place of legacy analytic thrust and gravity integrals.

Reconstructing the orbit of the Chelyabinsk meteor using satellite observations

DEFF Research Database (Denmark)

Proud, Simon Richard

2013-01-01

The large number of objects in a range of orbits around the Sun means that some will inevitably intersect the Earth, becoming a meteor. These objects are commonly comet fragments or asteroids. To determine the type of a particular meteor requires knowledge of its trajectory and orbital path...... that is typically estimated by using ground-based observations such as images or radar measurements. A lack of data can, however, make this difficult and create large uncertainties in the reconstructed orbit. Here I show a new method for estimating a meteor's trajectory, and hence allowing computation of the orbit...

Expected Increase of Activity of Eta Aquariids Meteor Shower

Science.gov (United States)

Kulikova, N. V.; Chepurova, V. M.

2018-04-01

Analysis of the results of modeling disintegration of Comet 1P/Halley after its flare in 1991 has allowed us to predict an increase of the activity of the associated Eta Aquariids meteor shower in April-May 2018.

Origin of meteor swarms of the Arietid and Geminid types

International Nuclear Information System (INIS)

Lebedinets, V.N.

1985-01-01

The author proposes a physical mechanism for the formation of meteor swarms on orbits of small size and very small perihelion distance, similar to the orbits of Arietid and Geminid meteor swarms, which are rarely encountered among the larger bodies of the solar system, and he justifies the mechanism mathematically. He shows that comets can transfer to such orbits from orbits of large size during evaporation of their ice nuclei under the action of reactive drag

DYNAMICAL MODEL FOR THE ZODIACAL CLOUD AND SPORADIC METEORS

Energy Technology Data Exchange (ETDEWEB)

Nesvorny, David; Vokrouhlicky, David; Pokorny, Petr; Bottke, William F. [Department of Space Studies, Southwest Research Institute, 1050 Walnut St., Suite 300, Boulder, CO 80302 (United States); Janches, Diego [Space Weather Laboratory, Code 674, GSFC/NASA, Greenbelt, MD 20771 (United States); Jenniskens, Peter [Carl Sagan Center, SETI Institute, 515 N. Whisman Road, Mountain View, CA 94043 (United States)

2011-12-20

The solar system is dusty, and would become dustier over time as asteroids collide and comets disintegrate, except that small debris particles in interplanetary space do not last long. They can be ejected from the solar system by Jupiter, thermally destroyed near the Sun, or physically disrupted by collisions. Also, some are swept by the Earth (and other planets), producing meteors. Here we develop a dynamical model for the solar system meteoroids and use it to explain meteor radar observations. We find that the Jupiter Family Comets (JFCs) are the main source of the prominent concentrations of meteors arriving at the Earth from the helion and antihelion directions. To match the radiant and orbit distributions, as measured by the Canadian Meteor Orbit Radar (CMOR) and Advanced Meteor Orbit Radar (AMOR), our model implies that comets, and JFCs in particular, must frequently disintegrate when reaching orbits with low perihelion distance. Also, the collisional lifetimes of millimeter particles may be longer ({approx}> 10{sup 5} yr at 1 AU) than postulated in the standard collisional models ({approx}10{sup 4} yr at 1 AU), perhaps because these chondrule-sized meteoroids are stronger than thought before. Using observations of the Infrared Astronomical Satellite to calibrate the model, we find that the total cross section and mass of small meteoroids in the inner solar system are (1.7-3.5) Multiplication-Sign 10{sup 11} km{sup 2} and {approx}4 Multiplication-Sign 10{sup 19} g, respectively, in a good agreement with previous studies. The mass input required to keep the zodiacal cloud in a steady state is estimated to be {approx}10{sup 4}-10{sup 5} kg s{sup -1}. The input is up to {approx}10 times larger than found previously, mainly because particles released closer to the Sun have shorter collisional lifetimes and need to be supplied at a faster rate. The total mass accreted by the Earth in particles between diameters D = 5 {mu}m and 1 cm is found to be {approx}15

DYNAMICAL MODEL FOR THE ZODIACAL CLOUD AND SPORADIC METEORS

International Nuclear Information System (INIS)

Nesvorný, David; Vokrouhlický, David; Pokorný, Petr; Bottke, William F.; Janches, Diego; Jenniskens, Peter

2011-01-01

The solar system is dusty, and would become dustier over time as asteroids collide and comets disintegrate, except that small debris particles in interplanetary space do not last long. They can be ejected from the solar system by Jupiter, thermally destroyed near the Sun, or physically disrupted by collisions. Also, some are swept by the Earth (and other planets), producing meteors. Here we develop a dynamical model for the solar system meteoroids and use it to explain meteor radar observations. We find that the Jupiter Family Comets (JFCs) are the main source of the prominent concentrations of meteors arriving at the Earth from the helion and antihelion directions. To match the radiant and orbit distributions, as measured by the Canadian Meteor Orbit Radar (CMOR) and Advanced Meteor Orbit Radar (AMOR), our model implies that comets, and JFCs in particular, must frequently disintegrate when reaching orbits with low perihelion distance. Also, the collisional lifetimes of millimeter particles may be longer (∼> 10 5 yr at 1 AU) than postulated in the standard collisional models (∼10 4 yr at 1 AU), perhaps because these chondrule-sized meteoroids are stronger than thought before. Using observations of the Infrared Astronomical Satellite to calibrate the model, we find that the total cross section and mass of small meteoroids in the inner solar system are (1.7-3.5) × 10 11 km 2 and ∼4 × 10 19 g, respectively, in a good agreement with previous studies. The mass input required to keep the zodiacal cloud in a steady state is estimated to be ∼10 4 -10 5 kg s –1 . The input is up to ∼10 times larger than found previously, mainly because particles released closer to the Sun have shorter collisional lifetimes and need to be supplied at a faster rate. The total mass accreted by the Earth in particles between diameters D = 5 μm and 1 cm is found to be ∼15,000 tons yr –1 (factor of two uncertainty), which is a large share of the accretion flux measured by the

Impact Vaporization as a Possible Source of Mercury's Calcium Exosphere

Science.gov (United States)

Killen, Rosemary M.; Hahn, Joseph M.

2015-01-01

Mercury's calcium exosphere varies in a periodic way with that planet's true anomaly. We show that this pattern can be explained by impact vaporization from interplanetary dust with variations being due to Mercury's radial and vertical excursions through an interplanetary dust disk having an inclination within 5 degrees of the plane of Mercury's orbit. Both a highly inclined dust disk and a two-disk model (where the two disks have a mutual inclination) fail to reproduce the observed variation in calcium exospheric abundance with Mercury true anomaly angle. However, an additional source of impacting dust beyond the nominal dust disk is required near Mercury's true anomaly (?) 25deg +/-5deg. This is close to but not coincident with Mercury's true anomaly (?=45deg) when it crosses comet 2P/Encke's present day orbital plane. Interestingly, the Taurid meteor storms at Earth, which are also due to Comet Encke, are observed to occur when Earth's true anomaly is +/-20 or so degrees before and after the position where Earth and Encke orbital planes cross. The lack of exact correspondence with the present day orbit of Encke may indicate the width of the potential stream along Mercury's orbit or a previous cometary orbit. The extreme energy of the escaping calcium, estimated to have a temperature greater than 50000 K if the source is thermal, cannot be due to the impact process itself but must be imparted by an additional mechanism such as dissociation of a calcium-bearing molecule or ionization followed by recombination.

Origin of Short-Perihelion Comets

Science.gov (United States)

Guliyev, A. S.

2011-01-01

New regularities for short-perihelion comets are found. Distant nodes of cometary orbits of Kreutz family are concentrated in a plane with ascending node 76 and inclination 267 at the distance from 2 up to 3 a.u. and in a very narrow interval of longitudes. There is a correlation dependence between q and cos I concerning the found plane (coefficient of correlation 0.41). Similar results are received regarding to cometary families of Meyer, Kracht and Marsden. Distant nodes of these comets are concentrated close three planes (their parameters are discussed in the article) and at distances 1.4; 0.5; 6 a.u. accordingly. It is concluded that these comet groups were formed as a result of collision of parent bodies with meteoric streams. One more group, consisting of 7 comets is identified. 5 comet pairs are selected among sungrazers.

Halley's Comet: A Bibliography.

Science.gov (United States)

Freitag, Ruth S., Comp.

Included in this bibliography are over 3,200 references to publications on Halley's Comet, its history, orbital motion, and physical characteristics, meteor streams associated with it, preparations for space missions to study it in 1986, and popular reaction to its appearances. Also cited are a few papers that, although they devote little…

Detection of the Phoenicids meteor shower in 2014

Science.gov (United States)

Sato, Mikiya; Watanabe, Jun-ichi; Tsuchiya, Chie; Moorhead, Althea V.; Moser, Danielle E.; Brown, Peter G.; Cooke, William J.

2017-09-01

An appearance of the Phoenicids meteor shower was predicted in 2014 by using a dust trail simulation of an outburst of 1956. We detected Phoenicids meteors on December 2 through multiple observation methods. The NASA All Sky Fireball Network and the Southern Ontario Meteor Network detected five meteors of Phoenicids via video observation. The Canadian Meteor Orbit Radar (CMOR) found fourteen candidate meteors, eight of which were confirmed as Phoenicids. The observed radiant point is consistent with that of our model predictions. In addition to the above observations, a visual observation was carried out by the Japanese team near the Observatorio del Roque de los Muchachos (ORM) of Instituto de Astrofisica de Canarias (IAC) in La Palma Island. The obtained zenithal hourly rate (ZHR) was 16.4±4.9. The maximum ZHR was roughly estimated to be between 20 and 30, which indicates that the cometary activity of parent object 289P/Blanpain in the early 20th century was only about one fifth or one eighth as high as its activity in the late 18th and early 19th century. Accordingly, it seems to be the case that 289P/Blanpain is gradually transforming from a comet to a dormant object.

Meteor Beliefs Project: Shakespeare revisited and the Elizabethan stage's `blazing star'

Science.gov (United States)

Gheorghe, Andrei Dorian; McBeath, Alastair

2007-06-01

Some fresh Shakespearean citations of meteors, further to those given previously in the Project, are presented, along with a discussion of the Elizabethan stage's use of the `blazing star', with especial reference to the great comet of 1577.

Atmospheric trajectories and light curves of shower meteors

Czech Academy of Sciences Publication Activity Database

Koten, Pavel; Borovička, Jiří; Spurný, Pavel; Betlem, H.; Evans, S.

2004-01-01

Roč. 428, č. 2 (2004), s. 683-690 ISSN 0004-6361 R&D Projects: GA ČR GP205/02/P038; GA ČR GA205/02/0982; GA ČR GA205/03/1404 Institutional research plan: CEZ:AV0Z1003909 Keywords : meteors * meteoroids * general-comets Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 3.694, year: 2004

Direct Characterization of Comets and Asteroids via Cosmic Dust Analysis from the Deep Space Gateway

Science.gov (United States)

Fries, M.; Fisher, K.

2018-01-01

The Deep Space Gateway (DSG) may provide a platform for direct sampling of a large number of comets and asteroids, through employment of an instrument for characterizing dust from these bodies. Every year, the Earth traverses through debris streams of dust and small particles from comets and asteroids in Earth-crossing orbits, generating short-lived outbursts of meteor activity commonly known as "meteor showers" (Figure 1). The material in each debris stream originates from a distinct parent body, many of which have been identified. By sampling this material, it is possible to quantitatively analyze the composition of a dozen or more comets and asteroids (See Figure 2, following page) without leaving cislunar space.

Spectra and physical properties of Taurid meteoroids

Science.gov (United States)

Matlovič, Pavol; Tóth, Juraj; Rudawska, Regina; Kornoš, Leonard

2017-09-01

Taurids are an extensive stream of particles produced by comet 2P/Encke, which can be observed mainly in October and November as a series of meteor showers rich in bright fireballs. Several near-Earth asteroids have also been linked with the meteoroid complex, and recently the orbits of two carbonaceous meteorites were proposed to be related to the stream, raising interesting questions about the origin of the complex and the composition of 2P/Encke. Our aim is to investigate the nature and diversity of Taurid meteoroids by studying their spectral, orbital, and physical properties determined from video meteor observations. Here we analyze 33 Taurid meteor spectra captured during the predicted outburst in November 2015 by stations in Slovakia and Chile, including 14 multi-station observations for which the orbital elements, material strength parameters, dynamic pressures, and mineralogical densities were determined. It was found that while orbits of the 2015 Taurids show similarities with several associated asteroids, the obtained spectral and physical characteristics point towards cometary origin with highly heterogeneous content. Observed spectra exhibited large dispersion of iron content and significant Na intensity in all cases. The determined material strengths are typically cometary in the KB classification, while PE criterion is on average close to values characteristic for carbonaceous bodies. The studied meteoroids were found to break up under low dynamic pressures of 0.02-0.10 MPa, and were characterized by low mineralogical densities of 1.3-2.5 g cm-3. The widest spectral classification of Taurid meteors to date is presented.

Association between meteor showers and asteroids using multivariate criteria

Science.gov (United States)

Dumitru, B. A.; Birlan, M.; Popescu, M.; Nedelcu, D. A.

2017-10-01

Context. Meteoroid streams are fragments of matter produced by comets or asteroids which intersects the orbit of Earth. Meteor showers are produced when Earth intersects these streams of matter. The discoveries of active asteroids and extinct comets open a new view of the relation between these objects as possible parent bodies at the origin of meteor showers. Aims: The aim of this work is to identify the asteroids that can produce or re-populate meteoroid streams by determining the similarity of their orbits and orbital evolution over 10 000 yr. Methods: The identification was carried out by evaluating several well known D-criteria metrics, the orbits being taken from the IAU Meteor Data Center database and from IAU Minor Planet Center. Finally, we analyzed the physical properties and the orbital stability (in the Lyapunov time sense) of the candidates as well as their possible relationship with meteorites. Results: 206 near-Earth asteroids (NEAs) were associated as possible parent bodies with 28 meteor showers, according to at least two of the criterion used. 50 of them satisfied all the criteria. Notable finds are: binary asteroid 2000UG11 associated with Andromedids (AND), while the tumbling asteroid (4179)Toutatis could be associated with October Capricornids (OCC). Other possible good candidates are 2004TG10, 2008EY5, 2010CF55, 2010TU149 and 2014OY1. These objects have low albedo, therefore can be primitive objects. Asteroid 2007LW19 which is a fast rotator and most probably has monolithic structure and so its physical characteristic does not support the association found based on the dynamical criteria.

The Implications of the Excited Rotation of Comet 252P/2000 G1 (LINEAR)

Science.gov (United States)

Li, Jian-Yang; Samarasinha, Nalin H.; Kelley, Michael S. P.; Farnocchia, Davide; Mutchler, Max J.; Ren, Yanqiong; Lu, Xiaoping; Tholen, David J.; Lister, Tim; Micheli, Marco

2018-01-01

Jupiter Family comet (JFC) 252P/LINEAR had a close encounter to Earth on 2016 March 21. We imaged the comet with the Hubble Space Telescope Wide Field Camera 3 UVIS channel through the V- and r’-band filters spanning ~8 hours on 2016 April 4. The pixel scale of 2.7 km/pixel allowed us to study the structure of the cometary coma at scales of a few kilometers to a few hundred kilometers from the nucleus, a characteristic that is unique to our data. The dust coma of 252P showed a strong, well defined, narrow and nearly linear feature in the sunward direction, and its projected position angle moved about the nucleus for ~60 deg in 8 hours, consistent with an apparent periodicity of ~7.24 hours. On the other hand, the lightcurve measured in both V- and r’-band images from a 13 km radius aperture, after corrected for color term, showed a variability of >0.14 mag that is consistent with an apparent periodicity of ~5.4 hours or its multiples. We suggest that the two different periodicities derived from coma morphology and the lightcurve is a strong indication that the nucleus of 252P is in a non-principal axis (NPA) rotation, joining two other confirmed NPA rotators (1P/Halley and 103P/Hartley 2) and comets that are potentially in NPA rotational states (e.g., 2P/Encke). However, this apparition has been unusual for 252P. In the past three perihelion passages since discovery, the comet was very weakly active compared to other JFCs. Meteor evidence also exists that it probably has been very weakly active for a few hundred years. But in our data, we saw a very active comet in this 2016 apparition with an active fraction of 40% to >100%, representing an increase of 100x with respect to its recent past. Based on our observations, 252P has a small nucleus with a radius of ~0.3 km, which suggests that its rotational state could be relatively easily changed by torques caused by outgassing. Since the very weak outgassing in the past is not likely to change the rotational state

Finding Long Lost Lexell's Comet: The Fate of the First Discovered Near-Earth Object

Science.gov (United States)

Ye, Quan-Zhi; Wiegert, Paul A.; Hui, Man-To

2018-04-01

Jupiter-family Comet D/1770 L1 (Lexell) was the first discovered Near-Earth Object (NEO) and passed the Earth on 1770 July 1 at a recorded distance of 0.015 au. The comet was subsequently lost due to unfavorable observing circumstances during its next apparition followed by a close encounter with Jupiter in 1779. Since then, the fate of D/Lexell has attracted interest from the scientific community, and now we revisit this long-standing question. We investigate the dynamical evolution of D/Lexell based on a set of orbits recalculated using the observations made by Charles Messier, the comet’s discoverer, and find that there is a 98% chance that D/Lexell remains in the solar system by the year of 2000. This finding remains valid even if a moderate non-gravitational effect is imposed. Messier’s observations also suggest that the comet is one of the largest known near-Earth comets, with a nucleus of ≳10 km in diameter. This implies that the comet should have been detected by contemporary NEO surveys regardless of its activity level if it has remained in the inner solar system. We identify asteroid 2010 JL33 as a possible descendant of D/Lexell, with a 0.8% probability of chance alignment, but a direct orbital linkage of the two bodies has not been successfully accomplished. We also use the recalculated orbit to investigate the meteors potentially originating from D/Lexell. While no associated meteors have been unambiguously detected, we show that meteor observations can be used to better constrain the orbit of D/Lexell despite the comet being long lost.

Evolution of comets into asteroids

International Nuclear Information System (INIS)

Weissman, P.R.; A'hearn, M.F.; Rickman, H.; Mcfadden, L.A.

1989-01-01

This paper presents observational evidence, together with recent theoretical developments, supporting the hypothesis that at least some asteroids might be extinct or dormant cometary nuclei. The observations include the discovery of a number of apparent asteroids in chaotic Jupiter-crossing orbits; the IRAS discovery of 1983 TB, an asteroid in the same orbit as the Geminid meteor shower; the apparent low activity levels determined for several short-period comet nuclei including Comet Halley; and observations of possible cometary activity in some earth-crossing asteroids. Theoretical developments include explorations of dynamical mechanisms capable of delivering main-belt asteroids into earth-crossing orbits, and an understanding of possible processes which may affect comets during their long residence in the Oort cloud and lead to the formation of nonvolatile crusts before and after they enter the planetary system. 143 refs

Dust Production of Comet 21P/Giacobini Zinner Using Broadband Photometry

Science.gov (United States)

Blaauw, Rhiannon; Suggs, Robert M.; Cooke, William

2012-01-01

Comet 21P/Giacobini-Zinner is a Jupiter family comet that was discovered in December of 1900 by the French astronomer Michel Giacobini, and rediscovered two orbits later by German astronomer Ernst Zinner in 1913. 21P is approximately 2 km in diameter, and is the parent of the Draconids, a meteor shower known to undergo dramatic outbursts. In 1933 and 1946, up to 10,000 meteors per hour were reported for the Draconids; and 2011 saw a minor Draconid outburst. As meteor stream modeling/ forecasting is a primary focus for the NASA Meteoroid Environment Office, it was decided to monitor 21P for three purposes: firstly to find the apparent and absolute magnitude with respect to heliocentric distance; second to calculate Af(rho), a quantity that describes the dust production rate and is used in models to predict the activity of the Draconids; thirdly to detect possible increases in cometary activity, which could correspond to future Draconid meteor outbursts. Giacobini-Zinner is unique in several ways. It was the first comet to have measurements made in situ. Comet 21P was visited by ICE (International Cometary Explorer) in 1985 to study the interaction of the cometary atmosphere with the flowing solar-wind plasma. It is a carbon-depleted comet, and most studies show that it peaks in gas and dust production pre-perihelion, specifically in two very studied passages; 1985 and 1998. A prior study was conducted by Pittichova et al (2008) for 21P during its 2004-2006 close approach to the Sun. Apparent and absolute magnitudes were measured at various heliocentric distances as well as the dust production. At 2.32 AU from the Sun, 21P exhibited an apparent magnitude of 17.05 and Af of 83 cm, and an apparent magnitude of 15.91/Af(rho) of 130.66 cm at 1.76 AU. Another such study performed by Lara et al.on 21P s 1998 apparition found values of Af(rho) of 1010 cm when 1.05 AU from the Sun, two weeks before perihelion, and 669 cm at perihelion, when 1.03 AU from the Sun

Dust Production of Comet 21P/Giacobini-Zinner Using Broadband Photometry

Science.gov (United States)

Blaauw, R. C.; Suggs, R. M.; Cooke, W.

2012-01-01

Comet 21P/Giacobini-Zinner is a Jupiter family comet, approximately 2 km in diameter, and is established to be the parent of the Draconids, a meteor shower known to outburst. In 1933 and 1946 up to 10,000 meteors per hour were reported for the Draconids, and 2011 saw a minor Draconid outburst. Meteor stream modeling/forecasting being a primary focus for the NASA Meteoroid Environment Office, it was decided to monitor 21P for three purposes: firstly to find the apparent and absolute magnitude with respect to heliocentric distance; second to calculate Af , a quantity that describes the dust production rate and is used in models to predict the activity of the Draconids; and thirdly to detect possible increases in cometary activity, which could correspond to future Draconid meteor outbursts. A similar study was done for 21P during its 2004-2006 close approach to the Sun in which apparent and absolute magnitudes were found with various heliocentric distances, as well as the dust production. At 2.32 AU from the Sun, 21P possessed an apparent magnitude of 17.05 and Af of 83 cm, and an apparent magnitude of 15.91 and Af of 130.66 cm at 1.76 AU from the sun.

International Halley watch amateur observers' manual for scientific comet studies. Part 1: Methods

Science.gov (United States)

Edberg, S. J.

1983-01-01

The International Halley Watch is described as well as comets and observing techniques. Information on periodic Comet Halley's apparition for its 1986 perihelion passage is provided. Instructions are given for observation projects valuable to the International Halley Watch in six areas of study: (1) visual observations; (2) photography; (3) astrometry; (4) spectroscopic observations; (5) photoelectric photometry; and (6) meteor observations.

Search for OH(A–X) and detection of N2+(B–X) in ultraviolet meteor spectrum

Czech Academy of Sciences Publication Activity Database

Abe, S.; Ebizuka, N.; Yano, H.; Watanabe, J.; Borovička, Jiří

2007-01-01

Roč. 39, č. 4 (2007), s. 538-543 ISSN 0273-1177 Institutional research plan: CEZ:AV0Z10030501 Keywords : astrobiology * comets * meteors Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 0.774, year: 2007

Meteor trajectory estimation from radio meteor observations

Science.gov (United States)

Kákona, J.

2016-01-01

Radio meteor observation techniques are generally accepted as meteor counting methods useful mainly for meteor flux detection. Due to the technical progress in radio engineering and electronics a construction of a radio meteor detection network with software defined receivers has become possible. These receivers could be precisely time synchronized and could obtain data which provide us with more information than just the meteor count. We present a technique which is able to compute a meteor trajectory from the data recorded by multiple radio stations.

Physical processes affecting the motion of small bodies in the solar system and their application to the evolution of meteor streams

International Nuclear Information System (INIS)

Williams, I.P.

1983-01-01

In addition to planetary perturbations, the small particles which make up a meteor stream are subject to outward radiation pressure and the Poynting-Robertson effect. New particles can also be generated in a stream through being released from the nucleus of a comet. The author summarises the main physical effects, discusses models for meteor stream evolution and gives a brief account of the observational data available. (Auth.)

The Zodiacal Cloud Model applied to the Martian atmosphere. Diurnal variations in meteoric ion layers

Science.gov (United States)

Carrillo-Sánchez, J. D.; Plane, J. M. C.; Withers, P.; Fallows, K.; Nesvorny, D.; Pokorný, P.

2016-12-01

Sporadic metal layers have been detected in the Martian atmosphere by radio occultation measurements using the Mars Express Orbiter and Mars Global Surveyor spacecraft. More recently, metallic ion layers produced by the meteor storm event following the close encounter between Comet Siding Spring (C/2013 A1) and Mars were identified by the Imaging UltraViolet Spectrograph (IUVS) and the Neutral Gas and Ion Mass Spectrometer (NGIMS) on the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft. Work is now in progress to detect the background metal layers produced by the influx of sporadic meteors. In this study we predict the likely appearance of these layers. The Zodiacal Dust Cloud (ZDC) model for particle populations released by asteroids (AST), and dust grains from Jupiter Family Comets (JFCs) and Halley-Type Comets (HTCs) has been combined with a Monte Carlo sampling method and the Chemical ABlation MODel (CABMOD) to predict the ablation rates of Na, K, Fe, Si, Mg, Ca and Al above 40 km altitude in the Martian atmosphere. CABMOD considers the standard treatment of meteor physics, including the balance of frictional heating by radiative losses and the absorption of heat energy through temperature increases, melting phase transitions and vaporization, as well as sputtering by inelastic collisions with the air molecules. The vertical injection profiles are input into the Leeds 1-D Mars atmospheric model which includes photo-ionization, and gas-phase ion-molecule and neutral chemistry, in order to explore the evolution of the resulting metallic ions and atoms. We conclude that the dominant contributor in the Martian's atmosphere is the JFCs over other sources. Finally, we explore the changes of the neutral and ionized Na, Mg and Fe layers over a diurnal cycle.

Strategy for infrared photometry of comets with ISO

Science.gov (United States)

Solc, M.; Vanysek, V.; Gruen, E.

1994-07-01

The launch of the ISO (Infrared Satellite Observatory) by the European Space Agency is scheduled for autumn 1995. Photometry and spectrophotometry observing programs of comets in the wavelength range 2.5-200 microns for the onboard spectrophotometer ISOPHOT is now under final preparation. Technical details for preparing propasals are given. Phenomena in comets to be studied are surface properties of bare cometary nuclei at large heliocentric distances, onset of coma activity, and coma dust and gas emission (in inner solar system). Dust production, dust/gas mass ratio, dust distribution in coma, and their temporal variability are important for understanding the physical processes on nuclei, and spectrophotometry in the range of 2.5-12 microns could provide us with data of the chemical composition of cometary dust. Several active comets expected for the 18-month lifetime of ISO in 1995-1997 were selected for the ISO Central Program according to their orbital and physical parameters: P/Schwassman-Wachmann 1, P/Encke, P/d'Arrest, P/Honda-Mrkos-Pajdusakova, P/Churyumov-Gerasimenko, P/Kopff, P/IRAS, P/Wirtanen, P/Wild 2, P/Grigg-Skjellerup, P/Schwassman-Wachmann 3, P/Machholz, and (2060) Chiron. Four of them match well various constraints put on the observations by the technical arrangement of the satellite and instrument. A simple four-parameter model (size, albedo, rotation, optical thickness)was developed to estimate the temperatures and thermal fluxes of both solid nuclei and dust coma.

Meteor Beliefs Project: ``Year of Meteors''

Science.gov (United States)

McBeath, Alastair; Drobnock, George J.; Gheorghe, Andrei Dorian

2011-10-01

We present a discussion linking ideas from a modern music album by Laura Veirs back to a turbulent time in American history 150 years ago, which inspired poet Walt Whitman to compose his poem "Year of Meteors", and the meteor beliefs of the period around 1859-1860, when collection of facts was giving way to analyses and theoretical explanations in meteor science.

Atmospheric deceleration and light curves of Draconid meteors and implications for the structure of cometary dust

Czech Academy of Sciences Publication Activity Database

Borovička, Jiří; Spurný, Pavel; Koten, Pavel

2007-01-01

Roč. 473, č. 2 (2007), s. 661-672 ISSN 0004-6361 R&D Projects: GA ČR GA205/05/0543; GA AV ČR KJB300030502 Institutional research plan: CEZ:AV0Z10030501 Keywords : meteor * meteoroid * comet Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 4.259, year: 2007

Migration of Interplanetary Dust and Comets

Science.gov (United States)

Ipatov, S. I.; Mather, J. C.

. The fraction of particles started from Encke-type comets is not large (<0.15) in order to fit the observational distributions of particles over their distances from the Sun. Studies of velocities of MgI line and corresponding eccentricities and inclinations in our runs showed that the mean eccentricity of zodiacal dust particles is about 0.5. [1] Ipatov S.I. and Mather J.C. (2004) Annals of the New York Acad. of Sciences, 1017, 46- 65. [2] Ipatov S.I., Mather J.C., and Taylor P. (2004) Annals of the New York Acad. of Sciences, 1017, 66-80. [3] Ipatov S.I. and Mather J.C. (2006) Advances in Space Research, 37, 126-137. [4] Ipatov S.I. et al. (2006) 37th LPSC, #1471.

Meteorites, Bolides and Comets: A Tale of Inconsistency

Science.gov (United States)

Jakes, P.; Padevet, V.

1992-07-01

Inhomogeneity of cometary nuclei has been established through the observed disruptions of comets [1] and through the determination of dust particle composition during the encounter of the Vega and Giotto satellites with comet Halley [2,3,4]. The raisin bread model of cometary nuclei [5,6] assumes the presence of solid (rock) and dust particle material set in the volatile rich, ice- cemented material. Rock material may contribute to the formation of dust particles. Gombosi and Houpis [5] argued that only the composition of dust particles derived from the icy, volatile component of the comet were analyzed and implied thus that the third cometary component present (raisins/rocks) has not been examined. The compositions of the cometary (Halley) dust and the interplanetary dust particles (IDPs) are "chondritic" (Blanford et al., 1988). It is difficult, therefore to estimate the proportion of cometary to asteroid-derived dust in near Earth space, e.g., among the IDPs [7] unless other criteria are available. Bolide multistation photographic tracking allows the determination of the orbital preencounter parameters of solid bodies (0.01-100,000 kg in mass) with the Earth, and allows us to classify them according to their ablation coefficient (tau), penetration depth into the atmosphere (PE), theoretical densities (sigma), and terminal velocities (V(sub)E). Four groups are recognized (Table 1). Three of the type I bolides were recovered as ordinary chondrites (Pribram, Lost City, and Innisfree). Ceplecha [8] has shown that 38% of bolides (fireballs) come from cometary orbits (11% from highly eccentric orbits typical of new comets), but most of the bolides (62%) originate at asteroidal orbits. Seven of the 14 known meteoric showers could be attributed to known comets: N,S Taurids to 1970 P/Encke, Lyrids to 1861 I Thatcher-Beaker, Perseids to 1862 III Swift-Tuttle- Simons, Orionids to 1835 III P/Halley, Draconids to 1946 V P/Giacobini-Zinner, Leonids to 1966 I Tempel

Meteor observation by the Kyoto meteor radar

International Nuclear Information System (INIS)

Kato, S.; Tsuda, T.

1987-01-01

The Kyoto Meteor Radar is a monostatic coherent pulsed Doppler radar operating on the frequency of 31.57 MH. The system is computer controlled and uses radio interferometry for echo height determination. The antenna, an improvement, can be directed either to the north or the east. The system has been continuously collecting data on winds at meteor heights by radar observation. The meteor echo rate was also measured, the echo rate distribution with height and the daily variation in height integrated echo rate are discussed. Investigations of atmospheric tides are being pursued by cooperative observations. A novel approach to the study of gravity waves was attempted using the meteor radar which is able to detect the horizontal propagation of the waves by observing the changing phase through the region illuminated by the radar

Mineralogy of Interplanetary Dust Particles from the Comet Giacobini-Zinner Dust Stream Collections

Science.gov (United States)

Nakamura-Messenger, K.; Messenger, S.; Westphal, A. J.; Palma, R. L.

2015-01-01

The Draconoid meteor shower, originating from comet 21P/Giacobini-Zinner, is a low-velocity Earth-crossing dust stream that had a peak anticipated flux on Oct. 8, 2012. In response to this prediction, NASA performed dedicated stratospheric dust collections to target interplanetary dust particles (IDPs) from this comet stream on Oct 15-17, 2012 [3]. Twelve dust particles from this targeted collection were allocated to our coordinated analysis team for studies of noble gas (Univ. Minnesota, Minnesota State Univ.), SXRF and Fe-XANES (SSL Berkeley) and mineralogy/isotopes (JSC). Here we report a mineralogical study of 3 IDPs from the Draconoid collection..

From interstellar dust to comets - A unification of observational constraints

International Nuclear Information System (INIS)

Greenberg, J.M.; Hage, J.I.

1990-01-01

The interstellar dust model of comets is numerically worked out to satisfy simultaneously several basic constraints provided by observations of Comet Halley, and to derive the porosity of coma dust. The observational constraints are (1) the strengths of the 3.4 and 9.7 micron emission bands, (2) the shape of the 9.7 micron band, (3) the amount of silicates relative to organic materials, and (4) the mass distribution of the dust. The method used involves precise calculations of temperatures and the emission characteristics of porous aggregates of interstellar dust as a function of their mass, porosity, and distance to the sun and the wavelength. The results indicate that coma dust has a porosity in the range 0.93-0.975, i.e., a packing factor of 0.07 or less, consistent with independent observations of comet densities of 0.6 to 0.26 g/cu cm and meteor densities of less than 0.2 g/cu cm. 63 refs

Giant comets and mass extinctions of life

Science.gov (United States)

Napier, W. M.

2015-03-01

I find evidence for clustering in age of well-dated impact craters over the last 500 Myr. At least nine impact episodes are identified, with durations whose upper limits are set by the dating accuracy of the craters. Their amplitudes and frequency are inconsistent with an origin in asteroid breakups or Oort cloud disturbances, but are consistent with the arrival and disintegration in near-Earth orbits of rare, giant comets, mainly in transit from the Centaur population into the Jupiter family and Encke regions. About 1 in 10 Centaurs in Chiron-like orbits enter Earth-crossing epochs, usually repeatedly, each such epoch being generally of a few thousand years' duration. On time-scales of geological interest, debris from their breakup may increase the mass of the near-Earth interplanetary environment by two or three orders of magnitude, yielding repeated episodes of bombardment and stratospheric dusting. I find a strong correlation between these bombardment episodes and major biostratigraphic and geological boundaries, and propose that episodes of extinction are most effectively driven by prolonged encounters with meteoroid streams during bombardment episodes. Possible mechanisms are discussed.

Meteor Beliefs Project: Meteoric references in Ovid's Metamorphoses

Science.gov (United States)

Gheorghe, A. D.; McBeath, A.

2003-10-01

Three sections of Ovid's Metamorphoses are examined, providing further information on meteoric beliefs in ancient Roman times. These include meteoric imagery among the portents associated with the death of Julius Caesar, which we mentioned previously from the works of William Shakespeare (McBeath and Gheorghe, 2003b).

Mesospheric temperature estimation from meteor decay times of weak and strong meteor trails

Science.gov (United States)

Kim, Jeong-Han; Kim, Yong Ha; Jee, Geonhwa; Lee, Changsup

2012-11-01

Neutral temperatures near the mesopause region were estimated from the decay times of the meteor echoes observed by a VHF meteor radar during a period covering 2007 to 2009 at King Sejong Station (62.22°S, 58.78°W), Antarctica. While some previous studies have used all meteor echoes to determine the slope from a height profile of log inverse decay times for temperature estimation, we have divided meteor echoes into weak and strong groups of underdense meteor trails, depending on the strength of estimated relative electron line densities within meteor trails. We found that the slopes from the strong group are inappropriate for temperature estimation because the decay times of strong meteors are considerably scattered, whereas the slopes from the weak group clearly define the variation of decay times with height. We thus utilize the slopes only from the weak group in the altitude region between 86 km and 96 km to estimate mesospheric temperatures. The meteor estimated temperatures show a typical seasonal variation near the mesopause region and the monthly mean temperatures are in good agreement with SABER temperatures within a mean difference of 4.8 K throughout the year. The meteor temperatures, representing typically the region around the altitude of 91 km, are lower on average by 2.1 K than simultaneously measured SATI OH(6-2) rotational temperatures during winter (March-October).

The KUT meteor radar: An educational low cost meteor observation system by radio forward scattering

Science.gov (United States)

Madkour, W.; Yamamoto, M.

2016-01-01

The Kochi University of Technology (KUT) meteor radar is an educational low cost observation system built at Kochi, Japan by successive graduate students since 2004. The system takes advantage of the continuous VHF- band beacon signal emitted from Fukui National College of Technology (FNCT) for scientific usage all over Japan by receiving the forward scattered signals. The system uses the classical forward scattering setup similar to the setup described by the international meteor organization (IMO), gradually developed from the most basic single antenna setup to the multi-site meteor path determination setup. The primary objective is to automate the observation of the meteor parameters continuously to provide amounts of data sufficient for statistical analysis. The developed software system automates the observation of the astronomical meteor parameters such as meteor direction, velocity and trajectory. Also, automated counting of meteor echoes and their durations are used to observe mesospheric ozone concentration by analyzing the duration distribution of different meteor showers. The meteor parameters observed and the methodology used for each are briefly summarized.

Comet and meteorite traditions of Aboriginal Australians

Science.gov (United States)

Hamacher, Duane W.

2014-06-01

This research contributes to the disciplines of cultural astronomy (the academic study of how past and present cultures understand and utilise celestial objects and phenomena) and geomythology (the study of geological events and the formation of geological features described in oral traditions). Of the hundreds of distinct Aboriginal cultures of Australia, many have oral traditions rich in descriptions and explanations of comets, meteors, meteorites, airbursts, impact events, and impact craters. These views generally attribute these phenomena to spirits, death, and bad omens. There are also many traditions that describe the formation of meteorite craters as well as impact events that are not known to Western science.

New meteor showers – yes or not?

Science.gov (United States)

Koukal, Jakub

2018-01-01

The development of meteor astronomy associated with the development of CCD technology is reflected in a huge increase in databases of meteor orbits. It has never been possible before in the history of meteor astronomy to examine properties of meteors or meteor showers. Existing methods for detecting new meteor showers seem to be inadequate in these circumstances. The spontaneous discovery of new meteor showers leads to ambiguous specifications of new meteor showers. There is a duplication of already discovered meteor showers and a division of existing meteor showers based on their own criteria. The analysis in this article considers some new meteor showers in the IAU MDC database.

Meteor researches at KHNURE

Science.gov (United States)

Kolomiyets, Svitlana V.; Voloshchuk, Yuri I.; Kashcheyev, Boris L.; Slipchenko, Nikolay I.

2005-01-01

The Scientific Educational Center of Radioengineering of the Kharkiv National University of Radioelectronics (KHNURE: ) is one of the oldest radar meteor centers which was founded by B. L. Kashcheyev in 1958. The first automatic meteor radar system in Ukraine “MARS” is connected with our University. There are long-term observational series of meteor rates and orbital data in the Center. Fields of the KHNURE researches are: a structure of meteor showers a determination of meteoroid orbits an influx of cosmic rubbish in the Earth atmosphere search of parental bodies of meteoroids a statistic analysis of measurement results of radiometeors an estimation of errors of meteor radar measurements a search for real hyperbolic orbits and interstellar meteoroids. KHNURE disposes a unique electronic orbital catalogue. This catalogue contains the primary information velocities radiants and orbits of nearly 250000 radiometeoroids with masses from 0.001 to 0.000001 g. The “MARS” registered these data during observations of 1972 1978. From these data 5160 meteor streams are singled out. New classification of streams is made in view of their structure. The study of meteor stream orbits from the KHNURE data bank allow to predict orbits of a big number of undiscovered “dangerous” NEOs.

Determination of the Meteor Limiting Magnitude

Science.gov (United States)

Kingery, A.; Blaauw, R.; Cooke, W. J.

2016-01-01

The limiting meteor magnitude of a meteor camera system will depend on the camera hardware and software, sky conditions, and the location of the meteor radiant. Some of these factors are constants for a given meteor camera system, but many change between meteor shower or sporadic source and on both long and short timescales. Since the limiting meteor magnitude ultimately gets used to calculate the limiting meteor mass for a given data set, it is important to have an understanding of these factors and to monitor how they change throughout the night, as a 0.5 magnitude uncertainty in limiting magnitude translates to a uncertainty in limiting mass by a factor of two.

Meteor showers an annotated catalog

CERN Document Server

Kronk, Gary W

2014-01-01

Meteor showers are among the most spectacular celestial events that may be observed by the naked eye, and have been the object of fascination throughout human history. In “Meteor Showers: An Annotated Catalog,” the interested observer can access detailed research on over 100 annual and periodic meteor streams in order to capitalize on these majestic spectacles. Each meteor shower entry includes details of their discovery, important observations and orbits, and gives a full picture of duration, location in the sky, and expected hourly rates. Armed with a fuller understanding, the amateur observer can better view and appreciate the shower of their choice. The original book, published in 1988, has been updated with over 25 years of research in this new and improved edition. Almost every meteor shower study is expanded, with some original minor showers being dropped while new ones are added. The book also includes breakthroughs in the study of meteor showers, such as accurate predictions of outbursts as well ...

METEOR v1.0 - A usage example; METEOR v1.0 - Un ejemplo de uso

Energy Technology Data Exchange (ETDEWEB)

Palomo, E.

1994-07-01

This script describes a detailed example of the use of the software package METEOR for statistical analysis of meteorological data series. A real spanish meteorological data set is chosen to show the capabilities of METEOR. Output files and resultant plots provided of their interpretations are compiled in three appendixes. The original version of METEOR have been developed by Ph. D.Elena Palomo, CIEMAT-IER, GIASE. It is built by linking programs and routines written in FORTRAN 77 and it adds the graphical capabilities of GNUPLOT. The shape of this toolbox was designed following the criteria of modularity, flexibility and agility criteria. All the input, output and analysis options are structured in three main menus: i) the first is aimed to evaluate the quality of the data set; ii) the second is aimed for pre-processing of the data; and iii) the third is aimed towards the statistical analyses and for creating the graphical outputs. Actually the information about METEOR is constituted by three documents written is spanish: 1) METEOR v1.0: User's guide; 2) METEOR v1.0: A usage example; 3) METEOR v1 .0: Design and structure of the software package. (Author)

Solar influence on meteor rates and atmospheric density variations at meteor heights

International Nuclear Information System (INIS)

Ellyett, C.

1977-01-01

A full analysis of radar-determined meteor rates from New Zealand, involving 3,085,574 meteors recorded over a total of 3 1/2 years, and 12,391,976 meteors recorded by the National Research Council of Canada in 8 1/2 years confirms an inverse relationship between meteor rates and solar activity as measured by sunspot numbers. The relationship, significant at the 1% level, appears in the Canadian annual average when the abnormal 1963 increase is removed, in monthly and 1/3-monthly results for the total Canadian period, and in monthly intervals for 1 year of the New Zealand data. This proven relationship of meteor rates with the solar cycle calls for a significant density gradient change over the solar cycle in the 70- to-120-km height range. Although some definite negative results have been reported, no unambiguous positive results are yet available supporting such a density gradient change. It is possible that density variations due to annual, semiannual, diurnal, and latitudinal changes obscure any 11-year density gradient change occurring at these heights. It is uncertain whether the 1963 increase represents density gradient changes in the meteor ablation region regularly brought about 1-2 years before each sunspot minimum or is a special event due to volcanic dust. The following additional facts have emerged from the present analysis. (1) Within a 1-year period the seasonal rate change of astronomical origin overrides any density gradient change in controlling the meteor rates in one of the two hemispheres. (2) The earth's daily rotation alters rates in phase with probable diurnal density gradient changes. (3) An effect due to D region absorption has been observed in the Canadian data

An Investigation of the Fine Spatial Structure of Meteor Streams Using the Relational Database ``Meteor''

Science.gov (United States)

Karpov, A. V.; Yumagulov, E. Z.

2003-05-01

We have restored and ordered the archive of meteor observations carried out with a meteor radar complex ``KGU-M5'' since 1986. A relational database has been formed under the control of the Database Management System (DBMS) Oracle 8. We also improved and tested a statistical method for studying the fine spatial structure of meteor streams with allowance for the specific features of application of the DBMS. Statistical analysis of the results of observations made it possible to obtain information about the substance distribution in the Quadrantid, Geminid, and Perseid meteor streams.

Meteors Without Borders: a global campaign

Science.gov (United States)

Heenatigala, T.

2012-01-01

"Meteors Without Borders" is a global project, organized by Astronomers Without Borders and launched during the Global Astronomy Month in 2010 for the Lyrid meteor shower. The project focused on encouraging amateur astronomy groups to hold public outreach events for major meteor showers, conduct meteor-related classroom activities, photography, poetry and art work. It also uses social-media platforms to connect groups around the world to share their observations and photography, live during the events. At the International Meteor Conference 2011, the progress of the project was presented along with an extended invitation for collaborations for further improvements of the project.

METEOR v1.0 - User's Guide; METEOR v1.0 - Guia de Usuarios

Energy Technology Data Exchange (ETDEWEB)

Palomo, E.

1994-07-01

This script is a User's Guide for the software package METEOR for statistical analysis of meteorological data series. The original version of METEOR have been developed by Ph.D. Elena Palomo, CIEMAT-IER, GIMASE. It is built by linking programs and routines written in FORTRAN 77 and it adds the graphical capabilities of GNUPLOT. The shape of this toolbox was designed following the criteria of modularity, flexibility and agility criteria. All the input, output and analysis options are structured in three main menus: i) the first is aimed to evaluate the quality of the data set; ii) the second is aimed for pre-processing of the data; and iii) the third is aimed towards the statistical analyses and for creating the graphical outputs. Actually the information about METEOR is constituted by three documents written in spanish: 1) METEOR v1.0: User's guide; 2) METEOR v1.0: A usage example; 3) METEOR v1.0: Design and structure of the software package. (Author)

Interferometric Meteor Head Echo Observations using the Southern Argentina Agile Meteor Radar (SAAMER)

Science.gov (United States)

Janches, D.; Hocking, W.; Pifko, S.; Hormaechea, J. L.; Fritts, D. C.; Brunini, C; Michell, R.; Samara, M.

2013-01-01

A radar meteor echo is the radar scattering signature from the free-electrons in a plasma trail generated by entry of extraterrestrial particles into the atmosphere. Three categories of scattering mechanisms exist: specular, nonspecular trails, and head-echoes. Generally, there are two types of radars utilized to detect meteors. Traditional VHF meteor radars (often called all-sky1radars) primarily detect the specular reflection of meteor trails traveling perpendicular to the line of sight of the scattering trail, while High Power and Large Aperture (HPLA) radars efficiently detect meteor head-echoes and, in some cases, non-specular trails. The fact that head-echo measurements can be performed only with HPLA radars limits these studies in several ways. HPLA radars are very sensitive instruments constraining the studies to the lower masses, and these observations cannot be performed continuously because they take place at national observatories with limited allocated observing time. These drawbacks can be addressed by developing head echo observing techniques with modified all-sky meteor radars. In addition, the fact that the simultaneous detection of all different scattering mechanisms can be made with the same instrument, rather than requiring assorted different classes of radars, can help clarify observed differences between the different methodologies. In this study, we demonstrate that such concurrent observations are now possible, enabled by the enhanced design of the Southern Argentina Agile Meteor Radar (SAAMER) deployed at the Estacion Astronomica Rio Grande (EARG) in Tierra del Fuego, Argentina. The results presented here are derived from observations performed over a period of 12 days in August 2011, and include meteoroid dynamical parameter distributions, radiants and estimated masses. Overall, the SAAMER's head echo detections appear to be produced by larger particles than those which have been studied thus far using this technique.

International cooperation and amateur meteor work

Science.gov (United States)

Roggemans, P.

Today, the existing framework for international cooperation among amateur meteor workers offers numerous advantages. However, this is a rather recent situation. Meteor astronomy, although popular among amateurs, was the very last topic within astronomy to benefit from a truly international approach. Anyone attempting long term studies of, for instance, meteor stream structures will be confronted with the systematic lack of usable observations due to the absence of any standards in observing, recording and reporting, any archiving or publishing policy. Visual meteor observations represent the overall majority of amateur efforts, while photographic and radio observing were developed only in recent decades as technological specialties of rather few meteor observing teams.

METEOR v1.0 - User's Guide

International Nuclear Information System (INIS)

Palomo, E.

1994-01-01

This script is a User's Guide for the software package METEOR for statistical analysis of meteorological data series. The original version of METEOR have been developed by Ph.D. Elena Palomo, CIEMAT-IER, GIMASE. It is built by linking programs and routines written in FORTRAN 77 and it adds the graphical capabilities of GNUPLOT. The shape of this toolbox was designed following the criteria of modularity, flexibility and agility criteria. All the input, output and analysis options are structured in three main menus: i) the first is aimed to evaluate the quality of the data set; ii) the second is aimed for pre-processing of the data; and iii) the third is aimed towards the statistical analyses and for creating the graphical outputs. Actually the information about METEOR is constituted by three documents written in spanish: 1) METEOR v1.0: User's guide; 2) METEOR v1.0: A usage example; 3) METEOR v1.0: Design and structure of the software package. (Author)

Global variation of meteor trail plasma turbulence

Directory of Open Access Journals (Sweden)

L. P. Dyrud

2011-12-01

Full Text Available We present the first global simulations on the occurrence of meteor trail plasma irregularities. These results seek to answer the following questions: when a meteoroid disintegrates in the atmosphere, will the resulting trail become plasma turbulent? What are the factors influencing the development of turbulence? and how do these trails vary on a global scale? Understanding meteor trail plasma turbulence is important because turbulent meteor trails are visible as non-specular trails to coherent radars. Turbulence also influences the evolution of specular radar meteor trails; this fact is important for the inference of mesospheric temperatures from the trail diffusion rates, and their usage for meteor burst communication. We provide evidence of the significant effect that neutral atmospheric winds and ionospheric plasma density have on the variability of meteor trail evolution and on the observation of non-specular meteor trails. We demonstrate that trails are far less likely to become and remain turbulent in daylight, explaining several observational trends for non-specular and specular meteor trails.

The number of Jupiter family comets as a constraint on the transneptunian population

Science.gov (United States)

Tancredi, G.; et al.

Several duynamical studies point out that the comets of the Jupiter family were originated in a flat belt in the transneptunian region. The Jupiter family is a transient dynamical state between the injection from the outer region and i) the ejection out of the Solar System, ii) the collision against one of its members or iii) the desintegration into a meteor stream. It has been generally assumed that the Jupiter family (JF) is in a steady state; i.e. the injection is balanced by the ejection+collision+ desintegration. Knowing the duration of a typical visit into the Jupiter family and the number of JF comets we could infer the injection rate. The rate of escapes from the transneptunian region and the fraction that reach the Jupiter family can be computed from massive integrations of particles starting in the outer region. An estimate of the required population of transneptunian objects can then be inferred from these numbers. There have been published several estimates of the dynamical parameters mentioned above but the total number of JF comets has been difficult to estimate. Based on a compilation of all the reported nuclear magnitudes of JF comets, we derive the total number of objects in the cometary population. The observed population (~ 200) is a tiny fraction of the total population (several thousands). Compiling all these numbers, we then derive the required trasneptunian population.

Meteors in Australian Aboriginal Dreamings

Science.gov (United States)

Hamacher, Duane W.; Norris, Ray P.

2010-06-01

We present a comprehensive analysis of Australian Aboriginal accounts of meteors. The data used were taken from anthropological and ethnographic literature describing oral traditions, ceremonies, and Dreamings of 97 Aboriginal groups representing all states of modern Australia. This revealed common themes in the way meteors were viewed between Aboriginal groups, focusing on supernatural events, death, omens, and war. The presence of such themes around Australia was probably due to the unpredictable nature of meteors in an otherwise well-ordered cosmos.

Opportunities for in-depth compositional studies of comets: Summary from semester 2017A observations and prospects for a 2018 observing campaign

Science.gov (United States)

DiSanti, Michael A.; Dello Russo, Neil; Bonev, Boncho P.; Gibb, Erika L.; Roth, Nathan; Vervack, Ronald J.; McKay, Adam J.; Kawakita, Hideyo; Cochran, Anita L.

2017-10-01

The period from late 2016 to mid 2017 provided unusually rich observational opportunities for compositional studies of comets using ground-based IR and optical spectroscopy. Three ecliptic comets - Jupiter-family comet (JFC) 45P/Honda-Mrkos-Pajdusakova, JFC 41P/Tuttle-Giacobini-Kresak, and 2P/Encke - as well as two moderately bright nearly istotropic comets from the Oort cloud (C/2015 ER61 PanSTARRS and C/2015 V2 Johnson) experienced highly favorable appritions.In the IR, very long on-source integration times were accumulated on all targets, primarily with the powerful new high-resolution, cross-dispersed iSHELL spectrograph at the IRTF (Rayner et al. 2016 SPIE 9908:1) but also with NIRSPEC at Keck II. This enabled accurate production rates and abundance ratios for 8-10 native ices, and spatially resolved studies of coma physics (H2O rotational temperatures and column abundances). The recent availability of iSHELL coupled with the daytime observing capability at the IRTF has opened a powerful window for conducting detailed compositional studies of comets over a range of heliocentric distances (Rh), particularly at small Rh where studies are relatively sparse. Our campaign provided detections of (or stringent abundance limits for) hyper-volatiles CO and CH4, which are severely lacking in compositional studies of JFCs.For all of these targets, optical spectra measured photo-dissociation product species using the Tull Coude spectrograph at McDonald Observatory, and ARCES at Apache Point Observatory. When possible optical and IR observations were obtained contemporaneously, with the goal of addressing potential parent-product relationships.We summarize our campaign and highlight related presentations. Prospects for investigations during the upcoming favorable apparitions of JFCs 21P/Giacobini-Zinner and 46P/Wirtanen will also be discussed, along with increased capabilities for serial studies (i.e., measurements at multiple Rh) of newly discovered (Oort cloud) comets

Radar meteor rates and solar activity

International Nuclear Information System (INIS)

Prikryl, P.

1983-01-01

The short-term variation of diurnal radar meteor rates with solar activity represented by solar microwave flux Fsub(10.7), and sunspots relative number Rsub(z), is investigated. Applying the superposed-epoch analysis to the observational material of radar meteor rates from Christchurch (1960-61 and 1963-65), a decrease in the recorded radar rates is found during days of enhanced solar activity. No effect of geomagnetic activity similar to the one reported for the Swedish and Canadian radar meteor data was found by the author in the Christchurch data. A possible explanation of the absence of the geomagnetic effect on radar meteor rates from New Zealand due to a lower echo ceiling height of the Christchurch radar is suggested. The variation of the atmospheric parameters as a possible cause of the observed variation in radar meteor rates is also discussed. (author)

An early look of comet C/2013 A1 (Siding Spring): Breathtaker or nightmare?

International Nuclear Information System (INIS)

Ye, Quan-Zhi; Hui, Man-To

2014-01-01

The dynamically new comet, C/2013 A1 (Siding Spring), is to make a close approach to Mars on 2014 October 19 at 18:30 UT at a distance of 40 ± 1 Martian radii. Such an extremely rare event offers a precious opportunity for the spacecrafts on Mars to closely study a dynamically new comet itself as well as the planet-comet interaction. Meanwhile, the high-speed meteoroids released from C/Siding Spring also pose a threat to physically damage the spacecrafts. Here we present our observations and modeling results of C/Siding Spring to characterize the comet and assess the risk posed to the spacecrafts on Mars. We find that the optical tail of C/Siding Spring is dominated by larger particles at the time of the observation. Synchrone simulation suggests that the comet was already active in late 2012 when it was more than 7 AU from the Sun. By parameterizing the dust activity with a semi-analytic model, we find that the ejection speed of C/Siding Spring is comparable to comets such as the target of the Rosetta mission, 67P/Churyumov-Gerasimenko. Under a nominal situation, the simulated dust cone will miss the planet by about 20 Martian radii. At the extreme ends of uncertainties, the simulated dust cone will engulf Mars, but the meteoric influx at Mars is still comparable to the nominal sporadic influx, seemly indicating that an intense and enduring meteoroid bombardment due to C/Siding Spring is unlikely. Further simulation also suggests that gravitational disruption of the dust tail may be significant enough to be observable at Earth.

SQCX X-ray Observations Of The Deep Impact Spacecraft Close Encounters With Comets 9P/Tempel 1 And 103P/Hartley 2

Science.gov (United States)

Lisse, Carey M.; Dennerl, K.; Wolk, S. J.; Christian, D. J.; Bodewits, D.; Zurbuchen, T. H.; Combi, M.

2010-03-01

We present results from the extensive Chandra, SWIFT, Spitzer, and groundbased observing campaigns studying Comet 9P/Tempel 1 in support of NASA's Deep Impact (DI) mission as an indication of the results expected for the next DI flyby of comet 103P/Hartley 2 at 0.1 AU geocentric distance in November 2010. 9P/Tempel 1 was observed for 300 ksec between 30th June and 24th July 2005, and continuously for 60 ksec on July 4th during the impact event. X-ray emission qualitatively similar to that observed for the collisionally thin, cold wind comet 2P/Encke system (Lisse et al. 2005) was found, with emission morphology centered on the nucleus and emission lines due to C, N, O, and Ne solar wind minor ions. The comet was relatively faint on July 4th, and the total increase in x-ray flux due to the Deep Impact excavation was small, 20% of the immediate pre-impact value, consistent with estimates that the total coma neutral gas release due to the impact was 5 x 106 kg ( 10 hrs of normal coma outflow). Over time, other temporally variable spectral features due to changing solar wind flux densities and charge states were clearly seen. Good agreement between the Chandra and SWIFT x-ray photometry was found. Two flares, much stronger than the man-made increase due to Deep Impact, were found in the observed x-rays on June 30th and July 8th, 2005, and are coincident with increases in the solar wind flux arriving at the comet. Modeling of the Chandra data using observed Spitzer gas production rates and ACE solar wind ion fluxes with a SWCX mechanism for the emission was found to be consistent with the temporal- and spectral behavior expected for a slow, hot wind typical of low latitude emission from the solar corona interacting with the comet's neutral coma.

METEOR v1.0 - A usage example

International Nuclear Information System (INIS)

Palomo, E.

1994-01-01

This script describes a detailed example of the use of the software package METEOR for statistical analysis of meteorological data series. A real spanish meteorological data set is chosen to show the capabilities of METEOR. Output files and resultant plots provided of their interpretations are compiled in three appendixes. The original version of METEOR have been developed by Ph. D.Elena Palomo, CIEMAT-IER, GIASE. It is built by linking programs and routines written in FORTRAN 77 and it adds the graphical capabilities of GNUPLOT. The shape of this toolbox was designed following the criteria of modularity, flexibility and agility criteria. All the input, output and analysis options are structured in three main menus: i) the first is aimed to evaluate the quality of the data set; ii) the second is aimed for pre-processing of the data; and iii) the third is aimed towards the statistical analyses and for creating the graphical outputs. Actually the information about METEOR is constituted by three documents written is spanish: 1) METEOR v1.0: User's guide; 2) METEOR v1.0: A usage example; 3) METEOR v1 .0: Design and structure of the software package. (Author)

METEOR v1.0 - Design and structure of the software package; METEOR v1.0 - Estructura y modulos informaticos

Energy Technology Data Exchange (ETDEWEB)

Palomo, E.

1994-07-01

This script describes the structure and the separated modules of the software package METEOR for the statistical analysis of meteorological data series. It contains a systematic description of the subroutines of METEOR and, also, of the required shape for input and output files. The original version of METEOR have been developed by Ph.D. Elena Palomo, CIEMAT-IER, GIMASE. It is built by linking programs and routines written in FORTRAN 77 and it adds thc graphical capabilities of GNUPLOT. The shape of this toolbox was designed following the criteria of modularity, flexibility and agility criteria. All the input, output and analysis options are structured in three main menus: i) the first is aimed to evaluate the quality of the data set; ii) the second is aimed for pre-processing of the data; and iii) the third is aimed towards the statistical analyses and for creating the graphical outputs. Actually the information about METEOR is constituted by three documents written in spanish: 1) METEOR v1.0: User's guide; 2) METEOR v1.0: A usage example; 3) METEOR v 1.0: Design and structure of the software package. (Author)

Observing comets

CERN Document Server

James, Nick

2003-01-01

Since comet Shoemaker-Levy collided with the planet Jupiter with stupendous force in 1994 there has been an upsurge of amateur interest in comets Most comets are first discovered by amateur astronomers because there are so many amateurs looking for them, and techniques and instruments have improved dramatically in the past few years After a short but detailed introduction to the comets themselves Nick James and Gerald North describe comet hunting, photographing and imaging comets, and digital image processing The use of computers for orbital calculations and even helping to discover new comets is given a full chapter, as are advanced techniques including comet photometry and spectroscopy This comprehensive book has an accompanying CD-ROM and is at once a "primer" for comet hunters and a reference text for more advanced amateur astronomers

New radio meteor detecting and logging software

Science.gov (United States)

Kaufmann, Wolfgang

2017-08-01

A new piece of software ``Meteor Logger'' for the radio observation of meteors is described. It analyses an incoming audio stream in the frequency domain to detect a radio meteor signal on the basis of its signature, instead of applying an amplitude threshold. For that reason the distribution of the three frequencies with the highest spectral power are considered over the time (3f method). An auto notch algorithm is developed to prevent the radio meteor signal detection from being jammed by a present interference line. The results of an exemplary logging session are discussed.

Seasonal Variation in Meteor Decay Time Profiles Measured by a Meteor Radar at King Sejong Station (62°S, 58°W), Antarctica

Science.gov (United States)

Kim, Y.; Kim, J.; Lee, C.; Jee, G.

2008-12-01

A VHF meteor radar at King Sejong Station (62°S, 58°W), Antarctica has been detecting echoes from more than 20,000 meteors per day since March 2007. Meteor echoes are decayed typically within seconds as meteor trail plasma spread away or are neutralized. Assuming that diffusion is the only process for decay of meteor echo signals, the atmospheric temperatures and pressures have been inferred from the measured meteor decay times at the peak meteor altitudes around 90 km. In this study, we analyze altitude profiles of meteor decay times in each month, which clearly show a maximum at 80 ~ 85 km. The maximum appears at higher altitude during austral summer than winter. The fast decay of meteor signals below the maximum cannot be explained by atmospheric diffusion which decreases with increasing atmospheric densities. We find that the measured meteor decay time profiles can be fitted with a loss rate profile, in addition to diffusion, with a peak altitude of 55 ~ 73 km and a peak rate of 4 ~ 15 sec- 1. The additional loss of meteor plasma may be due to electron absorption by icy particles in the mesosphere, but the estimated peak altitudes are much lower than the layers of NLC or PME. The estimated peak loss rates seem to be too large to be accounted by absorption by icy or dust particles. We will discuss other processes to explain the fast meteor times and their variation over season.

Problems in the design of multifunction meteor-radar networks

Science.gov (United States)

Nechitailenko, V. A.; Voloshchuk, Iu. I.

The design of meteor-radar networks is examined in connection with the need to conduct experiments on a mass scale in meteor geophysics and astronomy. Attention is given to network architecture features and procedures of communication-path selection in the organization of information transfer, with allowance for the features of the meteor communication link. The meteor link is considered as the main means to ensure traffic in the meteor-radar network.

Survival of Glycolaldehyde and Production of Sugar Compounds via Comet Impact Delivery

Science.gov (United States)

Zellner, N.; McCaffrey, V.; Crake, C.; Butler, J.; Robbins, J.; Fodor, A.

2017-12-01

Impact experiments using glycolaldehyde (GLA), a two-carbon sugar precursor that has been detected in regions of the interstellar medium and on comets, have been conducted at the Experimental Impact Laboratory at NASA's Johnson Space Center. Samples of GLA and GLA mixed with montmorillonite clays were subjected to the pressure conditions that are found during impact delivery of biomolecules by comets, asteroids, or meteors; pressures ranged from 4.5 GPa to 25 GPa. Results show that large amounts of GLA survived the impacts and moderate amounts of threose, erythrose, and glycolic acid were produced in these impacts. Total amounts are dependent on impact pressure. Ethylene glycol, a reduced variant of GLA that has also been detected in the interstellar medium and on comets, was also produced. The results of these experimental impacts provide evidence that large amounts of GLA, EG, and other biomolecules were available on habitable moons or planets, especially during the era of late heavy bombardment ( 4.2 to 3.7 billion years ago) when life may have been developing on Earth. The presence and availability of these biomolecules, under appropriate conditions, may be important for understanding the origin of life as we know it. Glycolaldehyde in particular, may be an important molecule in the production of ribose, the five-carbon sugar in RNA.

Thermal alteration in carbonaceous chondrites and implications for sublimation in rock comets

Science.gov (United States)

Springmann, Alessondra; Lauretta, Dante S.; Steckloff, Jordan K.

2015-11-01

Rock comets are small solar system bodies in Sun-skirting orbits (perihelion q CO2, etc.). B-class asteroid (3200) Phaethon, considered to be the parent body of the Geminid meteor shower, is the only rock comet currently known to periodically eject dust and form a coma. Thermal fracturing or thermal decomposition of surface materials may be driving Phaethon’s cometary activity (Li & Jewitt, 2013). Phaethon-like asteroids have dynamically unstable orbits, and their perihelia can change rapidly over their ~10 Myr lifetimes (de León et al., 2010), raising the possibility that other asteroids may have been rock comets in the past. Here, we propose using spectroscopic observations of mercury (Hg) as a tracer of an asteroid’s thermal metamorphic history, and therefore as a constraint on its minimum achieved perihelion distance.B-class asteroids such as Phaethon have an initial composition similar to aqueously altered primitive meteorites such as CI- or CM-type meteorites (Clark et al., 2010). Laboratory heating experiments of ~mm sized samples of carbonaceous chondrite meteorites from 300K to 1200K at a rate of 15K/minute show mobilization and volatilization of various labile elements at temperatures that could be reached by Mercury-crossing asteroids. Samples became rapidly depleted in labile elements and, in particular, lost ~75% of their Hg content when heated from ~500-700 K, which corresponds to heliocentric distances of ~0.15-0.3 au, consistent with our thermal models. Mercury has strong emission lines in the UV (~ 185 nm) and thus its presence (or absence) relative to carbonaceous chondrite abundances would indicate if these bodies had perihelia in their dynamical histories inside of 0.15 AU, and therefore may have previously been Phaethon-like rock comets. Future space telescopes or balloon-borne observing platforms equipped with a UV spectrometer could potentially detect the presence or absence of strong ultraviolet mercury lines on rock comets or rock

Goals, technique and equipment of meteor study in Russia

Science.gov (United States)

Kartashova, A.; Bagrov, A. V.; Bolgova, G. T.; Kruchkov, S. V.; Leonov, V. A.; Mazurov, V. A.

2013-09-01

Institute of Astronomy RAS is one of the science institutes in the Russian Federation providing systematic optical meteor observations and supervises several meteor groups in our country. The main tasks of our investigations are dedicated to study meteoroid nature as well as meteoroid streams and meteoroid population in the Solar System. In the XXI century we in Russia carry out the reconstruction of our meteor astronomy due to possibilities of new meteor observation equipment (more powerful than were used before as visual and photographic methods) had made possible to select more interesting goals. First of our task is investigation of meteoroid streams crossing the Earth's orbit, and character of meteoroid distributions along of them. The multi stations meteor monitoring from located in the both hemispheres of the Earth can help in this study. According to the analysis of the evolution of meteor orbits, the compact and long lived meteoroid streams consist mainly from large particles. The observation equipment (cheap TV-cameras) with low limiting magnitude we use for gathering observational data. On the other hand, the observations of weak meteors are needed for new meteor shower indication (or confirmation of known meteor shower). The more effective way to do it is comparison of individual meteor orbits parameters (then calculation of radiants of meteor showers). The observations of space debris (as the meteors with low velocity - less 11.2 km/s) can be taking up within this task. The combination of high sensitive TV-cameras WATEC and super-fast lenses COMPUTAR are widely used for meteor TV-monitoring. The TVsystems for round-year meteor observations are fixed and are permanently oriented to the zenith area (the patrol camera - PatrolCa). The mobile TV-cameras (MobileCa) are used for double station observations (if it is possible) and located not far from main cameras PatrolCa (20-30 km). The mobile TVcameras observe 90% of main PatrolCa cameras FOV at altitudes

Meteoric 10Be in soil profiles - A global meta-analysis

Science.gov (United States)

Graly, Joseph A.; Bierman, Paul R.; Reusser, Lucas J.; Pavich, Milan J.

2010-01-01

In order to assess current understanding of meteoric 10Be dynamics and distribution in terrestrial soils, we assembled a database of all published meteoric 10Be soil depth profiles, including 104 profiles from 27 studies in globally diverse locations, collectively containing 679 individual measurements. This allows for the systematic comparison of meteoric 10Be concentration to other soil characteristics and the comparison of profile depth distributions between geologic settings. Percent clay, 9Be, and dithionite-citrate extracted Al positively correlate to meteoric 10Be in more than half of the soils where they were measured, but the lack of significant correlation in other soils suggests that no one soil factor controls meteoric 10Be distribution with depth. Dithionite-citrate extracted Fe and cation exchange capacity are only weakly correlated to meteoric 10Be. Percent organic carbon and pH are not significantly related to meteoric 10Be concentration when all data are complied.The compilation shows that meteoric 10Be concentration is seldom uniform with depth in a soil profile. In young or rapidly eroding soils, maximum meteoric 10Be concentrations are typically found in the uppermost 20 cm. In older, more slowly eroding soils, the highest meteoric 10Be concentrations are found at depth, usually between 50 and 200 cm. We find that the highest measured meteoric 10Be concentration in a soil profile is an important metric, as both the value and the depth of the maximum meteoric 10Be concentration correlate with the total measured meteoric 10Be inventory of the soil profile.In order to refine the use of meteoric 10Be as an estimator of soil erosion rate, we compare near-surface meteoric 10Be concentrations to total meteoric 10Be soil inventories. These trends are used to calibrate models of meteoric 10Be loss by soil erosion. Erosion rates calculated using this method vary based on the assumed depth and timing of erosional events and on the reference data selected.

A spectral analysis of ablating meteors

Science.gov (United States)

Bloxam, K.; Campbell-Brown, M.

2017-09-01

Meteor ablation features in the spectral lines occurring at 394, 436, 520, and 589 nm were observed using a four-camera spectral system between September and December 2015. In conjunction with this multi-camera system the Canadian Automated Meteor Observatory was used to observe the orbital parameters and fragmentation of these meteors. In total, 95 light curves with complete data in the 520 and 589 nm filters were analyzed; some also had partial or complete data in the 394 nm filter, but no usable data was collected with the 436 nm filter. Of the 95 events, 70 exhibited some degree of differential ablation, and in all except 3 of these 70 events the 589 nm filter started or ended sooner compared with the 520 nm filter, indicating early ablation at the 589 nm wavelength. In the majority of cases the meteor showed evidence of fragmentation regardless of the type of ablation (differential or uniform). A surprising result was the lack of correlation found concerning the KB parameter, linked to meteoroid strength, and differential ablation. In addition, 22 shower-associated meteors were observed; Geminids showed mainly slight differential ablation, while Taurids were more likely to ablate uniformly.

Photoacoustic Sounds from Meteors.

Energy Technology Data Exchange (ETDEWEB)

Spalding, Richard E. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Tencer, John [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Sweatt, William C. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Hogan, Roy E. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Boslough, Mark B. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Spurny, Pavel [Academy of Sciences of the Czech Republic (ASCR), Prague (Czech Republic)

2015-03-01

High-speed photometric observations of meteor fireballs have shown that they often produce high-amplitude light oscillations with frequency components in the kHz range, and in some cases exhibit strong millisecond flares. We built a light source with similar characteristics and illuminated various materials in the laboratory, generating audible sounds. Models suggest that light oscillations and pulses can radiatively heat dielectric materials, which in turn conductively heats the surrounding air on millisecond timescales. The sound waves can be heard if the illuminated material is sufficiently close to the observer’s ears. The mechanism described herein may explain many reports of meteors that appear to be audible while they are concurrently visible in the sky and too far away for sound to have propagated to the observer. This photoacoustic (PA) explanation provides an alternative to electrophonic (EP) sounds hypothesized to arise from electromagnetic coupling of plasma oscillation in the meteor wake to natural antennas in the vicinity of an observer.

Comets

International Nuclear Information System (INIS)

Hughes, D.W.

1982-01-01

Comets are objects of considerable fascination and this paper reviews the present knowledge of the physical structure of the cometary nucleus, coma and tail, the orbits of comets in the Solar System, the proposed mechanisms of cometary origin, the decay processes suffered by comets, and the ways in which they can be observed from Earth and by spacecraft. (author)

Photochemistry of comets

International Nuclear Information System (INIS)

Huebner, W.F.

1985-01-01

The classification of comets, chemically rich mixtures of volatile materials and refractory grains, is described. The developments of coma and tails, and the composition and structure of coma, plasma tails, dust, and nucleus are examined. The differences between comets and planetary atmospheres are investigated. Three hypotheses on the origin of comets are proposed; one states that comets formed in the region of the giant planets, the second theory has the development of comets occuring in the outer parts of the solar nebula, and the third states that comets formed in a companion fragment of the nebula. The use of radar, photometric, spectral, and laboratory measurements for modeling comets is discussed. The physics and main photolytic and chemical reaction processes of a collision-dominated coma are analyzed; the influence of the solar wind on the coma is studied. A comparison of the model with observed data is presented; good correlation of data is observed. The features of Halley's Comet and other comets with distinctive characteristics are examined. Future comet exploration missions and the need to improve comet models are discussed. 31 references

Visually observing comets

CERN Document Server

Seargent, David A J

2017-01-01

In these days of computers and CCD cameras, visual comet observers can still contribute scientifically useful data with the help of this handy reference for use in the field. Comets are one of the principal areas for productive pro-amateur collaboration in astronomy, but finding comets requires a different approach than the observing of more predictable targets. Principally directed toward amateur astronomers who prefer visual observing or who are interested in discovering a new comet or visually monitoring the behavior of known comets, it includes all the advice needed to thrive as a comet observer. After presenting a brief overview of the nature of comets and how we came to the modern understanding of comets, this book details the various types of observations that can usefully be carried out at the eyepiece of a telescope. Subjects range from how to search for new comets to visually estimating the brightness of comets and the length and orientation of tails, in addition to what to look for in comet heads a...

The California All-sky Meteor Surveillance (CAMS) System

Science.gov (United States)

Gural, P. S.

2011-01-01

A unique next generation multi-camera, multi-site video meteor system is being developed and deployed in California to provide high accuracy orbits of simultaneously captured meteors. Included herein is a description of the goals, concept of operations, hardware, and software development progress. An appendix contains a meteor camera performance trade study made for video systems circa 2010.

OpenComet: An automated tool for comet assay image analysis

Directory of Open Access Journals (Sweden)

Benjamin M. Gyori

2014-01-01

Full Text Available Reactive species such as free radicals are constantly generated in vivo and DNA is the most important target of oxidative stress. Oxidative DNA damage is used as a predictive biomarker to monitor the risk of development of many diseases. The comet assay is widely used for measuring oxidative DNA damage at a single cell level. The analysis of comet assay output images, however, poses considerable challenges. Commercial software is costly and restrictive, while free software generally requires laborious manual tagging of cells. This paper presents OpenComet, an open-source software tool providing automated analysis of comet assay images. It uses a novel and robust method for finding comets based on geometric shape attributes and segmenting the comet heads through image intensity profile analysis. Due to automation, OpenComet is more accurate, less prone to human bias, and faster than manual analysis. A live analysis functionality also allows users to analyze images captured directly from a microscope. We have validated OpenComet on both alkaline and neutral comet assay images as well as sample images from existing software packages. Our results show that OpenComet achieves high accuracy with significantly reduced analysis time.

Creating cometary models using ancient Chinese data

Science.gov (United States)

Yeomans, D. K.

For more than two millennia, Chinese court astronomers maintained a rather comprehensive record of cometary sightings. Owing to the significance of comets as portents for the reigning emperor, early sky watchers from China (as well as their counterparts from Korea and Japan) carefully noted each cometary apparition for the purpose of astrological predictions. The dates and corresponding celestial locations and motions were usually recorded and in some cases, the colors, coma sizes, and tail lengths were also noted. These ancient observations represent the only source of information available for modeling the long-term behavior of periodic comets. For comets Halley and Swift-Tuttle, Chinese records have been identified as far back as 240 B.C. and 69 B.C. respectively and these data have been used to define their long-term motions. As a result, heliocentric and geocentric distances for each Chinese sighting of these two comets can be computed and estimates can be made for each comet's intrinsic brightness at various observed returns. Although the earliest identified apparition of comet Tempel-Tuttle is A.D. 1366, the associated Leonid meteor showers were noted back to at least A.D. 902. The Leonid meteor stream is young in the sense that outstanding meteor displays occur only near the time of the parent comet's perihelion passages. The ancient Chinese records of the Leonid meteor showers and storms have been used to map the particle distribution around the parent comet and this information was used to guide predictions for the 1998-1999 Leonid meteor showers.

IAU Meteor Data Center-the shower database: A status report

Science.gov (United States)

Jopek, Tadeusz Jan; Kaňuchová, Zuzana

2017-09-01

Currently, the meteor shower part of Meteor Data Center database includes: 112 established showers, 563 in the working list, among them 36 have the pro tempore status. The list of shower complexes contains 25 groups, 3 have established status and 1 has the pro tempore status. In the past three years, new meteor showers submitted to the MDC database were detected amongst the meteors observed by CAMS stations (Cameras for Allsky Meteor Surveillance), those included in the EDMOND (European viDeo MeteOr Network Database), those collected by the Japanese SonotaCo Network, recorded in the IMO (International Meteor Organization) database, observed by the Croatian Meteor Network and on the Southern Hemisphere by the SAAMER radar. At the XXIX General Assembly of the IAU in Honolulu, Hawaii in 2015, the names of 18 showers were officially accepted and moved to the list of established ones. Also, one shower already officially named (3/SIA the Southern iota Aquariids) was moved back to the working list of meteor showers. At the XXIX GA IAU the basic shower nomenclature rule was modified, the new formulation predicates ;The general rule is that a meteor shower (and a meteoroid stream) should be named after the constellation that contains the nearest star to the radiant point, using the possessive Latin form;. Over the last three years the MDC database was supplemented with the earlier published original data on meteor showers, which permitted verification of the correctness of the MDC data and extension of bibliographic information. Slowly but surely new database software options are implemented, and software bugs are corrected.

First results on video meteors from Crete, Greece

Science.gov (United States)

Maravelias, G.

2012-01-01

This work presents the first systematic video meteor observations from a, forthcoming permanent, station in Crete, Greece, operating as the first official node within the International Meteor Organization's Video Network. It consists of a Watec 902 H2 Ultimate camera equipped with a Panasonic WV-LA1208 (focal length 12mm, f/0.8) lens running MetRec. The system operated for 42 nights during 2011 (August 19-December 30, 2011) recording 1905 meteors. It is significantly more performant than a previous system used by the author during the Perseids 2010 (DMK camera 21AF04.AS by The Imaging Source, CCTV lens of focal length 2.8 mm, UFO Capture v2.22), which operated for 17 nights (August 4-22, 2010) recording 32 meteors. Differences - according to the author's experience - between the two softwares (MetRec, UFO Capture) are discussed along with a small guide to video meteor hardware.

Meteor head echoes - observations and models

Directory of Open Access Journals (Sweden)

A. Pellinen-Wannberg

2005-01-01

Full Text Available Meteor head echoes - instantaneous echoes moving with the velocities of the meteors - have been recorded since 1947. Despite many attempts, this phenomenon did not receive a comprehensive theory for over 4 decades. The High Power and Large Aperture (HPLA features, combined with present signal processing and data storage capabilities of incoherent scatter radars, may give an explanation for the old riddle. The meteoroid passage through the radar beam can be followed with simultaneous spatial-time resolution of about 100m-ms class. The current views of the meteor head echo process will be presented and discussed. These will be related to various EISCAT observations, such as dual-frequency target sizes, altitude distributions and vector velocities.

Charles Olivier and the rise of meteor science

CERN Document Server

Taibi, Richard

2017-01-01

This fascinating portrait of an amateur astronomy movement tells the story of how Charles Olivier recruited a hard-working cadre of citizen scientists to rehabilitate the study of meteors. By 1936, Olivier and members of his American Meteor Society had succeeded in disproving an erroneous idea about meteor showers. Using careful observations, they restored the public’s trust in predictions about periodic showers and renewed respect for meteor astronomy among professional astronomers in the United States. Charles Olivier and his society of observers who were passionate about watching for meteors in the night sky left a major impact on the field. In addition to describing Olivier’s career and describing his struggles with competitive colleagues in a hostile scientific climate, the author provides biographies of some of the scores of women and men of all ages who aided Olivier in making shower observations, from the Leonids and Perseids and others. Half of these amateur volunteers were from 13 to 25 years of...

Processing method and results of meteor shower radar observations

International Nuclear Information System (INIS)

Belkovich, O.I.; Suleimanov, N.I.; Tokhtasjev, V.S.

1987-01-01

Studies of meteor showers permit the solving of some principal problems of meteor astronomy: to obtain the structure of a stream in cross section and along its orbits; to retrace the evolution of particle orbits of the stream taking into account gravitational and nongravitational forces and to discover the orbital elements of its parent body; to find out the total mass of solid particles ejected from the parent body taking into account physical and chemical evolution of meteor bodies; and to use meteor streams as natural probes for investigation of the average characteristics of the meteor complex in the solar system. A simple and effective method of determining the flux density and mass exponent parameter was worked out. This method and its results are discussed

Chandra ACIS-S imaging spectroscopy of anomalously faint X-ray emission from Comet 103P/Hartley 2 during the EPOXI encounter

Science.gov (United States)

Lisse, C. M.; Christian, D. J.; Wolk, S. J.; Dennerl, K.; Bodewits, D.; Combi, M. R.; Lepri, S. T.; Zurbuchen, T. H.; Li, J. Y.; Dello-Russo, N.; Belton, M. J. S.; Knight, M. M.

2013-02-01

We present results from the Chandra X-ray Observatory's characterization of the X-ray emission from Comet 103P/Hartley 2, in support of NASA's Deep Impact Extended close flyby of the comet on 04 November 2010. The comet was observed 4 times for a total on target time of ˜60 ks between the 17th of October and 16th of November 2010, with two of the visits occurring during the EPOXI close approach on 04 November and 05 November 2010. X-ray emission from 103P was qualitatively similar to that observed for collisionally thin Comets 2P/Encke (Lisse, C.M. et al. [2005]. Astrophys. J. 635, 1329-1347) and 9P/Tempel 1 (Lisse, C.M. et al. [2007]. Icarus 190, 391-405). Emission morphology offset sunward but asymmetrical from the nucleus and emission lines produced by charge exchange between highly stripped C, N, and O solar wind minor ions and coma neutral gas species were found. The comet was very under-luminous in the X-ray at all times, representing the 3rd faintest comet ever detected (LX = 1.1 ± 0.3 × 1014 erg s-1). The coma was collisionally thin to the solar wind at all times, allowing solar wind ions to flow into the inner coma and interact with the densest neutral coma gas. Localization of the X-ray emission in the regions of the major rotating gas jets was observed, consistent with the major source of cometary neutral gas species being icy coma dust particles. Variable spectral features due to changing solar wind flux densities and charge states were also seen. Modeling of the Chandra observations from the first three visits using observed gas production rates and ACE solar wind ion fluxes with a charge exchange mechanism for the emission is consistent with the temporal and spectral behavior expected for a slow, hot wind typical of low latitude emission from the solar corona interacting with the comet's neutral coma. The X-ray emission during the 4th visit on 16 November 2010 is similar to the unusual behavior seen for Comet 17P/Holmes in 2007 (Christian, D.J. et

EMISSION LINES BETWEEN 1 AND 2 keV IN COMETARY X-RAY SPECTRA

Energy Technology Data Exchange (ETDEWEB)

Ewing, Ian; Christian, Damian J. [Department of Physics and Astronomy, California State University, 18111 Nordhoff Street, Northridge, CA 91330 (United States); Bodewits, Dennis [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States); Dennerl, Konrad [Max-Planck-Institut fuer extraterrestrische Physik, Postfach 1312, D-85741 Garching Germany (Germany); Lisse, Carey M. [Planetary Exploration Group, Space Department, Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Rd, Laurel, MD 20723 (United States); Wolk, Scott J., E-mail: ian.ewing.794@my.csun.edu, E-mail: daman.christian@csun.edu [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

2013-01-20

We present the detection of new cometary X-ray emission lines in the 1.0-2.0 keV range using a sample of comets observed with the Chandra X-Ray Observatory and ACIS spectrometer. We have selected five comets from the Chandra sample with good signal-to-noise spectra. The surveyed comets are C/1999 S4 (LINEAR), C/1999 T1 (McNaught-Hartley), 153P/2002 (Ikeya-Zhang), 2P/2003 (Encke), and C/2008 8P (Tuttle). We modeled the spectra with an extended version of our solar wind charge exchange (SWCX) emission model. Above 1 keV, we find Ikeya-Zhang to have strong emission lines at 1340 and 1850 eV which we identify as being created by SWCX lines of Mg XI and Si XIII, respectively, and weaker emission lines at 1470, 1600, and 1950 eV formed by SWCX of Mg XII, Mg XI, and Si XIV, respectively. The Mg XI and XII and Si XIII and XIV lines are detected at a significant level for the other comets in our sample (LS4, MH, Encke, 8P), and these lines promise additional diagnostics to be included in SWCX models. The silicon lines in the 1700-2000 eV range are detected for all comets, but with the rising background and decreasing cometary emission, we caution that these detections need further confirmation with higher resolution instruments.

Radar meteors range distribution model. I. Theory

Czech Academy of Sciences Publication Activity Database

Pecinová, Drahomíra; Pecina, Petr

2007-01-01

Roč. 37, č. 2 (2007), s. 83-106 ISSN 1335-1842 R&D Projects: GA ČR GA205/03/1405 Institutional research plan: CEZ:AV0Z10030501 Keywords : physics of meteors * radar meteors * range distribution Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics

Grain coma production by comet nuclei during their vaporization, under solar radiation action and through collision with meteoroids

International Nuclear Information System (INIS)

Matsuura, O.T.

1976-07-01

For a model of compact cometary nucleus made up of hydrates mixed or unmixed with meteoric dust, some observable properties for long period comets are derived. The dust production is first considered to be due only to the vaporization of the nucleus under the action of the solar radiation. Then, taking into account the probability for the occurrence of collision of a nucleus with a meteoroid, a production due to a collisional process is studied. Using previously catalogued observational data, an evaluation of the main results coming from the present model is carried out. (Author) [pt

Green corona, geomagnetic activity and radar meteor rates

International Nuclear Information System (INIS)

Prikryl, P.

1979-01-01

The short-term dependence of radar meteor rates on geomagnetic activity and/or central meridian passage (CMP) of bright or faint green corona regions is studied. A superimposed-epoch analysis was applied to radar meteor observations from the Ottawa patrol radar (Springhill, Ont.) and Ksub(p)-indices of geomagnetic activity for the period 1963 to 1967. During the minimum of solar activity (1963 to 1965) the CMP of bright coronal regions was followed by the maximum in the daily rates of persistent meteor echoes (>=4s), and the minimum in the daily sums of Ksub(p)-indices whereas the minimum or the maximum, respectively, occurs after the CMP of faint coronal regions. The time delay between the CMP of coronal structures and the corresponding maxima or minima is found to be 3 to 4 days. However, for the period immediately after the minimum of solar activity (1966 to 1967) the above correlation with the green corona is void both for the geomagnetic activity and radar meteor rates. An inverse correlation was found between the radar meteor rates and the geomagnetic activity irrespective of the solar activity. The observed effect can be ascribed to the solar-wind-induced ''geomagnetic'' heating of the upper atmosphere and to the subsequent change in the density gradient in the meteor zone. (author)

``Hiss, clicks and pops'' - The enigmatic sounds of meteors

Science.gov (United States)

Finnegan, J. A.

2015-04-01

The improbability of sounds heard simultaneously with meteors allows the phenomenon to remain on the margins of scientific interest and research. This is unjustified, since these audibly perceived electric field effects indicate complex, inconsistent and still unresolved electric-magnetic coupling and charge dynamics; interacting between the meteor; the ionosphere and mesosphere; stratosphere; troposphere and the surface of the earth. This paper reviews meteor acoustic effects, presents illustrating reports and hypotheses and includes a summary of similar and additional phenomena observed during the 2013 February 15 asteroid fragment disintegration above the Russian district of Chelyabinsk. An augmenting theory involving near ground, non uniform electric field production of Ozone, as a stimulated geo-physical phenomenon to explain some hissing `meteor sounds' is suggested in section 2.2. Unlike previous theories, electric-magnetic field fluctuation rates are not required to occur in the audio frequency range for this process to acoustically emit hissing and intermittent impulsive sounds; removing the requirements of direct conversion, passive human transduction or excited, localised acoustic `emitters'. Links to the Armagh Observatory All-sky meteor cameras, electrophonic meteor research and full construction plans for an extremely low frequency (ELF) receiver are also included.

Mystery of comets

International Nuclear Information System (INIS)

Whipple, F.L.

1985-01-01

An account is given of the growth of human understanding of comets with emphasis initially placed on theories developed before the twentieth century and subsequently on information regarding the nature of comets, their origin and possible relation to life on earth. Special consideration is given to a description of how the author arrived at his own model of the origin and nature of comets, the dirty snowball theory. The significance of comets (i.e. the hazards they may represent) is assessed and space missions to Halley's comet together with the first landing on a comet (tentatively planned for 1995) are described. It is noted that this growth of cometary understanding is presented as an integral part of the growth of science and technology. 14 references

A surprise southern hemisphere meteor shower on New-Year's Eve 2015: the Volantids (IAU#758, VOL)

Science.gov (United States)

Jenniskens, P.; Baggaley, J.; Crumpton, I.; Aldous, P.; Gural, P. S.; Samuels, D.; Albers, J.; Soja, R.

2016-04-01

A new 32-camera CAMS network in New Zealand, spread over two stations on South Island, has detected a high southern declination shower that was active on New Year's Eve, 2015 December 31. During the observing interval from 09h12m - 15h45m UT, 21 out of 59 detected meteors radiated from the constellation of Volans, the flying fish, with a geocentric radiant at RA = 122.9 deg +- 4.7 deg, Dec = -71.9 deg +- 1.9 deg, and speed V_g = 28.4 +- 1.5 km/s. The new year arrived in New Zealand at 11h00m UT. Two more were detected the next night. No activity from this shower was observed the year prior. The meteoroids move in a 48 deg-inclined Jupiter-family comet orbit. The parent body has not yet been identified.

Crowdsourcing, the great meteor storm of 1833, and the founding of meteor science.

Science.gov (United States)

Littmann, Mark; Suomela, Todd

2014-06-01

Yale science professor Denison Olmsted used crowdsourcing to gather observations from across the United States of the unexpected deluge of meteors on 13 November 1833--more than 72,000/h. He used these observations (and newspaper accounts and correspondence from scientists) to make a commendably accurate interpretation of the meteor storm, overturning 2100 years of erroneous teachings about shooting stars and establishing meteor science as a new branch of astronomy. Olmsted's success was substantially based on his use of newspapers and their practice of news pooling to solicit observations from throughout the country by lay and expert observers professionally unaffiliated with Yale College and him. In today's parlance, Olmsted was a remarkably successful early practitioner of scientific crowdsourcing, also known as citizen science. He may have been the first to use mass media for crowdsourcing in science. He pioneered many of the citizen-science crowdsourcing practices that are still in use today: an open call for citizen participation, a clearly defined task, a large geographical distribution for gathering data and a rapid response to opportunistic events. Olmsted's achievement is not just that he used crowdsourcing in 1833 but that crowdsourcing helped him to advance science significantly. Copyright © 2014 Elsevier Ltd. All rights reserved.

Physics of comets

CERN Document Server

Krishna Swamy, K S

1997-01-01

The study of Comet Halley in 1986 was a tremendous success for cometary science. In March of that year, six spacecrafts passed through Comet Halley as close as 600 km from the nucleus and made the in situ measurements of various kinds. These space missions to Comet Halley and that of the ICE spacecraft to Comet Giacobini-Zinner combined with studies, both ground-based and above the atmosphere, have increased our knowledge of cometary science in a dramatic way.This new edition of Physics of Comets incorporates these new and exciting findings. The emphasis of the book is on the physical processe

Linear feature detection algorithm for astronomical surveys - II. Defocusing effects on meteor tracks

Science.gov (United States)

Bektešević, Dino; Vinković, Dejan; Rasmussen, Andrew; Ivezić, Željko

2018-03-01

Given the current limited knowledge of meteor plasma micro-physics and its interaction with the surrounding atmosphere and ionosphere, meteors are a highly interesting observational target for high-resolution wide-field astronomical surveys. Such surveys are capable of resolving the physical size of meteor plasma heads, but they produce large volumes of images that need to be automatically inspected for possible existence of long linear features produced by meteors. Here, we show how big aperture sky survey telescopes detect meteors as defocused tracks with a central brightness depression. We derive an analytic expression for a defocused point source meteor track and use it to calculate brightness profiles of meteors modelled as uniform brightness discs. We apply our modelling to meteor images as seen by the Sloan Digital Sky Survey and Large Synoptic Survey Telescope telescopes. The expression is validated by Monte Carlo ray-tracing simulations of photons travelling through the atmosphere and the Large Synoptic Survey Telescope telescope optics. We show that estimates of the meteor distance and size can be extracted from the measured full width at half-maximum and the strength of the central dip in the observed brightness profile. However, this extraction becomes difficult when the defocused meteor track is distorted by the atmospheric seeing or contaminated by a long-lasting glowing meteor trail. The full width at half-maximum of satellite tracks is distinctly narrower than meteor values, which enables removal of a possible confusion between satellites and meteors.

Radar meteors range distribution model. IV. Ionization coefficient

Czech Academy of Sciences Publication Activity Database

Pecinová, Drahomíra; Pecina, Petr

2008-01-01

Roč. 38, č. 1 (2008), s. 12-20 ISSN 1335-1842 R&D Projects: GA ČR GA205/03/1405 Institutional research plan: CEZ:AV0Z10030501 Keywords : physics of meteors * radar meteors * range distribution Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics

Comets and their origin the tools to decipher a comet

CERN Document Server

Meierhenrich, Uwe

2014-01-01

Divided into two parts, the first four chapters of Comets and their Origin refer to comets and their formation in general, describing cometary missions, comet remote observations, astrochemistry, artificial comets, and the chirality phenomenon.The second part covers the cometary Rosetta mission, its launch, journey, scientific objectives, and instrumentations, as well as the landing scenario on a cometary nucleus. Along the way, the author presents general questions concerning the origin of terrestrial water and the molecular beginnings of lifeon Earth, as well as how the instruments used on

Detection and Characterisation of Meteors as a Big Data Citizen Science project

Science.gov (United States)

Gritsevich, M.

2017-12-01

Out of a total around 50,000 meteorites currently known to science, the atmospheric passage was recorded instrumentally in only 30 cases with the potential to derive their atmospheric trajectories and pre-impact heliocentric orbits. Similarly, while the observations of meteors, add thousands of new entries per month to existing databases, it is extremely rare they lead to meteorite recovery. Meteor studies thus represent an excellent example of the Big Data citizen science project, where progress in the field largely depends on the prompt identification and characterisation of meteor events as well as on extensive and valuable contributions by amateur observers. Over the last couple of decades technological advancements in observational techniques have yielded drastic improvements in the quality, quantity and diversity of meteor data, while even more ambitious instruments are about to become operational. This empowers meteor science to boost its experimental and theoretical horizons and seek more advanced scientific goals. We review some of the developments that push meteor science into the Big Data era that requires more complex methodological approaches through interdisciplinary collaborations with other branches of physics and computer science. We argue that meteor science should become an integral part of large surveys in astronomy, aeronomy and space physics, and tackle the complexity of micro-physics of meteor plasma and its interaction with the atmosphere. The recent increased interest in meteor science triggered by the Chelyabinsk fireball helps in building the case for technologically and logistically more ambitious meteor projects. This requires developing new methodological approaches in meteor research, with Big Data science and close collaboration between citizen science, geoscience and astronomy as critical elements. We discuss possibilities for improvements and promote an opportunity for collaboration in meteor science within the currently

A Numerical Model to Assess Soil Fluxes from Meteoric 10Be Data

Science.gov (United States)

Campforts, B.; Govers, G.; Vanacker, V.; Vanderborght, J.; Smolders, E.; Baken, S.

2015-12-01

Meteoric 10Be may be mobile in the soil system. The latter hampers a direct translation of meteoric 10Be inventories into spatial variations in erosion and deposition rates. Here, we present a spatially explicit 2D model that allows us to simulate the behaviour of meteoric 10Be in the soil system. The Be2D model is then used to analyse the potential impact of human-accelerated soil fluxes on meteoric 10Be inventories. The model consists of two parts. A first component deals with advective and diffusive mobility of meteoric 10Be within the soil profile including particle migration, chemical leaching and bioturbation, whereas a second component describes lateral soil (and meteoric 10Be) fluxes over the hillslope. Soil depth is calculated dynamically, accounting for soil production through weathering and lateral soil fluxes from creep, water and tillage erosion. Model simulations show that meteoric 10Be inventories can indeed be related to erosion and deposition, across a wide range of geomorphological and pedological settings. However, quantification of the effects of vertical mobility is essential for a correct interpretation of the observed spatial patterns in 10Be data. Moreover, our simulations suggest that meteoric 10Be can be used as a tracer to unravel human impact on soil fluxes when soils have a high retention capacity for meteoric meteoric 10Be. Application of the Be2D model to existing data sets shows that model parameters can reliably be constrained, resulting in a good agreement between simulated and observed meteoric 10Be concentrations and inventories. This confirms the suitability of the Be2D model as a robust tool to underpin quantitative interpretations of spatial variability in meteoric 10Be data for eroding landscapes.

Mesospheric sodium over Gadanki during Geminid meteor shower 2007

Science.gov (United States)

Lokanadham, B.; Rakesh Chandra, N.; Bhaskara Rao, S. Vijaya; Raghunath, K.; Yellaiah, G.

Resonance LIDAR system at Gadanki has been used for observing the mesospheric sodium during the night of 12-13 Dec 2007 when the peak activity of Geminid meteor shower occurred. Geminid meteor shower is observed along with the co-located MST radar in the altitude range 80-110 km. Sodium density profiles have been obtained with a vertical resolution of 300 m and a temporal resolution of 120 s with sodium resonance scattering LIDAR system. The sodium layers were found to exist in the altitude range 90-100 km. The enhanced Geminid meteor rates were recorded with the co-located MST radar in the same altitude range. The sodium concentration in the atmospheric altitude of ~93 km is estimated to be 2000 per cc where the meteoric concentration of Geminid is maximum and reduced to around 800 on the non activity of Geminid. These observations showed that the sodium levels in the E-region are found to be increasing during meteor shower nights at least by a factor of two.

Comet Giacobini-Zinner - a normal comet?

International Nuclear Information System (INIS)

Cochran, A.L.; Barker, E.S.

1987-01-01

Observations of Comet Giacobini-Zinner were obtained during its 1985 apparition using an IDS spectrograph at McDonald Observatory. Column densities and production rates were computed. The production rates were compared to observations of other normal comets. Giacobini-Zinner is shown to be depleted in C2 and C3 relative to CN. These production rates are down by a factor of 5. 12 references

Meteor Beliefs Project: some meteoric imagery in the works of William Shakespeare

Science.gov (United States)

McBeath, A.; Gheorghe, A. D.

2003-08-01

Passages from three of William Shakespeare's plays are presented, illustrating some of the beliefs in meteors in 16th-17th century England. They also reflect earlier beliefs and information which it is known Shakespeare drew on in constructing his works.

Advances in Meteoroid and Meteor Science

CERN Document Server

Trigo-Rodríguez, J. M; Llorca, J; Janches, D

2008-01-01

This volume is a compilation of articles that summarize the most recent results in meteor, meteoroid and related fields presented at the Meteoroids 2007 conference held at the impressive CosmoCaixa Science Museum in Barcelona, Spain. The conference took place between the 11th and the 15th of June and was organized by the Institute of Space Sciences (Consejo Superior de Investigaciones Científicas, CSIC) and the Institut d'Estudis Espacials de Catalunya (IEEC). Researchers in meteor science and supporting fields representing more than 20 countries participated at this international conference. The papers contained in this volume underwent the rigorous refereeing process, and they are good examples of the continuous progress being made in this research field. Technological advances in meteor and metoroid detection, the ever-increasing sophistication of computer modeling, and the proliferation of autonomous monitoring stations continue to create new niches for exciting research on meteoroids and their parent bo...

Origin and development of comets

International Nuclear Information System (INIS)

Kresak, L.

1989-01-01

The comets are the most primitive and probably also the oldest members of the solar system. Comet cores are brittle bodies of an irregular shape and of a size of 1 to 10 km whose main component is ice. Around 130 comets move along short-period paths whose aphelia are concentrated in the area of Jupiter. They are in the last stage of development. About 20 comets have periods of 20 to 200 years and feature higher motion stability. Roughly 180 comets have elliptical orbits of a period exceeding 200 years, 200 comets have parabolic and 120 comets have hyperbolic orbits. The most distant comets form the Oort cloud around the solar system consisting of about one billion comets. Comets originated roughly 4.6 thousand million years ago together with planets, probably inside the Oort cloud. (M.D.). 11 figs

METEOR v1.0 - Design and structure of the software package

International Nuclear Information System (INIS)

Palomo, E.

1994-01-01

This script describes the structure and the separated modules of the software package METEOR for the statistical analysis of meteorological data series. It contains a systematic description of the subroutines of METEOR and, also, of the required shape for input and output files. The original version of METEOR have been developed by Ph.D. Elena Palomo, CIEMAT-IER, GIMASE. It is built by linking programs and routines written in FORTRAN 77 and it adds thc graphical capabilities of GNUPLOT. The shape of this toolbox was designed following the criteria of modularity, flexibility and agility criteria. All the input, output and analysis options are structured in three main menus: i) the first is aimed to evaluate the quality of the data set; ii) the second is aimed for pre-processing of the data; and iii) the third is aimed towards the statistical analyses and for creating the graphical outputs. Actually the information about METEOR is constituted by three documents written in spanish: 1) METEOR v1.0: User's guide; 2) METEOR v1.0: A usage example; 3) METEOR v 1.0: Design and structure of the software package. (Author)

The effect of recombination and attachment on meteor radar diffusion coefficient profiles

Science.gov (United States)

Lee, C. S.; Younger, J. P.; Reid, I. M.; Kim, Y. H.; Kim, J.-H.

2013-04-01

Estimates of the ambipolar diffusion coefficient producedusing meteor radar echo decay times display an increasing trend below 80-85 km, which is inconsistent with a diffusion-only theory of the evolution of meteor trails. Data from the 33 MHz meteor radar at King Sejong Station, Antarctica, have been compared with observations from the Aura Earth Observing System Microwave Limb Sounder satellite instrument. It has been found that the height at which the diffusion coefficient gradient reverses follows the height of a constant neutral atmospheric density surface. Numerical simulations of meteor trail diffusion including dissociative recombination with atmospheric ions and three-body attachment of free electrons to neutral molecules indicate that three-body attachment is responsible for the distortion of meteor radar diffusion coefficient profiles at heights below 90 km, including the gradient reversal below 80-85 km. Further investigation has revealed that meteor trails with low initial electron line density produce decay times more consistent with a diffusion-only model of meteor trail evolution.

Physics-Based Modeling of Meteor Entry and Breakup

Science.gov (United States)

Prabhu, Dinesh K.; Agrawal, Parul; Allen, Gary A., Jr.; Bauschlicher, Charles W., Jr.; Brandis, Aaron M.; Chen, Yih-Kang; Jaffe, Richard L.; Palmer, Grant E.; Saunders, David A.; Stern, Eric C.;

The EISCAT meteor code

Directory of Open Access Journals (Sweden)

G. Wannberg

2008-08-01

Full Text Available The EISCAT UHF system has the unique capability to determine meteor vector velocities from the head echo Doppler shifts measured at the three sites. Since even meteors spending a very short time in the common volume produce analysable events, the technique lends itself ideally to mapping the orbits of meteors arriving from arbitrary directions over most of the upper hemisphere.

A radar mode optimised for this application was developed in 2001/2002. A specially selected low-sidelobe 32-bit pseudo-random binary sequence is used to binary phase shift key (BPSK the transmitted carrier. The baud-length is 2.4 μs and the receiver bandwidth is 1.6 MHz to accommodate both the resulting modulation bandwidth and the target Doppler shift. Sampling is at 0.6 μs, corresponding to 90-m range resolution. Target range and Doppler velocity are extracted from the raw data in a multi-step matched-filter procedure. For strong (SNR>5 events the Doppler velocity standard deviation is 100–150 m/s. The effective range resolution is about 30 m, allowing very accurate time-of-flight velocity estimates. On average, Doppler and time-of-flight (TOF velocities agree to within about one part in 10³. Two or more targets simultaneously present in the beam can be resolved down to a range separation <300 m as long as their Doppler shifts differ by more than a few km/s.

The EISCAT meteor code

Directory of Open Access Journals (Sweden)

G. Wannberg

2008-08-01

Full Text Available The EISCAT UHF system has the unique capability to determine meteor vector velocities from the head echo Doppler shifts measured at the three sites. Since even meteors spending a very short time in the common volume produce analysable events, the technique lends itself ideally to mapping the orbits of meteors arriving from arbitrary directions over most of the upper hemisphere. A radar mode optimised for this application was developed in 2001/2002. A specially selected low-sidelobe 32-bit pseudo-random binary sequence is used to binary phase shift key (BPSK the transmitted carrier. The baud-length is 2.4 μs and the receiver bandwidth is 1.6 MHz to accommodate both the resulting modulation bandwidth and the target Doppler shift. Sampling is at 0.6 μs, corresponding to 90-m range resolution. Target range and Doppler velocity are extracted from the raw data in a multi-step matched-filter procedure. For strong (SNR>5 events the Doppler velocity standard deviation is 100–150 m/s. The effective range resolution is about 30 m, allowing very accurate time-of-flight velocity estimates. On average, Doppler and time-of-flight (TOF velocities agree to within about one part in 103. Two or more targets simultaneously present in the beam can be resolved down to a range separation <300 m as long as their Doppler shifts differ by more than a few km/s.

Spectrophotometry of 25 comets - Post-Halley updates for 17 comets plus new observations for eight additional comets

Science.gov (United States)

Newburn, Ray L., Jr.; Spinrad, Hyron

1989-01-01

The best possible production figures within the current post-Halley framework and available observations are given for H2O, O(1D), CN, C3, C2 and dust in 25 comets. Of these, the three objects with the smallest mixing ratios of all minor species have moderate to little or no dust and appear 'old'. Comets with large amounts of CN are very dusty, and there is a clear correlation of CN with dust, although comets with little or no dust still have some CN. Thus, CN appears to have at least two sources, dust and one or more parent gases. Also, the C2/CN production ratio changes continuously with heliocentric distance in every comet considered, suggesting that C2 production may be a function of coma density as well as parental abundance. Dust production ranges from essentially zero in Comet Sugano-Saigusa-Fujikawa up to 67,000 kg/s for Halley on March 14, 1986.

Spectrophotometry of 25 comets - Post-Halley updates for 17 comets plus new observations for eight additional comets

International Nuclear Information System (INIS)

Newburn, R.L. Jr.; Spinrad, H.

1989-01-01

The best possible production figures within the current post-Halley framework and available observations are given for H2O, O(1D), CN, C3, C2 and dust in 25 comets. Of these, the three objects with the smallest mixing ratios of all minor species have moderate to little or no dust and appear 'old'. Comets with large amounts of CN are very dusty, and there is a clear correlation of CN with dust, although comets with little or no dust still have some CN. Thus, CN appears to have at least two sources, dust and one or more parent gases. Also, the C2/CN production ratio changes continuously with heliocentric distance in every comet considered, suggesting that C2 production may be a function of coma density as well as parental abundance. Dust production ranges from essentially zero in Comet Sugano-Saigusa-Fujikawa up to 67,000 kg/s for Halley on March 14, 1986. 61 references

Kinematic Characteristics of Meteor Showers by Results of the Combined Radio-Television Observations

Science.gov (United States)

Narziev, Mirhusen

2016-07-01

One of the most important tasks of meteor astronomy is the study of the distribution of meteoroid matter in the solar system. The most important component to address this issue presents the results of measurements of the velocities, radiants, and orbits of both showers and sporadic meteors. Radiant's and orbits of meteors for different sets of data obtained as a result of photographic, television, electro-optical, video, Fireball Network and radar observations have been measured repeatedly. However, radiants, velocities and orbits of shower meteors based on the results of combined radar-optical observations have not been sufficiently studied. In this paper, we present a methods for computing the radiants, velocities, and orbits of the combined radar-TV meteor observations carried out at HisAO in 1978-1980. As a result of the two-year cycle of simultaneous TV-radar observations 57 simultaneous meteors have been identified. Analysis of the TV images has shown that some meteor trails appeared as dashed lines. Among the simultaneous meteors of d-Aquariids 10 produced such dashed images, and among the Perseids there were only 7. Using a known method, for such fragmented images of simultaneous meteors - together with the measured radar distance, trace length, and time interval between the segments - allowed to determine meteor velocity using combined method. In addition, velocity of the same meteors was measured using diffraction and radar range-time methods based on the results of radar observation. It has been determined that the mean values of meteoroid velocity based on the combined radar-TV observations are greater in 1 ÷ 3 km / c than the averaged velocity values measured using only radar methods. Orbits of the simultaneously observed meteors with segmented photographic images were calculated on the basis of the average velocity observed using the combined radar-TV method. The measured results of radiants velocities and orbital elements of individual meteors

Numerical simulations of comets - predictions for Comet Giacobini-Zinner

International Nuclear Information System (INIS)

Fedder, J.A.; Lyon, J.G.; Giuliani, J.L. Jr.

1986-01-01

Simulations of Comet Giacobini-Zinner's interaction with solar wind are described and results are presented. The simulations are carried out via the numerical solution of the ideal MHD equations as an initial value problem in a uniform solar wind. The calculations are performed on a Cartesian mesh centered at the comet. Results reveal that the first significant modifications of the solar wind along the ISEE/ICE trajectory will occur 100,000 km from the solar wind comet axis. 6 references

Mission to the comets

International Nuclear Information System (INIS)

Hughes, D.

1980-01-01

The plans of space agencies in the United States and Europe for an exploratory comet mission including a one year rendezvous with comet Temple-2 and a fast fly-by of comet Halley are discussed. The mission provides an opportunity to make comparative measurements on the two different types of comets and also satisfies the three major scientific objectives of cometary missions namely: (1) To determine the chemical nature and the physical structure of cometary nuclei, and the changes that occur with time and orbital position. (2) To study the chemical and physical nature of the atmospheres and ionospheres of comets, the processes that occur in them, and their development with time and orbital position. (3) To determine the nature of the tails of comets and the processes by which they are formed, and to characterise the interaction of comets with solar wind. (UK)

CONTENUTO DI URANIO E TORIO NELLE METEORITI

Directory of Open Access Journals (Sweden)

M. SANTANGELO

1955-06-01

Full Text Available Molti ricercatori in questi ultimi anni si sono interessati al problema
della composizione delle meteoriti; dai risultati sperimentali si
è cercato trarre elementi circa la genesi di questi materiali, questione
ancora aperta, ed avere informazioni sui processi chimici e termodinamici
cui le meteoriti furono soggette prima della loro caduta sulla
terra.
Uno degli aspetti del problema è quello dell'abbondanza percentuale
degli elementi chimici e della loro composizione isotopica nella
materia meteorica dei diversi tipi : ciò perché esso è connesso con
quello piii generale dell'origine e distribuzione degli elementi nel cosmo
e nella terra, nonché con quello dell'età delle meteoriti (l .
In un recente lavoro Urey e collaboratori (-, esaminando un gran
numero di analisi chimiche effettuate su questi materiali, sono pervenuti
alla formulazione di alcuni criteri di classificazione in base alla
percentuale dei componenti più abbondanti ed alla presenza o meno
di disomogeneità strutturali nella massa fondamentale. Fra gli elementi
meno abbondanti presentano particolare interesse quelli delle due famiglie
radioattive naturali Torio e Uranio; le loro concentrazioni sono
state determinate per alcune meteoriti siliciche (stonv ineteorites e
per qualcuna ferrica (iron meteorites

Diurnal and annual variations of meteor rates at the arctic circle

Directory of Open Access Journals (Sweden)

W. Singer

2004-01-01

Full Text Available Meteors are an important source for (a the metal atoms of the upper atmosphere metal layers and (b for condensation nuclei, the existence of which are a prerequisite for the formation of noctilucent cloud particles in the polar mesopause region. For a better understanding of these phenomena, it would be helpful to know accurately the annual and diurnal variations of meteor rates. So far, these rates have been little studied at polar latitudes. Therefore we have used the 33 MHz meteor radar of the ALOMAR observatory at 69° N to measure the meteor rates at this location for two full annual cycles. This site, being within 3° of the Arctic circle, offers in addition an interesting capability: The axis of its antenna field points (almost towards the North ecliptic pole once each day of the year. In this particular viewing direction, the radar monitors the meteoroid influx from (almost the entire ecliptic Northern hemisphere. We report on the observed diurnal variations (averaged over one month of meteor rates and their significant alterations throughout the year. The ratio of maximum over minimum meteor rates throughout one diurnal cycle is in January and February about 5, from April through December 2.3±0.3. If compared with similar measurements at mid-latitudes, our expectation, that the amplitude of the diurnal variation is to decrease towards the North pole, is not really borne out. Observations with the antenna axis pointing towards the North ecliptic pole showed that the rate of deposition of meteoric dust is substantially larger during the Arctic NLC season than the annual mean deposition rate. The daylight meteor showers of the Arietids, Zeta Perseids, and Beta Taurids supposedly contribute considerably to the June maximum of meteor rates. We note, though, that with the radar antenna pointing as described above, all three meteor radiants are close to the local horizon but all three radiants were detected.

Ammonia abundances in comets

Science.gov (United States)

Wyckoff, S.; Tegler, S.; Engel, L.

The emission band strengths of the NH2 bands of Comets Halley, Hartley-Good, Thiele, and Borrelly were measured to determine the NH2 column densities for the comets. Production rates obtained using the Haser and vectorial models are in agreement within the observational errors, suggesting that a simple two-step decay model may be used to approximate the NH2 distribution in a comet's coma. Ammonia-to-water abundance ratios from 0.01 to 0.4 percent were found for the four comets. The ratio in Comet Halley is found to be Q(NH3)/Q(H2O) = 0.002 + or - 0.001. No significant difference in the ammonia abundance was found before or after perihelion in Comet Halley.

Photometry and Polarimetry of Comet 67P/Churyumov-Gerasimenko at the 6-m Telescope of the Special Astrophysical Observatory (SAO RAS)

Science.gov (United States)

Kolokolova, L.; Ivanova, O.; Rosenbush, V.; Kiselev, N.; Afanasiev, V.

2016-12-01

We report observations of comet 67P/Churyumov-Gerasimenko, performed by the co-authors from MAO NASU and SAO RAS at the SAO 6-m telescope with a focal reducer SCORPIO-2 used in the modes of broad-band photometry and of imaging polarimetry. Three sets of post-perihelion observations were made in November and December of 2015 and in April of 2016 covering heliocentric distance of the comet from 1.61 au to 2.72 au and phase angle from 33.2° to 10.4°. Imaging photometry of the comet in the g-sdss (465/65 nm) and r-sdss (620/60 nm) filters allowed us to derive maps of intensity and color. The tail and two bright persistent jets, observed from November 2015 to April 2016, had colors redder than the rest of the coma, indicating a difference in the dust particles. Color of the coma becomes bluer with increasing distance from the nucleus. Linear polarization maps and scans through the coma revealed that in April, at phase angle about 10°, the polarization varied from -0.6% in the near-nucleus area to -4% in the outer coma. In November and December, the polarization near the nucleus was 8%, dropped sharply to 2% at the distance 5000 km, and then gradually increased to >8% at 40000 km. The radial variations of polarization suggest an evolution of the dust properties. We suppose that they reflect decreasing particle size. This assumption is consistent with the laboratory studies by Hadamcik et al. (JQSRT, 2009), which showed that with decreasing size of particles from hundreds of micron (the size of dominating particles measured by the Rosetta dust instruments in the vicinity of the nucleus) to dozens of microns, their polarization decreases, whereas at smaller particle sizes polarization increases with decreasing size. Changing the color to a more blue with the nucleocentric distance is also consistent with decreasing particle size. Note that Jewitt (ApJ, 2004) observed similar dependences of polarization and color for comet 2P/Encke that may have a similar explanation.

American Meteor Society Fireball reporting system and mobile application

Science.gov (United States)

Hankey, M.

2014-07-01

The American Meteor Society (AMS) founded in 1911 pioneered the visual study of meteors and has collected data relating to meteor observations and bright fireballs for over 100 years. In December 2010, the online fireball reporting system was upgraded to an interactive application that utilizes Google Maps and other programmatic methods to pinpoint the observer's location, azimuth and elevation values with a high degree of precision. The AMS has collected 10s of 1000s of witness reports relating to 100s of events each year since the new application was released. Three dimensional triangulation methods that average the data collected from witnesses have been developed that can determine the start and end points of the meteor with an accuracy of web application. Users can file a new report directly on the phone or update the values submitted through a web report. After web users complete their fireball report online, they are prompted to download the app and update their observation with the more precise data provided by the sensors in the mobile device. The mobile app also provides an accurate means for the witness to report the elapsed time of the fireball. To log this value, the user drags the device across the sky where they saw the fireball. This process is designed to require no button click or user interaction to start and stop the time recording. A count down initiates the process and once the user's phone crosses the plane of azimuth for the end point of the fireball the velocity timer automatically stops. Users are asked to log the recording three times in an effort to minimize error. The three values are then averaged into a final score. Once enough witnesses have filed reports, elapsed time data collected from the mobile phone can be used to determine the velocity of the fireball. With the velocity, trajectory solution and RA/DEC the AMS can plot orbital estimates for significant fireball events reported to the society. Our hope is that overtime this

All-sky Meteor Orbit System AMOS and preliminary analysis of three unusual meteor showers

Czech Academy of Sciences Publication Activity Database

Tóth, J.; Kornoš, L.; Zigo, P.; Gajdoš, Š.; Kalmančok, D.; Világi, J.; Šimon, J.; Vereš, P.; Šilha, J.; Buček, M.; Galád, Adrián; Rusňák, P.; Hrábek, P.; Ďuriš, F.; Rudawska, R.

2015-01-01

Roč. 118, December (2015), s. 102-106 ISSN 0032-0633 Institutional support: RVO:67985815 Keywords : meteor * meteorite * meteoroid streams Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 1.942, year: 2015

Character of meteoric leaks in the salt mines of south Louisiana, U.S.A.

Science.gov (United States)

Kumar, Madhurendu B.

1983-10-01

The brine leaks of salt mines of south Louisiana are of two genetic categories: meteoric and non-meteoric (connate/formation water type), as established essentially on the basis of oxygen- and hydrogen-isotope analyses. This paper highlights the hydrochemical aspects of those mine leaks and develops simple non-isotopic criteria to differentiate the meteoric leaks from the non-meteoric. The meteoric leaks of the salt mines generally occur down to a depth level of 214 m (700 ft.) (below mean sea level) below which the leaks are mostly non-meteoric. The meteoric brine is essentially Na1bCl in type, reflecting the mineralogy of almost pure halite (with ˜ 1-2% anhydrite) of the Gulf (of Mexico) Coast dome salt. The meteoric leaks are distinctly different from the non-meteoric leaks on the log-log plots of chloride concentrations vs. those of Ca 2+, Mg 2+, K +, Sr + and Br -, in all of which the meteoric brines are conspicuously low. This study is potentially useful in the development of a mine or crypt in salt dome(s) under consideration for possible nuclear-waste isolation in the Gulf Coast region.

Improving Photometric Calibration of Meteor Video Camera Systems

Science.gov (United States)

Ehlert, Steven; Kingery, Aaron; Suggs, Robert

2017-01-01

We present the results of new calibration tests performed by the NASA Meteoroid Environment Office (MEO) designed to help quantify and minimize systematic uncertainties in meteor photometry from video camera observations. These systematic uncertainties can be categorized by two main sources: an imperfect understanding of the linearity correction for the MEO's Watec 902H2 Ultimate video cameras and uncertainties in meteor magnitudes arising from transformations between the Watec camera's Sony EX-View HAD bandpass and the bandpasses used to determine reference star magnitudes. To address the first point, we have measured the linearity response of the MEO's standard meteor video cameras using two independent laboratory tests on eight cameras. Our empirically determined linearity correction is critical for performing accurate photometry at low camera intensity levels. With regards to the second point, we have calculated synthetic magnitudes in the EX bandpass for reference stars. These synthetic magnitudes enable direct calculations of the meteor's photometric flux within the camera bandpass without requiring any assumptions of its spectral energy distribution. Systematic uncertainties in the synthetic magnitudes of individual reference stars are estimated at approx. 0.20 mag, and are limited by the available spectral information in the reference catalogs. These two improvements allow for zero-points accurate to 0.05 - 0.10 mag in both filtered and unfiltered camera observations with no evidence for lingering systematics. These improvements are essential to accurately measuring photometric masses of individual meteors and source mass indexes.

Comets in Australian Aboriginal Astronomy

Science.gov (United States)

Hamacher, Duane W.; Norris, Ray P.

2011-03-01

We present 25 accounts of comets from 40 Australian Aboriginal communities, citing both supernatural perceptions of comets and historical accounts of historically bright comets. Historical and ethnographic descriptions include the Great Comets of 1843, 1861, 1901, 1910, and 1927. We describe the perceptions of comets in Aboriginal societies and show that they are typically associated with fear, death, omens, malevolent spirits, and evil magic, consistent with many cultures around the world. We also provide a list of words for comets in 16 different Aboriginal languages.

Catalogue of Meteor Showers and Storms in Korean History

Directory of Open Access Journals (Sweden)

Sang-Hyeon Ahn

2004-03-01

Full Text Available We present a more complete and accurate catalogue of astronomical records for meteor showers and meteor storms appeared in primary official Korean history books, such as Samguk-sagi, Koryo-sa, Seungjeongwon-ilgi, and Choson-Wangjo-Sillok. So far the catalogue made by Imoto and Hasegawa in 1958 has been widely used in the international astronomical society. The catalogue is based on a report by Sekiguchi in 1917 that is mainly based on secondary history books. We observed that the catalogue has a number of errors in either dates or sources of the records. We have thoroughly checked the primary official history books, instead of the secondary ones, in order to make a corrected and extended catalogue. The catalogue contains 25 records of meteor storms, four records of intense meteor-showers, and five records of usual showers in Korean history. We also find that some of those records seem to correspond to some presently active meteor showers such as the Leonids, the Perseids, and the ¥ç-Aquarids-Orionids pair. However, a large number of those records do not correspond to such present showers. This catalogue we obtained can be useful for various astrophysical studies in the future.

Modern Meteor Science An Interdisciplinary View

CERN Document Server

Hawkes, Robert; Brown, Peter

2005-01-01

This volume represents a blend of leading edge research and authoritative reviews in meteor science. It provides a comprehensive view of meteoroid research including the dynamics, sources and distribution of these bodies, and their chemistry and physical processes in the interplanetary medium and the Earth’s atmosphere. Techniques for investigation of meteor phenomena in the book include conventional and large aperture radar systems, spacecraft detection, optical systems, spectral measurements, and laboratory based interplanetary dust particle studies. The book will be of interest to researchers and students in astronomy, astrophysics, cosmochemistry, space engineering and space science. Cover photograph was taken by Masayuki Toda.

Comet showers and the steady-state infall of comets from the Oort cloud

International Nuclear Information System (INIS)

Hills, J.G.

1981-01-01

The appearance of an inner edge to the Oort comet cloud at a semimajor axis of a = (1--2) x 10 4 AU is an observational artifact. Stellar perturbations are frequent enough and strong enough to assure that a constant fraction of the comets with semimajor axes greater than this are in orbits which bring them within the planetary region. Only infrequent, close stellar encounters are able to repopulate the planet-crossing orbits of comets with smaller semimajor axes. Owing to their relatively short orbital periods which return them frequently to the planetary system, the comets in these more tightly bound orbits will be deflected by Jupiter into drastically different orbits or be destroyed by solar heating before another close stellar passage repopulates their numbers. Comets with semimajor axes less than 2 x 10 4 AU appear in the inner solar system only in intense bursts or showers which last for a few orbital periods after the close passage of a star to the Sun. This is followed by a much longer span of time during which only comets with a>2 x 10 4 AU enter the planetary system. The theoretically determined location of the boundary between the semimajor axes of those comets which enter the planetary system only in bursts or showers and those which arrive in a steady stream is very abrupt and falls at the observed inner edge of the Oort cloud. We propose that the comets formed in the outer parts of the collapsing protosun, which had a radius of less than 5 x 10 3 AU. If this produced a first-generation comet cloud with a radius of 10 3 AU or greater, the coupled dynamical perturbations of passing stars and Jupiter will, of necessity, lead to the formation of a comet cloud similar that of the observed Oort comet cloud

Ammonia abundances in four comets

International Nuclear Information System (INIS)

Wickoff, S.; Tegler, S.C.; Engel, L.

1991-01-01

NH2 emission band strengths were measured in four comets and the NH2 column densities were determined in order to measure the ammonia content of the comets. The mean ammonia/water abundance ratio derived for the four comets is found to be 0.13 + or - 0.06 percent, with no significant variation among the comets. The uniformity of this abundance attests to a remarkable degree of chemical homogeneity over large scales in the comet-forming region of the primordial solar nebula, and contrasts with the CO abundance variations found previously in comets. The N2 and NH3 abundances indicate a condensation temperature in the range 20-160 K, consistent with virtually all comet formation hypotheses. 64 refs

Realm of the comets

International Nuclear Information System (INIS)

Weissman, P.R.

1987-01-01

Studies of Jovian perturbations of the orbits of long-period comets led to the concept of the Oort cloud of 180 billion comets at 50,000-150,000 AU from the sun. Several comets are induced to move toward the sun every million years by the passage of a star at a distance of a few light years. The location of the cloud has since been revised to 20,000-100,000 AU, and comets are now accepted as remnant material fron the proto-solar system epoch. The galactic disk and random, close-passing stars may also cause rare, large perturbations in the orbits of the cloud comets, sending large numbers of comets through the inner solar system. The resulting cometary storm is a candidate cause for the wholesale extinction of dinosaurs in the Cretaceous-Terniary transition due to large number of planetesimals, or one large comet, striking the earth, in a short period of time. The IRAS instruments have detected similar clouds of material around other stars

Comet thermal modeling

International Nuclear Information System (INIS)

Weissman, P.R.; Kieffer, H.H.

1987-01-01

The past year was one of tremendous activity because of the appearance of Halley's Comet. Observations of the comet were collected from a number of sources and compared with the detailed predictions of the comet thermal modeling program. Spacecraft observations of key physical parameters for cometary nucleus were incorporated into the thermal model and new cases run. These results have led to a much better understanding of physical processes on the nucleus and have pointed the way for further improvements to the modeling program. A model for the large-scale structure of cometary nuclei was proposed in which comets were envisioned as loosely bound agglomerations of smaller icy planetesimals, essentially a rubble pile of primordial dirty snowballs. In addition, a study of the physical history of comets was begun, concentrating on processes during formation and in the Oort cloud which would alter the volatile and nonvolatile materials in cometary nuclei from their pristine state before formation

The McDonald Observatory Faint Comet Survey - Gas production in 17 comets

Science.gov (United States)

Cochran, Anita L.; Barker, Edwin S.; Ramseyer, Tod F.; Storrs, Alex D.

1992-01-01

The complete Intensified Dissector Scanner data set on 17 comets is presented, and production rates are derived and analyzed. It is shown that there is a strong degree of homogenization in the production rate ratios of many comets. It also appears that the ratio of the production rates of the various species has no heliocentric distance dependence, except for the case of NH2. When speaking of the gas in the coma of a comet, it appears that comets must have been formed under remarkably uniform conditions, and that they must have evolved and formed their comae in a similar manner. The data presented here constitute strong evidence that the minor species must be bound up in a lattice and that the interior of a comet must be reasonably uniform.

Disintegration of comet nuclei

International Nuclear Information System (INIS)

Ksanfomality, Leonid V

2012-01-01

The breaking up of comets into separate pieces, each with its own tail, was seen many times by astronomers of the past. The phenomenon was in sharp contrast to the idea of the eternal and unchangeable celestial firmament and was commonly believed to be an omen of impending disaster, especially for comets with tails stretching across half the sky. It is only now that we have efficient enough space exploration tools to see comet nuclei and even - in the particular case of small comet Hartley-2 in 2010 - to watch their disintegration stage. There are also other suspected candidates for disintegration in the vast family of comet nuclei and other Solar System bodies. (physics of our days)

Disintegration of comet nuclei

Science.gov (United States)

Ksanfomality, Leonid V.

2012-02-01

The breaking up of comets into separate pieces, each with its own tail, was seen many times by astronomers of the past. The phenomenon was in sharp contrast to the idea of the eternal and unchangeable celestial firmament and was commonly believed to be an omen of impending disaster, especially for comets with tails stretching across half the sky. It is only now that we have efficient enough space exploration tools to see comet nuclei and even - in the particular case of small comet Hartley-2 in 2010 - to watch their disintegration stage. There are also other suspected candidates for disintegration in the vast family of comet nuclei and other Solar System bodies.

Optical observation of comets

International Nuclear Information System (INIS)

Tanabe, Hiroyoshi

1974-01-01

The observation of comets is proposed to study the state of interplanetary space. The behavior of the tails of comets shows the state of solar wind. On July 4, 1964, large bending was seen in the tail of the Tomita-Gerber-Handa comet. Then, on July 7, 1964, geomagnetic disturbance was observed. Disturbance in the tail of Kohoutek comet was seen on Jan. 19, 1974, and Ksub(p)--5 on the ground on Jan. 25. The effort for the quantitative measurement of the parameters of solar wind has been continued in various countries. Recently, the large scale observation of the Kohoutek comet was carried out in the world. Preliminary report is presented in this paper. Waving in the type 1 tail of the comet was seen, and this phenomenon may show some instability due to the interaction between the tail and the solar wind. Periodic variation of the direction of the tail has been reported. The present result also confirmed this report. In case of small comets, flare-up occurs and original luminous intensity is regained after several days. Measurement of the spectrum at the time of flare-up may show information concerning temporary variation of the state of interplanetary space. For the tracking of time variation of comets, cooperation of a number of stations at different positions is required. (Kato, T.)

Disappearance and disintegration of comets

Science.gov (United States)

Sekanina, Z.

1984-01-01

The present investigation has the objective to provide a summary of the existing evidence on the disappearance of comets and to draw conclusions regarding the physical processes involved in the disappearance. Information concerning the classification of evidence and the causes of apparent disappearance of comets is presented in a table. Attention is given to the dissipating comets, the headless sungrazing comet 1887 I, and the physical behavior of the dissipating comets and the related phenomena. It is found that all comets confined to the planetary region of the solar system decay on astronomically short time scales. However, only some of them appear to perish catastrophically. Some of the observed phenomena could be successfully interpreted. But little insight has been obtained into the character of the processes which the dissipating comets experience.

Plasma distributions in meteor head echoes and implications for radar cross section interpretation

Science.gov (United States)

Marshall, Robert A.; Brown, Peter; Close, Sigrid

2017-09-01

The derivation of meteoroid masses from radar measurements requires conversion of the measured radar cross section (RCS) to meteoroid mass. Typically, this conversion passes first through an estimate of the meteor plasma density derived from the RCS. However, the conversion from RCS to meteor plasma density requires assumptions on the radial electron density distribution. We use simultaneous triple-frequency measurements of the RCS for 63 large meteor head echoes to derive estimates of the meteor plasma size and density using five different possible radial electron density distributions. By fitting these distributions to the observed meteor RCS values and estimating the goodness-of-fit, we determine that the best fit to the data is a 1 /r2 plasma distribution, i.e. the electron density decays as 1 /r2 from the center of the meteor plasma. Next, we use the derived plasma distributions to estimate the electron line density q for each meteor using each of the five distributions. We show that depending on the choice of distribution, the line density can vary by a factor of three or more. We thus argue that a best estimate for the radial plasma distribution in a meteor head echo is necessary in order to have any confidence in derived meteoroid masses.

Physical processes in comets

International Nuclear Information System (INIS)

Newburn, R.L. Jr.

1988-01-01

When this program began in 1975 only limited photometry had been carried out on comets at any wavelength. Program goals were to observe many comets, including faint periodic comets, at a range of heliocentric distances in order to begin to understand the range of behavior among comets and in a given comet during its approach and departure from the sun. Then a study of the continuum of scattered light from dust was added. More recently the value of joint team observations in visible and infrared light has been recognized and utilized as often as possible. All 1978 to 1982 data was reanalyzed and 1983 to 1986 data analyzed in the framwork of the post-Halley paradigm, covering 25 comets in all. Four observing runs (June, July, Sept., and Jan.) with Hanner produced excellent results on Wilson, Bradfield, P/Klemola, and P/Borrelly and lesser data on other objects, including the last reported IR photometry of P/Halley. The Wilson and Halley data have been reduced

Meteor Beliefs Project: Meteoric imagery associated with the death of John Brown in 1859

Science.gov (United States)

Drobnock, G. J.; McBeath, A.; Gheorghe, A. D.

2009-12-01

An examination is made of metaphorical meteor imagery used in conjunction with the death of American anti-slavery activist John Brown, who was executed in December 1859. Such imagery continues to be used in this regard into the 21st century.

CO2 Orbital Trends in Comets

Science.gov (United States)

Kelley, Michael; Feaga, Lori; Bodewits, Dennis; McKay, Adam; Snodgrass, Colin; Wooden, Diane

2014-12-01

Spacecraft missions to comets return a treasure trove of details of their targets, e.g., the Rosetta mission to comet 67P/Churyumov-Gerasimenko, the Deep Impact experiment at comet 9P/Tempel 1, or even the flyby of C/2013 A1 (Siding Spring) at Mars. Yet, missions are rare, the diversity of comets is large, few comets are easily accessible, and comet flybys essentially return snapshots of their target nuclei. Thus, telescopic observations are necessary to place the mission data within the context of each comet's long-term behavior, and to further connect mission results to the comet population as a whole. We propose a large Cycle 11 project to study the long-term activity of past and potential future mission targets, and select bright Oort cloud comets to infer comet nucleus properties, which would otherwise require flyby missions. In the classical comet model, cometary mass loss is driven by the sublimation of water ice. However, recent discoveries suggest that the more volatile CO and CO2 ices are the likely drivers of some comet active regions. Surprisingly, CO2 drove most of the activity of comet Hartley 2 at only 1 AU from the Sun where vigorous water ice sublimation would be expected to dominate. Currently, little is known about the role of CO2 in comet activity because telluric absorptions prohibit monitoring from the ground. In our Cycle 11 project, we will study the CO2 activity of our targets through IRAC photometry. In conjunction with prior observations of CO2 and CO, as well as future data sets (JWST) and ongoing Earth-based projects led by members of our team, we will investigate both long-term activity trends in our target comets, with a particular goal to ascertain the connections between each comet's coma and nucleus.

Limits on radio emission from meteors using the MWA

Science.gov (United States)

Zhang, Xiang; Hancock, Paul; Devillepoix, Hadrien A. R.; Wayth, Randall B.; Beardsley, A.; Crosse, B.; Emrich, D.; Franzen, T. M. O.; Gaensler, B. M.; Horsley, L.; Johnston-Hollitt, M.; Kaplan, D. L.; Kenney, D.; Morales, M. F.; Pallot, D.; Steele, K.; Tingay, S. J.; Trott, C. M.; Walker, M.; Williams, A.; Wu, C.; Ji, Jianghui; Ma, Yuehua

2018-04-01

Recently, low frequency, broadband radio emission has been observed accompanying bright meteors by the Long Wavelength Array (LWA). The broadband spectra between 20 and 60 MHz were captured for several events, while the spectral index (dependence of flux density on frequency, with Sν∝να) was estimated to be -4 ± 1 during the peak of meteor afterglows. Here we present a survey of meteor emission and other transient events using the Murchison Widefield Array (MWA) at 72-103 MHz. In our 322-hour survey, down to a 5σ detection threshold of 3.5 Jy/beam, no transient candidates were identified as intrinsic emission from meteors. We derived an upper limit of -3.7 (95% confidence limit) on the spectral index in our frequency range. We also report detections of other transient events, like reflected FM broadcast signals from small satellites, conclusively demonstrating the ability of the MWA to detect and track space debris on scales as small as 0.1 m in low Earth orbits.

Tabulation of comet observations.

Science.gov (United States)

1991-07-01

Concerning comets: 1957 III Arend-Roland, 1957 V Mrkos, 1958 III Burnham, 1959 III Bester-Hoffmeister, 1959 VI Alcock, 1959 VIII P/Giacobini-Zinner, 1960 I P/Wild 1, 1960 II Burnham, 1960 III P/Schaumasse, 1960 VIII P/Finlay, 1961 V Wilson-Hubbard, 1961 VIII Seki, 1962 III Seki-Lines, 1962 VIII Humason, 1963 I Ikeya, 1963 III Alcock, 1963 V Pereyra, 1964 VI Tomita-Gerber-Honda, 1964 VIII Ikeya, 1964 IX Everhart, 1979 X Bradfield, 1980 X P/Stephan-Oterma, 1980 XII Meier, 1980 XIII P/Tuttle, 1981 II Panther, 1982 I Bowell, 1982 IV P/Grigg-Skjellerup, 1982 VII P/d'Arrest, 1986 III P/Halley, 1987 IV Shoemaker, 1987 XII P/Hartley 3, 1987 XIX P/Schwassmann-Wachmann 2, 1987 XXIX Bradfield, 1987 XXX Levy, 1987 XXXII McNaught, 1987 XXXIII P/Borrelly, 1987 XXXVI P/Parker-Hartley, 1987 XXXVII P/Helin- Roman-Alu 1, 1988 III Shoemaker-Holt, 1988 V Liller, 1988 VIII P/Ge-Wang, 1988 XI P/Shoemaker-Holt 2, 1988 XIV P/Tempel 2, 1988 XV Machholz, 1988 XX Yanaka, 1988 XXI Shoemaker, 1988 XXIV Yanaka, 1989 III Shoemaker, 1989 V Shoemaker-Holt-Rodriquez, 1989 VIII P/Pons-Winnecke, 1989 X P/Brorsen-Metcalf, 1989 XI P/Gunn, 1989 XIII P/Lovas 1, 1989 XVIII McKenzie-Russell, 1989 XIX Okazaki-Levy-Rudenko, 1989 XX P/Clark, 1989 XXI Helin-Ronan-Alu, 1989 XXII Aarseth-Brewington, 1989h P/Van Biesbroeck, 1989t P/Wild 2, 1989u P/Kearns-Kwee, 1989c1 Austin, 1989e1 Skorichenko-George, 1990a P/Wild 4, 1990b Černis-Kiuchi-Nakamura, 1990c Levy, 1990e P/Wolf-Harrington, 1990f P/Honda-Mrkos-Pajdušáková, 1990g McNaught-Hughes, 1990i Tsuchiya-Kiuchi, 1990n P/Taylor, 1990ο P/Shoemaker-Levy 1, 1991a P/Metcalf-Brewington, 1991b Arai, 1991c P/Swift-Gehrels, 1991d Shoemaker-Levy, 1991e P/Shoemaker-Levy 3, 1991h P/Takamizawa, 1991j P/Hartley 1, 1991k P/Mrkos, 1991l Helin-Lawrence, 1991n P/Faye, 1991q P/Levy, 1991t P/Hartley 2, P/Encke, P/Schwassmann-Wachmann 1.

Meteoric Impact and Ion Density Calculation in the Nighttime ...

Indian Academy of Sciences (India)

Bhavin

2013-11-08

Nov 8, 2013 ... Pandya, B. M., and S. A. Haider (2012), Meteor impact perturbation in the lower ionosphere of Mars: MGS observations,. Planet. Space Sci., 63, 105-109, doi: 10.1016/j.pss.2011.09.013. Page 6. Pandya, B. M., and S. A. Haider (2012), Meteor impact perturbation in the lower ionosphere of Mars: MGS ...

Cometography a catalog of comets

CERN Document Server

Kronk, Gary W; Seargent, David A J

2017-01-01

Cometography is a multi-volume catalog of every comet observed from ancient times up to the 1990s, when the internet took off as a medium of scientific record. It uses the most reliable orbits known to determine the distances from the Earth and Sun at the time of discovery and last observation, as well as the largest and smallest angular distance to the Sun, most northerly and southerly declination, closest distance to the Earth, and other details, to enable the reader to understand each comet's physical appearance. Volume 6, the final volume in the catalog, covers the observations and pertinent calculations for every comet seen between 1983 and 1993. The comets are listed in chronological order, with complete references to publications relating to each comet and physical descriptions of each comet's development throughout its apparition. Cometography is the definitive reference on comets through the ages, for astronomers and historians of science.

Detecting active comets with SDSS

Energy Technology Data Exchange (ETDEWEB)

Solontoi, Michael; Ivezic, Zeljko; /Washington U., Seattle, Astron. Dept.; West, Andrew A.; /MIT, MKI; Claire, Mark; /Washington U., Seattle, Astron. Dept.; Juric, Mario; /Princeton U. Observ.; Becker, Andrew; Jones, Lynne; /Washington U., Seattle, Astron. Dept.; Hall, Patrick B.; /York U., Canada; Kent, Steve; /Fermilab; Lupton, Robert H.; /Princeton U. Observ.; Quinn, Tom; /Washington U., Seattle, Astron. Dept. /Princeton U. Observ.

2010-12-01

Using a sample of serendipitously discovered active comets in the Sloan Digital Sky Survey (SDSS), we develop well-controlled selection criteria for greatly increasing the efficiency of comet identification in the SDSS catalogs. After follow-up visual inspection of images to reject remaining false positives, the total sample of SDSS comets presented here contains 19 objects, roughly one comet per 10 million other SDSS objects. The good understanding of selection effects allows a study of the population statistics, and we estimate the apparent magnitude distribution to r {approx} 18, the ecliptic latitude distribution, and the comet distribution in SDSS color space. The most surprising results are the extremely narrow range of colors for comets in our sample (e.g. root-mean-square scatter of only {approx}0.06 mag for the g-r color), and the similarity of comet colors to those of jovian Trojans. We discuss the relevance of our results for upcoming deep multi-epoch optical surveys such as the Dark Energy Survey, Pan-STARRS, and the Large Synoptic Survey Telescope (LSST), and estimate that LSST may produce a sample of about 10,000 comets over its 10-year lifetime.

Postencounter view of comets

International Nuclear Information System (INIS)

Mendis, D.A.

1988-01-01

Ground-based and space observations of Comet Halley during its 1986 perihelion passage are reviewed, with an emphasis on their implications for theoretical models. Consideration is given to the shape, surface morphology, and composition of the comet nucleus; the shape, dynamics, and composition of the dust tail; neutral and ionic gas species in the head and plasma tail; and the comet/solar-wind interaction. Extensive diagrams, graphs, and sample images are provided, and the potential value of the new kinds of data to be obtained with the NASA Comet-Rendezvous/Asteroid-Flyby spacecraft is discussed. 139 references

CometQ: An automated tool for the detection and quantification of DNA damage using comet assay image analysis.

Science.gov (United States)

Ganapathy, Sreelatha; Muraleedharan, Aparna; Sathidevi, Puthumangalathu Savithri; Chand, Parkash; Rajkumar, Ravi Philip

2016-09-01

DNA damage analysis plays an important role in determining the approaches for treatment and prevention of various diseases like cancer, schizophrenia and other heritable diseases. Comet assay is a sensitive and versatile method for DNA damage analysis. The main objective of this work is to implement a fully automated tool for the detection and quantification of DNA damage by analysing comet assay images. The comet assay image analysis consists of four stages: (1) classifier (2) comet segmentation (3) comet partitioning and (4) comet quantification. Main features of the proposed software are the design and development of four comet segmentation methods, and the automatic routing of the input comet assay image to the most suitable one among these methods depending on the type of the image (silver stained or fluorescent stained) as well as the level of DNA damage (heavily damaged or lightly/moderately damaged). A classifier stage, based on support vector machine (SVM) is designed and implemented at the front end, to categorise the input image into one of the above four groups to ensure proper routing. Comet segmentation is followed by comet partitioning which is implemented using a novel technique coined as modified fuzzy clustering. Comet parameters are calculated in the comet quantification stage and are saved in an excel file. Our dataset consists of 600 silver stained images obtained from 40 Schizophrenia patients with different levels of severity, admitted to a tertiary hospital in South India and 56 fluorescent stained images obtained from different internet sources. The performance of "CometQ", the proposed standalone application for automated analysis of comet assay images, is evaluated by a clinical expert and is also compared with that of a most recent and related software-OpenComet. CometQ gave 90.26% positive predictive value (PPV) and 93.34% sensitivity which are much higher than those of OpenComet, especially in the case of silver stained images. The

Composition of faint comets

International Nuclear Information System (INIS)

Brown, L.W.

1986-01-01

The study uses an emission line, differential imaging camera built by the Science Operations Branch. This instrument allows photometric data to be obtained over a large area of a comet in a large number of resolution elements. The detector is a 100x100 Reticon array which with interchangeable optics can give resolutions from 2'' to 30'' over a field of 1' to 15'. The camera through its controlling computer can simultaneously take images in on-line and continuum filters and through computer subtraction and calibration present a photometric image of the comet produced by only the emission of the molecule under study. Initial work has shown two significant problems. First the auxiliary equipment of the telescope has not allowed the unambiguous location of faint comets so that systematic observations could be made, and secondly initial data has not shown much molecular emission from the faint comets which were located. Work last year on a software and hardware display system and this year on additional guide motors on the 36-inch telescope has allowed the differential camera to act as its own finder and guide scope. Comet IRAS was observed in C2 and CO+, as well as an occultation by the comet of SAO029103. The perodic comet Giacobini-Zinner was also observed in C2

ISO's analysis of Comet Hale-Bopp

Science.gov (United States)

1997-03-01

The European Space Agency's Infrared Space Observatory ISO inspected Comet Hall-Bopp during the spring and autumn of 1996. The need to keep ISO's telescope extremely cold restricts the spacecraft's pointing in relation to the Sun and the Earth and it ruled out observations at other times. The analyses of the 1996 observations are not yet complete, but already they give new insight into the nature of comets. Comet Hale-Bopp is believed to be a large comet with a nucleus up to 40 kilometres wide. It was discovered in July 1995 by two American astronomers working independently, Alan Hale and Thomas Bopp. At that time, the comet was a billion kilometres away from the Sun, but 200 times brighter than Halley's Comet was, when at a comparable distance. Comet Hale-Bopp will make its closest approach to the Earth on 22 March, and its closest approach to the Sun (perihelion) on 1 April 1997. Some scientific results from ISO The discovery of Comet Hale-Bopp occurred before ISO's launch in November 1995. When first observed by ISO in March and April 1996, the comet was still 700 million kilometres from the Sun, and almost as far from the Earth and ISO. With its privileged view of infrared wavebands inaccessible from the Earth's surface, ISO's photometer ISOPHOT discovered that carbon dioxide was an important constituent of the comet's emissions of vapour.ISOPHOT measured the temperature of the dust cloud around Comet Hale-Bopp. In March 1996, when the comet was still more than 700 million kilometres from the Sun, the dust cloud was at minus 120 degrees C. When ISOPHOT made similar observations in October 1996, the comet was 420 million kilometres from the Sun, and the dust cloud had warmed to about minus 50 degrees C. Intensive observations of Comet Hale-Bopp were also made by ISO's Short-Wave Spectrometer SWS, the Long-Wave Spectrometer LWS, and the ISOPHOT spectrometer PHOT-S. Results are due for publication at the end of March. They will give details about the composition

Physics of comets

CERN Document Server

Krishna Swamy, K S

2010-01-01

This revised edition places a unique emphasis on all the new results from ground-based, satellites and space missions - detection of molecule H2 and prompt emission lines of OH for the first time; discovery of X-rays in comets; observed diversity in chemical composition among comets; the puzzle of the constancy of spin temperature; the well-established mineralogy of cometary dust; extensive theoretical modeling carried out for understanding the observed effects; and, the similarity in the mineralogy of dust in circumstellar shell of stars, comets, meteorites, asteroids and IDPs, thus indicatin

Comets in UV

Science.gov (United States)

Shustov, B.; Sachkov, M.; Gómez de Castro, A. I.; Vallejo, J. C.; Kanev, E.; Dorofeeva, V.

2018-04-01

Comets are important "eyewitnesses" of Solar System formation and evolution. Important tests to determine the chemical composition and to study the physical processes in cometary nuclei and coma need data in the UV range of the electromagnetic spectrum. Comprehensive and complete studies require additional ground-based observations and in situ experiments. We briefly review observations of comets in the ultraviolet (UV) and discuss the prospects of UV observations of comets and exocomets with space-borne instruments. A special reference is made to the World Space Observatory-Ultraviolet (WSO-UV) project.

Comet radar explorer

Science.gov (United States)

Farnham, Tony; Asphaug, Erik; Barucci, Antonella; Belton, Mike; Bockelee-Morvan, Dominique; Brownlee, Donald; Capria, Maria Teresa; Carter, Lynn; Chesley, Steve; Farnham, Tony; Gaskell, Robert; Gim, Young; Heggy, Essam; Herique, Alain; Klaasen, Ken; Kofman, Wlodek; Kreslavsky, Misha; Lisse, Casey; Orosei, Roberto; Plaut, Jeff; Scheeres, Dan

The Comet Radar Explorer (CORE) is designed to perform a comprehensive and detailed exploration of the interior, surface, and inner coma structures of a scientifically impor-tant Jupiter family comet. These structures will be used to investigate the origins of cometary nuclei, their physical and geological evolution, and the mechanisms driving their spectacular activity. CORE is a high heritage spacecraft, injected by solar electric propulsion into orbit around a comet. It is capable of coherent deep radar imaging at decameter wavelengths, high resolution stereo color imaging, and near-IR imaging spectroscopy. Its primary objective is to obtain a high-resolution map of the interior structure of a comet nucleus at a resolution of ¿100 elements across the diameter. This structure shall be related to the surface geology and morphology, and to the structural details of the coma proximal to the nucleus. This is an ideal complement to the science from recent comet missions, providing insight into how comets work. Knowing the structure of the interior of a comet-what's inside-and how cometary activity works, is required before we can understand the requirements for a cryogenic sample return mission. But more than that, CORE is fundamental to understanding the origin of comets and their evolution in time. The mission is made feasible at low cost by the use of now-standard MARSIS-SHARAD reflec-tion radar imaging hardware and data processing, together with proven flight heritage of solar electric propulsion. Radar flight heritage has been demonstrated by the MARSIS radar on Mars Express (Picardi et al., Science 2005; Plaut et al., Science 2007), the SHARAD radar onboard the Mars Reconnaissance Orbiter (Seu et al., JGR 2007), and the LRS radar onboard Kaguya (Ono et al, EPS 2007). These instruments have discovered detailed subsurface structure to depths of several kilometers in a variety of terrains on Mars and the Moon. A reflection radar deployed in orbit about a comet

The First Year of Croatian Meteor Network

Science.gov (United States)

Andreic, Zeljko; Segon, Damir

2010-08-01

The idea and a short history of Croatian Meteor Network (CMN) is described. Based on use of cheap surveillance cameras, standard PC-TV cards and old PCs, the Network allows schools, amateur societies and individuals to participate in photographic meteor patrol program. The network has a strong educational component and many cameras are located at or around teaching facilities. Data obtained by these cameras are collected and processed by the scientific team of the network. Currently 14 cameras are operable, covering a large part of the croatian sky, data gathering is fully functional, and data reduction software is in testing phase.

Development of the mesospheric Na layer at 69° N during the Geminids meteor shower 2010

Directory of Open Access Journals (Sweden)

T. Dunker

2013-01-01

Full Text Available The ECOMA sounding rocket campaign in 2010 was performed to investigate the charge state and number density of meteoric smoke particles during the Geminids meteor shower in December 2010. The ALOMAR Na lidar contributed to the campaign with measurements of sodium number density, temperature and line-of-sight wind between 80 and 110 km altitude over Andøya in northern Norway. This paper investigates a possible connection between the Geminids meteor shower and the mesospheric sodium layer. We compare with data from a meteor radar and from a rocket-borne in situ particle instrument on three days. Our main result is that the sodium column density is smaller during the Geminids meteor shower than the winter average at the same latitude. Moreover, during two of the three years considered, the sodium column density decreased steadily during these three weeks of the year. Both the observed decrease of Na column density by 30% and of meteoric smoke particle column density correlate well with a corresponding decrease of sporadic meteor echoes. We found no correlation between Geminids meteor flux rates and sodium column density, nor between sporadic meteors and Na column density (R = 0.25. In general, we found the Na column density to be at very low values for winter, between 1.8 and 2.6 × 1013 m−2. We detected two meteor trails containing sodium, on 13 December 2010 at 87.1 km and on 19 December 2010 at 84 km. From these meteor trails, we estimate a global meteoric Na flux of 121 kg d−1 and a global total meteoric influx of 20.2 t d−1.

Organic chemistry of cosmic dusts for understanding an intra-relationship between meteorites and comets: Toward a new frontier of astromaterial science

Science.gov (United States)

Yabuta, Hikaru

2012-07-01

and terrestrial contamination will be expected. A silica aerogel (0.03 and 0.01 g/cc) will be used for the sampling. As a ground-based experiment, we have been conducting a carefully-implemented, high-velocity double gas gun experiment of Murshison meteorite grains into a silica aerogel. It has been concluded that a major portion of aromatic carbon compositions of meteoritic organics are preserved at an impact velocity of 4 km/s, but the decrease of abundances of aliphatic carbon and slight modification of their compositions (e.g., CH2/CH3 ratio) are observed after the impact. This result will provide helpful knowledge not only for the correct interpretation of the chemical compositions of the collected IDP organics but also for that of comet dust particles collected by Stardust mission. References: [1] Brearley et al. (2006) Science 314, 1711. [2] Sandford et al. (2006) Science 314, 1720. [3] Cody et al. (2008) Meteor. Planet. Sci. 43, 353. [4] Messenger et al. (2000) Nature 404, 968. [5] Flynn et al. (2003). [6] Keller et al. (2004) GCA 68, 2577. [7] Busemann et al. (2009) EPSL 288, 44. [8] Nakamura et al. (2005) Meteor. Planet. Sci. 40, A110. [9] Duprat et al (2010) Science, 328, 742. [10] Yabuta et al. (2012) LPSC Abstract #2239

Ancient Chinese Observations and Modern Cometary Models

Science.gov (United States)

Yeomans, D. K.

1995-12-01

Ancient astronomical observations by Chinese, Japanese, and Korean observers represent the only data source for discerning the long-term behavior of comets. The primary source material is derived from Chinese astrologers who kept a vigilant celestial watch in an effort to issue up-to-date astrological forecasts for the reigning emperors. Surprisingly accurate records were kept on cometary apparitions with careful notes being made of an object's position, motion, size, color, and tail length. For comets Halley, Swift-Tuttle, and Tempel-Tuttle, Chinese observations have been used to model their motions over two millennia and to infer their photometric histories. One general result is that active comets must achieve an apparent magnitude of 3.5 or brighter before they become obvious naked-eye objects. For both comets Halley and Swift-Tuttle, their absolute magnitudes and hence their outgassing rates, have remained relatively constant for two millennia. Comet Halley's rocket-like outgassing has consistently delayed the comet's return to perihelion by 4 days so that the comet's spin axis must have remained stable for at least two millennia. Although its outgassing is at nearly the same rate as Halley's, comet Swift-Tuttle's motion has been unaffected by outgassing forces; this comet is likely to be ten times more massive than Halley and hence far more difficult for rocket-like forces to push it around. Although the earliest definite observations of comet Tempel-Tuttle were in 1366, the associated Leonid meteor showers have been identified as early as A.D. 902. The circumstance for each historical meteor shower and storm have been used to guide predictions for the upcoming 1998-1999 Leonid meteor displays.

A Global Atmospheric Model of Meteoric Iron

Science.gov (United States)

Feng, Wuhu; Marsh, Daniel R.; Chipperfield, Martyn P.; Janches, Diego; Hoffner, Josef; Yi, Fan; Plane, John M. C.

2013-01-01

The first global model of meteoric iron in the atmosphere (WACCM-Fe) has been developed by combining three components: the Whole Atmosphere Community Climate Model (WACCM), a description of the neutral and ion-molecule chemistry of iron in the mesosphere and lower thermosphere (MLT), and a treatment of the injection of meteoric constituents into the atmosphere. The iron chemistry treats seven neutral and four ionized iron containing species with 30 neutral and ion-molecule reactions. The meteoric input function (MIF), which describes the injection of Fe as a function of height, latitude, and day, is precalculated from an astronomical model coupled to a chemical meteoric ablation model (CABMOD). This newly developed WACCM-Fe model has been evaluated against a number of available ground-based lidar observations and performs well in simulating the mesospheric atomic Fe layer. The model reproduces the strong positive correlation of temperature and Fe density around the Fe layer peak and the large anticorrelation around 100 km. The diurnal tide has a significant effect in the middle of the layer, and the model also captures well the observed seasonal variations. However, the model overestimates the peak Fe+ concentration compared with the limited rocket-borne mass spectrometer data available, although good agreement on the ion layer underside can be obtained by adjusting the rate coefficients for dissociative recombination of Fe-molecular ions with electrons. Sensitivity experiments with the same chemistry in a 1-D model are used to highlight significant remaining uncertainties in reaction rate coefficients, and to explore the dependence of the total Fe abundance on the MIF and rate of vertical transport.

Molecular ions in comet tails

International Nuclear Information System (INIS)

Wyckoff, S.; Wehinger, P.A.

1976-01-01

Band intensities of the molecular ions CH + , CO + , N 2 + , and H 2 O + have been determined on an absolute scale from tail spectra of comet Kohoutek (1973f) and comet Bradfield (1974b). Photoionization and photodissociation rates have been computed for CH, CO, and N 2 . Also emission rate excitation g-factors for (1) photoionization plus excitation and (2) resonance fluorescence have been computed for the observed ions. It is shown that resonance fluorescence is the dominant excitation mechanism for observed comet tail ions at rapprox. =1 AU. Band system luminosities and molecular ion abundances within a projected nuclear distance rho 4 km have been determined for CH + , CO + , N 2 + , and H 2 O + in comet Kohoutek, and for H 2 O + in comet Bradfield. Estimates are also given for column densities of all observed ions at rhoapprox. =10 4 km on the tailward side of the coma. The observed H 2 O + column densities were found to be roughly the same in comet Kohoutek and comet Bradfield et equal heliocentric distances, while CO + was found to be approximately 100 times more abundant than H 2 O + , N 2 + , and CH + at rhoapprox. =10 4 km in comet Kohoutek. Finally, the relative abundances of the observed ions and of the presumed parent neutral species are briefly discussed

Comets and their composition

International Nuclear Information System (INIS)

Spinrad, H.

1987-01-01

Recent theoretical and observational studies of comets are reviewed, with an emphasis on in situ data from spacecraft encounters with P/Giacobini-Zinner (September 1985) and P/Halley (March 1986). Topics addressed include clues on the origin and permanence of the Oort cometary cloud, observations of cometary nuclei far from the sun, the Halley nucleus, compositional and physical data from comae studies, and the parent molecules in comet ices. Also discussed are quantitative analyses of coma production; special features in the tail of P/Giacobini-Zinner; and proposals for (1) observations to detect distant giant comets, (2) high-resolution spectroscopic studies of comae, and (3) additional spacecraft missions such as the NASA Comet Rendezvous and Asteroid Flyby. 121 references

Reasonable threshold value used to segment the individual comet from the comet assay image

International Nuclear Information System (INIS)

Yan Xuekun; Chen Ying; Du Jie; Zhang Xueqing; Luo Yisheng

2009-01-01

Reasonable segmentation of the individual comet contour from the Comet Assay (CA) images is the precondition for all of parameters analysis during the automatic analyzing for the CA. The Otsu method and several arithmetic operators for image segmentation, such as Sobel, Prewitt, Roberts and Canny were used to segment the comet contour, and characters of the CA images were analyzed firstly. And then the segmentation methods which had been adopted in the software for CA automatic analysis, such as the CASP, the TriTek CometScore TM , were put for-ward and compared. At last, a two-step procedure for threshold calculation based on image-content analysis is adopted to segment the individual comet from the CA images, and several principles for the segmentation are put forward too.(authors)

Singing comet changes its song

Science.gov (United States)

Volwerk, M.; Goetz, C.; Delva, M.; Richter, I.; Tsurutani, B. T.; Eriksson, A.; Odelstad, E.; Meier, P.; Nilsson, H.; Glassmeier, K.-H.

2017-09-01

The singing comet was discovered at the beginning of the Rosetta mission around comet 67P/Churyumov-Gerasimenko. Large amplitude compressional waves with frequencies between 10 and 100 mHz were observed. When the comet became more active this signal was no longer measured. During the so-called tail excursion, late in the mission after perihelion, with again a less active comet, the singing was observed again and interestingly, going from 26 March to 27 March 2016 the character of the singing changed.

Catalogue of representative meteor spectra

Czech Academy of Sciences Publication Activity Database

Vojáček, Vlastimil; Borovička, Jiří; Koten, Pavel; Spurný, Pavel; Štork, Rostislav

2015-01-01

Roč. 580, August (2015), A67/1-A67/31 ISSN 0004-6361 R&D Projects: GA ČR(CZ) GAP209/11/1382 Institutional support: RVO:67985815 Keywords : meteorites * meteors * meteoroids Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 4.378, year: 2014

Automatic Video System for Continues Monitoring of the Meteor Activity

Czech Academy of Sciences Publication Activity Database

Koten, Pavel; Fliegel, K.; Vítek, S.; Páta, P.

2011-01-01

Roč. 108, č. 1 (2011), s. 69-76 ISSN 0167-9295 R&D Projects: GA ČR GA205/09/1302 Grant - others:GA ČR(CZ) GAP102/10/1320 Institutional research plan: CEZ:AV0Z10030501 Keywords : meteor * meteor showers * instrumentation Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 0.667, year: 2011

Nature and origin of comets

International Nuclear Information System (INIS)

Fernandez, J.A.; Jockers, K.

1983-01-01

The review examines basic history and morphology, motion, dynamic evolution, physical properties of neutral gaseous matter, vaporization of gases and outflow from the nucleus, chemistry of the coma gases, the comet nucleus, dust particles, solar wind-comet interactions and tail formation and the origin of comets. (U.K.)

Meteor detection on ST (MST) radars

International Nuclear Information System (INIS)

Avery, S.K.

1987-01-01

The ability to detect radar echoes from backscatter due to turbulent irregularities of the radio refractive index in the clear atmosphere has lead to an increasing number of established mesosphere - stratosphere - troposphere (MST or ST) radars. Humidity and temperature variations are responsible for the echo in the troposphere and stratosphere and turbulence acting on electron density gradients provides the echo in the mesosphere. The MST radar and its smaller version, the ST radar, are pulsed Doppler radars operating in the VHF - UHF frequency range. These echoes can be used to determine upper atmosphere winds at little extra cost to the ST radar configuration. In addition, the meteor echoes can supplement mesospheric data from an MST radar. The detection techniques required on the ST radar for delineating meteor echo returns are described

A New Orbit for Comet C/1865 B1 (Great Southern Comet of 1865)

Science.gov (United States)

Branham, Richard L., Jr.

2018-04-01

Comet C/1865 B1 (Great southern comet of 1865), observed only in the southern hemisphere, is one of a large number of comets with parabolic orbits. Given that there are 202 observations in right ascension and 165 in declination it proves possible to calculate a better orbit than that Körber published in 1887, the orbit used in various catalogs and data bases. C/1865 B1's orbit is hyperbolic and statistically distinguishable from a parabola. This object, therefore, cannot be considered an NEO. The comet has a small perihelion distance of 0.026 AU.

French Meteor Network for High Precision Orbits of Meteoroids

Science.gov (United States)

Atreya, P.; Vaubaillon, J.; Colas, F.; Bouley, S.; Gaillard, B.; Sauli, I.; Kwon, M. K.

2011-01-01

There is a lack of precise meteoroids orbit from video observations as most of the meteor stations use off-the-shelf CCD cameras. Few meteoroids orbit with precise semi-major axis are available using film photographic method. Precise orbits are necessary to compute the dust flux in the Earth s vicinity, and to estimate the ejection time of the meteoroids accurately by comparing them with the theoretical evolution model. We investigate the use of large CCD sensors to observe multi-station meteors and to compute precise orbit of these meteoroids. An ideal spatial and temporal resolution to get an accuracy to those similar of photographic plates are discussed. Various problems faced due to the use of large CCD, such as increasing the spatial and the temporal resolution at the same time and computational problems in finding the meteor position are illustrated.

Halley comet, implication on the origin

International Nuclear Information System (INIS)

Festou, M.C.

1990-01-01

One will first give a rapid description of the different parts that compose a comet coma. Then one will describe the spectrum of comets from the UV to the IR regions with special emphasis on how information relative to the physico-chemistry of comet atmospheres can be retrieved. Our basic knowledge about the composition of comets before 1985 will be summarized and the input of the 1985-86 observing campaign of comet Halley will be shown (in situ, ground-based and space borne observations). One will see then that the chemical composition of comets appears as of today completely compatible with a formation from pre-solar matter that condensed inside the solar system [fr

An Automatic Video Meteor Observation Using UFO Capture at the Showa Station

Science.gov (United States)

Fujiwara, Y.; Nakamura, T.; Ejiri, M.; Suzuki, H.

2012-05-01

The goal of our study is to clarify meteor activities in the southern hemi-sphere by continuous optical observations with video cameras with automatic meteor detection and recording at Syowa station, Antarctica.

A Comet Engulfs Mars: MAVEN Observations of Comet Siding Spring's Influence on the Martian Magnetosphere

Science.gov (United States)

Espley, Jared R.; Dibraccio, Gina A.; Connerney, John E. P.; Brain, David; Gruesbeck, Jacob; Soobiah, Yasir; Halekas, Jasper S.; Combi, Michael; Luhmann, Janet; Ma, Yingjuan

2015-01-01

The nucleus of comet C/2013 A1 (Siding Spring) passed within 141,000?km of Mars on 19 October 2014. Thus, the cometary coma and the plasma it produces washed over Mars for several hours producing significant effects in the Martian magnetosphere and upper atmosphere. We present observations from Mars Atmosphere and Volatile EvolutioN's (MAVEN's) particles and field's instruments that show the Martian magnetosphere was severely distorted during the comet's passage. We note four specific major effects: (1) a variable induced magnetospheric boundary, (2) a strong rotation of the magnetic field as the comet approached, (3) severely distorted and disordered ionospheric magnetic fields during the comet's closest approach, and (4) unusually strong magnetosheath turbulence lasting hours after the comet left. We argue that the comet produced effects comparable to that of a large solar storm (in terms of incident energy) and that our results are therefore important for future studies of atmospheric escape, MAVEN's primary science objective.

Meteoric 10Be as a tool to investigate human induced soil fluxes: a conceptual model

Science.gov (United States)

Campforts, Benjamin; Govers, Gerard; Vanacker, Veerle; De Vente, Joris; Boix-Fayos, Carolina; Minella, Jean; Baken, Stijn; Smolders, Erik

2014-05-01

The use of meteoric 10Be as a tool to understand long term landscape behavior is becoming increasingly popular. Due its high residence time, meteoric 10Be allows in principle to investigate in situ erosion rates over time scales exceeding the period studied with classical approaches such as 137Cs. The use of meteoric 10Be strongly contributes to the traditional interpretation of sedimentary archives which cannot be unequivocally coupled to sediment production and could provide biased information over longer time scales (Sadler, 1981). So far, meteoric 10Be has successfully been used in geochemical fingerprinting of sediments, to date soil profiles, to assess soil residence times and to quantify downslope soil fluxes using accumulated 10Be inventories along a hill slope. However, less attention is given to the potential use of the tracer to directly asses human induced changes in soil fluxes through deforestation, cultivation and reforestation. A good understanding of the processes governing the distribution of meteoric 10Be both within the soil profile and at landscape scale is essential before meteoric 10Be can be successfully applied to assess human impact. We developed a spatially explicit 2D-model (Be2D) in order to gain insight in meteoric 10Be movement along a hillslope that is subject to human disturbance. Be2D integrates both horizontal soil fluxes and vertical meteoric 10Be movement throughout the soil prolife. Horizontal soil fluxes are predicted using (i) well studied geomorphical laws for natural erosion and soil formation as well as (ii) human accelerated water and tillage erosion. Vertical movement of meteoric 10Be throughout the soil profile is implemented by inserting depth dependent retardation calculated using experimentally determined partition coefficients (Kd). The model was applied to different environments such as (i) the Belgian loess belt, characterized by aeolian deposits enriched in inherited meteoric 10Be, (ii) highly degraded and stony

Studying Short-Period Comets and Long-Period Comets Detected by WISE/NEOWISE

Science.gov (United States)

Kramer, Emily A.; Fernández, Yanga R.; Bauer, James M.; Stevenson, Rachel; Mainzer, Amy K.; Grav, Tommy; Masiero, Joseph; Walker, Russell G.; Lisse, Carey M.

2014-11-01

The Wide-field Infrared Survey Explorer (WISE) mission surveyed the sky in four infrared wavelength bands (3.4, 4.6, 12 and 22-micron) between January 2010 and February 2011 [1, 2]. During the mission, WISE serendipitously observed 160 comets, including 21 newly discovered objects. About 89 of the comets observed by WISE displayed a significant dust tail in the 12 and 22-micron (thermal emission) bands, showing a wide range of activity levels and dust morphology. Since the observed objects are a mix of both long-period comets (LPCs) and short-period comets (SPCs), differences in their activity can be used to better understand the thermal evolution that each of these populations has undergone. For the comets that displayed a significant dust tail, we have estimated the sizes and ages of the particles using dynamical models based on the Finson-Probstein method [3, 4]. For a selection of 40 comets, we have then compared these models to the data using a novel tail-fitting method that allows the best-fit model to be chosen analytically rather than subjectively. For comets that were observed multiple times by WISE, the dust tail particle properties were estimated separately, and then compared. We find that the dust tails of both LPCs and SPCs are primarily comprised of ~mm to cm sized particles, which were the result of emission that occurred several months to several years prior to the observations. The LPCs nearly all have strong dust emission close to the comet's perihelion distance, and the SPCs mostly have strong dust emission close to perihelion, but some have strong dust emission well before perihelion. Acknowledgments: This publication makes use of data products from (1) WISE, which is a joint project of UCLA and JPL/Caltech, funded by NASA; and (2) NEOWISE, which is a project of JPL/Caltech, funded by the Planetary Science Division of NASA. EK was supported by a NASA Earth and Space Sciences Fellowship. RS gratefully acknowledges support from the NASA

Inside look at Halley's comet

International Nuclear Information System (INIS)

Beatty, J.K.

1986-01-01

The 1985-1986 emergence of Halley's comet, the first since the advent of the space age, was explored by a variety of spacecraft. The Vega 1, launched by the USSR together with the Eastern-block alliance, passed 5523 miles from the comet's nucleus at 7:20:06 Universal time. It indicated that the comet was about 300 miles closer to the sun than had been predicted. The Japanese spacecraft, Suisei, was created to map the distribution of neutral hydrogen atoms outside Halley's visible coma. Its pictures indicated that the comet's output of water varied between 25 and 60 tons per second. Five days after the Vega 2's passage through the comet, the Giotto (sponsored by the European Space Agency) probe appeared. Giotto's close approach took place 3.1 minutes after midnight UT on March 14th; the craft had passed 376 miles from its target. Giotto's data indicated that the nucleus was bigger than expected, and that the comet was composed primarily of water, CO2 and N2. The Vegas and Giotto found that as the solar wind approaches Halley, it slows gradually and the solar magnetic lines embedded in the wind begin to pile up. Pick-up ions, from the comet's halo of neutral hydrogen, were found in this solar wind. Sensors on the Vega spacecraft found a variety of plasma waves propagating inside the bow wave. In order to synthesize all the results, a conference on the exploration of Halley's comet will be held this October

Comet Mineralogy as Inferred from Infrared Spectra of Comets

Science.gov (United States)

Wooden, Diane H.

2006-01-01

For most comets, infrared (IR) spectroscopy (remote sensing) is the method through which we diagnose the mineralogy and size distribution of dust in their comae. The shape and contrast of the IR spectral features depend on the particle size: optically active minerals (absorbing of visible and near-IR solar photons) and submicron solid grains or highly porous (> 90% vacuum) grains primarily contribute to the shapes of the observed resonances. Comet mineralogies typically are determined by fitting thermal emission models of ensembles of discrete mineral grains to observed IR spectral energy distributions. The absorptivities (Q-abs) and scattering efficiencies (Q-scat) of the discrete mineral grains are computed using Mie scattering, Maxwell-Garnet mixing, Discrete Dipole Approximation, and Multi-Layered Sphere codes. These techniques when applied to crystalline minerals, specifically olivine (Mg_x, Fe_1-x)2 Si04, x>0.9, require the use of ellipsoidal shaped particles with elongated axial ratios or hollow spheres to produce the shapes of the resonances observed both from comet comae and laboratory samples. The wavelength positions of the distinct resonances from submicron-radii crystalline silicates, as well as their thermal equilibrium temperatures, constrain the crystalline olivine to have a relatively high Mg-content (x>0.9, or Fo>90). Only resonances computed for submicron Mg-rich crystalline olivine and crystalline orthopyroxene match the observed IR spectral features. However, this has led to the interpretation that micron-radii and larger crystals are absent from comet comae. Furthermore, the mass fraction of silicate crystals is dependent upon whether just the submicron portion of the size distribution is being compared or the submicron crystals compare to the aggregates of porous amorphous silicates that are computationally tractable as porous spheres. We will discuss the Deep Impact results as examples of these challenges to interpreting mid-IR spectra of

Comet Halley and interstellar chemistry

International Nuclear Information System (INIS)

Snyder, L.E.

1989-01-01

How complex is the chemistry of the interstellar medium? How far does it evolve and how has it interacted with the chemistry of the solar system? Are the galactic chemical processes destroyed, preserved, or even enhanced in comets? Are biogenic molecules formed in space and have the formation mechanisms interacted in any way with prebiotic organic chemical processes on the early earth? Radio molecular studies of comets are important for probing deep into the coma and nuclear region and thus may help answer these questions. Comets are believed to be pristine samples of the debris left from the formation of the solar system and may have been the carrier between interstellar and terrestrial prebiotic chemistries. Recent observations of Comet Halley and subsequent comets have given the author an excellent opportunity to study the relationship between interstellar molecular chemistry and cometary chemistry

CAMS newly detected meteor showers and the sporadic background

Science.gov (United States)

Jenniskens, P.; Nénon, Q.; Gural, P. S.; Albers, J.; Haberman, B.; Johnson, B.; Morales, R.; Grigsby, B. J.; Samuels, D.; Johannink, C.

2016-03-01

The Cameras for Allsky Meteor Surveillance (CAMS) video-based meteoroid orbit survey adds 60 newly identified showers to the IAU Working List of Meteor Showers (numbers 427, 445-446, 506-507, and part of 643-750). 28 of these are also detected in the independent SonotaCo survey. In total, 230 meteor showers and shower components are identified in CAMS data, 177 of which are detected in at least two independent surveys. From the power-law size frequency distribution of detected showers, we extrapolate that 36% of all CAMS-observed meteors originated from ∼700 showers above the N = 1 per 110,000 shower limit. 71% of mass falling to Earth from streams arrives on Jupiter-family type orbits. The transient Geminids account for another 15%. All meteoroids not assigned to streams form a sporadic background with highest detected numbers from the apex source, but with 98% of mass falling in from the antihelion source. Even at large ∼7-mm sizes, a Poynting-Robertson drag evolved population is detected, which implies that the Grün et al. collisional lifetimes at these sizes are underestimated by about a factor of 10. While these large grains survive collisions, many fade on a 104-y timescale, possibly because they disintegrate into smaller particles by processes other than collisions, leaving a more resilient population to evolve.

X-rays from comets - a surprising discovery

CERN Document Server

CERN. Geneva

2000-01-01

Comets are kilometre-size aggregates of ice and dust, which remained from the formation of the solar system. It was not obvious to expect X-ray emission from such objects. Nevertheless, when comet Hyakutake (C/1996 B2) was observed with the ROSAT X-ray satellite during its close approach to Earth in March 1996, bright X-ray emission from this comet was discovered. This finding triggered a search in archival ROSAT data for comets, which might have accidentally crossed the field of view during observations of unrelated targets. To increase the surprise even more, X-ray emission was detected from four additional comets, which were optically 300 to 30 000 times fainter than Hyakutake. For one of them, comet Arai (C/1991 A2), X-ray emission was even found in data which were taken six weeks before the comet was optically discovered. These findings showed that comets represent a new class of celestial X-ray sources. The subsequent detection of X-ray emission from several other comets in dedicated observations confir...

Unusual Radar Echo from the Wake of Meteor Fireball in Nearly

Directory of Open Access Journals (Sweden)

Young-Sook Lee

2018-06-01

Full Text Available The summer polar lower thermosphere (90–100 km has an interesting connection to meteors, adjacent to the mesopause region attaining the lowest temperature in summer. Meteors supply condensation nuclei for charged ice particles causing polar mesospheric summer echoes (PMSE. We report the observation of meteor trail with nearly horizontal transit at high speed (20–50 km/s, and at last with re-enhanced echo power followed by diffusive echoes. Changes in phase difference between radar receivers aligned in meridional and zonal directions are used to determine variations in horizontal displacements and speeds with respect to time by taking advantage of radar interferometric analysis. The actual transit of echo target is observed along the straight pathway vertically and horizontally extended as much as a distance of at least 24 km and at most 29 km. The meteor trail initially has a signature similar to ‘head echoes’, with travel speeds from 20 – 50 km/s. It subsequently transforms into a different type of echo target including specular echo and then finally the power reenhanced. The reenhancement of echo power is followed by fume-like diffusive echoes, indicating sudden release of plasma as like explosive process probably involved. We discuss a possible role of meteor-triggered secondary plasma trail, such as fireball embedded with electrical discharge that continuously varies the power and transit speed.

Seismic characterization of the Chelyabinsk meteor's terminal explosion

Science.gov (United States)

González, Álvaro; Heimann, Sebastian; Wang, Rongjiang; Cesca, Simone; Dahm, Torsten

2014-05-01

On February 15th, 2013, an exceptionally large meteor in the region of Chelyabinsk, Russia, produced a powerful shock wave which caused unprecedented damage to people and property, the strongest atmospheric infrasound signal ever recorded, and remarkable ground motion. Here we describe and model the resulting Rayleigh waves, recorded at broadband seismic stations at distances from ~230 to ~4,100 km. Our full-waveform modeling uses a seismogram simulation code specifically tailored to consider wave propagation in the atmosphere and solid Earth, and the coupling at the interface between them. An isotropic point-like airburst reproduces very well the available seismic observations, without requiring a more complex explanation, such as a moving source. The measured seismic shaking was generated by direct coupling of the atmospheric shock wave to the ground, and then it propagated outwards faster than the atmospheric shock wave itself, at up to 3.9 km/s. The best-fitting airburst location (61.22° E, 54.88° N) is SW of Chelyabinsk city, exactly at the terminal part of the meteor's trajectory, just after it experienced a dramatic flare, with apparent brightness larger than the Sun's. We estimated the meteor's ground path from published trajectory data, eyewitness observations, and detailed satellite imagery of the exact location where a major meteorite fragment landed, in the frozen Lake Chebarkul (60.32074° E, 54.95966° N). Fixing the source origin time allowed us calculating that the explosion took place in the stratosphere, at an altitude of 22.5 ± 1.5 km. This value is lower than the reported altitude of peak brightness (about 29.5 km), but more consistent with the observations of shock wave travel times. Such results highlight the importance of terminal energy release down to lower altitude. We analyzed a surveillance video recorded inside a factory (61.347° E, 54.902° N) at Korkino, a locality close to the airburst. It shows a time delay of 87.5 seconds

Estimation of Mesospheric Densities at Low Latitudes Using the Kunming Meteor Radar Together With SABER Temperatures

Science.gov (United States)

Yi, Wen; Xue, Xianghui; Reid, Iain M.; Younger, Joel P.; Chen, Jinsong; Chen, Tingdi; Li, Na

2018-04-01

Neutral mesospheric densities at a low latitude have been derived during April 2011 to December 2014 using data from the Kunming meteor radar in China (25.6°N, 103.8°E). The daily mean density at 90 km was estimated using the ambipolar diffusion coefficients from the meteor radar and temperatures from the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument. The seasonal variations of the meteor radar-derived density are consistent with the density from the Mass Spectrometer and Incoherent Scatter (MSIS) model, show a dominant annual variation, with a maximum during winter, and a minimum during summer. A simple linear model was used to separate the effects of atmospheric density and the meteor velocity on the meteor radar peak detection height. We find that a 1 km/s difference in the vertical meteor velocity yields a change of approximately 0.42 km in peak height. The strong correlation between the meteor radar density and the velocity-corrected peak height indicates that the meteor radar density estimates accurately reflect changes in neutral atmospheric density and that meteor peak detection heights, when adjusted for meteoroid velocity, can serve as a convenient tool for measuring density variations around the mesopause. A comparison of the ambipolar diffusion coefficient and peak height observed simultaneously by two co-located meteor radars indicates that the relative errors of the daily mean ambipolar diffusion coefficient and peak height should be less than 5% and 6%, respectively, and that the absolute error of the peak height is less than 0.2 km.

Isotopic meteoric line for Colombia

International Nuclear Information System (INIS)

Rodriguez N, Cesar O

2004-01-01

Isotope analyses from representative rainfall samples taken from different areas in Colombia were processed to yield the meteoric line. Stable isotope composition in precipitation reflects the effects of temperature, altitude and of the continental site, being affected by different sources of atmospheric humidity over the Colombian territory. There is a seasonal variation in isotopic composition of precipitation with grater σ deviation during the rainy season and lower values in the dry season. In coastal areas the variation is smaller and is more pronounced than at continental stations. Correlation between altitude and isotope content led to equations, which indicate, on a regional level, a change in isotopic composition with altitude, of about 0.5 σ units per 200 m, for O 18 and 4 σ units per 200 m for H 2 . Such equations may be used to identify the original altitude of precipitation water, in hydrological surface and groundwater studies. Meteoric line and the concepts derived from the resulting equations presented in this paper may be applied to the interpretation of isotope analysis in future hydrological studies, particularly in areas without available data

The Halley comet

International Nuclear Information System (INIS)

Encrenaz, T.; Festou, M.

1985-01-01

The conspicuous part of a comet, made of tenuous gas and dusts, represents only a tiny part of its mass. The main information is hidden in the central part: a solid nucleus, ice and rock blocks with a radius less than 10 km, completely invisible from the Earth. The knowledge of the nucleus structure and its composition could give the key of the planet creation mechanisms. That is a reason why it has been decided to send an automatic device to penetrate the Halley comet atmosphere and that two Soviet probes, Vega 1 and 2, one European probe Giotto, and two Japanese, Planet-A and MS-TS, will explore in-situ in March 1986, for the first time, a comet at atmosphere [fr

Optical observations of enhanced activity of the 2005 Draconid meteor shower

Czech Academy of Sciences Publication Activity Database

Koten, Pavel; Borovička, Jiří; Spurný, Pavel; Štork, Rostislav

2007-01-01

Roč. 466, č. 2 (2007), s. 729-735 ISSN 0004-6361 R&D Projects: GA AV ČR KJB300030502; GA ČR GA205/05/0543 Institutional research plan: CEZ:AV0Z10030501 Keywords : meteors * meteor shower s * Draconids Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 4.259, year: 2007

Results of the first continuous meteor head echo survey at polar latitudes

Science.gov (United States)

Schult, Carsten; Stober, Gunter; Janches, Diego; Chau, Jorge L.

2017-11-01

We present the first quasi continuous meteor head echo measurements obtained during a period of over two years using the Middle Atmosphere ALOMAR Radar System (MAARSY). The measurements yield information on the altitude, trajectory, vector velocity, radar cross section, deceleration and dynamical mass of every single event. The large statistical amount of nearly one million meteor head detections provide an excellent overview of the elevation, altitude, velocity and daily count rate distributions during different times of the year at polar latitudes. Only 40% of the meteors were detected within the full width half maximum of the specific sporadic meteor sources. Our observation of the sporadic meteors are compared to the observations with other radar systems and a meteor input function (MIF). The best way to compare different radar systems is by comparing the radar cross section (RCS), which is the main detection criterion for each system. In this study we aim to compare our observations with a MIF, which provides information only about the meteoroid mass. Thus, we are using a statistical approach for the elevation and velocity dependent visibility and a specific mass selection. The predicted absolute count rates from the MIF are in a good agreement with the observation when it is assumed that the radar system is only sensitive to meteoroids with masses higher than one microgram. The analysis of the dynamic masses seems to be consistent with this assumption since the count rate of events with smaller masses are low and decrease even more by using events with relatively small errors.

Comet prospects for 2004

Science.gov (United States)

Shanklin, J. D.

2003-12-01

2004 sees the return of 18 periodic comets. None are particularly bright and the best are likely to be 78P/Gehrels and 88P/Howell. Three new long period comets are likely to put on a good show: 2001 Q4 (NEAT) reaches perihelion in May, when it could make at least 3rd magnitude. Northern hemisphere observers will first pick it up just after perihelion as it rapidly moves north. 2002 T7 (LINEAR) could also reach 3rd magnitude at closest approach in May, however northern hemisphere observers will have lost it as a binocular object in mid-March. Observers at far southern latitudes may be able to see these two naked eye comets at the same time. 2003 K4 (LINEAR) could reach 6th magnitude as it brightens on its way to perihelion. Several other long period comets discovered in previous years are also still visible.

Double station observation of Draconid meteor outburst from two moving aircraft

Czech Academy of Sciences Publication Activity Database

Koten, Pavel; Vaubaillon, J.; Margonis, A.; Toth, J.; Ďuriš, F.; McAulliffe, J.; Oberst, J.

2015-01-01

Roč. 118, December (2015), s. 112-119 ISSN 0032-0633 R&D Projects: GA ČR GA14-25251S; GA ČR(CZ) GAP209/11/1382; GA MŠk 7AMB13FR006 Institutional support: RVO:67985815 Keywords : meteors * meteor showers * Draconids Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 1.942, year: 2015

X-ray emission from comets

International Nuclear Information System (INIS)

Dennerl, Konrad

1999-01-01

When comet Hyakutake (C/1996 B2) encountered Earth in March 1996 at a minimum distance of only 15 million kilometers (40 times the distance of the moon), x-ray and extreme ultraviolet emission was discovered for the first time from a comet. The observations were performed with the astronomy satellites ROSAT and EUVE. A systematic search for x-rays from comets in archival data, obtained during the ROSAT all-sky survey in 1990/91, resulted in the discovery of x-ray emission from four additional comets. They were detected at seven occasions in total, when they were optically 300 to 30 000 times fainter than Hyakutake. These findings indicated that comets represent a new class of celestial x-ray sources. Subsequent detections of x-ray emission from additional comets with the satellites ROSAT, EUVE, and BeppoSAX confirmed this conclusion. The x-ray observations have obviously revealed the presence of a process in comets which had escaped attention until recently. This process is most likely charge exchange between highly charged heavy ions in the solar wind and cometary neutrals. The solar wind, a stream of particles continuously emitted from the sun with ≅ 400 km s -1 , consists predominantly of protons, electrons, and alpha particles, but contains also a small fraction (≅0.1%) of highly charged heavier ions, such as C 6+ ,O 6+ ,Ne 8+ ,Si 9+ ,Fe 11+ . When these ions capture electrons from the cometary gas, they attain highly excited states and radiate a large fraction of their excitation energy in the extreme ultraviolet and x-ray part of the spectrum. Charge exchange reproduces the intensity, the morphology and the spectrum of the observed x-ray emission from comets very well

METEOR: An Enterprise Health Informatics Environment to Support Evidence-Based Medicine.

Science.gov (United States)

Puppala, Mamta; He, Tiancheng; Chen, Shenyi; Ogunti, Richard; Yu, Xiaohui; Li, Fuhai; Jackson, Robert; Wong, Stephen T C

2015-12-01

The aim of this paper is to propose the design and implementation of next-generation enterprise analytics platform developed at the Houston Methodist Hospital (HMH) system to meet the market and regulatory needs of the healthcare industry. For this goal, we developed an integrated clinical informatics environment, i.e., Methodist environment for translational enhancement and outcomes research (METEOR). The framework of METEOR consists of two components: the enterprise data warehouse (EDW) and a software intelligence and analytics (SIA) layer for enabling a wide range of clinical decision support systems that can be used directly by outcomes researchers and clinical investigators to facilitate data access for the purposes of hypothesis testing, cohort identification, data mining, risk prediction, and clinical research training. Data and usability analysis were performed on METEOR components as a preliminary evaluation, which successfully demonstrated that METEOR addresses significant niches in the clinical informatics area, and provides a powerful means for data integration and efficient access in supporting clinical and translational research. METEOR EDW and informatics applications improved outcomes, enabled coordinated care, and support health analytics and clinical research at HMH. The twin pressures of cost containment in the healthcare market and new federal regulations and policies have led to the prioritization of the meaningful use of electronic health records in the United States. EDW and SIA layers on top of EDW are becoming an essential strategic tool to healthcare institutions and integrated delivery networks in order to support evidence-based medicine at the enterprise level.

Meteor Shower Forecast Improvements from a Survey of All-Sky Network Observations

Science.gov (United States)

Moorhead, Althea V.; Sugar, Glenn; Brown, Peter G.; Cooke, William J.

2015-01-01

Meteoroid impacts are capable of damaging spacecraft and potentially ending missions. In order to help spacecraft programs mitigate these risks, NASA's Meteoroid Environment Office (MEO) monitors and predicts meteoroid activity. Temporal variations in near-Earth space are described by the MEO's annual meteor shower forecast, which is based on both past shower activity and model predictions. The MEO and the University of Western Ontario operate sister networks of all-sky meteor cameras. These networks have been in operation for more than 7 years and have computed more than 20,000 meteor orbits. Using these data, we conduct a survey of meteor shower activity in the "fireball" size regime using DBSCAN. For each shower detected in our survey, we compute the date of peak activity and characterize the growth and decay of the shower's activity before and after the peak. These parameters are then incorporated into the annual forecast for an improved treatment of annual activity.

The extra-atmospheric masses of small meteoric fireballs from the Prairie and the Canadian camera networks.

Science.gov (United States)

Popelenskaya, N.

2007-08-01

Existing methods of definition of extra-atmospheric masses of small meteoric bodies according to supervision of their movement in an atmosphere contain the certain arbitrariness. Vigorous attempts to overcome a divergence of results of calculations on the basis of various approaches often lead to physically incorrect conclusions. The output consists in patient accumulation of estimations and calculations for gradual elimination uncertainties. The equations of meteoric physics include two dimensionless parameters - factor ablation ? and factor of braking ?. In work are cited the data processing supervision of small meteors Prairie and Canadian networks, by a finding of values of parameters ? and ? with use of a method of the least squares. Also values of heights blackout a meteor which turn out from conditions of full destruction or final braking with use of the received values of ? and ? are considered. In prevailing number of supervision for considered meteors braking is insignificant. Results of calculations of height of blackout meteors confirm suitability of the approximations used in work for the description of movement of small meteors. In work results of calculation of extra-atmospheric masses with use of factor of braking for meteoric bodies of the spherical form with density of an ice and a stone are presented. On the basis of the received results discrepancy of photometric masses to values of masses of the input, received on observable braking proves to be true. In most cases received magnitude of masses essentially less photometric masses. Processing of supervision of small meteors Prairie and Canadian camera networks has shown, that the so-called photometric mass mismatches values of mass of the input, defined on observable braking. Acceptance of photometric value as the mass defining braking of a body, leads to obviously underestimated values of density of substance meteoric body. The further researches on specification of interpretation of supervision

OpenComet: An automated tool for comet assay image analysis

OpenAIRE

Gyori, Benjamin M.; Venkatachalam, Gireedhar; Thiagarajan, P.S.; Hsu, David; Clement, Marie-Veronique

2014-01-01

Reactive species such as free radicals are constantly generated in vivo and DNA is the most important target of oxidative stress. Oxidative DNA damage is used as a predictive biomarker to monitor the risk of development of many diseases. The comet assay is widely used for measuring oxidative DNA damage at a single cell level. The analysis of comet assay output images, however, poses considerable challenges. Commercial software is costly and restrictive, while free software generally requires ...

Comets and How to Observe Them

CERN Document Server

Schmude, Richard

2010-01-01

Comets have inspired wonder, excitement and even fear ever since they were first observed. They contain material from early in the life of the Solar System, held in deep-freeze. This makes them key in our understanding of the formation and evolution of many Solar System bodies. Recent ground- and space-based observations have changed much in our understanding of comets. Comets and How to Observe Them gives a summary of our current knowledge and describes how amateur astronomers can contribute to the body of scientific knowledge of comets. This book contains many practical examples of how to construct comet light-curves, measure how fast a comet’s coma expands, and determine the rotation period of the nucleus. All these examples are illustrated with drawings and photographs.

Astrobiology of Comets

Science.gov (United States)

Hoover, Richard B.; Wickramasinghe, Nalin C.; Wallis, Max K.; Sheldon, Robert B.

2004-01-01

We review the current state of knowledge concerning microbial extremophiles and comets and the potential significance of comets to Astrobiology. We model the thermal history of a cometary body, regarded as an assemblage of boulders, dust, ices and organics, as it approaches a perihelion distance of - IAU. The transfer of incident energy from sunlight into the interior leads to the melting of near surface ices, some under stable porous crust, providing possible habitats for a wide range of microorganisms. We provide data concerning new evidence for indigenous microfossils in CI meteorites, which may be the remains of extinct cometary cores. We discuss the dominant microbial communities of polar sea-ice, Antarctic ice sheet, and cryoconite environments as possible analogs for microbial ecosystems that may grow in sub-crustal pools or in ice/water films in comets.

Meteor reporting made easy- The Fireballs in the Sky smartphone app

Science.gov (United States)

Sansom, E.; Ridgewell, J.; Bland, P.; Paxman, J.

2016-01-01

Using smartphone technology, the award-winning 'Fireballs in the Sky' app provides a new approach to public meteor reporting. Using the internal GPS and sensors of a smartphone, a user can record the start and end position of a meteor sighting with a background star field as reference. Animations are used to visualize the duration and characteristics of the meteor. The intuitive application can be used in situ, providing a more accurate eye witness account than after-the-fact reports (although reports may also be made through a website interface). Since its launch in 2013, the app has received over 2000 submissions, including 73 events which were reported by multiple users. The app database is linked to the Desert Fireball Network in Australia (DFN), meaning app reports can be confirmed by DFN observatories. Supporting features include an integrated meteor shower tool that provides updates on active showers, their visibility based on moon phase, as well as a tool to point the user toward the radiant. The locations of reports are also now shown on a live map on the Fireballs in the Sky webpage.

Comparison with Russian analyses of meteor impact

Energy Technology Data Exchange (ETDEWEB)

Canavan, G.H.

1997-06-01

The inversion model for meteor impacts is used to discuss Russian analyses and compare principal results. For common input parameters, the models produce consistent estimates of impactor parameters. Directions for future research are discussed and prioritized.

Radar observations of meteor trails, and their interpretation using Fresnel holography: a new tool in meteor science

Directory of Open Access Journals (Sweden)

W. G. Elford

2004-01-01

Full Text Available A Fresnel transform technique has been developed at Adelaide to analyse radar meteor echoes detected in the transverse mode. The genesis for this technique was the study of the structure of the scattering ionization immediately behind the head of the trail, in order to deduce the degree of fragmentation of the ablating meteoroid. The technique has been remarkably successful in not only giving insight into the fragmentation of meteoroids, but also revealing other significant features of the trails including diffusion, lateral motion of the trail during formation due to wind drift, and phase of the scattered signal in the vicinity of the head of the trail. A serendipitous outcome of the analysis is the measurement of the speed and deceleration of the meteoroid producing the trail to a precision far exceeding that available from any other method applied to transverse scatter data. Examples of the outcomes of the technique applied to meteor echoes obtained with a 54MHz narrow beam radar are presented.

Earth-return trajectory options for the 1985-86 Halley opportunity

Science.gov (United States)

Farquhar, R. W.; Dunham, D. W.

1982-01-01

A unique and useful family of ballistic trajectories to Halley's comet is described. The distinguishing feature of this family is that all of the trajectories return to the Earth's vicinity after the Halley intercept. It is shown that, in some cases, the original Earth-return path can be reshaped by Earth-swingby maneuvers to achieve additional small-body encounters. One mission profile includes flybys of the asteroid Geographos and comet Tempel-2 following the Halley intercept. Dual-flyby missions involving comets Encke and Borrelly and the asteroid Anteros are also discussed. Dust and gas samples are collected during the high-velocity (about 70 km/sec) flythrough of Halley, and then returned to a high-apogee Earth orbit. Aerobraking maneuvers are used to bring the sample-return spacecraft to a low-altitude circular orbit where it can be recovered by the Space Shuttle.

PMN-Portuguese Meteor Network and OLA-Observatório do Lago Alqueva agreement

Science.gov (United States)

Saraiva, C.

2018-01-01

The PMN-Portuguese Meteor Network has two new video meteor detecting systems at OLA- Observartório do Lago Alqueva, situated at the South East Portuguese territory with a pristine night sky and more than 290 clear nights each year.

Be2D: A model to understand the distribution of meteoric 10Be in soilscapes

Science.gov (United States)

Campforts, Benjamin; Vanacker, Veerle; Vanderborght, Jan; Govers, Gerard

2016-04-01

Cosmogenic nuclides have revolutionised our understanding of earth surface process rates. They have become one of the standard tools to quantify soil production by weathering, soil redistribution and erosion. Especially Beryllium-10 has gained much attention due to its long half-live and propensity to be relatively conservative in the landscape. The latter makes 10Be an excellent tool to assess denudation rates over the last 1000 to 100 × 103 years, bridging the anthropogenic and geological time scale. Nevertheless, the mobility of meteoric 10Be in soil systems makes translation of meteoric 10Be inventories into erosion and deposition rates difficult. Here we present a coupled soil hillslope model, Be2D, that is applied to synthetic and real topography to address the following three research questions. (i) What is the influence of vertical meteoric Be10 mobility, caused by chemical mobility, clay translocation and bioturbation, on its lateral redistribution over the soilscape, (ii) How does vertical mobility influence erosion rates and soil residence times inferred from meteoric 10Be inventories and (iii) To what extent can a tracer with a half-life of 1.36 Myr be used to distinguish between natural and human-disturbed soil redistribution rates? The model architecture of Be2D is designed to answer these research questions. Be2D is a dynamic model including physical processes such as soil formation, physical weathering, clay migration, bioturbation, creep, overland flow and tillage erosion. Pathways of meteoric 10Be mobility are simulated using a two step approach which is updated each timestep. First, advective and diffusive mobility of meteoric 10Be is simulated within the soil profile and second, lateral redistribution because of lateral soil fluxes is calculated. The performance and functionality of the model is demonstrated through a number of synthetic and real model runs using existing datasets of meteoric 10Be from case-studies in southeastern US. Brute

COMET concept; COMET-Konzept

Energy Technology Data Exchange (ETDEWEB)

Alsmeyer, H.; Tromm, W.

1995-08-01

Studies of the COMET core catcher concept developed for a future PWR have been continued. The concept is based on the spreading of a core melt on a sacrificial layer and its erosion, until a subsequent addition of water from below causes a fragmentation of the melt. A porous solidification of the melt would then admit a complete flooding within a short period. (orig.)

An Initial Meteoroid Stream Survey in the Southern Hemisphere Using the Southern Argentina Agile Meteor Radar (SAAMER)

Science.gov (United States)

Janches, D.; Hormaechea, J. L.; Brunini, C.; Hocking, W.; Fritts, D. C.

2013-01-01

We present in this manuscript a 4 year survey of meteor shower radiants utilizing the Southern Argentina Agile Meteor Radar (SAAMER). SAAMER, which operates at the southern most region of South America, is a new generation SKiYMET system designed with significant differences from typical meteor radars including high transmitted power and an 8-antenna transmitting array enabling large detected rates at low zenith angles. We applied the statistical methodology developed by Jones and Jones (Jones, J., Jones, W. [2006]. Month. Not. R. Astron. Soc. 367, 1050-1056) to the data collected each day and compiled the results into 1 composite representative year at 1 resolution in Solar Longitude. We then search for enhancements in the activity which last for at least 3 days and evolve temporally as is expected from a meteor shower. Using this methodology, we have identified in our data 32 shower radiants, two of which were not part of the IAU commission 22 meteor shower working list. Recently, SAAMER's capabilities were enhanced by adding two remote stations to receive meteor forward scatter signals from meteor trails and thus enable the determination of meteoroid orbital parameters. SAAMER started recording orbits in January 2012 and future surveys will focus on the search for unknown meteor streams, in particular in the southern ecliptic sky.

Comets in Indian Scriptures

Science.gov (United States)

Das Gupta, P.

2016-01-01

The Indo-Aryans of ancient India observed stars and constellations for ascertaining auspicious times in order to conduct sacrificial rites ordained by the Vedas. Naturally, they would have sighted comets and referred to them in the Vedic texts. In Rigveda (circa 1700-1500 BC) and Atharvaveda (circa 1150 BC), there are references to dhumaketus and ketus, which stand for comets in Sanskrit. Rigveda speaks of a fig tree whose aerial roots spread out in the sky (Parpola 2010). Had this imagery been inspired by the resemblance of a comet's tail with long and linear roots of a banyan tree (ficus benghalensis)? Varahamihira (AD 550) and Ballal Sena (circa AD 1100-1200) described a large number of comets recorded by ancient seers, such as Parashara, Vriddha Garga, Narada, and Garga, to name a few. In this article, we propose that an episode in Mahabharata in which a radiant king, Nahusha, who rules the heavens and later turns into a serpent after he kicked the seer Agastya (also the star Canopus), is a mythological retelling of a cometary event.

Jupiter Laser Facility - COMET Laser

Data.gov (United States)

Federal Laboratory Consortium — COMET has 4 beam configurations with uncompressed pulse lengths from 500 ps to 6 ns, compressed pulses to 0.5 ps, and beam energies up to 20 J. COMET can fire every...

Comet-Narval acquisition notice

International Nuclear Information System (INIS)

Le Bris, J.; Sellem, R.; Artiges, J.C.; Clavelin, J.F.; Du, S.; Grave, X.; Hubert, O.; Sauvage, J.; Roussiere, B.

2006-01-01

The COMET cards (encoding and time marking) serve to determine the energies and the time correlations of radiations detected during a multiparameter experiment while avoiding any extra specific module like coincidence circuits or delays) to set this time correlation. For each detected radiation, the arrival time information as well as the amplitude of the detected signal, are encoded. The results of these amplitude and time coding are associated to create an event. In this way, each detector is an independent source which provides a building block of the general information obtained by all the detectors. The COMET cards are associated with a NARVAL data acquisition system. This document is the instruction booklet of the COMET-NARVAL acquisition system

Comet: Multifunction VOEvent broker

Science.gov (United States)

Swinbank, John

2014-04-01

Comet is a Python implementation of the VOEvent Transport Protocol (VTP). VOEvent is the IVOA system for describing transient celestial events. Details of transients detected by many projects, including Fermi, Swift, and the Catalina Sky Survey, are currently made available as VOEvents, which is also the standard alert format by future facilities such as LSST and SKA. The core of Comet is a multifunction VOEvent broker, capable of receiving events either by subscribing to one or more remote brokers or by direct connection from authors; it can then both process those events locally and forward them to its own subscribers. In addition, Comet provides a tool for publishing VOEvents to the global VOEvent backbone.

Comets in the space age

International Nuclear Information System (INIS)

Whipple, F.L.

1989-01-01

The historical development of the study of the nature of comets and their origin is discussed, emphasizing the use of aerospace technology in cometary science. The use of satellites to study the Comet Kohoutek 1973 XII, advances between Kohoutek and P/Halley, and studies of P/Halley during its 1986 return are examined. Consideration is given to data from ground, air, and space sensors, and from the Giotto and Vega spacecraft missions. Also, the physical structure of the nucleus of Comet Halley is described. 136 refs

Radar meteors range distribution model. II. Shower flux density and mass distribution index

Czech Academy of Sciences Publication Activity Database

Pecinová, Drahomíra; Pecina, Petr

2007-01-01

Roč. 37, č. 2 (2007), s. 107-124 ISSN 1335-1842 R&D Projects: GA ČR GA205/03/1405 Institutional research plan: CEZ:AV0Z10030501 Keywords : physics of meteors * radar meteors * range distribution Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics

Radar meteors range distribution model. III. Ablation, shape-density and self-similarity parameters

Czech Academy of Sciences Publication Activity Database

Pecinová, Drahomíra; Pecina, Petr

2007-01-01

Roč. 37, č. 3 (2007), s. 147-160 ISSN 1335-1842 R&D Projects: GA ČR GA205/03/1405 Institutional research plan: CEZ:AV0Z10030501 Keywords : physics of meteors * radar meteors * range distribution Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics

Observations of the Perseids 2013 using SPOSH cameras

Science.gov (United States)

Margonis, A.; Elgner, S.; Christou, A.; Oberst, J.; Flohrer, J.

2013-09-01

Earth is constantly bombard by debris, most of which disintegrates in the upper atmosphere. The collision of a dust particle, having a mass of approximately 1g or larger, with the Earth's atmosphere results into a visible streak of light in the night sky, called meteor. Comets produce new meteoroids each time they come close to the Sun due to sublimation processes. These fresh particles are moving around the Sun in orbits similar to their parent comet forming meteoroid streams. For this reason, the intersection of Earth's orbital path with different comets, gives rise to anumber of meteor showers throughout the year. The Perseids are one of the most prominent annual meteor showers occurring every summer, having its origin in Halley-type comet 109P/Swift-Tuttle. The dense core of this stream passes Earth's orbit on the 12th of August when more than 100 meteors per hour can been seen by a single observer under ideal conditions. The Technical University of Berlin (TUB) and the German Aerospace Center (DLR) together with the Armagh observatory organize meteor campaigns every summer observing the activity of the Perseids meteor shower. The observations are carried out using the Smart Panoramic Optical Sensor Head (SPOSH) camera system [2] which has been developed by DLR and Jena-Optronik GmbH under an ESA/ESTEC contract. The camera was designed to image faint, short-lived phenomena on dark planetary hemispheres. The camera is equipped with a highly sensitive back-illuminated CCD chip having a pixel resolution of 1024x1024. The custom-made fish-eye lens offers a 120°x120° field-of-view (168° over the diagonal) making the monitoring of nearly the whole night sky possible (Fig. 1). This year the observations will take place between 3rd and 10th of August to cover the meteor activity of the Perseids just before their maximum. The SPOSH cameras will be deployed at two remote sites located in high altitudes in the Greek Peloponnese peninsula. The baseline of ∼50km

Report of Some Comets: The Discovery of Uranus and Comets by William, Caroline, and John Herschel

Science.gov (United States)

Pasachoff, Jay M.; Olson, R. J. M.

2011-01-01

We report on the discovery and drawings of comets by William, Caroline, and John Herschel. The first discovery, by William Herschel, in 1781 from Bath, published in the Philosophical Transactions of the Royal Society with the title "Report of a Comet," turned out to be Uranus, the first planet ever discovered, Mercury through Saturn having been known since antiquity. William's sister Caroline was given duties of sweeping the skies and turned out to be a discoverer of 8 comets in her own right, in addition to keeping William's notes. Caroline's comets were discovered from Slough between 1786 and 1797. In the process, we also discuss original documents from the archives of the Royal Society and of the Royal Astronomical Society. We conclude by showing comet drawings that we have recently attributed to John Herschel, including Halley's Comet from 1836, recently located in the Ransom Center of the University of Texas at Austin. Acknowledgments: Planetary astronomy at Williams College is supported in part by grant NNX08AO50G from NASA Planetary Astronomy. We thank Peter Hingley of the Royal Astronomical Society and Richard Oram of the Harry Ransom Center of The University of Texas at Austin for their assistance.

Nucleus of Comet IRAS-Araki-Alcock (1983 VII)

International Nuclear Information System (INIS)

Sekanina, Z.

1988-01-01

Optical, radar, infrared, UV, and microwave-continuum observations of Comet IRAS-Araki-Alcok were obtained in May 1983, the week of the comet's close approach to earth. The comet has a nucleus dimension and a rotation period which are similar to those of Comet Halley, but a different morphological signature (a persisting sunward fan-shaped coma). Time variations are noted in the projected nucleus cross section. Results suggest significant limb-darkening effects in the relevant domains of radio waves, and that the comet's interior must be extremely cold. It is found that the thermal-infrared fluxes from the inner coma of the comet are dominated by the nucleus. 63 references

EPOXI at comet Hartley 2.

Science.gov (United States)

A'Hearn, Michael F; Belton, Michael J S; Delamere, W Alan; Feaga, Lori M; Hampton, Donald; Kissel, Jochen; Klaasen, Kenneth P; McFadden, Lucy A; Meech, Karen J; Melosh, H Jay; Schultz, Peter H; Sunshine, Jessica M; Thomas, Peter C; Veverka, Joseph; Wellnitz, Dennis D; Yeomans, Donald K; Besse, Sebastien; Bodewits, Dennis; Bowling, Timothy J; Carcich, Brian T; Collins, Steven M; Farnham, Tony L; Groussin, Olivier; Hermalyn, Brendan; Kelley, Michael S; Kelley, Michael S; Li, Jian-Yang; Lindler, Don J; Lisse, Carey M; McLaughlin, Stephanie A; Merlin, Frédéric; Protopapa, Silvia; Richardson, James E; Williams, Jade L

2011-06-17

Understanding how comets work--what drives their activity--is crucial to the use of comets in studying the early solar system. EPOXI (Extrasolar Planet Observation and Deep Impact Extended Investigation) flew past comet 103P/Hartley 2, one with an unusually small but very active nucleus, taking both images and spectra. Unlike large, relatively inactive nuclei, this nucleus is outgassing primarily because of CO(2), which drags chunks of ice out of the nucleus. It also shows substantial differences in the relative abundance of volatiles from various parts of the nucleus.

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

A Global Model of Meteoric Sodium

Science.gov (United States)

Marsh, Daniel R.; Janches, Diego; Feng, Wuhu; Plane, John M. C.

2013-01-01

A global model of sodium in the mesosphere and lower thermosphere has been developed within the framework of the National Center for Atmospheric Research's Whole Atmosphere Community Climate Model (WACCM). The standard fully interactive WACCM chemistry module has been augmented with a chemistry scheme that includes nine neutral and ionized sodium species. Meteoric ablation provides the source of sodium in the model and is represented as a combination of a meteoroid input function (MIF) and a parameterized ablation model. The MIF provides the seasonally and latitudinally varying meteoric flux which is modeled taking into consideration the astronomical origins of sporadic meteors and considers variations in particle entry angle, velocity, mass, and the differential ablation of the chemical constituents. WACCM simulations show large variations in the sodium constituents over time scales from days to months. Seasonality of sodium constituents is strongly affected by variations in the MIF and transport via the mean meridional wind. In particular, the summer to winter hemisphere flow leads to the highest sodium species concentrations and loss rates occurring over the winter pole. In the Northern Hemisphere, this winter maximum can be dramatically affected by stratospheric sudden warmings. Simulations of the January 2009 major warming event show that it caused a short-term decrease in the sodium column over the polar cap that was followed by a factor of 3 increase in the following weeks. Overall, the modeled distribution of atomic sodium in WACCM agrees well with both ground-based and satellite observations. Given the strong sensitivity of the sodium layer to dynamical motions, reproducing its variability provides a stringent test of global models and should help to constrain key atmospheric variables in this poorly sampled region of the atmosphere.

Calibration-free quantitative elemental analysis of meteor plasma using reference laser-induced breakdown spectroscopy of meteorite samples

Science.gov (United States)

Ferus, Martin; Koukal, Jakub; Lenža, Libor; Srba, Jiří; Kubelík, Petr; Laitl, Vojtěch; Zanozina, Ekaterina M.; Váňa, Pavel; Kaiserová, Tereza; Knížek, Antonín; Rimmer, Paul; Chatzitheodoridis, Elias; Civiš, Svatopluk

2018-03-01

Aims: We aim to analyse real-time Perseid and Leonid meteor spectra using a novel calibration-free (CF) method, which is usually applied in the laboratory for laser-induced breakdown spectroscopic (LIBS) chemical analysis. Methods: Reference laser ablation spectra of specimens of chondritic meteorites were measured in situ simultaneously with a high-resolution laboratory echelle spectrograph and a spectral camera for meteor observation. Laboratory data were subsequently evaluated via the CF method and compared with real meteor emission spectra. Additionally, spectral features related to airglow plasma were compared with the spectra of laser-induced breakdown and electric discharge in the air. Results: We show that this method can be applied in the evaluation of meteor spectral data observed in real time. Specifically, CF analysis can be used to determine the chemical composition of meteor plasma, which, in the case of the Perseid and Leonid meteors analysed in this study, corresponds to that of the C-group of chondrites.

Simulating the mobility of meteoric 10Be in the landscape through a coupled soil-hillslope model (Be2D)

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Campforts, Benjamin; Vanacker, Veerle; Vanderborght, Jan; Baken, Stijn; Smolders, Erik; Govers, Gerard

2016-04-01

Meteoric 10Be allows for the quantification of vertical and lateral soil fluxes over long time scales (103-105 yr). However, the mobility of meteoric 10Be in the soil system makes a translation of meteoric 10Be inventories into erosion and deposition rates complex. Here, we present a spatially explicit 2D model simulating the behaviour of meteoric 10Be on a hillslope. The model consists of two parts. The first component deals with advective and diffusive mobility of meteoric 10Be within the soil profile, and the second component describes lateral soil and meteoric 10Be fluxes over the hillslope. Soil depth is calculated dynamically, accounting for soil production through weathering as well as downslope fluxes of soil due to creep, water and tillage erosion. Synthetic model simulations show that meteoric 10Be inventories can be related to erosion and deposition across a wide range of geomorphological and pedological settings. Our results also show that meteoric 10Be can be used as a tracer to detect human impact on soil fluxes for soils with a high affinity for meteoric 10Be. However, the quantification of vertical mobility is essential for a correct interpretation of the observed variations in meteoric 10Be profiles and inventories. Application of the Be2D model to natural conditions using data sets from the Southern Piedmont (Bacon et al., 2012) and Appalachian Mountains (Jungers et al., 2009; West et al., 2013) allows to reliably constrain parameter values. Good agreement between simulated and observed meteoric 10Be concentrations and inventories is obtained with realistic parameter values. Furthermore, our results provide detailed insights into the processes redistributing meteoric 10Be at the soil-hillslope scale.

Comet formation

Science.gov (United States)

Blum, J.

2014-07-01

There has been vast progress in our understanding of planetesimal formation over the past decades, owing to a number of laboratory experiments as well as to refined models of dust and ice agglomeration in protoplanetary disks. Coagulation rapidly forms cm-sized ''pebbles'' by direct sticking in collisions at low velocities (Güttler et al. 2010; Zsom et al. 2010). For the further growth, two model approaches are currently being discussed: (1) Local concentration of pebbles in nebular instabilities until gravitational instability occurs (Johansen et al. 2007). (2) A competition between fragmentation and mass transfer in collisions among the dusty bodies, in which a few ''lucky winners'' make it to planetesimal sizes (Windmark et al. 2012a,b; Garaud et al. 2013). Predictions of the physical properties of the resulting bodies in both models allow a distinction of the two formation scenarios of planetesimals. In particular, the tensile strength (i.e, the inner cohesion) of the planetesimals differ widely between the two models (Skorov & Blum 2012; Blum et al. 2014). While model (1) predicts tensile strengths on the order of ˜ 1 Pa, model (2) results in rather compactified dusty bodies with tensile strengths in the kPa regime. If comets are km-sized survivors of the planetesimal-formation era, they should in principle hold the secret of their formation process. Water ice is the prime volatile responsible for the activity of comets. Thermophysical models of the heat and mass transport close to the comet-nucleus surface predict water-ice sublimation temperatures that relate to maximum sublimation pressures well below the kPa regime predicted for formation scenario (2). Model (1), however, is in agreement with the observed dust and gas activity of comets. Thus, a formation scenario for cometesimals involving gravitational instability is favored (Blum et al. 2014).

Assessing soil fluxes using meteoric 10Be: development and application of the Be2D model

Science.gov (United States)

Campforts, Benjamin; Govers, Gerard; Vanacker, Veerle; Baken, Stijn; Smolders, Erik; Vanderborght, Jan

2015-04-01

Meteoric 10Be is a promising and increasingly popular tool to better understand soil fluxes at different timescales. Unlike other, more classical, methods such as the study of sedimentary archives it enables a direct coupling between eroding and deposition sites. However, meteoric 10Be can be mobilized within the soil. Therefore, spatial variations in meteoric 10Be inventories cannot directly be translated into spatial variations in erosion and sedimentation rates: a correct interpretation of measured 10Be inventories requires that both lateral and vertical movement of meteoric 10Be are accounted for. Here, we present a spatially explicit 2D model that allows to simulate the behaviour of meteoric 10Be in the soil system over timescales of up to 1 million year and use the model to investigate the impact of accelerated erosion on meteoric 10Be inventories. The model consists of two parts. A first component deals with advective and diffusive mobility within the soil profile, whereas a second component describes lateral soil (and meteoric 10Be) fluxes over the hillslope. Soil depth is calculated dynamically, accounting for soil production through weathering and lateral soil fluxes. Different types of erosion such as creep, water and tillage erosion are supported. Model runs show that natural soil fluxes can be well reconstructed based on meteoric 10Be inventories, and this for a wide range of geomorphological and pedological conditions. However, extracting signals of human impact and distinguishing them from natural soil fluxes is only feasible when the soil has a rather high retention capacity so that meteoric 10Be is retained in the top soil layer. Application of the Be2D model to an existing data set in the Appalachian Mountains [West et al.,2013] using realistic parameter values for the soil retention capacity as well as for vertical advection resulted in a good agreement between simulated and observed 10Be inventories. This confirms the robustness of the model. We

Comet Halley Returns. A Teacher's Guide, 1985-1986.

Science.gov (United States)

Chapman, Robert D.; Bondurant, R. Lynn, Jr.

This booklet was designed as an aid for elementary and secondary school teachers. It is divided into two distinct parts. Part I is a brief tutorial which introduces some of the most important concepts about comets. Areas addressed include: the historical importance of Comet Halley; how comets are found and names; cometary orbits; what Comet Halley…

Comets and the origin and evolution of life

CERN Document Server

McKay, Christopher P

2006-01-01

Nine years after the publication of Comets and the Origin and Evolution of Life, one of the pioneering books in Astrobiology, this second edition revisits the role comets may have played in the origins and evolution of life. Recent analyses of Antarctic micrometeorites and ancient rocks in Australia and South Africa, the continuing progress in discovering complex organic macromolecules in comets, protostars and interstellar clouds, new insights into organic synthesis in comets, and numerical simulations of comet impacts on the Earth and other members of the solar system yield a spectacular wea

Mesospheric temperatures estimated from the meteor radar observations at Mohe, China

Science.gov (United States)

Liu, Libo; Liu, Huixin; Chen, Yiding; Le, Huijun

2017-04-01

In this work, we report the estimation of mesospheric temperatures at 90 km height from the observations of the VHF all-sky meteor radar operated at Mohe (53.5 °N, 122.3° E), China, since August 2011. The kinetic temperature profiles retrieved from the observations of Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) onboard the Thermosphere, Ionosphere, Mesosphere, Energetics, and Dynamics (TIMED) satellite are processed to provide the temperature (TSABER) and temperature gradient (dT/dh) at 90 km height. Based on the SABER temperature profile data an empirical dT/dh model is developed for the Mohe latitude. First, we derive the temperatures from the meteor decay times (Tmeteor) and the Mohe dT/dh model gives prior information of temperature gradients. Secondly, the full-width of half maximum (FWHM) of the meteor height profiles is calculated and further used to deduce the temperatures (TFWHM) based on the strong linear relationship between FWHM and TSABER. The temperatures at 90 km deduced from the decay times (Tmeteor) and from the meteor height distributions (TFWHM) at Mohe are validated/calibrated with TSABER. The temperatures present a considerable annual variation, being maximum in winter and minimum in summer. Harmonic analyses reveal that the temperatures have an annual variation consistent with TSABER. Our work suggests that the FWHM has a good performance in routine estimation of the temperatures. It should be pointed out that the slope of FWHM and TSABER is 10.1 at Mohe, which is different from that of 15.71 at King Sejong (62.2° S, 58.8° E) station. Acknowledgments The TIMED/SABER kinetic temperature (version 2.0) data are provided by the SABER team through http://saber.gats-inc.com/. The temperatures from the NRLMSISE-00 model are calculated using Aerospace Blockset toolbox of MATLAB (2016a). This research was supported by National Natural Science Foundation of China (41231065, 41321003). We acknowledge the use of meteor radar

Lorentz-Shaped Comet Dust Trail Cross Section from New Hybrid Visual and Video Meteor Counting Technique - Implications for Future Leonid Storm Encounters

Science.gov (United States)

Jenniskens, Peter; Crawford, Chris; Butow, Steven J.; Nugent, David; Koop, Mike; Holman, David; Houston, Jane; Jobse, Klaas; Kronk, Gary

2000-01-01

A new hybrid technique of visual and video meteor observations was developed to provide high precision near real-time flux measurements for satellite operators from airborne platforms. A total of 33,000 Leonids. recorded on video during the 1999 Leonid storm, were watched by a team of visual observers using a video head display and an automatic counting tool. The counts reveal that the activity profile of the Leonid storm is a Lorentz profile. By assuming a radial profile for the dust trail that is also a Lorentzian, we make predictions for future encounters. If that assumption is correct, we passed 0.0003 AU deeper into the 1899 trailet than expected during the storm of 1999 and future encounters with the 1866 trailet will be less intense than. predicted elsewhere.

Detection of radiation-induced apoptosis using the comet assay

International Nuclear Information System (INIS)

Wada, Seiichi; Kobayashi, Yasuhiko; Funayama, Tomoo; Yamamoto, Kazuo; Khoa, Tran Van; Natsuhori, Masahiro; Ito, Nobuhiko

2003-01-01

The electrophoresis pattern of apoptotic cells detected by the comet assay has a characteristic small head and spread tail. This image has been referred to as an apoptotic comet, but it has not been previously proven to be apoptotic cells by any direct method. In order to identify this image obtained by the comet assay as corresponding to an apoptotic cell, the frequency of appearance of apoptosis was examined using CHO-K1 and L5178Y cells which were exposed to gamma irradiation. As a method for detecting apoptosis, the terminal deoxynucleotidyl transferase mediated dUTP nick end labeling (TUNEL) assay was used. When the frequency of appearance of apoptotic cells following gamma irradiation was observed over a period of time, there was a significant increase in appearance of apoptosis when using the TUNEL assay. However, there was only a slight increase when using the comet assay. In order to verify the low frequency of appearance of apoptosis when using the comet assay, we attempted to use the TUNEL assay to satin the apoptotic comets detected in the comet assay. The apoptotic comets were TUNEL positive and the normal comets were TUNEL negative. This indicates that the apoptotic comets were formed from DNA fragments with 3'-hydroxy ends that are generated as cells undergo apoptosis. Therefore, it was understood that the characteristic pattern of apoptotic comets detected by the comet assay corresponds to cells undergoing apoptosis. (author)

Comets - cosmic 'snowballs'

International Nuclear Information System (INIS)

Luest, R.

1979-01-01

Non-periodic comets come from regions at the limit of our solar system and have conserved their original structure and composition since they have originated from a pre-solar nebuly together with the sun and the planets about 4.5 x 10 9 years ago. They are icy bodies of kilometer size whose structure and chemical composition is of great interest also with respect to the origin of the solar system. It is hoped to send a space craft to comet Halley in 1986 to get more detailed informations. (orig.) [de

Nitrogen abundance in Comet Halley

International Nuclear Information System (INIS)

Wyckoff, S.; Tegler, S.C.; Engel, L.

1991-01-01

Data on the nitrogen-containing compounds that observed spectroscopically in the coma of Comet Halley are summarized, and the elemental abundance of nitrogen in the Comet Halley nucleus is derived. It is found that 90 percent of elemental nitrogen is in the dust fraction of the coma, while in the gas fraction, most of the nitrogen is contained in NH3 and CN. The elemental nitrogen abundance in the ice component of the nucleus was found to be deficient by a factor of about 75, relative to the solar photosphere, indicating that the chemical partitioning of N2 into NH3 and other nitrogen compounds during the evolution of the solar nebula cannot account completely for the low abundance ratio N2/NH3 = 0.1, observed in the comet. It is suggested that the low N2/NH3 ratio in Comet Halley may be explained simply by physical fractionation and/or thermal diffusion. 88 refs

Observations on Stratospheric-Mesospheric-Thermospheric temperatures using Indian MST radar and co-located LIDAR during Leonid Meteor Shower (LMS

Directory of Open Access Journals (Sweden)

R. Selvamurugan

2002-11-01

Full Text Available The temporal and height statistics of the occurrence of meteor trails during the Leonid meteor shower revealed the capability of the Indian MST radar to record large numbers of meteor trails. The distribution of radio meteor trails due to a Leonid meteor shower in space and time provided a unique opportunity to construct the height profiles of lower thermospheric temperatures and winds, with good time and height resolution. There was a four-fold increase in the meteor trails observed during the LMS compared to a typical non-shower day. The temperatures were found to be in excellent continuity with the temperature profiles below the radio meteor region derived from the co-located Nd-Yag LIDAR and the maximum height of the temperature profile was extended from the LIDAR to ~110 km. There are, how-ever, some significant differences between the observed profiles and the CIRA-86 model profiles. The first results on the meteor statistics and neutral temperature are presented and discussed below.  Key words. Atmospheric composition and structure (pres-sure, density, and temperature History of geophysics (at-mospheric sciences Meteorology and atmospheric dynamics (middle atmosphere dynamics

Comet nuclei and Trojan asteroids - A new link and a possible mechanism for comet splittings

International Nuclear Information System (INIS)

Hartmann, W.K.; Tholen, D.J.

1990-01-01

Relatively elongated shapes, implied by recent evidence of a greater incidence of high amplitude lightcurves for comet nuclei and Trojan asteroids than for similarly scaled main belt asteroids, are suggested to have evolved among comet nuclei and Trojans due to volatile loss. It is further suggested that such an evolutionary course may account for observed comet splitting; rotational splitting may specifically occur as a result of evolution in the direction of an elongated shape through sublimation. Supporting these hypotheses, the few m/sec separation velocities projected for rotationally splitting elongated nuclei are precisely in the observed range. 40 refs

Meteor localization via statistical analysis of spatially temporal fluctuations in image sequences

Science.gov (United States)

Kukal, Jaromír.; Klimt, Martin; Šihlík, Jan; Fliegel, Karel

2015-09-01

Meteor detection is one of the most important procedures in astronomical imaging. Meteor path in Earth's atmosphere is traditionally reconstructed from double station video observation system generating 2D image sequences. However, the atmospheric turbulence and other factors cause spatially-temporal fluctuations of image background, which makes the localization of meteor path more difficult. Our approach is based on nonlinear preprocessing of image intensity using Box-Cox and logarithmic transform as its particular case. The transformed image sequences are then differentiated along discrete coordinates to obtain statistical description of sky background fluctuations, which can be modeled by multivariate normal distribution. After verification and hypothesis testing, we use the statistical model for outlier detection. Meanwhile the isolated outlier points are ignored, the compact cluster of outliers indicates the presence of meteoroids after ignition.

About Catalogue of Orbit and Atmospheric Trajectory of 4500 Radio Meteors Brighter +5m

Science.gov (United States)

Narziev, M.; Tshebotaryov, P.

2017-09-01

Published by this time the majority of catalogues of a radiant, speeds and elements of orbits of meteors, basically, are based on a interpretation of the given radio observations by diffraction-time a method. However the given method is applicable for processing of 15-25 % of observed meteors that leads to loss of the most part of an observed material. Besides, the error of measurement of an antiaircraft corner of a radiant σZr with increase in a corner to 60°÷70 ° will be increased in 2-3 times, and at the further increase in a corner the error grows even faster, so measurements lose meaning. In 1968-1970 in action period of the Soviet equatorial meteor expedition to Somalia, simultaneously and radio observations of meteors in HisAO from four points have been resulted. For interpretation of the radar data the bearing-time method radio method developed and applied for the first time in Tajikistan is used. This approximately twice increases number of the measured radiant and speeds. What's more, the error of measurement of an antiaircraft corner does not depend on antiaircraft distance of a radiant. The velocity of meteor is determined by the bearing-time method, and by the diffraction picture. In the catalogue along with a radiant, speeds and elements of orbits, for the first time the height, value of linear electronic density, radio magnitude and masses of each of 4500 radio meteors registered since December 1968 till May, 1969 are resulted.

Solar wind interaction with type-1 comet tails

International Nuclear Information System (INIS)

Ershkovich, A.I.

1977-01-01

A comet tail is considered as a plasma cylinder separated by a tangential discontinuity surface from the solar wind. Under typical conditions a comet tail boundary is shown to undergo the Kelvin-Helmholtz instability. With infinite amplitude the stabilizing effect of the magnetic field increases, and waves become stable. The proposed model supplies the detailed quantitative description of helical waves observed in type-1 comet tails. This theory enables the evaluation of the comet tail magnetic field by means of the observations of helical waves. The magnetic field in the comet tail turns out to be of the order of the interplanetary field. This conclusion seems to be in accordance with Alfven's idea that the magnetic field in type-1 comet tails is a captured interplanetary field. (Auth.)

Instrument for the detection of meteors in the infrared

Science.gov (United States)

Svedhem, H.; Koschny, D.; Ter Haar, J.

2014-07-01

The flux of interplanetary particles in the size range 2 mm to 20 m is poorly constrained due to insufficient data --- the larger bodies may be observed remotely by ground-based or space-based telescopes and the smaller particles are measured by in-situ impact detectors in space or by meteor cameras from ground. An infrared video rate imager in Earth orbit would enable a systematic characterization for an extended period, day and night, of the flux in this range by monitoring the bright meteor/fireball generated during atmospheric entry. Due to the low flux of meteoroids in this range a very large detector is required. With this method a large portion of the Earth atmosphere is in fact used as a huge detector. Such an instrument has never flown in Earth orbit. The only sensors of a similar kind fly on US defense satellites for monitoring launches of ballistic missiles. The data from these sensors, however, is largely inaccessible to scientists. The knowledge on emission of light by meteors/bolides at infrared wavelengths is very limited while it can be suspected that the continuum emission from meteors/bolides have stronger emission at infrared wavelengths than in the visible due to the likely low temperatures of these events. At the same time line emission is dominating over the continuum in the visible so it is not clear how this will compare with the continuum in the infrared. We have developed a bread-board version of an IR video rate camera, the SPOSH-IR. The instrument is based on an earlier technology development, SPOSH --- Smart Panoramic Optical Sensor Head, for operation in the visible range, but with the sensor replaced by a cooled IR detector and new infrared optics. The earlier work has proven the concept of the instrument and of automatic detection of meteors/bolides in the visible wavelength range. The new hardware has been built by Jena-Optronik, Jena, Germany and has been tested during several meteor showers in the Netherlands and at ESA's OGS

Where are the mini Kreutz-family comets?

International Nuclear Information System (INIS)

Ye, Quan-Zhi; Wiegert, Paul A.; Hui, Man-To; Kracht, Rainer

2014-01-01

The Kreutz family of sungrazing comets contains over 2000 known members, many of which are believed to be under ∼100 m sizes (mini comets) and have only been studied at small heliocentric distances (r H ) with space-based SOHO/STEREO spacecraft. To understand the brightening process of mini Kreutz comets, we conducted a survey using CFHT/MegaCam at moderate r H guided by SOHO/STEREO observations. We identify two comets that should be in our search area but are not detected, indicating that the comets have either followed a steeper brightening rate within the previously reported rapid brightening stage (the brightening burst), or the brightening burst starts earlier than expected. We present a composite analysis of the pre-perihelion light curves of five Kreutz comets that cover to ∼1 AU. We observe significant diversity in the light curves that can be used to grossly classify them into two types: C/Ikeya-Seki and C/SWAN follow the canonical r H −4 while the others follow r H −7 . In particular, C/SWAN seems to have undergone an outburst (Δm > 5 mag) or a rapid brightening (n ≳ 11) between r H = 1.06 AU and 0.52 AU, and shows hints of structural/compositional differences compared to other bright Kreutz comets. We also find evidence that the Kreutz comets as a population lose their mass less efficiently than the dynamically new comet, C/ISON, and are relatively devoid of species that drive C/ISON's activity at large r H . Concurrent observations of C/STEREO in different wavelengths also suggest that a blueward species such as CN may be the main driver for brightening bursts, instead of sodium as previously thought

COLOR SYSTEMATICS OF COMETS AND RELATED BODIES

Energy Technology Data Exchange (ETDEWEB)

Jewitt, David, E-mail: jewitt@ucla.edu [Department of Earth, Planetary and Space Sciences, UCLA, 595 Charles Young Drive East, Los Angeles, CA 90095-1567 (United States)

2015-12-15

Most comets are volatile-rich bodies that have recently entered the inner solar system following long-term storage in the Kuiper belt and the Oort cloud reservoirs. These reservoirs feed several distinct, short-lived “small body” populations. Here, we present new measurements of the optical colors of cometary and comet-related bodies including long-period (Oort cloud) comets, Damocloids (probable inactive nuclei of long-period comets) and Centaurs (recent escapees from the Kuiper belt and precursors to the Jupiter family comets). We combine the new measurements with published data on short-period comets, Jovian Trojans and Kuiper belt objects to examine the color systematics of the comet-related populations. We find that the mean optical colors of the dust in short-period and long-period comets are identical within the uncertainties of measurement, as are the colors of the dust and of the underlying nuclei. These populations show no evidence for scattering by optically small particles or for compositional gradients, even at the largest distances from the Sun, and no evidence for ultrared matter. Consistent with earlier work, ultrared surfaces are common in the Kuiper belt and on the Centaurs, but not in other small body populations, suggesting that this material is hidden or destroyed upon entry to the inner solar system. The onset of activity in the Centaurs and the disappearance of the ultrared matter in this population begin at about the same perihelion distance (∼10 AU), suggesting that the two are related. Blanketing of primordial surface materials by the fallback of sub-orbital ejecta, for which we calculate a very short timescale, is the likely mechanism. The same process should operate on any mass-losing body, explaining the absence of ultrared surface material in the entire comet population.

Theories of comets to the age of Laplace

Science.gov (United States)

Heidarzadeh, Tofigh

Although the development of ideas about cometary motion has been investigated in several projects, a comprehensive and detailed survey of physical theories of comets has not been conducted. The available works either illustrate relatively short periods in the history of physical cometology or portray a landscape view without adequate details. The present study is an attempt to depict the details of the major physical theories of comets from Aristotle to the age of Laplace. The basic question from which this project originated was simple: how did natural philosophers and astronomers define the nature and place of a new category of celestial objects--the comets--after Brahe's estimation of cometary distances? However, a study starting merely from Brahe without covering classical and medieval thought about comets would be incomplete. Thus, based on the fundamental physical characteristics attributed to comets, the history of cometology may be divided into three periods: from Aristotle to Brahe, in which comets were assumed to be meteorological phenomena; from Brahe to Newton, when comets were admitted as celestial bodies but with unknown trajectories; and from Newton to Laplace, in which they were treated as members of the solar system having more or less the same properties of the planets. By estimating the mass of comets in the 1800s, Laplace diverted cometology into a different direction wherein they were considered among the smallest bodies in the solar system and deprived of the most important properties that had been used to explain their physical constitution during the previous two millennia. Ideas about the astrological aspects of comets are not considered in this study. Also, topics concerning the motion of comets are explained to the extent that is helpful in illustrating their physical properties. The main objective is to demonstrate the foundations of physical theories of comets, and the interaction between observational and mathematical astronomy, and

The Innisfree meteorite: Dynamical history of the orbit - Possible family of meteor bodies

Science.gov (United States)

Galibina, I. V.; Terent'eva, A. K.

1987-09-01

Evolution of the Innisfree meteorite orbit caused by secular perturbations is studied over the time interval of 500000 yrs (from the current epoch backwards). Calculations are made by the Gauss-Halphen-Gorjatschew method taking into account perturbations from the four outer planets - Jupiter, Saturn, Uranus and Neptune. In the above mentioned time interval the meteorite orbit has undergone no essential transformations. The Innisfree orbit intersected in 91 cases the Earth orbit and in 94 - the Mars orbit. A system of small and large meteor bodies (producing ordinary meteors and fireballs) which may be genetically related to the Innisfree meteorite has been found, i.e. there probably exists an Innisfree family of meteor bodies.

THE PLASMA ENVIRONMENT IN COMETS OVER A WIDE RANGE OF HELIOCENTRIC DISTANCES: APPLICATION TO COMET C/2006 P1 (MCNAUGHT)

Energy Technology Data Exchange (ETDEWEB)

Shou, Y.; Combi, M.; Gombosi, T.; Toth, G. [Department of Atmospheric, Oceanic and Space Sciences, University of Michigan, Ann Arbor, MI (United States); Jia, Y.-D. [IGPP, and EPSS, University of California, Los Angeles, CA 90095 (United States); Rubin, M. [Physikalisches Institut, University of Bern, Sidlerstrasse. 5, CH-3012 Bern (Switzerland)

2015-08-20

On 2007 January 12, comet C/2006 P1 (McNaught) passed its perihelion at 0.17 AU. Abundant remote observations offer plenty of information on the neutral composition and neutral velocities within 1 million kilometers of the comet nucleus. In early February, the Ulysses spacecraft made an in situ measurement of the ion composition, plasma velocity, and magnetic field when passing through the distant ion tail and the ambient solar wind. The measurement by Ulysses was made when the comet was at around 0.8 AU. With the constraints provided by remote and in situ observations, we simulated the plasma environment of Comet C/2006 P1 (McNaught) using a multi-species comet MHD model over a wide range of heliocentric distances from 0.17 to 1.75 AU. The solar wind interaction of the comet at various locations is characterized and typical subsolar standoff distances of the bow shock and contact surface are presented and compared to analytic solutions. We find the variation in the bow shock standoff distances at different heliocentric distances is smaller than the contact surface. In addition, we modified the multi-species model for the case when the comet was at 0.7 AU and achieved comparable water group ion abundances, proton densities, plasma velocities, and plasma temperatures to the Ulysses/SWICS and SWOOPS observations. We discuss the dominating chemical reactions throughout the comet-solar wind interaction region and demonstrate the link between the ion composition near the comet and in the distant tail as measured by Ulysses.

THE PLASMA ENVIRONMENT IN COMETS OVER A WIDE RANGE OF HELIOCENTRIC DISTANCES: APPLICATION TO COMET C/2006 P1 (MCNAUGHT)

International Nuclear Information System (INIS)

Shou, Y.; Combi, M.; Gombosi, T.; Toth, G.; Jia, Y.-D.; Rubin, M.

2015-01-01

On 2007 January 12, comet C/2006 P1 (McNaught) passed its perihelion at 0.17 AU. Abundant remote observations offer plenty of information on the neutral composition and neutral velocities within 1 million kilometers of the comet nucleus. In early February, the Ulysses spacecraft made an in situ measurement of the ion composition, plasma velocity, and magnetic field when passing through the distant ion tail and the ambient solar wind. The measurement by Ulysses was made when the comet was at around 0.8 AU. With the constraints provided by remote and in situ observations, we simulated the plasma environment of Comet C/2006 P1 (McNaught) using a multi-species comet MHD model over a wide range of heliocentric distances from 0.17 to 1.75 AU. The solar wind interaction of the comet at various locations is characterized and typical subsolar standoff distances of the bow shock and contact surface are presented and compared to analytic solutions. We find the variation in the bow shock standoff distances at different heliocentric distances is smaller than the contact surface. In addition, we modified the multi-species model for the case when the comet was at 0.7 AU and achieved comparable water group ion abundances, proton densities, plasma velocities, and plasma temperatures to the Ulysses/SWICS and SWOOPS observations. We discuss the dominating chemical reactions throughout the comet-solar wind interaction region and demonstrate the link between the ion composition near the comet and in the distant tail as measured by Ulysses

To Catch A Comet...Learning From Halley's.

Science.gov (United States)

National Aeronautics and Space Administration, Washington, DC.

Comet chronicles and stories extend back over thousands of years. A common theme has been that comets are a major cause of catastrophe and tragedy here on earth. In addition, both Aristotle and Ptolemy believed that comets were phenomena within the earth's atmosphere, and it wasn't until the 16th century, when Danish astronomer Tycho Brache…

An orbital meteoroid stream survey using the Southern Argentina Agile MEteor Radar (SAAMER) based on a wavelet approach

Science.gov (United States)

Pokorný, P.; Janches, D.; Brown, P. G.; Hormaechea, J. L.

2017-07-01

Over a million individually measured meteoroid orbits were collected with the Southern Argentina Agile MEteor Radar (SAAMER) between 2012-2015. This provides a robust statistical database to perform an initial orbital survey of meteor showers in the Southern Hemisphere via the application of a 3D wavelet transform. The method results in a composite year from all 4 years of data, enabling us to obtain an undisturbed year of meteor activity with more than one thousand meteors per day. Our automated meteor shower search methodology identified 58 showers. Of these showers, 24 were associated with previously reported showers from the IAU catalogue while 34 showers are new and not listed in the catalogue. Our searching method combined with our large data sample provides unprecedented accuracy in measuring meteor shower activity and description of shower characteristics in the Southern Hemisphere. Using simple modeling and clustering methods we also propose potential parent bodies for the newly discovered showers.

Autonomous Onboard Science Data Analysis for Comet Missions

Science.gov (United States)

Thompson, David R.; Tran, Daniel Q.; McLaren, David; Chien, Steve A.; Bergman, Larry; Castano, Rebecca; Doyle, Richard; Estlin, Tara; Lenda, Matthew

2012-01-01

Coming years will bring several comet rendezvous missions. The Rosetta spacecraft arrives at Comet 67P/Churyumov-Gerasimenko in 2014. Subsequent rendezvous might include a mission such as the proposed Comet Hopper with multiple surface landings, as well as Comet Nucleus Sample Return (CNSR) and Coma Rendezvous and Sample Return (CRSR). These encounters will begin to shed light on a population that, despite several previous flybys, remains mysterious and poorly understood. Scientists still have little direct knowledge of interactions between the nucleus and coma, their variation across different comets or their evolution over time. Activity may change on short timescales so it is challenging to characterize with scripted data acquisition. Here we investigate automatic onboard image analysis that could act faster than round-trip light time to capture unexpected outbursts and plume activity. We describe one edge-based method for detect comet nuclei and plumes, and test the approach on an existing catalog of comet images. Finally, we quantify benefits to specific measurement objectives by simulating a basic plume monitoring campaign.

Developing Dynamic Single Page Web Applications Using Meteor : Comparing JavaScript Frameworks: Blaze and React

OpenAIRE

Yetayeh, Asabeneh

2017-01-01

This paper studies Meteor which is a JavaScript full-stack framework to develop interactive single page web applications. Meteor allows building web applications entirely in JavaScript. Meteor uses Blaze, React or AngularJS as a view layer and Node.js and MongoDB as a back-end. The main purpose of this study is to compare the performance of Blaze and React. A multi-user Blaze and React web applications with similar HTML and CSS were developed. Both applications were deployed on Heroku’s w...

Reservoirs for Comets: Compositional Differences Based on Infrared Observations

Science.gov (United States)

Disanti, Michael A.; Mumma, Michael J.

Tracing measured compositions of comets to their origins continues to be of keen interest to cometary scientists and to dynamical modelers of Solar System formation and evolution. This requires building a taxonomy of comets from both present-day dynamical reservoirs: the Kuiper Belt (hereafter KB), sampled through observation of ecliptic comets (primarily Jupiter Family comets, or JFCs), and the Oort cloud (OC), represented observationally by the long-period comets and by Halley Family comets (HFCs). Because of their short orbital periods, JFCs are subjected to more frequent exposure to solar radiation compared with OC comets. The recent apparitions of the JFCs 9P/Tempel 1 and 73P/Schwassmann-Wachmann 3 permitted detailed observations of material issuing from below their surfaces—these comets added significantly to the compositional database on this dynamical class, which is under-represented in studies of cometary parent volatiles. This chapter reviews the latest techniques developed for analysis of high-resolution spectral observations from ˜2-5 μm, and compares measured abundances of native ices among comets. While no clear compositional delineation can be drawn along dynamical lines, interesting comparisons can be made. The sub-surface composition of comet 9P, as revealed by the Deep Impact ejecta, was similar to the majority of OC comets studied. Meanwhile, 73P was depleted in all native ices except HCN, similar to the disintegrated OC comet C/1999 S4 (LINEAR). These results suggest that 73P may have formed in the inner giant planets' region while 9P formed farther out or, alternatively, that both JFCs formed farther from the Sun but with 73P forming later in time.

What's Causing the Activity on Comet 67P?

Science.gov (United States)

Kohler, Susanna

2015-09-01

Comet 67P/ChuryumovGerasimenko made famous by the explorations of the Rosetta mission has been displaying puzzling activity as it hurtles toward the Sun. However, recent modeling of the comet by a group of scientists from the Cte dAzur University may now explain whats causing 67Ps activity.Shadowed ActivityA model of comet 67P, with the colors indicating the rate of change of the temperature on the comets surface. The most rapid temperature changes are seen at the comets neck, in the same locations as the early activity seen in the Rosetta images. [Al-Lagoa et al. 2015] Between June and September of 2014, Rosetta observed comet 67P displaying early activity in the form of jets of dust emitted from near the neck of the comet (its narrowest point). Such activity is usually driven by the sublimation of volatiles from the comets surface as a result of sun exposure. But the neck of the comet is frequently shadowed as the comet rotates, and it receives significantly less sunlight than the rest of the comet. So why would the early activity originate from the comets neck?The authors of a recent study, led by Victor Al-Lagoa, hypothesize that its precisely because the neck is receiving alternating sunlight/shadows that its displaying activity. They suggest that thermal cracking of the surface of the comet is happening faster in this region, due to the rapid changes in temperature that result from the shadows cast by the surrounding terrain. The cracking exposes subsurface ices in the neck faster than in other regions, and the ensuing sublimation of that ice is what creates the activity were seeing.Temperature Models: To test their hypothesis, the authors study the surface temperatures on comet 67P by means of a thermophysical model a model used to calculate the temperatures on an airless body, both on and below the surface. The model takes into account factors like thermal inertia (how quickly the bodys temperature responds to changes in the incident energy), shadowing, and

Eclipses, transits, and comets of the nineteenth century how America's perception of the skies changed

CERN Document Server

Cottam, Stella

2015-01-01

Grabbing the attention of poets, politicians and the general public alike, a series of spectacular astronomical events in the late 1800s galvanized Americans to take a greater interest in astronomy than ever before. At a time when the sciences were not yet as well established in the United States as they were in Europe, this public interest and support provided the growing scientific community in the United States with the platform they needed to advance the field of astronomy in the United States.   Earlier in the 19th century comets, meteors and the discovery of the planet Neptune were all sources of inspiration to the general public. The specific events to be considered here are the total solar eclipses of 1868, 1869 and 1878 and the transits of Venus of 1874 and 1882. The available media responded to public interest as well as generating more interest. These events laid the groundwork that led to today's thriving network of American amateur astronomers, and provide a fascinating look at earlier conc...

Modeling Formaldehyde Emission in Comets

Science.gov (United States)

Disanti, M. A.; Reuter, D. C.; Bonev, B. P.; Mumma, M. J.; Villanueva, G. L.

Modeling fluorescent emission from monomeric formaldehyde (H2CO) forms an integral part of our overall comprehensive program of measuring the volatile composition of comets through high-resolution (RP ~ 25,000) infrared spectroscopy using CSHELL at the IRTF and NIRSPEC at Keck II. The H2CO spectra contain lines from both the nu1 (symmetric CH2 stretch) and nu5 (asymmetric CH2 stretch) bands near 3.6 microns. We have acquired high-quality spectra of twelve Oort cloud comets, and at least six of these show clear emission from H2CO. We also detected H2CO with NIRSPEC in one Jupiter Family comet, 9P/Tempel 1, during Deep Impact observations. Our H2CO model, originally developed to interpret low-resolution spectra of comets Halley and Wilson (Reuter et al. 1989 Ap J 341:1045), predicts individual line intensities (g-factors) as a function of rotational temperature for approximately 1300 lines having energies up to approximately 400 cm^-1 above the ground state. Recently, it was validated through comparison with CSHELL spectra of C/2002 T7 (LINEAR), where newly developed analyses were applied to obtain robust determinations of both the rotational temperature and abundance of H2CO (DiSanti et al. 2006 Ap J 650:470). We are currently in the process of extending the model to higher rotational energy (i.e., higher rotational quantum number) in an attempt to improve the fit to high-J lines in our spectra of C/T7 and other comets. Results will be presented, and implications discussed.Modeling fluorescent emission from monomeric formaldehyde (H2CO) forms an integral part of our overall comprehensive program of measuring the volatile composition of comets through high-resolution (RP ~ 25,000) infrared spectroscopy using CSHELL at the IRTF and NIRSPEC at Keck II. The H2CO spectra contain lines from both the nu1 (symmetric CH2 stretch) and nu5 (asymmetric CH2 stretch) bands near 3.6 microns. We have acquired high-quality spectra of twelve Oort cloud comets, and at least six of

Aedes Hartwellianae

Science.gov (United States)

Smyth, William Henry

2014-02-01

1. Details respecting the parish and manor of Hartwell: locality, geology, produce, and general statistics; 2. The successive lords of the manor of Hartwell, from the Conquest to the present time: Peverel, De Hertewell, Luton, Hampden, and Lee; 3. Particulars respecting Hartwell House: its appartments, paintings, library, museum, numismata, and Egyptian antiquities; 4. Origin of the Hartwell Observatory. The transit-room. The equatorial tower. Mr Epps's meridional observations. The double-stars measured by Captain Smyth. Encke's comet. The meteorological department; Appendix; Index.

The COMET Sleep Research Platform.

Science.gov (United States)

Nichols, Deborah A; DeSalvo, Steven; Miller, Richard A; Jónsson, Darrell; Griffin, Kara S; Hyde, Pamela R; Walsh, James K; Kushida, Clete A

2014-01-01

The Comparative Outcomes Management with Electronic Data Technology (COMET) platform is extensible and designed for facilitating multicenter electronic clinical research. Our research goals were the following: (1) to conduct a comparative effectiveness trial (CET) for two obstructive sleep apnea treatments-positive airway pressure versus oral appliance therapy; and (2) to establish a new electronic network infrastructure that would support this study and other clinical research studies. The COMET platform was created to satisfy the needs of CET with a focus on creating a platform that provides comprehensive toolsets, multisite collaboration, and end-to-end data management. The platform also provides medical researchers the ability to visualize and interpret data using business intelligence (BI) tools. COMET is a research platform that is scalable and extensible, and which, in a future version, can accommodate big data sets and enable efficient and effective research across multiple studies and medical specialties. The COMET platform components were designed for an eventual move to a cloud computing infrastructure that enhances sustainability, overall cost effectiveness, and return on investment.

Comet Halley and its historic passages during the past millennium

International Nuclear Information System (INIS)

Legrand, J.P.

1986-01-01

The March 12, 1759 return of Comet Halley verified Halley's hypothesis on the existence of periodic comets and supported Newton's principle of universal attraction. Comet Halley's appearances before the 16th century are traced and it is noted that the length of the comet's tail has varied greatly. The comet's rendezvous with ESA's satellite Giotto is discussed briefly

The Comet Halley Handbook: An Observer's Guide. Second Edition.

Science.gov (United States)

Yeomans, Donald K.

This handbook contains information on: (1) the orbit of comet Halley; (2) the expected physical behavior of comet Halley in 1985-1986, considering brightness estimates, coma diameters, and tail lengths; (3) observing conditions for comet Halley in 1985-1986; and (4) observing conditions for the dust tail of comet Halley in 1985-1986. Additional…

67P, Singing Comet

Science.gov (United States)

Smirnova, Ekaterina

2017-04-01

I would like to propose to present a short science-art-music collaboration film called "67P, Singing Comet" (5:27 min). If time of the session will allow, prior to the film I would like to make a slide show introduction to this project, highlighting the inspiration - the mission Rosetta by the European Space Agency (ESA) - and the artistic collaboration that took place in creating this piece. Inspired by the ESA Rosetta mission to the comet 67P, Ekaterina Smirnova (artist and project director, New York), Lee Mottram (clarinetist, Wales), Takuto Fukuda (composer, Japan) and Brian Hekker (video editor, New York) collaborated to create a unique atmospheric piece. Water and the origins of life throughout the Universe (specifically the Earth) is an element of the mission and the focus of Ekaterina's artistic vision. Ekaterina literally and figuratively paints a sensory assemblage using a combination of synthetic and natural elements to shape this artistic creation. To paint her watercolor works she is using a replica of the water found on the comet and implementing her own heartbeat into the music to create a recognizable inward sound of life. The Electro-Acoustic composition by Takuto Fukuda features an electronically manipulated performance by clarinetist Lee Mottram. The piece ceremoniously begins with reverberant bursts of low-register atonal bells transporting the listener to their ethereal inner origins of body and mind. The imagination takes the experience to an unknown destination as it gains speed gliding through the visual and audible textures of space and time. The comet's water similarly reacts with an ebb and flow thawing ice to potentially give life a chance as it is thrust along an orbit around the Sun. Near then far from the heat the comet forms frozen particles from vapors as it reaches it's furthest stretches creating an aerodynamic tail of icicles that slowly dissipate in a cycle that repeats itself until the comet's ultimate collision with an

Study of Comets Composition and Structure

Science.gov (United States)

Khalaf, S. Z.; Selman, A. A.; Ali, H. S.

2008-12-01

The present paper focuses on the nature of the different interactions between cometary nucleus and tail with solar wind. The dynamics of the comet will impose many features that provide unique behavior of the comet when entering the solar system. These features are reviewed in this paper and few investigations are made. The calculations made in this work represent the analysis and interpretation of the different features of the comet, such as perihelion and eccentricity dependence on the gas production rate, and the dependence of the latter on the composition of the comet nucleus. The dependences of the heliocentric, bow shock, contact surface, and stand-off distances with gas production rate for many types of comets that cover linear and non-linear types are studied in this work. Important results are obtained which indicated the different physical interactions between cometary ions and solar wind. Furthermore, the important relation between mean molecular weight and gas production rate are analyzed and studied in this work and a conclusion is made that, as the gas production rate increases, the mean molecular weight will decrease exponentially. A detailed discussion for this unique relation is given.

Comet assay on mice testicular cells

Directory of Open Access Journals (Sweden)

Anoop Kumar Sharma

2015-05-01

Full Text Available Heritable mutations may result in a variety of adverse outcomes including genetic disease in the offspring. In recent years the focus on germ cell mutagenicity has increased and the “Globally Harmonized System of Classification and Labelling of Chemicals (GHS” has published classification criteria for germ cell mutagens (Speit et al., 2009. The in vivo Comet assay is considered a useful tool for investigating germ cell genotoxicity. In the present study DNA strand breaks in testicular cells of mice were investigated. Different classes of chemicals were tested in order to evaluate the sensitivity of the comet assay in testicular cells. The chemicals included environmentally relevant substances such as Bisphenol A, PFOS and Tetrabrombisphenol A. Statistical power calculations will be presented to aid in the design of future Comet assay studies on testicular cells. Power curves were provided with different fold changes in % tail DNA, different number of cells scored and different number of gels (Hansen et al., 2014. An example is shown in Figure 1. A high throughput version of the Comet assay was used. Samples were scored with a fully automatic comet assay scoring system that provided faster scoring of randomly selected cells.

A GREAT search for Deuterium in Comets

Science.gov (United States)

Mumma, Michael

2013-10-01

Comets are understood to be the most pristine bodies in the Solar System. Their compositions reflect the chemical state of materials at the very earliest evolutionary stages of the protosolar nebula and, as such, they provide detailed insight into the physical and chemical processes operating in planet-forming disks. Isotopic fractionation ratios of the molecular ices in the nucleus are regarded as signatures of formation processes. These ratios provide unique information on the natal heritage of those ices, and can also test the proposal that Earth's water and other volatiles were delivered by cometary bombardment. Measurement of deuterium fractionation ratios is thus a major goal in contemporary cometary science and the D/H ratio of water - the dominant volatile in comets - holds great promise for testing the formation history of cometary matter. The D/H ratio in cometary water has been measured in only eight comets. Seven were from the Oort Cloud reservoir and the D/H ratio was about twice that of the Earth's oceans. However, the recent Herschel measurement of HDO/H2O in 103P/Hartley-2 (the first from the Kuiper Belt) was consistent with exogenous delivery of Earth's water by comets. Outstanding questions remain: are cometary HDO/H2O ratios consistent with current theories of nebular chemical evolution or with an interstellar origin? Does the HDO/H2O ratio vary substantially among comet populations? Hartley-2 is the only Kuiper Belt comet with measured HDO/H2O, are there comets with similar ratios in the Oort cloud? These questions can only be addressed by measuring HDO/H2O ratios in many more suitable bright comets. We therefore propose to measure the D/H ratio in water in a suitable target-of-opportunity comet by performing observations of HDO and OH with the GREAT spectrometer on SOFIA. A multi-wavelength, ground-based observing campaign will also be conducted in support of the airborne observations.

Building single-page web apps with meteor

CERN Document Server

Vogelsteller, Fabian

2015-01-01

If you are a web developer with basic knowledge of JavaScript and want to take on Web 2.0, build real-time applications, or simply want to write a complete application using only JavaScript and HTML/CSS, this is the book for you.This book is based on Meteor 1.0.

A quantitative comet infection assay for influenza virus

Science.gov (United States)

Lindsay, Stephen M.; Timm, Andrea; Yin, John

2011-01-01

Summary The virus comet assay is a cell-based virulence assay used to evaluate an antiviral drug or antibody against a target virus. The comet assay differs from the plaque assay in allowing spontaneous flows in 6-well plates to spread virus. When implemented quantitatively the comet assay has been shown to have an order-of-magnitude greater sensitivity to antivirals than the plaque assay. In this study, a quantitative comet assay for influenza virus is demonstrated, and is shown to have a 13-fold increase in sensitivity to ribavirin. AX4 cells (MDCK cells with increased surface concentration of α2–6 sialic acid, the influenza virus receptor) have reduced the comet size variability relative to MDCK cells, making them a better host cell for use in this assay. Because of enhanced antiviral sensitivity in flow-based assays, less drug is required, which could lead to lower reagent costs, reduced cytotoxicity, and fewer false-negative drug screen results. The comet assay also serves as a readout of flow conditions in the well. Observations from comets formed at varying humidity levels indicate a role for evaporation in the mechanism of spontaneous fluid flow in wells. PMID:22155578

CLATHRATE HYDRATES FORMATION IN SHORT-PERIOD COMETS

International Nuclear Information System (INIS)

Marboeuf, Ulysse; Mousis, Olivier; Petit, Jean-Marc; Schmitt, Bernard

2010-01-01

The initial composition of current models of cometary nuclei is only based on two forms of ice: crystalline ice for long-period comets and amorphous ice for short-period comets. A third form of ice, i.e., clathrate hydrate, could exist within the short-period cometary nuclei, but the area of formation of this crystalline structure in these objects has never been studied. Here, we show that the thermodynamic conditions in the interior of short-period comets allow the existence of clathrate hydrates in Halley-type comets. We show that their existence is viable in the Jupiter family comets only when the equilibrium pressure of CO clathrate hydrate is at least 1 order of magnitude lower than the usually assumed theoretical value. We calculate that the amount of volatiles that could be trapped in the clathrate hydrate layer may be orders of magnitude greater than the daily amount of gas released at the surface of the nucleus at perihelion. The formation and the destruction of the clathrate hydrate cages could then explain the diversity of composition of volatiles observed in comets, as well as some pre-perihelion outbursts. We finally show that the potential clathrate hydrate layer in comet 67P/Churyumov-Gerasimenko would, unfortunately, be deep inside the nucleus, out of reach of the Rosetta lander. However, such a clathrate hydrate layer would show up by the gas composition of the coma.

Stardust: Catching a Comet and Bringing it Home

Science.gov (United States)

Brownlee, Donald E.

2007-01-01

The NASA STARDUST mission collected thousands of particles from Comet Wild 2 that are now being studied by two hundred scientists around the world. The spacecraft captured the samples during a close flyby of the comet in 2004 and returned them to Earth with a dramatic entry into the atmosphere early in 2006. The precious cargo of comet dust is being studied to determine new information about the origin of the Sun and planets. The comet formed at the edge of the solar system, beyond the orbit of Neptune, and is a sample of the material from which the solar system was formed. One of the most dramatic early findings from the mission was that a comet that formed in the coldest place in the solar system contained minerals that formed in the hottest place in the solar system. The comet samples are telling stories of fire and ice and they providing fascinating and unexpected information about our origins.

Comets, Asteroids, and the Origin of the Biosphere

Science.gov (United States)

Hoover, Richard B.

2006-01-01

During the past few decades, the role of comets in the delivery of water, organics, and prebiotic chemicals to the Biosphere of Earth during the Hadean (4.5-3.8 Ga) period of heavy bombardment has become more widely accepted. However comets are still largely regarded as frigid, pristine bodies of protosolar nebula material that are entirely devoid of liquid water and consequently unsuitable for life in any form. Complex organic compounds have been observed comets and on the water rich asteroid 1998 KY26, which has color and radar reflectivity similar to the carbonaceous meteorites. Near infrared observations have indicated the presence of crystalline water ice and ammonia hydrate on the large Kuiper Belt object (50000) Quaoar with resurfacing that may indicate cryovolcanic outgassing and the Cassini spacecraft has detected water-ice geysers on Saturn s moon Enceladus. Spacecraft observations of the chemical compositions and characteristics of the nuclei of several comets (Halley, Borrelly, Wild 2, and Tempel 1) have now firmly established that comets contain a suite of complex organic chemicals; water is the predominant volatile; and that extremely high temperatures (approx.350-400 K) can be reached on the surface of the very black (albedo-0.03) nuclei when the comets are with 1.5 AU from the Sun. Impact craters and pinnacles observed on comet Wild 2 suggest a thick crust and episodic outbursts and jets observed on the nuclei of several comets are interpreted as indications that localized regimes of liquid water and water vapor can periodically exist beneath the crust of some comets. The Deep Impact observations indicate that the temperature on the nucleus of of comet Tempel 1 at 1.5 AU varied from 330K on the sunlit side to a minimum of 280+/-8 K. It is interesting that even the coldest region of the comet surface was slightly above the ice/liquid water phase transition temperature. These results suggest that pools and films of liquid water can exist in a wide

ACTIVITY OF 50 LONG-PERIOD COMETS BEYOND 5.2 au

Energy Technology Data Exchange (ETDEWEB)

Sárneczky, K.; Szabó, Gy. M.; Csák, B.; Kelemen, J.; Pál, A.; Szakáts, R.; Szegedi-Elek, E.; Vida, K.; Vinkó, J.; Kiss, L. L. [Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, Hungarian Academy of Sciences, H-1121 Budapest, Konkoly Thege Miklós út 15-17 (Hungary); Marschalkó, G. [Eötvös Loránd Tudományegyetem, H-1117 Pázmány Péter sétány 1/A, Budapest (Hungary); Szalai, T. [Department of Optics and Quantum Electronics, University of Szeged, H-6720 Szeged, Dóm tér 9 (Hungary); Székely, P. [Department of Experimental Physics, University of Szeged, Szeged H-6720, Dóm tér 9 (Hungary)

2016-12-01

Remote investigations of ancient matter in the solar system have traditionally been carried out through observations of long-period (LP) comets, which are less affected by solar irradiation than their short-period counterparts orbiting much closer to the Sun. Here we summarize the results of our decade-long survey of the distant activity of LP comets. We found that the most important separation in the data set is based on the dynamical nature of the objects. Dynamically new comets are characterized by a higher level of activity on average: the most active new comets in our sample can be characterized by Afρ values >3–4, higher than those for our most active returning comets. New comets develop more symmetric comae, suggesting a generally isotropic outflow. In contrast to this, the comae of recurrent comets can be less symmetrical, ocassionally exhibiting negative slope parameters, which suggest sudden variations in matter production. The morphological appearance of the observed comets is rather diverse. A surprisingly large fraction of the comets have long, tenuous tails, but the presence of impressive tails does not show a clear correlation with the brightness of the comets.

ACTIVITY OF 50 LONG-PERIOD COMETS BEYOND 5.2 au

International Nuclear Information System (INIS)

Sárneczky, K.; Szabó, Gy. M.; Csák, B.; Kelemen, J.; Pál, A.; Szakáts, R.; Szegedi-Elek, E.; Vida, K.; Vinkó, J.; Kiss, L. L.; Marschalkó, G.; Szalai, T.; Székely, P.

2016-01-01

Remote investigations of ancient matter in the solar system have traditionally been carried out through observations of long-period (LP) comets, which are less affected by solar irradiation than their short-period counterparts orbiting much closer to the Sun. Here we summarize the results of our decade-long survey of the distant activity of LP comets. We found that the most important separation in the data set is based on the dynamical nature of the objects. Dynamically new comets are characterized by a higher level of activity on average: the most active new comets in our sample can be characterized by Afρ values >3–4, higher than those for our most active returning comets. New comets develop more symmetric comae, suggesting a generally isotropic outflow. In contrast to this, the comae of recurrent comets can be less symmetrical, ocassionally exhibiting negative slope parameters, which suggest sudden variations in matter production. The morphological appearance of the observed comets is rather diverse. A surprisingly large fraction of the comets have long, tenuous tails, but the presence of impressive tails does not show a clear correlation with the brightness of the comets.

ESA Unveils Its New Comet Chaser.

Science.gov (United States)

1999-07-01

The objective is to study one of these primordial objects at close quarters by placing a lander on its surface and chasing, with an orbiter, the comet for millions of kilometres through space. Comets - among the oldest (4.6 billion years!) and last altered objects in the solar system - are regarded as the building blocks from which the planets formed. Thus the Rosetta's discoveries will allow the scientists to learn more about birth and evolution of the planets and about the origin of life on the Earth. The final design of the Rosetta orbiter will be revealed for the first time at the Royal Society in London on 1 July when a 1:4 scale model will be unveiled by ESA's Director of Science, Prof.. Roger Bonnet. (The full size version of the spacecraft is 32 metres across, so large that it would stretch the entire width of a football pitch. Almost 90 of this is accounted for by the giant solar panels which are needed to provide electrical power in the dark depths of the Solar System). "Rosetta is a mission of major scientific importance," said Prof. Bonnet. "It will build on the discoveries made by Giotto and confirm ESA's leading role in the exploration of the Solar System and the Universe as a whole." The timing of this event has been chosen to coincide with the London meeting of the Rosetta Science Working Team and the second Earth flyby of the now non-operational Giotto spacecraft. In addition, the opening of the British Museum's 'Cracking Codes' Exhibition, for which the Rosetta Stone is the centrepiece, is set to take place on 10 July. The Rosetta mission. Rosetta is the third Cornerstone in ESA's 'Horizon 2000' long-term scientific programme. It will be launched by Ariane 5 rocket from Kourou spaceport in French Guiana in January 2003. In order to gain sufficient speed to reach the distant comet, Rosetta will require gravity assists from the Earth (twice) and Mars. After swinging around Mars in May 2005, Rosetta will return to Earth's vicinity in October 2005 and

Giacobini-Zinner comet: polarimetric and physical observations

International Nuclear Information System (INIS)

Martel, M.T.; Maines, P.; Grudzinska, S.; Stawikowski, A.

1984-10-01

The results of observations of the Giacobini-Zinner comet on 25 and 31 October 1959 are presented. The magnitude of the comet was measured photoelectrically in two spectral regions. The radius is on the order of one kilometer. The photoelectric measurements of comets 1959b and 1957c were used to measure the abundances of the CN and C2 radicals and of solid particles in the heads

Spectroscopic Observations of the 2011 Draconids Meteor Shower

Czech Academy of Sciences Publication Activity Database

Rudawska, R.; Zender, J.; Jenniskens, P.; Vaubaillon, J.; Koten, Pavel; Margonis, A.; Toth, J.; McAuliffe, J.; Koschny, D.

2014-01-01

Roč. 112, 1-4 (2014), s. 45-57 ISSN 0167-9295 R&D Projects: GA ČR GA205/09/1302 Institutional support: RVO:67985815 Keywords : meteorites * meteors * meteoroids Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 0.667, year: 2014

The determination of parameters of the upper atmosphere by the radio-meteor measurements

Science.gov (United States)

Shamukov, Damir; Fahrutdinova, Antonina; Nugmanov, Ildus

Study of the parameters of the upper atmosphere on the basis of amplitude-time characteristics of meteor ionization. Together with various methods meteor observations (optical, photographic, visual, spectral, television), the most effective modern method of studying meteors means is radar. The development of modern radar technology allows us to apply this tool to monitor meteors. This method allows to determine the parameters of temperature and atmospheric pressure. Actual issue is the development of methods of determining the coefficient of ambipolar diffusion, pressure, density and temperature of the atmosphere in the meteor zone. Graph of amplitude-time characteristic has the exponential form. This fact allows to determine the coefficient of ambipolar diffusion. New algorithm for estimation of the ambipolar diffusion coefficient based on a set of statistical methods and techniques of digital signal processing. There are decomposition of data on singular values and Prony's method. This method of modeling the sample data as a linear combination of exponential. Prony’s method approximates the amplitude-time characteristics of using a deterministic exponential model. Input data is amplitude-time characteristics of the meteor trail x[1]…x[N]. The method allows to estimate x[n] p-membered exponential model: begin{center} x[n]=Sigma2A_{k}exp[a _{k}(n-1)]Cos[2Pif_{k}(n-1)T+Fi_{k}] (1) end{center} 1<=n<=N, T - time range in seconds, A_{k} and a_{k} - amplitude and damping coefficient, f_{k} and Fi_{k} - frequency and initial phase. The equation describing the decay of radio signal: begin{center} A=A_{0}exp(-16Pi^{2}$D_{a}t/λ (2) ). (2) lambdaλ - radar wavelength. The output of the algorithm - the ambipolar diffusion coefficient values D_{a}. begin{center} T=0.5lnD-T_{0}+mg/2kT_{0} (3) Last equation allows to obtain temperature values using the coefficient of ambipolar diffusion depends on the height.

Definitions of terms in meteor astronomy

Science.gov (United States)

Koschny, Detlef; Borovicka, Jiri

2017-10-01

Over the last year, the IAU commission F1 (Meteors, Meteorites and Interplanetary Dust) has discussed and agreed a new definition of terminology related to our field of interest. It is available online at this link: https://www.iau.org/static/science/scientific_bodies/commissions/f1/meteordefinitions_approved.pdf. For your convenience it is reproduced here. Please keep these definitions in mind in any future communications about our topic.

On the origin of comets

Science.gov (United States)

Mendis, A.; Alfven, H.

1976-01-01

Physico-chemical processes leading to the dynamic formation and physical evolution of comets are reviewed in relationship to the various theories that propose solar origins, protoplanetary origins, planetary origins and interstellar origins. Evidence points to the origins of comets by the growth and agglomeration of small particles from gas and dust at very low temperatures at undetermined regions in space.

Planetary perturbations and the origins of short-period comets

International Nuclear Information System (INIS)

Quinn, T.; Tremaine, S.; Duncan, M.

1990-01-01

To investigate the dynamical plausibility of possible sources for the short-period comets, a representative sample of comet orbits in the field of the sun and the giant planets was integrated, with the aim to determine whether the distribution of orbits from a proposed source that reach observable perihelia (q less than 2.5 AU) matches the observed distribution of short-period orbits. It is found that the majority of the short-period comets, those with orbital period P less than 20 yr (the Jupiter family), cannot arise from isotropic orbits with perihelia near Jupiter's orbit, because the resulting observable comet orbits have the wrong distribution in period, inclination, and argument of perihelion. The simulations also show that Jupiter-family comets cannot arise from isotropic orbits with perihelia in the Uranus-Neptune region. On the other hand, a source of low-inclination Neptune-crossing orbits yields a distribution of observable Jupiter-family comets that is consistent with the data in all respects. These results imply that the Jupiter-family comets arise from a disk source in the outer solar system rather than from the Oort comet cloud. 30 refs

Comet Tempel 1 Went Back to Sleep

Science.gov (United States)

2005-07-01

Astronomers Having Used ESO Telescopes Start Analysing Unique Dataset on the Comet Following the Deep Impact Mission Ten days after part of the Deep Impact spacecraft plunged onto Comet Tempel 1 with the aim to create a crater and expose pristine material from beneath the surface, astronomers are back in the ESO Offices in Santiago, after more than a week of observing at the ESO La Silla Paranal Observatory. In this unprecedented observing campaign - among the most ambitious ever conducted by a single observatory - the astronomers have collected a large amount of invaluable data on this comet. The astronomers have now started the lengthy process of data reduction and analysis. Being all together in a single place, and in close contacts with the space mission' scientific team, they will try to assemble a clear picture of the comet and of the impact. The ESO observations were part of a worldwide campaign to observe this unique experiment. During the campaign, ESO was connected by phone, email, and videoconference with colleagues in all major observatories worldwide, and data were freely exchanged between the different groups. This unique collaborative spirit provides astronomers with data taken almost around the clock during several days and this, with the largest variety of instruments, making the Deep Impact observing campaign one of the most successful of its kind, and thereby, ensuring the greatest scientific outcome. From the current analysis, it appears most likely that the impactor did not create a large new zone of activity and may have failed to liberate a large quantity of pristine material from beneath the surface. ESO PR Photo 22/05 ESO PR Photo 22/05 Evolution of Comet Tempel 1 (FORS2/VLT) [Preview - JPEG: 400 x 701 pix - 128k] [Normal - JPEG: 800 x 1401 pix - 357k] ESO PR Photo 22/05 Animated Gif Caption: ESO PR Photo 22/05 shows the evolution of Comet Tempel 1 as observed with the FORS2 instrument on Antu (VLT). The images obtained at the VLT show that

Random, double- and single-strand DNA breaks can be differentiated in the method of Comet assay by the shape of the comet image.

Science.gov (United States)

Georgieva, Milena; Zagorchev, Plamen; Miloshev, George

2015-10-01

Comet assay is an invaluable tool in DNA research. It is widely used to detect DNA damage as an indicator of exposure to genotoxic stress. A canonical set of parameters and specialized software programs exist for Comet assay data quantification and analysis. None of them so far has proven its potential to employ a computer-based algorithm for assessment of the shape of the comet as an indicator of the exact mechanism by which the studied genotoxins cut in the molecule of DNA. Here, we present 14 unique measurements of the comet image based on the comet morphology. Their mathematical derivation and statistical analysis allowed precise description of the shape of the comet image which in turn discriminated the cause of genotoxic stress. This algorithm led to the development of the "CometShape" software which allowed easy discrimination among different genotoxins depending on the type of DNA damage they induce. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A dynamical study on extrasolar comets

Science.gov (United States)

Loibnegger, B.; Dvorak, R.

2017-09-01

Since the detection of absorption features in spectra of beta Pictoris varying on short time scales it is known that comets exist in other stellar systems. We investigate the dynamics of comets in two differently build systems (HD 10180 and HIP 14810). The outcomes of the scattering process, as there are collisions with the planets, captures and ejections from the systems are analysed statistically. Collisions and close encounters with the planets are investigated in more detail in order to conclude about transport of water and organic material. We will also investigate the possibility of detection of comets in other planetary systems.

MU head echo observations of the 2010 Geminids: radiant, orbit, and meteor flux observing biases

Directory of Open Access Journals (Sweden)

J. Kero

2013-03-01

Full Text Available We report Geminid meteor head echo observations with the high-power large-aperture (HPLA Shigaraki middle and upper atmosphere (MU radar in Japan (34.85° N, 136.10° E. The MU radar observation campaign was conducted from 13 December 2010, 08:00 UTC to 15 December, 20:00 UTC and resulted in 48 h of radar data. A total of ~ 270 Geminids were observed among ~ 8800 meteor head echoes with precisely determined orbits. The Geminid head echo activity is consistent with an earlier peak than the visual Geminid activity determined by the International Meteor Organization (IMO. The observed flux of Geminids is a factor of ~ 3 lower than the previously reported flux of the 2009 Orionids measured with an identical MU~radar setup. We use the observed flux ratio to discuss the relation between the head echo mass–velocity selection effect, the mass distribution indices of meteor showers and the mass threshold of the MU radar.

Vaporization of comet nuclei: Light curves and life times

Energy Technology Data Exchange (ETDEWEB)

Cowan, J J [Harvard Univ., Cambridge, MA (USA). Center for Astrophysics; A' Hearn, M F [Maryland Univ., College Park (USA)

1979-10-01

The authors have examined the effects of vaporization from the nucleus of a comet and show that a latitude dependence of vaporization can, in some cases, explain asymmetries in commetary light curves. They also find that a non-uniform distribution of solar radiation over a comet can considerably shorten the vaporization lifetime compared to the results normally obtained by assuming that the nuclear surface is isothermal. Independent of any latitude effects, comets with CO/sub 2/-dominated nuclei and with periherlion distances less than 0.5 AU have vaporization lifetimes less than or comparable to their dynamical ejection times. This may explain the observed deficit of comets with small perihelion distances. Similarly comets with CO/sub 2/-dominated nuclei and perihelia near Jupiter's orbit have vaporization lifetimes that are shorter than the time for capture into short-period orbits. They suggest, therefore, that at least some new comets are composed in large part of CO/sub 2/, while only H/sub 2/O-dominated comets, with lower vaporization rates, can survive to be captured into short-period orbits.

Catastrophic Disruption of Comet ISON

Science.gov (United States)

Keane, Jacqueline V.; Milam, Stefanie N.; Coulson, Iain M.; Kleyna, Jan T.; Sekanina, Zdenek; Kracht, Rainer; Riesen, Timm-Emmanuel; Meech, Karen J.; Charnley, Steven B.

2016-01-01

We report submillimeter 450 and 850 microns dust continuum observations for comet C/2012 S1 (ISON) obtained at heliocentric distances 0.31-0.08 au prior to perihelion on 2013 November 28 (rh?=?0.0125 au). These observations reveal a rapidly varying dust environment in which the dust emission was initially point-like. As ISON approached perihelion, the continuum emission became an elongated dust column spread out over as much as 60? (greater than 10(exp 5) km in the anti-solar direction. Deconvolution of the November 28.04 850 microns image reveals numerous distinct clumps consistent with the catastrophic disruption of comet ISON, producing approximately 5.2?×?10(exp 10) kg of submillimeter-sized dust. Orbital computations suggest that the SCUBA-2 emission peak coincides with the comet's residual nucleus.

Hyakutake, Hale-Bopp and the chemistry of comets

International Nuclear Information System (INIS)

Bachiller, R.; Planesas, P.

1997-01-01

Comets can be regarded as messengers from the primitive solar system which can provide precious pieces of information on the composition of the protosolar nebula. Physical and chemical phenomena within comets (shock waves, photodissociation caused by solar radiation, some endothermic chemical reactions, etc) are of the highest interest and cannot be reproduced at terrestrial laboratories in many cases. The passage of Hyakutake in 1996 and that of Hale-Bopp in 1997 are allowing remarkable progress in the understanding of the physico-chemistry of comets. Observations of such comets can be crucial in the study of the origin of life on Earth. (Author)

Changes of 2H and 18O enrichment of meteoric water and Pleistocene glaciation

International Nuclear Information System (INIS)

Harmon, R.S.; Schwarcz, H.P.

1981-01-01

Isotopic data on fluid inclusions and host speleothems are presented which support the hypothesis that the deltaD-delta 18 O relationship for modern meteoric waters may have changed during the Pleistocene glacial periods in response to increased ocean surface air humidity. Palaeotemperatures for five areas of east-central North America and Bermuda, calculated assuming the present deltaDdelta 18 O meteoric water relationship for fluid inclusion waters, are observed to be too low during late Pleistocene glacial periods (in some instances falling below O 0 C) while interglacial palaeotemperatures are largely equivalent to those in the areas at present. As speleothem deposition cannot occur at subzero temperatures, a possible solution to this dilemma is a shift in the intercept of the meteoric water relationship. (U.K.)

Optical Detection of Anomalous Nitrogen in Comets

Science.gov (United States)

2003-12-01

VLT Opens New Window towards Our Origins Summary A team of European astronomers [1] has used the UVES spectrograph on the 8.2-m VLT KUEYEN telescope to perform a uniquely detailed study of Comet LINEAR (C/2000 WM1) . This is the first time that this powerful instrument has been employed to obtain high-resolution spectra of a comet. At the time of the observations in mid-March 2002, Comet LINEAR was about 180 million km from the Sun, moving outwards after its perihelion passage in January. As comets are believed to carry "pristine" material - left-overs from the formation of the solar system, about 4,600 million years ago - studies of these objects are important to obtain clues about the origins of the solar system and the Earth in particular. The high quality of the data obtained of this moving 9th-magnitude object has permitted a determination of the cometary abundance of various elements and their isotopes [2]. Of particular interest is the unambiguous detection and measurement of the nitrogen-15 isotope. The only other comet in which this isotope has been observed is famous Comet Hale-Bopp - this was during the passage in 1997, when it was much brighter than Comet LINEAR. Most interestingly, Comet LINEAR and Comet Hale-Bopp display the same isotopic abundance ratio, about 1 nitrogen-15 atom for each 140 nitrogen-14 atoms ( 14 N/ 15 N = 140 ± 30) . That is about half of the terrestrial value (272). It is also very different from the result obtained by means of radio measurements of Comet Hale-Bopp ( 14 N/ 15 N = 330 ± 75). Optical and radio measurements concern different molecules (CN and HCN, respectively), and this isotopic anomaly must be explained by some differentiation mechanism. The astronomers conclude that part of the cometary nitrogen is trapped in macromolecules attached to dust particles . The successful entry of UVES into cometary research now opens eagerly awaited opportunities for similiar observations in other, comparatively faint comets. These

The spacecraft encounters of Comet Halley

Science.gov (United States)

Asoka Mendis, D.; Tsurutani, Bruce T.

1986-01-01

The characteristics of the Comet Halley spacecraft 'fleet' (VEGA 1 and VEGA 2, Giotto, Suisei, and Sakigake) are presented. The major aims of these missions were (1) to discover and characterize the nucleus, (2) to characterize the atmosphere and ionosphere, (3) to characterize the dust, and (4) to characterize the nature of the large-scale comet-solar wind interaction. While the VEGA and Giotto missions were designed to study all four areas, Suisei addressed the second and fourth. Sakigake was designed to study the solar wind conditions upstream of the comet. It is noted that NASA's Deep Space Network played an important role in spacecraft tracking.

Ensemble Properties of Comets in the Sloan Digital Sky Survey

Energy Technology Data Exchange (ETDEWEB)

Solontoi, Michael; /Adler Planetarium, Chicago; Ivezic, Zeljko; /Washington U., Seattle, Astron. Dept.; Juric, Mario; /Harvard Coll. Observ.; Becker, Andrew C.; /Washington U., Seattle, Astron. Dept.; Jones, Lynne; /Washington U., Seattle, Astron. Dept.; West, Andrew A.; /Boston U.; Kent, Steve; /Fermilab; Lupton, Robert H.; /Princeton U. Observ.; Claire, Mark; /Washington U., Seattle, Astron. Dept.; Knapp, Gillian R.; /Princeton U. Observ.; Quinn, Tom; /Washington U., Seattle, Astron. Dept. /Princeton U. Observ.

2012-02-01

We present the ensemble properties of 31 comets (27 resolved and 4 unresolved) observed by the Sloan Digital Sky Survey (SDSS). This sample of comets represents about 1 comet per 10 million SDSS photometric objects. Five-band (u, g, r, i, z) photometry is used to determine the comets colors, sizes, surface brightness profiles, and rates of dust production in terms of the Afp formalism. We find that the cumulative luminosity function for the Jupiter Family Comets in our sample is well fit by a power law of the form N(comets. The resolved comets show an extremely narrow distribution of colors (0.57 {+-} 0.05 in g - r for example), which are statistically indistinguishable from that of the Jupiter Trojans. Further, there is no evidence of correlation between color and physical, dynamical, or observational parameters for the observed comets.

Unveiling the formation and evolution of comets

Science.gov (United States)

Lasue, J.; Levasseur-Regourd, A. C.; Botet, R.; Coradini, A.; Desanctis, M. C.; Kofman, W.

2007-08-01

Comet nuclei are considered as the most pristine bodies of the solar system and consequently their study sheds an important light on the processes occurring during the initial stages of the solar system formation. The analysis of the porosity and bulk density of such primordial bodies is especially important to understand their capacity to retain volatile components (organics and ices) present in the early solar nebula. Typical tensile strengths deduced for comet nuclei range from below 102N.m-2 from the Deep Impact mission [1] up to 104N.m-2 from the study of comet C/1999 S4 LINEAR breakup [2] and meteoroids [3]. A bulk density of about 350 kg/m3 has been obtained for 9P/Tempel 1 from the Deep Impact mission [4]. Moreover the properties of dust released from the comets strongly confirm such values. Instruments flying-by comet 1P/Halley had discovered the presence of organics, and pointed out the dust low albedo and extremely low density while analyses of Interplanetary Dust Particles collected in the stratosphere and remote spectroscopic observations have indicated that cometary dust consists of an un-equilibrated heterogeneous mixture of organic refractory materials and of amorphous and crystalline silicate minerals [5], as recently confirmed by Stardust [6]. Observations of the solar scattered light, together with elaborate simulations, give an estimation of the mass ratio between silicates and absorbing organics, the size distribution and the structure of the dust particles, suggesting that a fair amount consists in fluffy aggregates built up from submicronic grains [7,8], as recently confirmed by the analysis of dust craters and aerogel tracks on Stardust collector showing for some large particles (up to 100 μm) an extraordinary fluffy structure [9]. Simulations have been developed in our teams to describe the aspects of comet aggregation and evolution that have not been thoroughly explained yet. Particle aggregation simulations taking into account cohesive

Comet 67P Through the Lens of Art

Science.gov (United States)

Smirnova, Ekaterina

2017-04-01

My proposal is to share my artistic exploration of a comet through the bodily senses, while finding inspiration in scientific data. I will present my artwork as a slideshow, showcasing: large scale paintings, ceramic sculptures, music and interactive augmented reality. The Rosetta mission of the European Space Agency (ESA) to comet 67P/ Churyumov-Gerasimenko is remarkable. The scientific investigation of the comet's composition, atmosphere, dust, vapor, surface and internal structure are crucial to help researchers understand the origin of the solar system and our own planet. Sight: Paintings Rosetta mission discovered that the water on the comet is different from the water on Earth; as measured with the ROSINA-DFMS instrument on Rosetta, water on 67P contains approximately 3 times more hydrogen­deuterium oxide - HDO, than found in Earth's oceans. In the art studio I re-create water that is close in composition to the water on the comet, by concentrating the level of HDO. With this water I paint large scale watermedia paintings, based on the photographs by Rosetta (OSIRIS, Nav. Cam.). Touch: Sculptures While exploring the comet's three-dimensional form, I focus more deeply on the composition of the comet. Stoneware clay and my choice of a glaze both include iron oxide, a common constituent of meteorites and comets. Hearing: Music An audio piece "A Singing Comet", by Manuel Senfft, based on the Rosetta Plasma Consortium data, inspired me to make a musical piece. In collaboration with clarinetist Lee Mottram (Wales) and composer Takuto Fukuda (Japan) we created an electro­acoustic composition in which we tell the story of comets visiting our Solar System, repeating their cycle, curving around the sun and releasing water, carrying away dust to form their tails. Smell In collaboration with The Open University, UK, postcards with a smell of the comet were created, introducing the chemical components of the comet. The smell was recreated by combining several molecules

On the existence of a comet belt beyond Neptune

International Nuclear Information System (INIS)

Fernandez, J.A.

1980-01-01

The possible existence of a comet belt in connection with the origin of the short-period comets is analysed. It is noted that the current theory - that these comets originate as near-parabolic comets captured by Jupiter and the other giant planets - implies an excessive wastage of comets lost in hyperbolic orbits, which is avoided in the present model. The following picture is predicted. Solid conglomerates up to approximately 10 18 g were formed by gravitational instabilities in the belt region (about 35 to 50 AU). A further fragmentation-accretion process led to a power-law mass distribution similar to that observed in the asteroids. Since then, close encounters between members of the belt have provoked the diffusion of some of them with the effect that they have become subject to the strong perturbations of Neptune. Of these a small number pass from one planet to the next inside and end as short-period comets. By means of a Monte Carlo method, the influence of close encounters between belt comets is then studied in relation to the diffusion of their orbits. It is concluded that if such a belt contains members with masses equal to or greater than that of Ceres, the orbital diffusion could proceed fast enough to maintain the number of observed short-period comets in a steady state. (author)

Ambilpolar Electric Field and Diffusive Cooling of Electrons in Meteor Trails

Science.gov (United States)

Pasko, V. P.; Kelley, M. C.

2017-12-01

Kelley and Price [GRL, 44, 2987, 2017] recently indicated that ambipolar electric fields may play a role in dynamics of dense plasmas generated by meteors. In the present work we discuss time dynamics of relaxation of electron temperature in meteor trails under relatively common conditions when meteor trail diffusion is not affected by the geomagnetic field (i.e., at low altitudes where both electrons and ions are not magnetized, or at higher altitudes in the plane defined by the trail and magnetic field when meteor trail is not aligned with the geomagnetic field [Ceplecha et al., Space Sci. Rev., 84, 327, 1998, and references therein]). The rate of ambipolar diffusion is a function of temperature and pressure [e.g., Hocking et al., Ann. Geophys., 34, 1119, 2016; Silber et al., Mon. Not. RAS, 469, 1869, 2017] and there is a significant spectroscopic evidence of initial plasma temperatures in meteor trails on the order 4400 deg K [Jennikens et al., Astrobiology, 4, 81, 2004]. For a representative altitude of 105 km chosen for our studies the results are consistent with previous analysis conducted in [Baggeley and Webb, J. Atm. Terr. Phys., 39, 1399, 1977; Ceplecha et al., 1998] indicating that the electron temperature remains elevated for significant time durations measured in tens of milliseconds. Our results indicate that in terms of their magnitudes the ambipolar electric fields can exceed the critical breakdown field of air, consistent with ideas expressed by Kelley and Price [GRL, 44, 2987, 2017], however, under considered conditions these fields lead to acceleration of electron cooling, with electron temperatures falling below the ambient air temperature (below 224 deg K at 105 km altitude). These effects are referred to as diffusive cooling [e.g., Rozhansky and Tsendin, Transport phenomena in partially ionized plasma, Taylor & Francis, 2001, p. 449] and represent a process in which diffusing electrons move against the force acting on them from ambipolar

CATASTROPHIC DISRUPTION OF COMET ISON

Energy Technology Data Exchange (ETDEWEB)

Keane, Jacqueline V.; Kleyna, Jan T.; Riesen, Timm-Emmanuel; Meech, Karen J. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Milam, Stefanie N.; Charnley, Steven B. [Astrochemistry Laboratory, NASA GSFC, MS 690, Greenbelt, MD 20771 (United States); Coulson, Iain M. [Joint Astronomy Center, 660 North Aohoku Place, Hilo, HI 96720 (United States); Sekanina, Zdenek [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Kracht, Rainer, E-mail: keane@ifa.hawaii.edu [Ostlandring 53, D-25335 Elmshorn, Schleswig-Holstein (Germany)

2016-11-10

We report submillimeter 450 and 850 μ m dust continuum observations for comet C/2012 S1 (ISON) obtained at heliocentric distances 0.31–0.08 au prior to perihelion on 2013 November 28 ( r {sub h} = 0.0125 au). These observations reveal a rapidly varying dust environment in which the dust emission was initially point-like. As ISON approached perihelion, the continuum emission became an elongated dust column spread out over as much as 60″ (>10{sup 5} km) in the anti-solar direction. Deconvolution of the November 28.04 850 μ m image reveals numerous distinct clumps consistent with the catastrophic disruption of comet ISON, producing ∼5.2 × 10{sup 10} kg of submillimeter-sized dust. Orbital computations suggest that the SCUBA-2 emission peak coincides with the comet's residual nucleus.

Meteor head echo polarization at 930 MHz studied with the EISCAT UHF HPLA radar

Directory of Open Access Journals (Sweden)

G. Wannberg

2011-06-01

Full Text Available The polarization characteristics of 930-MHz meteor head echoes have been studied for the first time, using data obtained in a series of radar measurements carried out with the tristatic EISCAT UHF high power, large aperture (HPLA radar system in October 2009. An analysis of 44 tri-static head echo events shows that the polarization of the echo signal recorded by the Kiruna receiver often fluctuates strongly on time scales of tens of microseconds, illustrating that the scattering process is essentially stochastic. On longer timescales (> milliseconds, more than 90 % of the recorded events show an average polarization signature that is independent of meteor direction of arrival and echo strength and equal to that of an incoherent-scatter return from underdense plasma filling the tristatic observation volume. This shows that the head echo plasma targets scatter isotropically, which in turn implies that they are much smaller than the 33-cm wavelength and close to spherically symmetric, in very good agreement with results from a previous EISCAT UHF study of the head echo RCS/meteor angle-of-incidence relationship. Significant polarization is present in only three events with unique target trajectories. These all show a larger effective target cross section transverse to the trajectory than parallel to it. We propose that the observed polarization may be a signature of a transverse charge separation plasma resonance in the region immediately behind the meteor head, similar to the resonance effects previously discussed in connection with meteor trail echoes by Herlofson, Billam and Browne, Jones and Jones and others.

Telescopic and meteor observation of `Oumuamua, the first known interstellar asteroid

Science.gov (United States)

Ye, Quan-Zhi

2018-04-01

1I/2017 U1 ('Oumuamua), a recently discovered asteroid in a hyperbolic orbit, is the first macroscopic object of extrasolar origin identified in the solar system. I will present imaging and spectroscopic observations of 'Oumuamua as well as a search of meteor activity potentially linked to this object using the Canadian Meteor Orbit Radar. We find that 'Oumuamua exhibits a moderate spectral gradient of 10%+-6% per 100 nm, a value lower than that of outer solar system bodies, indicative of a formation and/or previous residence in a warmer environment. Imaging observation and spectral line analysis show no evidence that 'Oumuamua is presently active. Negative meteor observation is as expected, since ejection driven by sublimation of commonly known cometary species such as CO requires an extreme ejection speed of ~40 m/s at ~100 au in order to reach the Earth. No obvious candidate stars are proposed as the point of origin for 'Oumuamua. Given a mean free path of ~109 ly in the solar neighborhood, 'Oumuamua has likely spent a very long time in interstellar space before encountering the solar system.

Insights into Meteoric 10Be Dynamics and Climate Stability along the Hawaiian Kohala Climosequence

Science.gov (United States)

Dixon, J. L.; Chadwick, O.

2017-12-01

We measure meteoric 10Be in soils across a well-studied climate gradient spanning Kohala, Hawaii to provide new understanding of the isotope behavior in soils and constraints on nuclide delivery rates to Earth's surface. Annual rainfall across the Kohala climogradient varies from 16 - 300 cm, with Hawaiian soils reflecting evolution over the past 150 ka, the nominal age of the volcanic parent material. We analyzed a sequence of nine soil profiles for meteoric 10Be and compared with previously measured data on soil chemistry and dust fluxes. In the Kohala system, soil inventories of 10Be span 40-300 x 109 atom/cm2 and generally increase linearly with rainfall, consistent with precipitation-driven fluxes and the high retention of 10Be in clay-rich soil horizons. However, nuclide inventories dramatically decrease for soils at rainfall >140 cm/y. The observed decrease corresponds with other strong changes in weathering intensity across the climate gradient, associated with previously studied and recognized pedogenic thresholds. These thresholds represent abrupt transitions in soil chemistry related to increased throughflow of soil solutions, decreases in base saturation and pH, and the destruction of phyllosilicates and replacement with amorphous oxyhydroxides. Meteoric-derived ages, based on 10Be-flux estimates and measured inventories are uniform for dry soils ( 60ka), but far less than the known substrate age (150ka), indicating that actual delivery rates are lower than predicted from current models in this region. Despite the offset in predicted and substrate ages, the consistency in pattern suggests that the rainfall gradient over the 150 thousand years of soil development has not deviated significantly from its present structure. Furthermore, based on clear 10Be losses in soils with high moisture availability, our results indicate meteoric 10Be may not be a robust tracer of soil age and movement in systems with high rainfall and weathering intensity and low soil

Comet showers and Nemesis, the death star

International Nuclear Information System (INIS)

Hills, J.G.

1984-01-01

The recently proposed hypothesis that the periodic extinctions of terrestrial species are the result of comet showers catalyzed by a hypothetical distant solar companion, Nemesis, a tale of global death by comet bombardment of the earth, is discussed

Comments on comet shapes and aggregation processes

International Nuclear Information System (INIS)

Hartmann, W.K.

1989-01-01

An important question for a comet mission is whether comet nuclei preserve information clarifying aggregation processes of planetary matter. New observational evidence shows that Trojan asteroids, as a group, display a higher fraction of highly-elongated objects than the belt. More recently evidence has accumulated that comet nuclei, as a group, also display highly-elongated shapes at macro-scale. This evidence comes from the several comets whose nuclear lightcurves or shapes have been well studied. Trojans and comet nuclei share other properties. Both groups have extremely low albedos and reddish-to neutral-black colors typical of asteroids of spectral class D, P, and C. Both groups may have had relatively low collision frequencies. An important problem to resolve with spacecraft imaging is whether these elongated shapes are primordial, or due to evolution of the objects. Two hypotheses that might be tested by a combination of global-scale and close-up imaging from various directions are: (1) The irregular shapes are primordial and related to the fact that these bodies have had lower collision frequencies than belt asteroids; or (2) The irregular shapes may be due to volatile loss

COMET SHOWERS ARE NOT INDUCED BY INTERSTELLAR CLOUDS

Energy Technology Data Exchange (ETDEWEB)

Morris, D.E.

1985-11-01

Encounters with interstellar clouds (IC) have been proposed by Rampino and Stothers as a cause of quasi-periodic intense comet showers leading to earth impacts, in order to explain the periodicity in marine mass extinctions found by Raup and Sepkoski. The model was described further, criticized and defended. The debate has centered on the question of whether the scale height of the clouds is small enough (in comparison to the amplitude of the oscillation of the solar system about the plane of the Galaxy) to produce a modulation in the rate of encounters. We wish to point out another serious, we believe fatal, defect in this model - the tidal fields of ICs are not strong enough to produce intense comet showers leading to earth impacts by bringing comets of the postulated inner Oort cloud into earth crossing orbits, except possibly during very rare encounters with very dense clouds. We will show that encounters with abundant clouds of low density cannot produce comet showers; cloud density N > 10{sup 3} atoms cm{sup -3} is needed to produce an intense comet shower leading to earth impacts. Furthermore, the tidal field of a dense cloud during a distant encounter is too weak to produce such showers. As a consequence, comet showers induced by ICs will be far less frequent than showers caused by passing stars. This conclusion is independent of assumptions about the radial distribution of comets in the inner Oort cloud.

New Application of the Comet Assay

Science.gov (United States)

Cortés-Gutiérrez, Elva I.; Dávila-Rodríguez, Martha I.; Fernández, José Luís; López-Fernández, Carmen; Gosálbez, Altea; Gosálvez, Jaime

2011-01-01

The comet assay is a well-established, simple, versatile, visual, rapid, and sensitive tool used extensively to assess DNA damage and DNA repair quantitatively and qualitatively in single cells. The comet assay is most frequently used to analyze white blood cells or lymphocytes in human biomonitoring studies, although other cell types have been examined, including buccal, nasal, epithelial, and placental cells and even spermatozoa. This study was conducted to design a protocol that can be used to generate comets in subnuclear units, such as chromosomes. The new technique is based on the chromosome isolation protocols currently used for whole chromosome mounting in electron microscopy, coupled to the alkaline variant of the comet assay, to detect DNA damage. The results show that migrant DNA fragments can be visualized in whole nuclei and isolated chromosomes and that they exhibit patterns of DNA migration that depend on the level of DNA damage produced. This protocol has great potential for the highly reproducible study of DNA damage and repair in specific chromosomal domains. PMID:21540337

Discovery of the Upsilon Andromedids (UAN, IAU #507)

Science.gov (United States)

Holman, David; Jenniskens, Peter

2013-04-01

During routine low-light level video observations with CAMS (Cameras for Allsky Meteor Surveillance) made from 2011 June 2 to August 7, a weak shower with a radiant near Upsilon Andromedae was discovered. In that same section of the sky, the Phi Piscids (PPS) were detected, listed as #372 in the IAU Working List of Meteor Showers. The Alpha Triangulids (ATR, IAU #414) and August Piscids (AUP, IAU #415) are activity from the same stream and should be removed from the list. Radiant and speed of the July Pegasids (JPE, IAU #175) match the Great Comet of 1771 (C/1771 A1) as well as earlier identified comet C/1979 Y1 Bradfield.

Comet LINEAR C/1999 S4 - an absolutely well-behaved comet before breakup

Science.gov (United States)

Peschke, S. B.; Lisse, C. M.; Fernandez, Y. R.; Ressler, M.; Stickel, M.; Kaminski, C.; Golish, B.

2000-10-01

We present results from infrared imaging of comet LINEAR C/1999 S4 on June 17 - 19, 2000 (pre-breakup), using the near-IR camera NSFCAM and the mid-IR camera MIRLIN at the 3m NASA/IRTF. Images and multi-wavelength spectroscopy were obtained in the zJHK'L'MNQ bands, and were used to create a 1.0 - 25 μ m SED of the comet's dust and nucleus. The coma's contribution at each wavelength was modeled using spatial fitting (Fernandez 1999, PhD thesis; Lisse et al. 1999, Icarus 140, 189). The resulting comatic and nuclear SEDs were then modeled using modified Mie theory (Lisse et al. 1998, ApJ 496, 971) and the standard nuclear thermal models (Lebofsky and Spencer 1989, Asteroids II, 128), respectively. We report the resulting dust PSD, mass loss rate, and albedo, as well as the nuclear radius, and we compare these results to those obtained by others from optical data both before and after the comet's breakup in late July 2000.

The shortage of long-period comets in elliptical orbits

International Nuclear Information System (INIS)

Everhart, E.

1979-01-01

Based on the number of 'new' comets seen on near-parabolic orbits, one can predict the number of comets that should be found on definitely elliptical orbits on their subsequent returns. The author shows that about three out of four of these returning comets are not observed. (Auth.)

Assessment and reduction of comet assay variation in relation to DNA damage: studies from the European Comet Assay Validation Group

DEFF Research Database (Denmark)

Møller, Peter; Möller, Lennart; Godschalk, Roger W L

2010-01-01

The alkaline single cell gel electrophoresis (comet) assay has become a widely used method for the detection of DNA damage and repair in cells and tissues. Still, it has been difficult to compare results from different investigators because of differences in assay conditions and because the data...... are reported in different units. The European Comet Assay Validation Group (ECVAG) was established for the purpose of validation of the comet assay with respect to measures of DNA damage formation and its repair. The results from this inter-laboratory validation trail showed a large variation in measured level...... reliability for the measurement of DNA damage by the comet assay but there is still a need for further validation to reduce both assay and inter-laboratory variation....

Comet Shoemaker-Levy 9 meets Jupiter.

Science.gov (United States)

Levy, D. H.; Shoemaker, E. M.; Shoemaker, C. S.

1995-08-01

The impact of comet D/1993 F2 (Shoemaker-Levy 9) with Jupiter was unforgettable, an event probably not to be repeated for millennia to come. One year later the astronomers who first spotted the comet reflect on their discovery, on the anxious months of anticipation before the collision and on what has been learned since.

Comet West: a view from the HELIOS zodiacal light photometers

International Nuclear Information System (INIS)

Benensohn, R.M.; Jackson, B.V.

1987-01-01

Comet West passed through perihelion on February 25, 1976. The comet crossed the HELIOS A and B spacecraft zodiacal light photometer fields of view as the spacecraft orbited the Sun, allowing them to record the brightness, polarization, and color of the comet and its surrounding interplanetary medium. Data from the U, B, and V photometers across the tail shows a distinct bluing followed by a slight reddening corresponding to the ion and dust tails, respectively, entering the field of view. The non-Earth perspective of the HELIOS photometers allows a comparison of the tail with Earth observations at the same time. Precise location of the nucleus and tail allow the photometer data to be searched for evidence of the comet bow shock and orbital dust. A brightness bump present in the data before the comet reaches some photometer positions, can be shown to approximately form a parabolic shape Sunward and ahead of the orbital motion of the Comet West nucleus. If this is the comet bow shock or bow compression, then it corresponds to a density enhancement of the ambient medium by 1.5 to 2 times in the vicinity of the comet. The distance of the brightness increase from the nucleus by comparison with Comet Halley implies a neutral gas production rate of approximately 3 times that of Halley

Seasonal temperature variation around the mesopause inferred from a VHF meteor radar at King Sejong Station (62S, 59W), Antarctica

Science.gov (United States)

Kim, Yongha; Kim, Jeong-Han; Lee, Changsup; Jee, Gun-Hwa

A VHF meteor radar, installed at King Sejong Station in March, 2007, has been detecting echoes from more than 20,000 meteors per day. Meteor echoes are decayed typically within seconds as meteors spread away by atmospheric diffusion. The diffusion coefficients can thus be obtained from decay times of meteor echo signals, providing with information on the atmospheric temperatures and pressures at meteor altitudes from 70 to 100 km. In this study, we present altitude profiles of 15-min averaged diffusion coefficients in each month, which clearly show a minimum at 80 - 85 km. The minimum appears at higher altitude during austral summer than winter, and seems to be near the lower level of two temperature minimum structure around the mesopause seen by TIMED/SABER data at high latitudes. The higher mesopause level (95-100 km) of the SABER data does not appear in our diffusion profiles probably because it is too close the limit of meaningful diffusion coefficients that can be derived from meteor decay detection. In order to understand temperature variation around the mesopause more directly, we will discuss various methods to extract temperature profiles from the diffusion profiles. We will also present monthly averaged OH and O2 airglow temperatures observed at the same site, and compare them with those derived from the meteor radar observation.

The Rosetta Mission to Comet 67P/ Churyumov-Gerasimenko

Science.gov (United States)

Buratti, Bonnie J.

2017-06-01

As remnant bodies left over from the formation of the Solar System, comets offer clues to the physical conditions and architecture of the protosolar nebula. The Rosetta spacecraft, which included an orbiter and a lander that were built and managed by the European Space Agency with NASA contributing four instruments and scientific expertise, was the first mission to orbit and study a comet through a perihelion passage. The targeted Jupiter-family comet 67P/ Churyumov-Gerasimenko, is seemingly two distinct planetesimals stuck together. The comet has not melted or been processed substantially, except for its outer layers, which consist of reaccreted dust and a crust of heated, devolatized, and annealed refractory materials and organics. The exceptionally low density (0.53 gm/cc) of 67P/ implies it is a rubble pile. The comet also appears to contain a hierarchy of building blocks: smaller spherically shaped meter-sized bodies can be seen in its interior, and even smaller cm-sized pebbles were imaged by the camera as the spacecraft made a soft crash landing on the comet’s surface on 30 September 2016. The unexpected discovery of molecular oxygen, nitrogen, and hydrogen imply that 67P/ was formed under cold conditions not exceeding 30K. The discovery of many organic compounds, including the amino acid glycine, lends support to the idea that comets, which originate in the Kuiper Belt and the Oort Cloud, brought the building blocks of life to Earth. More laboratory data on organic compounds would help to identify additional organic compounds on the comet. The differences between cometary and terrestrial D/H ratios suggest that comets are not the primary source of terrestrial water, although data on more comets is needed to confirm this result.Besides being primordial objects offering a window into the formation of solar systems, comets are astrophysical laboratories, ejecting dust and charged particles into the plasma comprising the solar wind. Several unusual phenomena

The comet rendezvous asteroid flyby mission

International Nuclear Information System (INIS)

Morrison, D.; Neugebauer, M.; Weissman, P.R.

1989-01-01

The Comet Rendezvous Asteroid Flyby (CRAF) mission is designed to answer the many questions raised by the Halley missions by exploring a cometary nucleus in detail, following it around its orbit and studying its changing activity as it moves closer to and then away from the Sun. In addition, on its way to rendezvous with the comet, CRAF will fly by a large, primitive class main belt asteroid and will return valuable data for comparison with the comet results. The selected asteroid is 449 Hamburga with a diameter of 88 km and a surface composition of carbonaceous chondrite meteorites. The expected flyby date is January, 1998. The CRAF spacecraft will continue to make measurements in orbit around the cometary nucleus as they both move closer to the Sun, until the dust and gas hazard becomes unsafe. At that point the spacecraft will move in and out between 50 and 2,500 kilometers to study the inner coma and the cometary ionosphere, and to collect dust and gas samples for onboard analysis. Following perihelion, the spacecraft will make a 50,000 km excursion down the comet's tail, further investigating the solar wind interaction with the cometary atmosphere. The spacecraft will return to the vicinity of the nucleus about four months after perihelion to observe the changes that have taken place. If the spacecraft remains healthy and adequate fuel is still onboard, an extended mission to follow the comet nucleus out to aphelion is anticipated

Hummingbird Comet Nucleus Analysis Mission

Science.gov (United States)

Kojiro, Daniel; Carle, Glenn C.; Lasher, Larry E.

2000-01-01

Hummingbird is a highly focused scientific mission, proposed to NASA s Discovery Program, designed to address the highest priority questions in cometary science-that of the chemical composition of the cometary nucleus. After rendezvous with the comet, Hummingbird would first methodically image and map the comet, then collect and analyze dust, ice and gases from the cometary atmosphere to enrich characterization of the comet and support landing site selection. Then, like its namesake, Hummingbird would carefully descend to a pre-selected surface site obtaining a high-resolution image, gather a surface material sample, acquire surface temperature and then immediately return to orbit for detailed chemical and elemental analyses followed by a high resolution post-sampling image of the site. Hummingbird s analytical laboratory contains instrumentation for a comprehensive molecular and elemental analysis of the cometary nucleus as well as an innovative surface sample acquisition device.

Rocket Detection of Argon in Comet Hale-Bopp

Science.gov (United States)

Stern, S. A.; Festou, M. C.; Parker, J. Wm.; Slater, D. C.; Gladstone, G. R.; A'Hearn, M. F.

1998-12-01

The EUVS planetary sounding rocket spectrograph was flown on 30.2 March 1997 (UT) from White Sands, New Mexico to observe comet Hale-Bopp in the bandpass from 830--1120 A. At the time of launch the comet was near perihelion, 0.915 AU from the Sun, 1.340 AU from Earth, and traveling at a heliocentric radial velocity of +0.70 km/s. EUVS obtained its primary spectra of the comet at resolution near 12 A, collecting 9340 counts over approximately 330 seconds of integration time. To our knowledge, the resulting dataset is both the most sensitive and the highest spectral resolution probe of a comet in the UV below 1200 A as yet achieved, and contains signatures of both the 1048.2 A and 1066.7 A Ar I resonance lines. These features represent the first-ever detections of any noble gas in a comet. The spectrum also includes significant detections which we tentatively attribute to due to 834 A 0 II, 972 A Lyman gamma, 989 A O I, the 1026 A H I Lyman beta/O I. We will discuss the Ar features, retrieve the Ar column in the coma, and discuss the implications of the total Ar/O abundance ratio in Hale-Bopp for the comet's origin.

''Meteor'' radio/television satellites for study of earth's natural resources

Energy Technology Data Exchange (ETDEWEB)

Selivanov, A S; Tuchin, Yu M

1981-01-01

Two types of wide sweep multi-zonal scanning devices are included in the Meteor units, including radio-transmitting, and memory units. Data is transmitted within the wave range assigned to meteorologic earth satellites.

100 and counting : SOHO's score as the world's top comet finder

Science.gov (United States)

2000-02-01

Like nearly all of SOHO's discoveries, the 100th comet showed up in images from the LASCO instrument. This is a set of coronagraphs that view the space around the Sun out to 20 million kilometres, while blotting out the bright solar disk with masks. Developed for SOHO by a multinational team led by the US Naval Research Laboratory, LASCO watches for mass ejections from the Sun that threaten to disturb the Earth's space environment. The comet discoveries are a big bonus. SOHO's experts spot many of the comets as soon as the images come in. But still pictures and movies from LASCO are freely available on the Internet to astronomers around the world, who can discover less obvious comets without leaving their desks. This was the case when Kazimieras Cernis of the Institute of Theoretical Physics and Astronomy in Vilnius, Lithuania, found SOHO-100. "On 4 February I saw the comet as a small speck of light in the previous day's LASCO images," Cernis explained. "It had no visible tail, but it was too fuzzy to be an asteroid. By the time I had seen the object moving steadily across the sky in six successive images, I was convinced it was a comet and I sent the details to the SOHO scientists for verification." The competition to find SOHO's 100th comet was keen. An amateur astronomer, Maik Meyer of Frauenstein, Germany, discovered SOHO-98 and 99. On 5 February, less than 24 hours after Cernis reported the candidate SOHO-100, Meyer found the candidate SOHO-101. On the same day and in the same LASCO images Douglas Biesecker, a member of the SOHO science team, spotted the candidate SOHO-102 travelling ahead of 101. Computations have now validated the orbits for all three candidates, and shown them to be bona fide comet discoveries. Other amateur astronomers have used the LASCO images to find comets. In the summer of 1999 Terry Lovejoy in Australia found five, and since September 1999 an amateur in England, Jonathan Shanklin, has spotted three more. "SOHO is a special chance for

Rosetta - a comet ride to solve planetary mysteries

Science.gov (United States)

2003-01-01

Comets are very interesting objects for scientists, since their composition reflects how the Solar System was when it was very young and still 'unfinished', more than 4600 million years ago. Comets have not changed much since then. By orbiting Comet Wirtanen and landing on it, Rosetta will collect essential information to understand the origin and evolution of our Solar System. It will also help discover whether comets contributed to the beginnings of life on Earth. In fact comets are carriers of complex organic molecules, that - delivered to Earth through impacts - perhaps played a role in the origin of living forms. Furthermore, “volatile” light elements carried by comets may have also played an important role in forming the Earth’s oceans and atmopshere. “Rosetta is one of the most challenging missions ever undertaken so far”, says Prof. David Southwood, ESA Director of Science, “No one before attempted a similar mission, unique for its scientific implications as well as for its complex and spectacular interplanetary space manoeuvres”. Before reaching its target in 2011, Rosetta will circle the Sun almost four times on wide loops in the inner Solar System. During its long trek, the spacecraft will have to endure some extreme thermal conditions. Once it is close to Comet Wirtanen, scientists will take it through a delicate braking manoeuvre; then the spacecraft will closely orbit the comet, and gently drop a lander on it. It will be like landing on a small, fast-moving cosmic bullet that still has - at present - an almost unknown 'geography'. An amazing 8-year interplanetary trek Rosetta is a 3-tonne box-type spacecraft about 3 metres high, with two 14-metre long solar panels. It consists of an orbiter and a lander. The lander is approximately 1 metre across and 80 centimetres high. It will be attached to the side of the Rosetta orbiter during the journey to Comet Wirtanen. Rosetta carries 21 experiments in total, 10 of them on the lander. They will

Outbursting comet P/2010 V1 (Ikeya-Murakami): A miniature comet Holmes

Energy Technology Data Exchange (ETDEWEB)

Ishiguro, Masateru [Department of Physics and Astronomy, Seoul National University, Gwanak, Seoul 151-742 (Korea, Republic of); Jewitt, David [Department of Earth, Planetary and Space Sciences, University of California at Los Angeles, 595 Charles Young Drive East, Los Angeles, CA 90095-1567 (United States); Hanayama, Hidekazu; Miyaji, Takeshi; Fukushima, Hideo; Watanabe, Jun-ichi [Ishigakijima Astronomical Observatory, National Astronomical Observatory of Japan, Ishigaki, Okinawa 907-0024 (Japan); Usui, Fumihiko [Department of Astronomy, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Sekiguchi, Tomohiko [Department of Teacher Training, Hokkaido University of Education, 9 Hokumon, Asahikawa 070-8621 (Japan); Yanagisawa, Kenshi; Kuroda, Daisuke [Okayama Astrophysical Observatory, National Astronomical Observatory of Japan, Asaguchi, Okayama 719-0232 (Japan); Yoshida, Michitoshi [Hiroshima Astrophysical Science Center, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526 (Japan); Ohta, Kouji [Department of Astronomy, Kyoto University, Kyoto 606-8502 (Japan); Kawai, Nobuyuki [Department of Physics, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8551 (Japan)

2014-05-20

The short-period comet P/2010 V1 (Ikeya-Murakami, hereafter {sup V}1{sup )} was discovered visually by two amateur astronomers. The appearance of the comet was peculiar, consisting of an envelope, a spherical coma near the nucleus and a tail extending in the anti-solar direction. We investigated the brightness and the morphological development of the comet by taking optical images with ground-based telescopes. Our observations show that V1 experienced a large-scale explosion between UT 2010 October 31 and November 3. The color of the comet was consistent with the Sun (g' – R {sub C} = 0.61 ± 0.20, R {sub C} – I {sub C} = 0.20 ± 0.20, and B – R {sub C} = 0.93 ± 0.25), suggesting that dust particles were responsible for the brightening. We used a dynamical model to understand the peculiar morphology, and found that the envelope consisted of small grains (0.3-1 μm) expanding at a maximum speed of 500 ± 40 m s{sup –1}, while the tail and coma were composed of a wider range of dust particle sizes (0.4-570 μm) and expansion speeds 7-390 m s{sup –1}. The total mass of ejecta is ∼5 × 10{sup 8} kg and kinetic energy ∼5 × 10{sup 12} J. These values are much smaller than in the historic outburst of 17P/Holmes in 2007, but the energy per unit mass (1 × 10{sup 4} J kg{sup –1}) is comparable. The energy per unit mass is about 10% of the energy released during the crystallization of amorphous water ice suggesting that crystallization of buried amorphous ice can supply the mass and energy of the outburst ejecta.

The Comet Assay: Tails of the (Unexpected. Use of the comet assay in pharmaceutical development.

Directory of Open Access Journals (Sweden)

Bas-jan Van Der Leede

2015-08-01

Full Text Available In genotoxicity testing of pharmaceuticals the rodent alkaline comet assay is being increasingly used as a second in vivo assay in addition to the in vivo micronucleus assay to mitigate in vitro positive results as recommended by regulatory guidance. In this presentation we want to give insight into the circumstances in vivo comet assay is deployed in a Genetic Toxicology Department of a pharmaceutical company. As the in vivo comet assay is a salvage assay, it means that some events have occurred in an in vitro assay and that the compound (or metabolite responsible for this signal is potentially deselected for further development. More than often the decision to perform an in vivo comet assay is at a very early stage in development and the first time that the compound will be tested in vivo at high/toxic dose levels. As almost no toxicokinetic data and tissue distribution data are available a careful design with maximizes the chances for successful mitigation is necessary. Decisions on acute or repeated dosing need to be made and arrangements for combining the in vivo comet assay with the in vivo micronucleus assay are to be considered. Often synthesis methods need to be scaled up fast to provide the required amount of compound and information on suitable formulations needs to be in place. As exposure data is crucial for interpretation of results, analytical methods need to be brought in place rapidly. An experienced multi skilled and communicative team needs to be available to deploy successfully this kind of assays at an early stage of development. We will present a few scenarios on study conduct and demonstrate how this assay can make a difference for the further development of a new drug.

Time-dependent injection of Oort Cloud comets into earth-crossing orbits

International Nuclear Information System (INIS)

Fernandez, J.A.; Ip, W.H.; Max-Planck-Institut fuer Aeronomie, Katlenburg-Lindau, West Germany)

1987-01-01

The present consideration of close stellar encounter-induced modulations of the influx rate of Oort Cloud comets notes that comet showers sufficiently intense for emergence in cratering statistics are produced at 80-Myr intervals, on the assumption of an Oort Cloud heavy comet core. Numerical simulations of the time evolution of comet showers or bursts indicate that a long tail of residual shower comets follows the major event with an intensity of about 0.01 of the peak rate after 20-30 Myr, thereby suggesting that residual comet showers are primarily clustered in certain areas of the sky, rendering them observable at virtually any time. 33 references

Dynamical evolution and disintegration of comets

Science.gov (United States)

Kresak, L.

Current concepts of the origin and evolution of comets are reviewed. The place of their formation from which they have been delivered into the Oort reservoir is still an open problem, but the region of the outermost planets appears most probable. The interplay of stellar and planetary perturbations can be traced by model computations which reveal both the general trends and the variety of individual evolutionary paths. The present structure of the system of comets is controlled by the dynamical evolution of its individual members, limited by their physical aging by disintegration. Where the lifetimes are short, as in the Jupiter family of short-period comets, an equilibrium between elimination and replenishment is established. The role of different destructive processes and the resulting survival times are discussed.

Spectral investigation of two asteroidal fireballs

Czech Academy of Sciences Publication Activity Database

Borovička, Jiří

2006-01-01

Roč. 97, 3-4 (2006), s. 279-293 ISSN 0167-9295. [Asteroids, Comets, Meteors 2005. Búzios, 07.08.2005-12.08.2005] R&D Projects: GA ČR GA205/05/0543; GA ČR GA205/03/1404 Institutional research plan: CEZ:AV0Z10030501 Keywords : asteroids * meteors * spectroscopy Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 0.252, year: 2006

Meteors, space aliens, and other exotic encounters

Science.gov (United States)

Tom. Hofacker

1998-01-01

Exotics have had a big impact on our environment. If you do not think so, just look at how many people believe that humans would not exist on this planet were it not for exotics. This belief centers on two main theories: (1) that humans could not have evolved were it not for a huge meteor from outer space striking the earth resulting in extinction of the dinasours, the...

Comets, Asteroids, Meteorites, and the Origin of the Biosphere

Science.gov (United States)

Hoover, Richard B.

2006-01-01

During the past few decades, the delivery of water, organics, and prebiotic chemicals to the Biosphere of Earth during the Hadean (4.5-3.8 Ga) period of heavy bombardment by comets and asteroids has become more widely accepted. Comets are still largely regarded as frigid, pristine bodies of protosolar nebula material that are devoid of liquid water and therefore unsuitable for life. Complex organic compounds have been observed in comets and on the water-rich asteroid 1998 KY26 and near IR observations have indicated the presence of crystalline water ice and ammonia hydrate on the large Kuiper Belt object (50000) Quaoar that has resurfacing suggesting cryovolcanic outgassing. Spacecraft observations of the chemical compositions and characteristics of the nuclei of several comets (Halley, Borrelly, Wild 2, and Tempel 1) have shown that comets contain complex organic chemicals; that water is the predominant volatile; and that extremely high temperatures (approx. 350-400 K) can be reached on the surfae of the very black (albedo approx. 0.03) nuclei of comets when they approach the Sun. Impact craters and pinnacles observed on comet Wild 2 suggest a thick crust. Episodic outbursts and jets from the nuclei of several comets indicate that localized regimes of liquid water and water vapor can periodically exist beneath the comet crust. The Deep Impact mission found the temperature of the nucleus of comet Tempel 1 at 1.5 AU varied from a minimum of 280 plus or minus 8 K the 330K (57 C) on the sunlit side. In this paper it is argued that that pools and films of liquid water exist (within a wide range of temperatures) in cavities and voids just beneath the hot, black crust. The possibility of liquid water existing over a wide range of temperatures significantly enhances the possibility that comets might contain niches suitable for the growth of microbial communities and ecosystems. These regimes would be ideal for the growth of psychrophilic, mesophilic, and thermophilic

Data Reduction and Control Software for Meteor Observing Stations Based on CCD Video Systems

Science.gov (United States)

Madiedo, J. M.; Trigo-Rodriguez, J. M.; Lyytinen, E.

2011-01-01

The SPanish Meteor Network (SPMN) is performing a continuous monitoring of meteor activity over Spain and neighbouring countries. The huge amount of data obtained by the 25 video observing stations that this network is currently operating made it necessary to develop new software packages to accomplish some tasks, such as data reduction and remote operation of autonomous systems based on high-sensitivity CCD video devices. The main characteristics of this software are described here.

The Composition of Comet C/2012 K1 (PanSTARRS) and the Distribution of Primary Volatile Abundances Among Comets

Energy Technology Data Exchange (ETDEWEB)

Roth, Nathan X.; Gibb, Erika L. [Department of Physics and Astronomy, University of Missouri-St. Louis, 503 Benton Hall, One University Blvd., St. Louis, MO 63121 (United States); Bonev, Boncho P.; DiSanti, Michael A.; Mumma, Michael J.; Villanueva, Geronimo L.; Paganini, Lucas, E-mail: nxrq67@mail.umsl.edu [Goddard Center for Astrobiology, NASA Goddard Space Flight Center, Mail Stop 690, Greenbelt, MD 20771 (United States)

2017-04-01

On 2014 May 22 and 24 we characterized the volatile composition of the dynamically new Oort cloud comet C/2012 K1 (PanSTARRS) using the long-slit, high resolution ( λ /Δ λ  ≈ 25,000) near-infrared echelle spectrograph (NIRSPEC) at the 10 m Keck II telescope on Maunakea, Hawaii. We detected fluorescent emission from six primary volatiles (H{sub 2}O, HCN, CH{sub 4}, C{sub 2}H{sub 6}, CH{sub 3}OH, and CO). Upper limits were derived for C{sub 2}H{sub 2}, NH{sub 3}, and H{sub 2}CO. We report rotational temperatures, production rates, and mixing ratios (relative to water). Compared with median abundance ratios for primary volatiles in other sampled Oort cloud comets, trace gas abundance ratios in C/2012 K1 (PanSTARRS) for CO and HCN are consistent, but CH{sub 3}OH and C{sub 2}H{sub 6} are enriched while H{sub 2}CO, CH{sub 4}, and possibly C{sub 2}H{sub 2} are depleted. When placed in context with comets observed in the near-infrared to date, the data suggest a continuous distribution of abundances of some organic volatiles (HCN, C{sub 2}H{sub 6}, CH{sub 3}OH, CH{sub 4}) among the comet population. The level of “enrichment” or “depletion” in a given comet does not necessarily correlate across all molecules sampled, suggesting that chemical diversity among comets may be more complex than the simple organics-enriched, organics-normal, and organics-depleted framework.

Disintegration phenomena in Comet West

Science.gov (United States)

Sekanina, Z.

1976-01-01

Two peculiarities of Comet West, the multiple splitting of the nucleus as seen in telescope observations and the complex structure of the dust tail, are discussed. A method of analysis based on the premise that the observed rate of separation of a fragment from the principal nucleus is determined by the difference in effective solar attraction acting on the bodies is applied to investigate the motion of the four fragments that separated from the nucleus of Comet West. The predicted motion of the fragments is in good agreement with available observations. It is suggested that the 'synchronic' bands of the dust tail consist of tiny fragments from relatively large particles that burst after release from the comet. The unusual orientation of these bands and their high surface brightness relative to the diffuse tail are explained by a sudden increase in the particle acceleration and in the total scattering surface as the result of the disintegration of the larger particles.

Origin of comets - implications for planetary formation

International Nuclear Information System (INIS)

Weissman, P.R.; Arizona Univ., Tucson)

1985-01-01

Primordial and episodic theories for the origin of comets are discussed. The implications of the former type for the origin of the solar system are considered. Candidate sites for the formation of comets are compared. The possible existence of a massive inner Oort cloud is discussed

Asteroid Family Associations of Main-Belt Comets

Science.gov (United States)

Hsieh, Henry H.; Novakovic, Bojan; Kim, Yoonyoung; Brasser, Ramon

2016-10-01

We present a population-level analysis of the asteroid family associations of known main-belt comets or main-belt comet candidates (which, to date, have largely just been analyzed on individual bases as they have been discovered). In addition to family associations that have already been reported in the literature, we have identified dynamical relationships between 324P/La Sagra and the Alauda family, P/2015 X6 (PANSTARRS) and the Aeolia family, and P/2016 G1 (PANSTARRS) and the Adeona family. We will discuss the overall implications of these family associations, particularly as they pertain to the hypothesis that members of primitive asteroid family members may be more susceptible to producing observable sublimation-driven dust emission activity, and thus becoming main-belt comets. We will also discuss the significance of other dynamical and physical properties of a family or sub-family as they relate to the likelihood of that family containing one or more currently active main-belt comets.

Learned modesty and the first lady's comet: a commentary on Caroline Herschel (1787) 'An account of a new comet'.

Science.gov (United States)

Winterburn, Emily

2015-04-13

Long before women were allowed to become Fellows of the Royal Society, or obtain university degrees, one woman managed to get her voice heard, her discovery verified and her achievement celebrated. That woman was Caroline Herschel, who, as this paper will discuss, managed to find ways to fit comet discoveries into her domestic life, and present them in ways that were socially acceptable. Caroline lived in a time when strict rules dictated how women (and men) should behave and present themselves and their work. Caroline understood these rules, and used them carefully as she announced each discovery, starting with this comet which she found in 1786. Caroline discovered her comets at a time when astronomers were mainly concerned with position, identifying where things were and how they were moving. Since her discoveries, research has moved on, as astronomers, using techniques from other fields, and most recently sending experiments into space, have learned more about what comets are and what they can tell us about our solar system. Caroline's paper marks one small, early step in this much bigger journey to understand comets. This commentary was written to celebrate the 350th anniversary of the journal Philosophical Transactions of the Royal Society.

Anisotropic diffusion of meteor trails due to the geomagnetic field over King Sejong Station (62.2°S, 58.8°W), Antarctica

Science.gov (United States)

Choi, Jong-Min; Kwak, Young-Sil; Kim, Yong Ha; Lee, Changsup; Kim, Jeong-Han; Jee, Geonhwa; Yang, Tae-Yong

2018-06-01

We analyzed meteor decay times measured by a VHF meteor radar at King Sejong Station, Antarctica (62.22°S, 58.78°W) to study diffusion processes of the meteor trails above the altitude of ˜93 km. Above this altitude, where the atmospheric density is so dilute that collisions between trail ions and ambient molecules become rare, diffusion of a meteor trail can be greatly affected by the geomagnetic field, resulting in anisotropic distribution of measured decay times over the azimuthal and elevation angles. Our preliminary analysis confirm the anisotropic nature of meteor decay times due to geomagnetic field.

The C-12/C-13 abundance ratio in Comet Halley

International Nuclear Information System (INIS)

Wyckoff, S.; Lindholm, E.; Wehinger, P.A.; Peterson, B.A.; Zucconi, J.M.

1989-01-01

The individual (C-13)N rotational lines in Comet Halley are resolved using high-resolution spectra of the CN B2Sigma(+)-X2Sigma(+) (0,0) band. The observe C-12/C-13 abundance ratio excludes a site of origin for the comet near Uranus and Neptune and suggests a condensation environment quite distinct from other solar system bodies. Two theories are presented for the origin of Comet Halley. One theory suggest that the comet originated 4.5 Gyr ago in an inner Oort cloud at a heliocentric distance greater than 100 AU where chemical fractionation led to the C-13 enrichment in the CN parent molecule prior to condensation of the comet nucleus. According to the other, more plausible theory, the comet nucleus condensed relatively recently from the interstellar medium which has become enriches in C-13 and was subsequently gravitationally captured by the solar system. 107 refs

On the nature of the Halley comet

International Nuclear Information System (INIS)

Dobrovol'skij, O.V.; Ioffe, Z.M.

1987-01-01

The results of study of the Halley comet by means of the ''Vega'', ''Suisej'', ''Sakigaki'' and ''Jotton'' space probes are presented in the popular form. The form and composition of the comet nucleus, its atmosphere and processes ocurring when moving in the near-the-solar space are described

An analysis of the physical, chemical, optical, and historical impacts of the 1908 Tunguska meteor fall

Science.gov (United States)

Turco, R. P.; Toon, O. B.; Park, C.; Whitten, R. C.; Pollack, J. B.; Noerdlinger, P.

1982-01-01

An analysis is presented of the physical characteristics and photochemical aftereffects of the 1908 Tunguska explosive cometary meteor, whose physical manifestations are consistent with a five million ton object's entry into the earth's atmosphere at 40 km/sec. Aerodynamic calculations indicate that the shock waves emanating from the falling meteor could have generated up to 30 million tons of nitric oxide in the stratosphere and mesosphere. A fully interactive one-dimensional chemical-kinetics model of atmospheric trace constituents is used to estimate the photochemical consequences of such a large NO injection. The 35-45% hemispherical ozone depletion predicted by the model is in keeping with the 30 + or - 15% ozone variation reported for the first year after the Tunguska fall. Attention is also given to the optical anomalies which followed the event for indications of NO(x)-O(x) chemiluminescent emissions, NO2 solar absorption, and meteoric dust turbidity, along with possible climate changes due to the nearly one million tons of pulverized dust deposited in the mesosphere and stratosphere by the meteor.

The exploration of Halley's comet - An example of international cooperation

Science.gov (United States)

Rahe, Jurgen H.; Newburn, Ray L., Jr.

1987-01-01

The history of international cooperation in studies of comets started with observations in 1577 and 1680, when Tycho Brahe and Newton, respectively, collected position measurements made in different countries to determine the paths of the comets observed. In the fall of 1979, a worldwide Comet Halley watch was proposed. As a result of international cooperation, Comet Halley was explored during its recent appearance from the ground, earth orbit, Venus orbit, interplanetary space, and from within the comet itself. The various activities in space were coordinated by the ESA, the USSR Intercosmos, the Japanese ISAS, and NASA, through the Inter-Agency Consultative Group. The activities of the ground-based observers were coordinated by the International Halley Watch.

Dynamical evolution and disintegration of comets

International Nuclear Information System (INIS)

Kresak, L.

1982-01-01

Current concepts of the origin and evolution of comets are reviewed. The place of their formation from which they have been delivered into the Oort reservoir is still an open problem, but the region of the outermost planets appears most probable. The interplay of stellar and planetary perturbations can be traced by model computations which reveal both the general trends and the variety of individual evolutionary paths. The present structure of the system of comets is controlled by the dynamical evolution of its individual members limited by their physical aging by disintegration. Where the lifetimes are short, as in the Jupiter family of short-period comets, an equilibrium between elimination and replenishment is established. The role of different destructive processes and the resulting survival times are discussed. (Auth.)

On the influence of neutral turbulence on ambipolar diffusivities deduced from meteor trail expansion

Directory of Open Access Journals (Sweden)

C. M. Hall

2002-11-01

Full Text Available By measuring fading times of radar echoes from underdense meteor trails, it is possible to deduce the ambipolar diffusivities of the ions responsible for these radar echoes. It could be anticipated that these diffusivities increase monotonically with height akin to neutral viscosity. In practice, this is not always the case. Here, we investigate the capability of neutral turbulence to affect the meteor trail diffusion rate.Key words. Meteorology and atmospheric dynamics (middle atmosphere dynamics; turbulence

AKARI NEAR-INFRARED SPECTROSCOPIC SURVEY FOR CO2 IN 18 COMETS

International Nuclear Information System (INIS)

Ootsubo, Takafumi; Kawakita, Hideyo; Hamada, Saki; Kobayashi, Hitomi; Yamaguchi, Mitsuru; Usui, Fumihiko; Nakagawa, Takao; Ueno, Munetaka; Ishiguro, Masateru; Sekiguchi, Tomohiko; Watanabe, Jun-ichi; Sakon, Itsuki; Shimonishi, Takashi; Onaka, Takashi

2012-01-01

We conducted a spectroscopic survey of cometary volatiles with the Infrared Camera on board the Japanese infrared satellite AKARI in the wavelength range from 2.5 to 5 μm. In our survey, 18 comets, including both the Oort cloud comets and the Jupiter-family comets, were observed in the period from 2008 June to 2010 January, most of which were observed at least twice. The prominent emission bands in the observed spectra are the fundamental vibrational bands of water (H 2 O) at 2.7 μm and carbon dioxide (CO 2 ) at 4.3 μm. The fundamental vibrational band of carbon monoxide (CO) around 4.7 μm and the broad emission feature, probably related to carbon-hydrogen-bearing molecules, can also be recognized around the 3.3-3.5-μm region in some of the comets. With respect to H 2 O, gas production rate ratios of CO 2 have been derived in 17 comets, except for the comet 29P/Schwassmann-Wachmann 1. Our data set provides the largest homogeneous database of CO 2 /H 2 O production rate ratios in comets obtained so far. The CO 2 /H 2 O production rate ratios are considered to reflect the composition of cometary ice when a comet is observed at a heliocentric distance within ∼2.5 AU, since H 2 O ice fully sublimates there. The CO 2 /H 2 O ratio in cometary ice spans from several to ∼30% among the comets observed at 2 in the comets seems to be smaller than unity based on our observations, although we only obtain upper limits for CO in most of the comets.

MOLECULAR OXYGEN IN OORT CLOUD COMET 1P/HALLEY

Energy Technology Data Exchange (ETDEWEB)

Rubin, M.; Altwegg, K. [Physikalisches Institut, University of Bern, Sidlerstrasse 5, CH-3012 Bern (Switzerland); Dishoeck, E. F. van [Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden (Netherlands); Schwehm, G. [ESA (retired) Science Operations Department, ESTEC, Keplerlaan 1, 2201 AZ Noordwijk (Netherlands)

2015-12-10

Recently, the ROSINA mass spectrometer suite on board the European Space Agency's Rosetta spacecraft discovered an abundant amount of molecular oxygen, O{sub 2}, in the coma of Jupiter family comet 67P/Churyumov–Gerasimenko of O{sub 2}/H{sub 2}O = 3.80 ± 0.85%. It could be shown that O{sub 2} is indeed a parent species and that the derived abundances point to a primordial origin. Crucial questions are whether the O{sub 2} abundance is peculiar to comet 67P/Churyumov–Gerasimenko or Jupiter family comets in general, and also whether Oort cloud comets such as comet 1P/Halley contain similar amounts of molecular oxygen. We investigated mass spectra obtained by the Neutral Mass Spectrometer instrument during the flyby by the European Space Agency's Giotto probe of comet 1P/Halley. Our investigation indicates that a production rate of O{sub 2} of 3.7 ± 1.7% with respect to water is indeed compatible with the obtained Halley data and therefore that O{sub 2} might be a rather common and abundant parent species.

Trajectories for spacecraft encounters with Comet Honda-Mrkos-Pajdusakova in 1996

Science.gov (United States)

Dunham, David W.; Jen, Shao-Chiang; Farquhar, Robert W.

1989-01-01

Early in 1996, the relatively bright short-period Comet Honda-Mrkos-Pajdusakova (HMP) will pass only 0.17 astronomical unit from the earth, providing both an unusually favorable apparition for ground-based observers and an opportunity for a spacecraft to reach Comet HMP on relatively low-energy trajectories. The Japanense Institute of Space and Astronautical Sciences Sakigake spacecraft is expected to fly by Comet HMP on February 3, 1996, after utilizing four earth swingbys to modify its orbit. If the camera on the ESA Giotto spacecraft is inoperable, Giotto may also be sent to Comet HMP. In addition, 1-year earth-return trajectories to Comet HMP are described, along with some that can be extended to encounter Comet Giacobini-Zinner in 1998.

On the observed excess of retrograde orbits among long-period comets

International Nuclear Information System (INIS)

Fernandez, J.A.

1981-01-01

The distribution of orbital inclinations of the observed long-period comets is analysed. An excess of retrograde orbits is found which increases with the perihelion distance, except for the range 1.1 10 3 A U) has the same behaviour as the total sample. It is thus suggested that the excess of retrograde orbits among long-period comets is related to an already existent excess among the incoming new comets (i.e. comets driven into the planetary region by stellar perturbations). Using theoretical considerations and a numerical model it is proposed that an important fraction of the so-called new comets are actually repeating passages through the planetary region. Nearly a half of the new comets with q > 2 A U may be repeating passages. An important consequence of the presence of comets repeating passages among the new ones is the production of an excess of retrograde orbits in the whole sample. (author)

On the relationship between gas and dust in 15 comets: an application to Comet 103P/Hartley 2 target of the NASA EPOXI mission of opportunity

Science.gov (United States)

Sanzovo, G. C.; Sanzovo, D. Trevisan; de Almeida, A. A.

After the success of Deep Impact mission to hit the nucleus of Comet 9P/Tempel 1 with an impactor, the concerns are turned now to the possible reutilization of this dormant flyby spacecraft in the study of another comet, for only about 10% of the cost of the original mission. Comet 103P/Hartley 2 on UT 2010 October 11 is the most attractive target in terms of available fuel at rendezvous and arrival time at the comet. In addition, the comet has a low inclination so that major orbital plane changes in the spacecraft trajectory are unnecessary. In an effort to provide information concerning the planning of this new NASA EPOXI space mission of opportunity, we use in this work, visual magnitudes measurements available from International Comet Quarterly (ICQ) to obtain, applying the Semi-Empirical Method of Visual Magnitudes - SEMVM (de Almeida, Singh, & Huebner 1997), the water production rates (in molecules/s) related to its perihelion passage of 1997. When associated to the water vaporization theory of Delsemme (1982), these rates allowed the acquisition of the minimum dimension for the effective nuclear radius of the comet. The water production rates were then converted into gas production rates (in g/s) so that, with the help of the strong correlation between gas and dust found for 12 periodic comets and 3 non-period comets (Trevisan Sanzovo 2006), we obtained the dust loss rates (in g/s), its behavior with the heliocentric distance and the dust-to-gas ratios in this physically attractive rendezvous target-comet to Deep Impact spacecraft at a closest approach of 700 km.

Halley comet position in structure of the comet origin general scheme

International Nuclear Information System (INIS)

Davydov, V.D.

1988-01-01

Attempt to explain data on the Halley comet nucleus figure by photographes received from space probes in 1986 was undertaken. Peanut-like nucleus might be formed from two bodies former system under specific conditions. This hypothesis preliminary development is made; solution way for the problem about quantitative characteristics of collision and destruction is found. Quantitative assessments confirm retention possibility of two space icebergs original form after their ''docking'' within relative velocity range up to a few meters per second. Then complex with visible saddle point between two jointed fragments is formed. The hypothesis suggested is well inscribed in the origin general scheme of comets with nucleus different types, and from general scheme one may draw up the most important details to this hypothesis (for example, power mechanism of binary system formation and reasons of its destabilization)

Formation and past evolution of the showers of 96P/Machholz complex

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Abedin, Abedin; Wiegert, Paul; Janches, Diego; Pokorný, Petr; Brown, Peter; Hormaechea, Jose Luis

2018-01-01

In this work we model the dynamical evolution of meteoroid streams of comet 96P/Machholz, and the largest member of the Marsden sunskirters, comet P/1999 J6. We simultaneously fit the characteristics of eight meteor showers which have been proposed to be linked to the complex, using observations from a range of techniques - visual, video, TV and radar. The aim is to obtain a self-consistent scenario of past capture of a large comet into a short-period orbit, and its subsequent fragmentation history. Moreover, we also aim to constrain the dominant parent of these showers. The fit of our simulated shower characteristics to observations is consistent with the scenario of a capture of a proto-comet 96P/Machholz by Jupiter circa 20000 BCE, and a subsequent major breakup around 100-950 CE which resulted in the formation of the Marsden group of comets. We find that the Marsden group of comets are not the immediate parents of the daytime Arietids and Northern and Southern δ-Aquariids, as previously suggested. In fact, the hypothesis that the Northern δ-Aquariids are related to the Marsden group of comets is not supported by this study. The bulk of the observational characteristics of all eight showers can be explained by meteoroid ejection primarily from comet 96P/Machholz between 10000 BCE and 20000 BCE. Assuming the Marsden group of comets originated between 100 CE-950 CE, we conclude that sunskirting comets contribute mainly to the meteoroid stream near the time of the peak of the daytime Arietids, Southern δ-Aquariids, κ-Velids. Finally, we find that the meteor showers identified by Babadzhanov and Obrubov (1992) as the α-Cetids, the Ursids and Carinids correspond to the daytime λ-Taurids, the November ι-Draconids or December α-Draconids and the θ-Carinids.

The comet assay: ready for 30 more years.

Science.gov (United States)

Møller, Peter

2018-02-24

During the last 30 years, the comet assay has become widely used for the measurement of DNA damage and repair in cells and tissues. A landmark achievement was reached in 2016 when the Organization for Economic Co-operation and Development adopted a comet assay guideline for in vivo testing of DNA strand breaks in animals. However, the comet assay has much more to offer than being an assay for testing DNA strand breaks in animal organs. The use of repair enzymes increases the range of DNA lesions that can be detected with the assay. It can also be modified to measure DNA repair activity. Still, despite the long-term use of the assay, there is a need for studies that assess the impact of variation in specific steps of the procedure. This is particularly important for the on-going efforts to decrease the variation between experiments and laboratories. The articles in this Special Issue of Mutagenesis cover important technical issues of the comet assay procedure, nanogenotoxicity and ionising radiation sensitivity on plant cells. The included biomonitoring studies have assessed seasonal variation and certain predictors for the basal level of DNA damage in white blood cells. Lastly, the comet assay has been used in studies on genotoxicity of environmental and occupational exposures in human biomonitoring studies and animal models. Overall, the articles in this Special Issue demonstrate the versatility of the comet assay and they hold promise that the assay is ready for the next 30 years.

On the influence of neutral turbulence on ambipolar diffusivities deduced from meteor trail expansion

Directory of Open Access Journals (Sweden)

C. M. Hall

Full Text Available By measuring fading times of radar echoes from underdense meteor trails, it is possible to deduce the ambipolar diffusivities of the ions responsible for these radar echoes. It could be anticipated that these diffusivities increase monotonically with height akin to neutral viscosity. In practice, this is not always the case. Here, we investigate the capability of neutral turbulence to affect the meteor trail diffusion rate.

Key words. Meteorology and atmospheric dynamics (middle atmosphere dynamics; turbulence

Seasonal variation of meteor decay times observed at King Sejong Station (62.22°S, 58.78°W), Antarctica

Science.gov (United States)

Kim, Jeong-Han; Kim, Yong Ha; Lee, Chang-Sup; Jee, Geonhwa

2010-07-01

We analyzed meteor decay times measured by a VHF radar at King Sejong Station by classifying strong and weak meteors according to their estimated electron line densities. The height profiles of monthly averaged decay times show a peak whose altitude varies with season at altitudes of 80-85 km. The higher peak during summer is consistent with colder temperatures that cause faster chemical reactions of electron removal. By adopting temperature dependent empirical recombination rates from rocket experiments and meteor electron densities of 2×105-2×106 cm-3 in a decay time model, we are able to account for decreasing decay times below the peak for all seasons without invoking meteor electron removal by hypothetical icy particles.

Comet Kohoutek, 1973-1974, A Teachers' Guide with Student Activities.

Science.gov (United States)

Chapman, Robert D.

This teacher's guide provides background information, curriculum source materials, and suggested class activities for class discussion and study. Information related to the discovery of the comet is presented as well as photographic and schematic pictures showing the sky through which the comet travels. Historical data regarding comets of the past…

An analysis of the BVRI colors of 22 active comets

Science.gov (United States)

Betzler, A. S.; Almeida, R. S.; Cerqueira, W. J.; Araujo, L. A.; Prazeres, C. J. M.; Jesus, J. N.; Bispo, P. A. S.; Andrade, V. B.; Freitas, Y. A. S.; Betzler, L. B. S.

2017-08-01

Our aim was to analyze the variation of Johnson-Kron-Cousins BVRI color indexes of a sample with 22 active comets of various dynamic groups with the time, geometrical, observational and dynamical parameters. We performed photometric observations of 16 comets between 2010 and 2014, using robotic telescopes in three continents. In addition to the sample, we used data of six comets available in the literature. A statistical comparison between the distributions of color indexes was performed using the Kruskal-Wallis H-test. The color indexes of active comets can vary a few tenths up to a magnitude on time scales that range from hours to weeks. Using the B-V colors of the observed comets, we generated a relationship that correlates the cometary visual and CCD magnitudes. We did not identify any relationship between B-V and V-R colors with heliocentric distance and phase angle. The color B-V is correlated with the photometric aperture that can be described by a logarithmic function. We did not identify any differences in the distribution of B-V color among the comets analyzed at a confidence level equal to or greater than 95%. The mean color of active comets are B-R = 1.20 ± 0.24 , B-V = 0.76 ± 0.16 and V-R = 0.42 ± 0.16 . Active comets with V-R colors outside the three standard deviation interval can be considered objects with unusual physical characteristics.

The Rotation Temperature of Methanol in Comet 103P/Hartley 2

Science.gov (United States)

Chuang, Yo-Ling; Kuan, Yi-Jehng; Milam, Stefanie; Charnley, Steven B.; Coulson, Iain M.

2012-01-01

Considered to be relics from Solar System formation, comets may provide the vital information connecting Solar Nebula and its parent molecular cloud. Study of chemical and physical properties of comets is thus important for our better understanding of the formation of Solar System. In addition, observing organic molecules in comets may provide clues fundamental to our knowledge on the formation of prebiotically important organic molecules in interstellar space, hence, may shed light on the origin of life on the early Earth. Comet 103PIHartley 2 was fIrst discovered in 1986 and had gone through apparitions in 1991, 1997, and 2004 with an orbital period of about 6 years, before its latest return in 2010. 2010 was also a special year for Comet 103PIHartley 2 because of the NASA EPOXI comet-flyby mission.

Silicate emission feature in the spectrum of comet Mueller 1993a

Science.gov (United States)

Hanner, Martha S.; Hackwell, John A.; Russell, Ray W.; Lynch, David K.

1994-01-01

An 8- to 13-micron spectrum of comet Mueller 1993a, a dynamically new comet, was acquired when the comet was at R = 2 AU. Strong, structured silicate emission is present, closely resembling that seen in Comet P/Halley at smaller R. For the first time in a new comet, the 11.2-micron peak of crystalline olivine was detected, demonstrating that crystalline olivine particles were widespread in the solar nebula. Crystalline olivine particles could have formed in the inner protosolar nebula at temperatures greater than 1200 K; extensive radial mixing would have been required to transport these grains to the region of comet formation. Either there was more radial mixing in the solar nebula than some current theories predict or the olivine grains have a presolar origin.

Leonid storm research

CERN Document Server

Rietmeijer, Frans; Brosch, Noah; Fonda, Mark

2000-01-01

This book will appeal to all researchers that have an interest in the current Leonid showers It contains over forty research papers that present some of the first observational results of the November 1999 Leonid meteor storm, the first storm observed by modern observing techniques The book is a first glimpse of the large amount of information obtained during NASA's Leonid Multi-Instrument Aircraft Campaign and groundbased campaigns throughout the world It provides an excellent overview on the state of meteor shower research for any professional researcher or amateur meteor observer interested in studies of meteors and meteoroids and their relation to comets, the origin of life on Earth, the satellite impact hazard issue, and upper atmosphere studies of neutral atom chemistry, the formation of meteoric debris, persistent trains, airglow, noctilucent clouds, sprites and elves

The persistent coma of Comet P/Schwassmann-Wachmann 1

International Nuclear Information System (INIS)

Jewitt, D.

1990-01-01

Time-series photometry of Comet P/Schwassmann-Wachmann 1 in both 1987 and 1988 shows that this comet is continually active despite its large heliocentric distance. The observed activity, upon which the famous outbursts of this comet are superposed, may be driven by the sublimation of crystalline water ice at the nucleus surface. A simple model which accounts for both the continuous activity and the sporadic outbursts is suggested. 34 refs

The mass disruption of Jupiter Family comets

Science.gov (United States)

Belton, Michael J. S.

2015-01-01

I show that the size-distribution of small scattered-disk trans-neptunian objects when derived from the observed size-distribution of Jupiter Family comets (JFCs) and other observational constraints implies that a large percentage (94-97%) of newly arrived active comets within a range of 0.2-15.4 km effective radius must physically disrupt, i.e., macroscopically disintegrate, within their median dynamical lifetime. Additional observational constraints include the numbers of dormant and active nuclei in the near-Earth object (NEO) population and the slope of their size distributions. I show that the cumulative power-law slope (-2.86 to -3.15) of the scattered-disk TNO hot population between 0.2 and 15.4 km effective radius is only weakly dependent on the size-dependence of the otherwise unknown disruption mechanism. Evidently, as JFC nuclei from the scattered disk evolve into the inner Solar System only a fraction achieve dormancy while the vast majority of small nuclei (e.g., primarily those with effective radius <2 km) break-up. The percentage disruption rate appears to be comparable with that of the dynamically distinct Oort cloud and Halley type comets (Levison, H.F., Morbidelli, A., Dones, L., Jedicke, R., Wiegert, P.A., Bottke Jr., W.F. [2002]. Science 296, 2212-2215) suggesting that all types of comet nuclei may have similar structural characteristics even though they may have different source regions and thermal histories. The typical disruption rate for a 1 km radius active nucleus is ∼5 × 10-5 disruptions/year and the dormancy rate is typically 3 times less. We also estimate that average fragmentation rates range from 0.01 to 0.04 events/year/comet, somewhat above the lower limit of 0.01 events/year/comet observed by Chen and Jewitt (Chen, J., Jewitt, D.C. [1994]. Icarus 108, 265-271).

The development and validation of EpiComet-Chip, a modified high-throughput comet assay for the assessment of DNA methylation status.

Science.gov (United States)

Townsend, Todd A; Parrish, Marcus C; Engelward, Bevin P; Manjanatha, Mugimane G

2017-08-01

DNA damage and alterations in global DNA methylation status are associated with multiple human diseases and are frequently correlated with clinically relevant information. Therefore, assessing DNA damage and epigenetic modifications, including DNA methylation, is critical for predicting human exposure risk of pharmacological and biological agents. We previously developed a higher-throughput platform for the single cell gel electrophoresis (comet) assay, CometChip, to assess DNA damage and genotoxic potential. Here, we utilized the methylation-dependent endonuclease, McrBC, to develop a modified alkaline comet assay, "EpiComet," which allows single platform evaluation of genotoxicity and global DNA methylation [5-methylcytosine (5-mC)] status of single-cell populations under user-defined conditions. Further, we leveraged the CometChip platform to create an EpiComet-Chip system capable of performing quantification across simultaneous exposure protocols to enable unprecedented speed and simplicity. This system detected global methylation alterations in response to exposures which included chemotherapeutic and environmental agents. Using EpiComet-Chip on 63 matched samples, we correctly identified single-sample hypermethylation (≥1.5-fold) at 87% (20/23), hypomethylation (≥1.25-fold) at 100% (9/9), with a 4% (2/54) false-negative rate (FNR), and 10% (4/40) false-positive rate (FPR). Using a more stringent threshold to define hypermethylation (≥1.75-fold) allowed us to correctly identify 94% of hypermethylation (17/18), but increased our FPR to 16% (7/45). The successful application of this novel technology will aid hazard identification and risk characterization of FDA-regulated products, while providing utility for investigating epigenetic modes of action of agents in target organs, as the assay is amenable to cultured cells or nucleated cells from any tissue. Environ. Mol. Mutagen. 58:508-521, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Meteoric ions in the corona and solar wind

International Nuclear Information System (INIS)

Lemaire, J.

1990-01-01

The total mass of refractory material of interplanetary origin penetrating and evaporated in the meltosphere surrounding the sun has been inferred from observations of meteoroids and fireballs falling in earth's atmosphere. The amount of iron atoms deposited this way in the solar corona is of the order of 3000 t/s or larger. The measured flux of outflowing solar wind iron ions is equal to 2200 t/s. The close agreement of both fluxes is evidence that a significant fraction of iron ions observed in the solar wind and in the corona must be of meteoric origin. A similar accord is also obtained for silicon ions. The mean velocity of meteoroid ions formed in the solar corona is equal to the free-fall velocity: i.e., independent of their atomic mass as the thermal speed of heavy ion measured in low-density solar wind streams at 1 AU. Furthermore, the heavy ions of meteoric origin escape out of the corona with a larger bulk velocity than the protons which are mainly of solar origin. These differences of heavy ion and proton bulk velocities are also observed in the solar wind. 52 refs

Plasma Waves Associated with Mass-Loaded Comets

Science.gov (United States)

Tsurutani, Bruce; Glassmeier, Karl-Heinz

2015-01-01

Plasma waves and instabilities are integrally involved with the plasma "pickup" process and the mass loading of the solar wind (thus the formation of ion tails and the magnetic tails). Anisotropic plasmas generated by solar wind-comet interactions (the bow shock, magnetic field pileup) cause the generation of plasma waves which in turn "smooth out" these discontinuities. The plasma waves evolve and form plasma turbulence. Comets are perhaps the best "laboratories" to study waves and turbulence because over time (and distance) one can identify the waves and their evolution. We will argue that comets in some ways are better laboratories than magnetospheres, interplanetary space and fusion devices to study nonlinear waves and their evolution.

New Image of Comet Halley in the Cold

Science.gov (United States)

2003-09-01

VLT Observes Famous Traveller at Record Distance Summary Seventeen years after the last passage of Comet Halley , the ESO Very Large Telescope at Paranal (Chile) has captured a unique image of this famous object as it cruises through the outer solar system. It is completely inactive in this cold environment. No other comet has ever been observed this far - 4200 million km from the Sun - or that faint - nearly 1000 million times fainter than what can be perceived with the unaided eye. This observation is a byproduct of a dedicated search [1] for small Trans-Neptunian Objects, a population of icy bodies of which more than 600 have been found during the past decade. PR Photo 27a/03 : VLT image (cleaned) of Comet Halley PR Photo 27b/03 : Sky field in which Comet Halley was observed PR Photo 27c/03 : Combined VLT image with star trails and Comet Halley The Halley image ESO PR Photo 27a/03 ESO PR Photo 27a/03 [Preview - JPEG: 546 x 400 pix - 207k] [Normal - JPEG: 1092 x 800 pix - 614k] [FullRes - JPEG: 1502 x 1100 pix - 1.1M] Caption : PR Photo 27a/03 shows the faint, star-like image of Comet Halley (centre), observed with the ESO Very Large Telescope (VLT) at the Paranal Observatory on March 6-8, 2003. 81 individual exposures from three of the four 8.2-m VLT telescopes with a total exposure time of about 9 hours were combined to show the magnitude 28.2 object. At this time, Comet Halley was about 4200 million km from the Sun (28.06 AU) and 4080 million km (27.26 AU) from the Earth. All images of stars and galaxies in the field were removed during the extensive image processing needed to produce this unique image. Due to the remaining, unavoidable "background noise", it is best to view the comet image from some distance. The field measures 60 x 40 arcsec 2 ; North is up and East is left. Remember Comet Halley - the famous "haired star" that has been observed with great regularity - about once every 76 years - during more than two millennia? Which was visited by an

Results from the UMD physical properties of comets survey

Science.gov (United States)

Lisse, Carey M.; A'Hearn, Michael F.; Fernandez, Yanga R.

2005-01-01

We report on an ongoing statistical study of the emitted dust and exposed nuclei of a survey of the brightest near-Earth comets over the last 13 years. Combined thermal infrared and optical observations are analyzed using dynamical spectral and morphological coma models [123] to update and improve dust emission rates [4] and nucleus size estimates [5]. Using these results we show that 1) there is more than enough dust emitted from short period comets into bound solar system orbits to create and support the current interplanetary dust cloud (IPD); 2) that a population of dormant or extinct comets in the solar system is quite plausible; and 3) that the lifetime versus sublimation for the short period comets is much longer than their dynamical lifetime. [1] C.M. Lisse et al. (1998) Ap J 496 971. [2] C.M. Lisse et al. (1999) Icarus 140 189. [3] Y.R. Fernandez et al. (2000) Icarus 147 145 [4] L. Kresak and M. Kresakova (1987) in Symposium on Diversity and Similarity of Comets ESA SP-278 739 [5] D.C.Jewitt (1991) in Comets in the Post-Halley Era (R.L. Newburn M. Neugebauer and J. Rahe Eds.) Kluwer Academic Dordecht 19.

Physical Mechanism of Comet Outbursts: The Movie

Science.gov (United States)

Hartmann, William K.

2014-11-01

During experiments conducted in 1976 at the NASA Ames Research Center’s Vertical Gun Facility (VGF), the author studied low velocity impacts into simulated regolith powders and gravels, in order to examine physics of low-velocity collisions during early solar system planetesimal formation. In one “accidental” experiment, the bucket of powder remained gas-charged during evacuation of the VGF vacuum chamber. The impactor, moving at 5.5 m/s, disturbed the surface, initiating eruptions of dust-charged gas, shooting in jets from multiple vents at speeds up to about 3 m/s, with sporadic venting until 17 seconds after the impact. This experiment was described in [1], which concluded that it simulated comet eruption phenomena. In this hypothesis, a comet nucleus develops a lag deposit of regolith in at least some regions. At a certain distance from the sun, the thermal wave penetrates to an ice-rich depth, causing sublimation. Gas rises into the regolith, collects in pore spaces, and creates a gas-charged powder, as in our experiment. Any surface disturbance, such as a meteoroid, may initiate a temporary eruption, or eventually the gas pressure becomes sufficient to blow off the overburden. Our observed ejection speed would be sufficient to launch dust off of a kilometer-scale comet nucleus.Film (100 frames/s) of the event was obtained, but was partially torn up in a projector. It has recently been reconstituted (Centric Photo Labs, Tucson) and dramatically illustrates various cometary phenomena. Parabolic curtains of erupted material resemble curtains of material photographed from earth in real comet comas, “falling back” under solar wind forces. In retrospect, the mechanism photographed here helps explain:*sporadic eruptions in Comet P/Schwassmann-Wachmann 1 (near-circular orbit at ~6 A.U., where repeated recharge may occur).*sporadic eruptions on “asteroid” 2060 Chiron (which stays beyond 8.5 A.U.). *the thicker dust curtain (and longer eruption?) than

Mesospheric Temperatures and Winds measured by a VHF Meteor Radar at King Sejong Station (62.2S, 58.8W), Antarctica

Science.gov (United States)

Kim, Yongha; Kim, Jeong-Han; Jee, Geonwha; Lee, Chang-Sup

2010-05-01

A VHF radar at King Sejong Station, Antarctica has been measuring meteor echoes since March 2007. Temperatures near the mesopause are derived from meteor decay times with an improved method of selecting meteor echo samples, and compared with airglow temperatures simultaneously observed by a spectral airglow temperature imager (SATI). The temperatures derived from meteor decay times are mostly consistent with the rotational temperatures of SATI OH(6-2) and O2(0-1) emissions from March through October. During southern summer when SATI cannot be operated due to brief night time, the meteor radar observation shows cold mesospheric temperatures, significantly lower than the CIRA86 model. The meteor radar observation also provides wind field information between 80 and 100 km of altitude. The measured meridional winds seem to follow the summer pole to winter pole circulation, and thus are correlated with the measured seasonal temperature change. However, the correlation between meridional winds and temperatures is not found in day by day base, as a previous study reported. Tidal characteristics of both zonal and meridional winds will also be compared with those of other Antarctic stations.

Competitive Memory Training (COMET) for OCD: a self-treatment approach to obsessions.

Science.gov (United States)

Schneider, Brooke C; Wittekind, Charlotte E; Talhof, Alina; Korrelboom, Kees; Moritz, Steffen

2015-01-01

Competitive Memory Training (COMET) is a cognitive intervention that aims to change the maladaptive cognitive-emotional networks underlying obsessive-compulsive disorder (OCD). COMET has not been previously tried as a self-help intervention. The present study tested the preliminary feasibility, acceptability, and effectiveness of COMET for OCD implemented as a self-help intervention. Sixty-five participants with OCD recruited through online OCD self-help fora completed an online baseline assessment including measures of OCD symptoms, self-esteem, and depression. Participants were randomly assigned to either COMET or a wait-list control group. All participants were approached 4 weeks later to complete an online post-assessment. There was no evidence for a greater decline of OCD symptoms or depression under COMET. When analyses were limited to only those participants who reported reading the entire manual at least once, self-esteem was higher at post-assessment in the COMET group. Although 78.1% of patients in the COMET group rated it as appropriate for self-administration, only 56.5% performed COMET exercises regularly and 26.4% read the entire manual at least once. The feasibility and effectiveness of COMET as a self-help internet intervention for OCD was not supported in this study. Further work is needed to better understand if modifications to our implementation of COMET may yield improved outcomes.

The Meteor and Fireball Network of the Sociedad Malagueña de Astronomía

Science.gov (United States)

Aznar, J. C.; Castellón, A.; Gálvez, F.; Martínez, E.; Troughton, B.; Núñez, J. M.; Villalba, F.

2016-12-01

One of the most active fields in which has been dedicated the Málaga Astronomical Society (SMA) is the meteors and meteor showers. Since 2006 the SMA refers parts of visual observations and photographic detections from El Pinillo station (Torremolinos, Spain). In 2013 it was decided to give an extra boost to get a camera network that allowed the calculation of the atmospheric trajectory of a meteoroid and, where possible, obtaining the orbital elements.

Recommendations for safety testing with the in vivo comet assay.

Science.gov (United States)

Vasquez, Marie Z

2012-08-30

While the in vivo comet assay increases its role in regulatory safety testing, deliberations about the interpretation of comet data continue. Concerns can arise regarding comet assay publications with limited data from non-blind testing of positive control compounds and using protocols (e.g. dose concentrations, sample times, and tissues) known to give an expected effect. There may be a tendency towards bias when the validation or interpretation of comet assay data is based on results generated by widely accepted but non-validated assays. The greatest advantages of the comet assay are its sensitivity and its ability to detect genotoxicity in tissues and at sample times that could not previously be evaluated. Guidelines for its use and interpretation in safety testing should take these factors into account. Guidelines should be derived from objective review of data generated by blind testing of unknown compounds dosed at non-toxic concentrations and evaluated in a true safety-testing environment, where the experimental design and conclusions must be defensible. However, positive in vivo comet findings with such compounds are rarely submitted to regulatory agencies and this data is typically unavailable for publication due to its proprietary nature. To enhance the development of guidelines for safety testing with the comet assay, and with the permission of several sponsors, this paper presents and discusses relevant data from multiple GLP comet studies conducted blind, with unknown pharmaceuticals and consumer products. Based on these data and the lessons we have learned through the course of conducting these studies, I suggest significant adjustments to the current conventions, and I provide recommendations for interpreting in vivo comet assay results in situations where risk must be evaluated in the absence of carcinogenicity or clinical data. Copyright © 2012 Elsevier B.V. All rights reserved.

Improved orbits of two periodic comets: Tsuchinshan 1 and Tsuchinshan 2

International Nuclear Information System (INIS)

Szutowicz, S.

1986-01-01

The observations made during four apparitions of two comets were collected and the orbits of the comets were improved; 86 observations of Comet Tsuchinshan 1 and 50 observations of Comet Tsuchinshan 2 made in the period 1965-1985 were used. The orbit of Comet Tsuchinshan 1 was improved taking into account nongravitational effects in its motion as well as a displacement of the photometric center from the center of mass. The following values of nongravitational parameters and of observational parameter D were obtained: A 1 = 0.75953 x 10 -8 , A 2 0.00375 x 10 -8 , D = 0.34698 x 10 -3 . To link all observations of Comet Tsuchinshan 2 by one system of elements it was sufficient to add observational effects as a displacement of the photometric center from the center of mass. The following value of parameter D was obtained: D = 1.00200 x 10 -3 . The equations of motion of both comets were integrated backwards and forwards till 1992. Ephemerides for their next returns were computed. 6 refs., 5 tabs. (author)

Comets Nature, Dynamics, Origin, and their Cosmogonical Relevance

CERN Document Server

Fernández, Julio Angel

2005-01-01

The book covers the most recent ideas about the nature and dynamics of comets, including a thorough discussion on Oort cloud dynamics which has not received due attention in other books on the subject. It also discusses the most relevant aspects of the physics and chemistry of comet nuclei, highlighting their importance as relics of the protoplanetary disk and, perhaps, as carriers of water and organics that permitted the development of life on Earth. The book contains several tables with useful data, and an ample bibliography covering the most recent work as well as some historical key contributions to the subject. It may be suitable as a textbook for graduate students with some basic knowledge of celestial mechanics and astrophysics, as well as a consult book for comet researchers, or researchers from other related fields willing to start working on comets, or get an updated view of the subject.

AKARI NEAR-INFRARED SPECTROSCOPIC SURVEY FOR CO{sub 2} IN 18 COMETS

Energy Technology Data Exchange (ETDEWEB)

Ootsubo, Takafumi [Astronomical Institute, Graduate School of Science, Tohoku University, Aramaki, Aoba-ku, Sendai 980-8578 (Japan); Kawakita, Hideyo; Hamada, Saki; Kobayashi, Hitomi; Yamaguchi, Mitsuru [Koyama Astronomical Observatory, Kyoto Sangyo University, Motoyama, Kamigamo, Kita-Ku, Kyoto 603-8555 (Japan); Usui, Fumihiko; Nakagawa, Takao; Ueno, Munetaka [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan); Ishiguro, Masateru [Department of Physics and Astronomy, Seoul National University, 599 Gwanak-ro, Gwanak-gu, Seoul 151-742 (Korea, Republic of); Sekiguchi, Tomohiko [Department of Teacher Training, Hokkaido University of Education, Asahikawa Campus, Hokumon 9, Asahikawa, Hokkaido 070-8621 (Japan); Watanabe, Jun-ichi [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Sakon, Itsuki; Shimonishi, Takashi; Onaka, Takashi, E-mail: ootsubo@astr.tohoku.ac.jp [Department of Astronomy, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan)

2012-06-10

We conducted a spectroscopic survey of cometary volatiles with the Infrared Camera on board the Japanese infrared satellite AKARI in the wavelength range from 2.5 to 5 {mu}m. In our survey, 18 comets, including both the Oort cloud comets and the Jupiter-family comets, were observed in the period from 2008 June to 2010 January, most of which were observed at least twice. The prominent emission bands in the observed spectra are the fundamental vibrational bands of water (H{sub 2}O) at 2.7 {mu}m and carbon dioxide (CO{sub 2}) at 4.3 {mu}m. The fundamental vibrational band of carbon monoxide (CO) around 4.7 {mu}m and the broad emission feature, probably related to carbon-hydrogen-bearing molecules, can also be recognized around the 3.3-3.5-{mu}m region in some of the comets. With respect to H{sub 2}O, gas production rate ratios of CO{sub 2} have been derived in 17 comets, except for the comet 29P/Schwassmann-Wachmann 1. Our data set provides the largest homogeneous database of CO{sub 2}/H{sub 2}O production rate ratios in comets obtained so far. The CO{sub 2}/H{sub 2}O production rate ratios are considered to reflect the composition of cometary ice when a comet is observed at a heliocentric distance within {approx}2.5 AU, since H{sub 2}O ice fully sublimates there. The CO{sub 2}/H{sub 2}O ratio in cometary ice spans from several to {approx}30% among the comets observed at <2.5 AU (13 out of the 17 comets). Alternatively, the ratio of CO/CO{sub 2} in the comets seems to be smaller than unity based on our observations, although we only obtain upper limits for CO in most of the comets.

CINE: Comet INfrared Excitation

Science.gov (United States)

de Val-Borro, Miguel; Cordiner, Martin A.; Milam, Stefanie N.; Charnley, Steven B.

2017-08-01

CINE calculates infrared pumping efficiencies that can be applied to the most common molecules found in cometary comae such as water, hydrogen cyanide or methanol. One of the main mechanisms for molecular excitation in comets is the fluorescence by the solar radiation followed by radiative decay to the ground vibrational state. This command-line tool calculates the effective pumping rates for rotational levels in the ground vibrational state scaled by the heliocentric distance of the comet. Fluorescence coefficients are useful for modeling rotational emission lines observed in cometary spectra at sub-millimeter wavelengths. Combined with computational methods to solve the radiative transfer equations based, e.g., on the Monte Carlo algorithm, this model can retrieve production rates and rotational temperatures from the observed emission spectrum.

The challenge associated with the robust computation of meteor velocities from video and photographic records

Science.gov (United States)

Egal, A.; Gural, P. S.; Vaubaillon, J.; Colas, F.; Thuillot, W.

2017-09-01

The CABERNET project was designed to push the limits for obtaining accurate measurements of meteoroids orbits from photographic and video meteor camera recordings. The discrepancy between the measured and theoretic orbits of these objects heavily depends on the semi-major axis determination, and thus on the reliability of the pre-atmospheric velocity computation. With a spatial resolution of 0.01° per pixel and a temporal resolution of up to 10 ms, CABERNET should be able to provide accurate measurements of velocities and trajectories of meteors. To achieve this, it is necessary to improve the precision of the data reduction processes, and especially the determination of the meteor's velocity. In this work, most of the steps of the velocity computation are thoroughly investigated in order to reduce the uncertainties and error contributions at each stage of the reduction process. The accuracy of the measurement of meteor centroids is established and results in a precision of 0.09 pixels for CABERNET, which corresponds to 3.24‧‧. Several methods to compute the velocity were investigated based on the trajectory determination algorithms described in Ceplecha (1987) and Borovicka (1990), as well as the multi-parameter fitting (MPF) method proposed by Gural (2012). In the case of the MPF, many optimization methods were implemented in order to find the most efficient and robust technique to solve the minimization problem. The entire data reduction process is assessed using simulated meteors, with different geometrical configurations and deceleration behaviors. It is shown that the multi-parameter fitting method proposed by Gural(2012)is the most accurate method to compute the pre-atmospheric velocity in all circumstances. Many techniques that assume constant velocity at the beginning of the path as derived from the trajectory determination using Ceplecha (1987) or Borovicka (1990) can lead to large errors for decelerating meteors. The MPF technique also allows one to

Spiral arms, comets and terrestrial catastrophism

International Nuclear Information System (INIS)

Clube, S.V.M.; Napier, W.M.

1982-01-01

A review is presented of an hypothesis of terrestrial catastrophism in which comets grow in molecular clouds and are captured by the Sun as it passes through the spiral arms of the Galaxy. Assuming that comets are a major supplier of the Earth-crossing (Appollo) asteroid population, the latter fluctuates correspondingly and leads to episodes of terrestrial bombardment. Changes in the rotational momentum of core and mantle, generated by impacts, lead to episodes of magnetic field reversal and tectonic activity, while surface phenomena lead to ice-ages and mass extinctions. An episodic geophysical history with an interstellar connection is thus implied. If comets in spiral arms are necessary intermediaries in the process of star formation, the theory also has implications relating to early solar system history and galactic chemistry. These aspects are briefly discussed with special reference to the nature of spiral arms. (author)

Origin Of The Near-earth Asteroid Phaethon And The Geminids Meteor Shower

Science.gov (United States)

de Leon, Julia; Campins, H.; Tsiganis, K.; Morbidelli, A.; Licandro, J.

2010-10-01

Asteroid (3200) Phaethon is a remarkable Near Earth Asteroid (NEA). It was the first asteroid associated with a meteor shower, namely the Geminid stream1. Phaethon's unusual orbit has a high inclination and a very low perihelion distance (0.14 AU). Its reflectance spectrum suggests a connection with primitive meteorites, best fitting with CI/CM carbonaceous chondrites2, aqueously altered and rich in hydrated silicates. However, its origin is not well determined. Recent studies suggest a connection with the population of main-belt comets3, classifying Phaethon as an activated asteroid. Here we show that the most likely source of Phaethon and the Geminids is the asteroid (2) Pallas, one of the largest asteroids in the main belt, which is surrounded by a collisional family, containing several Phaethon-sized objects. Pallas’ highly inclined orbit and surface composition, also primitive and with evidence of hydration4, support this connection. Our analysis reveals a striking similarity between Phaethon's visual spectrum and those of Pallas family members. Moreover, our numerical simulations show the existence of a robust dynamical pathway, connecting the orbital neighborhood of Pallas with that of Phaethon. In this respect, the Pallas family may constitute a source of primitive NEAs. (The author gratefully acknowledges support from the Spanish "Ministerio de Ciencia e Innovación" projects AYA2005-07808-C03-02 and AYA2008-06202-C03-02.) References 1. Whipple, F. L. 1983, IAU Circular, 3881 2. Licandro, J., Campins, H., Mothe-Diniz, T., Pinilla-Alonso, N. & de Leon, J. 2007, Astron. Astrophys. 461, 751-757 3. Hsieh, H. H., & Jewitt, D. 2006, Science, 312, 561-563 4. Rivkin, A. S., Howell, E. S., Vilas, F. & Lebofsky, L. A. in Asteroids III (eds Bottke, W. F., Cellino, A., Paolicchi, P. & Binzel, R. P.) 235-253 (Univ. Arizona Press, 2002).

Mission to a comet that could save earth

CERN Multimedia

Utton, T

2003-01-01

Scientists are going to attempt to land a probe on the comet Wirtanen. The GBP640million unmanned craft will travel four billion miles before catching up with the comet Wirtanen and launching a robotic lander called Rosetta, on to its surface (1/2 page).

Terrestrial cometary tail and lunar corona induced by small comets: Predictions for Galileo

International Nuclear Information System (INIS)

Dessler, A.J.; Sandel, B.R.; Vasyliunas, V.M.

1990-01-01

A search for small comets near 1 AU is an objective of the Galileo mission. If small comets are as numerous and behave as has been proposed, two near-Earth signatures of small comets should be observable by the UVS experiment on the Earth flybys of Galileo; (1) a comet-like tail of Earth created by small comets that come close to Earth, break up and vaporize, but just miss the atmosphere and proceed back into interplanetary space, and (2) a corona surrounding the Moon induced by lunar impact of small comets

Infrared imaging and photometry of Comet Giacobini-Zinner

International Nuclear Information System (INIS)

Campins, H.

1986-01-01

Infrared images and photometry were obtained to determine the spatial distribution and physical characteristics (temperature, albedo, size distribution, total mass, etc.) of the grains in the coma of Comet GZ. A 10.8 m image of Comet GZ obtained on August 4 represents the first ground-based thermal-infrared image of a Comet. Among the most significant results are: (1) an estimate of the number of grains that the ICE spacecraft must have encountered, which led the plasma wave team to conclude that they could only detect impacts on the antennae and not on the whole body of the ICE spacecraft; (2) the discovery of a population of large grains (radius > 100 micrometer), not observed in most other comets, which formed a curved tail near the nucleus (within 80 arcsec or 34,000 km); and (3) the detection of structure in the spatial distribution in the coma of the particle albedo, which was tentatively attributed to the presence of very fluffy grains which are likely to have multiple internal scattering of incident sunlight. The albedo map of Comet GZ was obtained by combining the 10.8 micrometer image shown with a simultaneous image taken at 0.68 micrometer, a bandpass which isolates the scattered continuum

Catastrophic disruptions as the origin of bilobate comets

Science.gov (United States)

Schwartz, Stephen R.; Michel, Patrick; Jutzi, Martin; Marchi, Simone; Zhang, Yun; Richardson, Derek C.

2018-05-01

Several comets observed at close range have bilobate shapes1, including comet 67P/Churyumov-Gerasimenko (67P/C-G), which was imaged by the European Space Agency's Rosetta mission2,3. Bilobate comets are thought to be primordial because they are rich in supervolatiles (for example, N2 and CO) and have a low bulk density, which implies that their formation requires a very low-speed accretion of two bodies. However, slow accretion does not only occur during the primordial phase of the Solar System; it can also occur at later epochs as part of the reaccumulation process resulting from the collisional disruption of a larger body4, so this cannot directly constrain the age of bilobate comets. Here, we show by numerical simulation that 67P/C-G and other elongated or bilobate comets can be formed in the wake of catastrophic collisional disruptions of larger bodies while maintaining their volatiles and low density throughout the process. Since this process can occur at any epoch of our Solar System's history, from early on through to the present day5, there is no need for these objects to be formed primordially. These findings indicate that observed prominent geological features, such as pits and stratified surface layers4,5, may not be primordial.

Meteor Observational Data Visualisation in the Equatorial Coordinate System Using Information Technology

Science.gov (United States)

Golovashchenko, V. A.; Kolomiyets, S. V.

As a result of dynamic evolution of IT industry and astronomical research in the XXI century, which have resulted in obtaining large and complex data sets known as Big Data (e.g. data from the European Space Agency missions, such as GAIA mission, etc.), as well as due to rapid development of computer technologies, astronomy and computer science have become closely linked to each other. In the XXI century, Information technology has become an essential part of understanding the world around. This paper presents a solution to the problem of meteor data representation in the second equatorial coordinate (RA-Dec) system using Information Technology. Such a visualisation solution is needed to analyse the results of experiments based on the radar observations conducted in 1972-1978 (stage 1 - the data obtained in 1972 comprise 10,247 meteor orbits), which have been accumulated and stored in the Meteor Database of the Kharkiv National University of Radio Electronics (KNURE). A sample set of data with their characteristics and details about their delivery has been presented by (Kashcheyev & Tkachuk, 1980). An electronic calculator application was developed by employing the model of data visualisation in the form of celestial hemispheres using the object-oriented programming language C#.

Comet mission hopes to uncover Earth's origins

CERN Multimedia

Henderson, M

2004-01-01

"A European spacecraft that will hunt down a comet in search of clues to the origin of life on Earth will blast off tomorrow from the Kourou spaceport in French Guiana. The Rosetta probe will take 12 years to catch up with Churyumov-Gerasimenko before becoming the first spacecraft to make a soft, controlled landing on a comet's nucleus" (1 page).

Dynamics of comets: their origin and evolution

International Nuclear Information System (INIS)

Carusi, A.; Valsecchi, G.B.

1985-01-01

Comets can be considered as remnants of the original population of planetesimals and the study of their origin and dynamical histories can provide insight into the accretion phenomena; the original mass, energy and angular momentum distribution across the solar system; the collisional fragmentation of minor bodies; the impact rates on planets and the nature of impacting bodies. The interaction of comets with other solar system bodies certainly provides one of the best possibilities for a deeper understanding of the dynamics of the whole system, and a challenging test for all theories of celestial mechanics dealing with the gravitational behaviour of multiple-body systems. Comets could also be considered as the last footprints left by the interaction of the protosun and its original galactic environment. (orig.)

Comet Hyakutake to Approach the Earth in Late March 1996

Science.gov (United States)

1996-03-01

Astronomers Prepare for a Rare Event In the early morning of January 31, 1996, Japanese amateur astronomer Yuji Hyakutake made his second comet discovery within five weeks. He found the new comet near the border between the southern constellations of Hydra (The Water-Snake) and Libra (The Scales), amazingly just three degrees from the position where he detected another comet on December 26, 1995. After two weeks of hectic activity among amateur and professional astronomers all over the world, much interesting information has now been gathered about the new comet which has been designated C/1996 B2 (Hyakutake) . In particular, it has been found to move in a near-parabolic orbit that will bring it unusually close to the Earth next month. It is then expected to become bright enough to be seen with the unaided eye and to remain so during several weeks thereafter. Preparations are now made to observe the celestial visitor with a large number of telescopes, on the ground and in space. This event offers a rare opportunity to study the immediate surroundings of a cometary nucleus in detail and the specialists intend to make the most of it. Discovery and orbit Yuji Hyakutake, of profession photoengraver and a well-known amateur astronomer, announced his new discovery without delay, and within 24 hours, it had been sighted by several other observers in Japan and Australia. Experienced comet-watchers described its appearance as `diffuse with central condensation and of magnitude 11-12', i.e. a little more than 100 times fainter than what can be seen with the unaided eye. This brightness is not unusual for a comet discovered by an amateur, although it would probably have been missed, had it been just a little fainter. In the present case, the decisive factors for Hyakutake's success were undoubtedly his very powerful equipment (25 x 150 binoculars) and the advantageous combination of the comet's southern position in the sky and his location in Kagoshima, the southernmost

The Science of Sungrazers, Sunskirters, and Other Near-Sun Comets

Science.gov (United States)

Jones, Geraint H.; Knight, Matthew M.; Battams, Karl; Boice, Daniel C.; Brown, John; Giordano, Silvio; Raymond, John; Snodgrass, Colin; Steckloff, Jordan K.; Weissman, Paul; Fitzsimmons, Alan; Lisse, Carey; Opitom, Cyrielle; Birkett, Kimberley S.; Bzowski, Maciej; Decock, Alice; Mann, Ingrid; Ramanjooloo, Yudish; McCauley, Patrick

2018-02-01

This review addresses our current understanding of comets that venture close to the Sun, and are hence exposed to much more extreme conditions than comets that are typically studied from Earth. The extreme solar heating and plasma environments that these objects encounter change many aspects of their behaviour, thus yielding valuable information on both the comets themselves that complements other data we have on primitive solar system bodies, as well as on the near-solar environment which they traverse. We propose clear definitions for these comets: We use the term near-Sun comets to encompass all objects that pass sunward of the perihelion distance of planet Mercury (0.307 AU). Sunskirters are defined as objects that pass within 33 solar radii of the Sun's centre, equal to half of Mercury's perihelion distance, and the commonly-used phrase sungrazers to be objects that reach perihelion within 3.45 solar radii, i.e. the fluid Roche limit. Finally, comets with orbits that intersect the solar photosphere are termed sundivers. We summarize past studies of these objects, as well as the instruments and facilities used to study them, including space-based platforms that have led to a recent revolution in the quantity and quality of relevant observations. Relevant comet populations are described, including the Kreutz, Marsden, Kracht, and Meyer groups, near-Sun asteroids, and a brief discussion of their origins. The importance of light curves and the clues they provide on cometary composition are emphasized, together with what information has been gleaned about nucleus parameters, including the sizes and masses of objects and their families, and their tensile strengths. The physical processes occurring at these objects are considered in some detail, including the disruption of nuclei, sublimation, and ionisation, and we consider the mass, momentum, and energy loss of comets in the corona and those that venture to lower altitudes. The different components of comae and

COMET concept

International Nuclear Information System (INIS)

Alsmeyer, H.; Tromm, W.

1995-01-01

Studies of the COMET core catcher concept developed for a future PWR have been continued. The concept is based on the spreading of a core melt on a sacrificial layer and its erosion, until a subsequent addition of water from below causes a fragmentation of the melt. A porous solidification of the melt would then admit a complete flooding within a short period. (orig.)

A shower look-up table to trace the dynamics of meteoroid streams and their sources

Science.gov (United States)

Jenniskens, Petrus

2018-04-01

Meteor showers are caused by meteoroid streams from comets (and some primitive asteroids). They trace the comet population and its dynamical evolution, warn of dangerous long-period comets that can pass close to Earth's orbit, outline volumes of space with a higher satellite impact probability, and define how meteoroids evolve in the interplanetary medium. Ongoing meteoroid orbit surveys have mapped these showers in recent years, but the surveys are now running up against a more and more complicated scene. The IAU Working List of Meteor Showers has reached 956 entries to be investigated (per March 1, 2018). The picture is even more complicated with the discovery that radar-detected streams are often different, or differently distributed, than video-detected streams. Complicating matters even more, some meteor showers are active over many months, during which their radiant position gradually changes, which makes the use of mean orbits as a proxy for a meteoroid stream's identity meaningless. The dispersion of the stream in space and time is important to that identity and contains much information about its origin and dynamical evolution. To make sense of the meteor shower zoo, a Shower Look-Up Table was created that captures this dispersion. The Shower Look-Up Table has enabled the automated identification of showers in the ongoing CAMS video-based meteoroid orbit survey, results of which are presented now online in near-real time at http://cams.seti.org/FDL/. Visualization tools have been built that depict the streams in a planetarium setting. Examples will be presented that sample the range of meteoroid streams that this look-up table describes. Possibilities for further dynamical studies will be discussed.

Kelvin-Helmholtz instability in type-1 comet tails and associated phenomena

International Nuclear Information System (INIS)

Ershkovich, A.I.

1980-01-01

Selected problems of the solar wind - comet tail coupling that are currently accessible to quantitative analysis are reviewed. The model of a comet tail as a plasma cylinder separated by a tangential discontinuity surface from the solar wind is discussed in detail. This model is compatible with the well-known Alfven mechanism of formation of the comet tail. The stability problem of the comet tail boundary (considered as a discontinuity surface) is solved. Under typical conditions a comet tail boundary can undergo the Kelvin-Helmholtz instability. With finite amplitude the stabilizing effect of the magnetic field increases, and waves become stabilized. This model supplies a detailed quantitative description of helical waves observed in type-1 comet tails. A more general model of the tail boundary as a transition layer with a continuous change of the plasma parameters within it is also considered. This theory, in principle, enables us to solve one of the fundamental problems of cometary physics: the magnetic field of the comet tail can be derived from the observations of helical waves. This field turns out to be of the order of the interplanetary field. Various other considerations, discussed in this review also support this conclusion. (orig.)

Application of the DNA comet assay for detection of irradiated meat

International Nuclear Information System (INIS)

Kruszewski, M.; Iwanenko, T.; Wojewodzka, M.; Malec-Czechowska, K.; Dancewicz, A. M.; Szot, Z.

1998-01-01

Radiation induces damage to the DNA. This damage (fragmentation) can be assessed in the irradiated food using Single Cell Gel Electrophoresis (SCGE), known as DNA comet assay. Fragmentation of DNA may also be caused by improper storage of meat and repeated freezing and thawing. This makes identification of irradiated meat by this assay not reliable enough. In order to know the scale of the processes imitating radiation effects in DNA of the comets, their shape and lengths were examined in both irradiated and unirradiated fresh meat (D = 1.5 or 3.0 kGy) stored at 4 o C or frozen (-21 o ) up to 5 months. Comets formed upon SCGE were stained with DAPI or silver and examined in fluorescent or light microscope. They were divided arbitrarily into 4 classes. Comets of IV class were found quite often in fresh meat stored at 4 o C. In meat samples that were irradiated and stored frozen, comets of class I, II and III were observed. The negative comet test is univocal. Positive comet test, however, needs confirmation. The meat should be subjected to further analysis with other validated methods. (author)

Spectral, Photometric, and Dynamic Analysis of Eight Draconid Meteors

Czech Academy of Sciences Publication Activity Database

Borovička, Jiří; Koten, Pavel; Shrbený, Lukáš; Štork, Rostislav; Hornoch, Kamil

2014-01-01

Roč. 113, 1-4 (2014), s. 15-31 ISSN 0167-9295 R&D Projects: GA ČR(CZ) GAP209/11/1382; GA ČR GPP209/11/P651; GA ČR GA205/09/1302 Institutional support: RVO:67985815 Keywords : meteors * meteoroids * Draconids Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 0.667, year: 2014

The 2011 Draconids: The First European Airborne Meteor Observation Campaign

Czech Academy of Sciences Publication Activity Database

Vaubaillon, J.; Koten, Pavel; Margonis, A.; Toth, J.; Rudawska, R.; Gritsevich, M.; Zender, J.; McAuliffe, J.; Pautet, D.; Jenniskens, P.; Koschny, D.; Colas, F.; Bouley, S.; Maquet, L.; Leroy, A.; Lecacheux, J.; Borovička, Jiří; Watanabe, J.; Oberst, J.

2015-01-01

Roč. 114, 3-4 (2015), s. 137-157 ISSN 0167-9295 R&D Projects: GA ČR GA14-25251S Institutional support: RVO:67985815 Keywords : meteors * Draconids * 21P/Giacobini-Zinner Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 0.659, year: 2015

Long-Term Continuous Double Station Observation of Faint Meteor Showers

Czech Academy of Sciences Publication Activity Database

Vítek, S.; Páta, P.; Koten, Pavel; Fliegel, K.

2016-01-01

Roč. 16, č. 9 (2016), 1493/1-1493/10 ISSN 1424-8220 R&D Projects: GA ČR GA14-25251S Institutional support: RVO:67985815 Keywords : faint meteor shower * meteoroid * CCD camera Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 2.677, year: 2016

Prediction of the return of Comet P/Grigg-Skjellerup in 1987

International Nuclear Information System (INIS)

Sitarski, G.

1986-01-01

Using 82 observations made in the period 1966-1982 during the last four apparitions of the comet, the corrections of orbital elements were determined together with nongravitational parameters A 1 , A 2 and with a parameter D of a displacement of the photometric center from the center of mass of the comet. It was found that a value of the secular acceleration diminished in comparison with such a value before the close approach of the comet Jupiter in 1964; the nongravitational parameters of Style 2 in Marsden's notation now are: A 1 = +0.0371, A 2 = +0.008. To make the best prediction of the comet's return in 1987, the orbit was improved using 67 observations from the last two apparitions of the comet in 1977 and 1982, and taking the constant values of A 1 , A 2 as determined earlier; basing on the latter orbit the ephemeris of the comet for 1987 was computed. 3 refs., 2 tabs. (author)

COMET Multimedia modules and objects in the digital library system

Science.gov (United States)

Spangler, T. C.; Lamos, J. P.

2003-12-01

Over the past ten years of developing Web- and CD-ROM-based training materials, the Cooperative Program for Operational Meteorology, Education and Training (COMET) has created a unique archive of almost 10,000 multimedia objects and some 50 web based interactive multimedia modules on various aspects of weather and weather forecasting. These objects and modules, containing illustrations, photographs, animations,video sequences, audio files, are potentially a valuable resource for university faculty and students, forecasters, emergency managers, public school educators, and other individuals and groups needing such materials for educational use. The COMET Modules are available on the COMET educational web site http://www.meted.ucar.edu, and the COMET Multimedia Database (MMDB) makes a collection of the multimedia objects available in a searchable online database for viewing and download over the Internet. Some 3200 objects are already available at the MMDB Website: http://archive.comet.ucar.edu/moria/

Characterizing Outbursts and Nucleus Properties of Comet 29P/Schwassmann-Wachmann 1

Science.gov (United States)

Fernandez, Yanga

2015-10-01

Today's comets are remnant bodies leftover from the era of planet formation in our own Solar System. Therefore characterizing cometary structure and composition can give clues to the thermal, physical, and chemical environment of the protoplanetary disk. However before this long-term 'holy grail' of planetary astronomy can be achieved, we must understand cometary evolution so that we can know how comets have changed since their formation. The phenomenon of cometary activity, where a porous matrix of icy and rocky material turns into the gases and the dust grains we see in a comet's coma, remains a poorly-understood puzzle of short-term cometary evolution. We are in the midst of an ongoing project to understand cometary activity in a particular comet, 29P/Schwassmann-Wachmann 1, by taking advantage of existing imaging datasets that show the comet in outburst. Outbursts are useful for constraining the nucleus's spin state and the location of active areas. We propose here to analyze archival WFPC2 images of comet 29P obtained in March 1996 (Cycle 5, Project 5829), spanning 21 hours, that show the comet in outburst. These data are the highest-resolution imaging of this comet ever obtained while it was in outburst. We will analyze the morphology of the comet's dust coma to constrain properties of the nucleus and of the dust grains themselves. Additionally, we will analyze images taken in May 2000 (Cycle 8, Project 8274) that show the comet at its steady-state level of activity but may also allow us to place further constraints on the nucleus's active regions.

Meteor Film Recording with Digital Film Cameras with large CMOS Sensors

Science.gov (United States)

Slansky, P. C.

2016-12-01

In this article the author combines his professional know-how about cameras for film and television production with his amateur astronomy activities. Professional digital film cameras with high sensitivity are still quite rare in astronomy. One reason for this may be their costs of up to 20 000 and more (camera body only). In the interim, however,consumer photo cameras with film mode and very high sensitivity have come to the market for about 2 000 EUR. In addition, ultra-high sensitive professional film cameras, that are very interesting for meteor observation, have been introduced to the market. The particular benefits of digital film cameras with large CMOS sensors, including photo cameras with film recording function, for meteor recording are presented by three examples: a 2014 Camelopardalid, shot with a Canon EOS C 300, an exploding 2014 Aurigid, shot with a Sony alpha7S, and the 2016 Perseids, shot with a Canon ME20F-SH. All three cameras use large CMOS sensors; "large" meaning Super-35 mm, the classic 35 mm film format (24x13.5 mm, similar to APS-C size), or full format (36x24 mm), the classic 135 photo camera format. Comparisons are made to the widely used cameras with small CCD sensors, such as Mintron or Watec; "small" meaning 12" (6.4x4.8 mm) or less. Additionally, special photographic image processing of meteor film recordings is discussed.

Comet or Asteroid?

Science.gov (United States)

1997-11-01

When is a minor object in the solar system a comet? And when is it an asteroid? Until recently, there was little doubt. Any object that was found to display a tail or appeared diffuse was a comet of ice and dust grains, and any that didn't, was an asteroid of solid rock. Moreover, comets normally move in rather elongated orbits, while most asteroids follow near-circular orbits close to the main plane of the solar system in which the major planets move. However, astronomers have recently discovered some `intermediate' objects which seem to possess properties that are typical for both categories. For instance, a strange object (P/1996 N2 - Elst-Pizarro) was found last year at ESO ( ESO Press Photo 36/96 ) which showed a cometary tail, while moving in a typical asteroidal orbit. At about the same time, American scientists found another (1996 PW) that moved in a very elongated comet-type orbit but was completely devoid of a tail. Now, a group of European scientists, by means of observations carried out at the ESO La Silla observatory, have found yet another object that at first appeared to be one more comet/asteroid example. However, continued and more detailed observations aimed at revealing its true nature have shown that it is most probably a comet . Consequently, it has received the provisional cometary designation P/1997 T3 . The Uppsala-DLR Trojan Survey Some time ago, Claes-Ingvar Lagerkvist (Astronomical Observatory, Uppsala, Sweden), in collaboration with Gerhard Hahn, Stefano Mottola, Magnus Lundström and Uri Carsenty (DLR, Institute of Planetary Exploration, Berlin, Germany), started to study the distribution of asteroids near Jupiter. They were particularly interested in those that move in orbits similar to that of Jupiter and which are located `ahead' of Jupiter in the so-called `Jovian L4 Lagrangian point'. Together with those `behind' Jupiter, these asteroids have been given the names of Greek and Trojan Heroes who participated in the famous Trojan war

Detection of garlic gamma-irradiated by assay comet

International Nuclear Information System (INIS)

Moreno Alvarez, Damaris L.; Miranda, Enrique F. Prieto; Carro, Sandra; Iglesias Enrique, Isora; Matos, Wilberto

2009-01-01

The garlic samples were irradiated in a facility with 60 Co sources, at absorbed dose values of 0-0,15 kGy. The detection method utilized for the identification of the irradiated garlic was biological comet assay. The samples were classified post-irradiation several times. The irradiated samples showed high strand breaks of DNA exhibiting comets of several forms, while the not irradiated and lower dose samples showed a behavior like round shape and light comets. Significant differences were found for higher absorbed dose values at 0.06 kGy, this absorbed dose value is corresponding with the applied dose value at this food in order to avoid the germination. (author)

Comets As Objects of High Energy Astrophysics

Science.gov (United States)

Ibadov, S.

2000-10-01

Strong soft X-ray emission from comet Hyakutake C/1996 B2 was discovered with ROSAT in March 27, 1996 (Lisse et al. 1996, Science 274, 205-209) and the results of a theoretical approach (Ibadov 1990, Icarus 86, 283-288) served as a motive for that observations (Dennerl, Lisse and Truemper 1998, Private Communications). It is now well established that comets emit EUV and X-rays regularly (Dennerl, Englhauser and Truemper 1997, Science 277, 1625-1630; Dennerl 1998, Proc. 16th Int. Conf. Atomic Physics, Windsor, Ontario, Canada). To explain this phenomenon different theoretical models were proposed (Krasnopolsky 1997, Icarus 128, 365-385; Ibadov 1998, Proc. First XMM Workshop, Noordwijk, The Netherlands, and references therein). In the paper the problem of identifying X-ray generation mechanisms in comets will be considered.

Activity of the Leonid meteor shower on 2009 November 17

Czech Academy of Sciences Publication Activity Database

Koten, Pavel; Borovička, Jiří; Kokhirova, G.I.

2011-01-01

Roč. 528, April (2011), A94/1-A94/4 ISSN 0004-6361 R&D Projects: GA ČR GA205/09/1302 Institutional research plan: CEZ:AV0Z10030501 Keywords : meteorites * meteors * meteoroids Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 4.587, year: 2011

Autonomous Navigation Performance During The Hartley 2 Comet Flyby

Science.gov (United States)

Abrahamson, Matthew J; Kennedy, Brian A.; Bhaskaran, Shyam

2012-01-01

On November 4, 2010, the EPOXI spacecraft performed a 700-km flyby of the comet Hartley 2 as follow-on to the successful 2005 Deep Impact prime mission. EPOXI, an extended mission for the Deep Impact Flyby spacecraft, returned a wealth of visual and infrared data from Hartley 2, marking the fifth time that high-resolution images of a cometary nucleus have been captured by a spacecraft. The highest resolution science return, captured at closest approach to the comet nucleus, was enabled by use of an onboard autonomous navigation system called AutoNav. AutoNav estimates the comet-relative spacecraft trajectory using optical measurements from the Medium Resolution Imager (MRI) and provides this relative position information to the Attitude Determination and Control System (ADCS) for maintaining instrument pointing on the comet. For the EPOXI mission, AutoNav was tasked to enable continuous tracking of a smaller, more active Hartley 2, as compared to Tempel 1, through the full encounter while traveling at a higher velocity. To meet the mission goal of capturing the comet in all MRI science images, position knowledge accuracies of +/- 3.5 km (3-?) cross track and +/- 0.3 seconds (3-?) time of flight were required. A flight-code-in-the-loop Monte Carlo simulation assessed AutoNav's statistical performance under the Hartley 2 flyby dynamics and determined optimal configuration. The AutoNav performance at Hartley 2 was successful, capturing the comet in all of the MRI images. The maximum residual between observed and predicted comet locations was 20 MRI pixels, primarily influenced by the center of brightness offset from the center of mass in the observations and attitude knowledge errors. This paper discusses the Monte Carlo-based analysis that led to the final AutoNav configuration and a comparison of the predicted performance with the flyby performance.

Isotopic ratios in outbursting comet C/2015 ER61

Science.gov (United States)

Yang, Bin; Hutsemékers, Damien; Shinnaka, Yoshiharu; Opitom, Cyrielle; Manfroid, Jean; Jehin, Emmanuël; Meech, Karen J.; Hainaut, Olivier R.; Keane, Jacqueline V.; Gillon, Michaël

2018-02-01

Isotopic ratios in comets are critical to understanding the origin of cometary material and the physical and chemical conditions in the early solar nebula. Comet C/2015 ER61 (PANSTARRS) underwent an outburst with a total brightness increase of 2 magnitudes on the night of 2017 April 4. The sharp increase in brightness offered a rare opportunity to measure the isotopic ratios of the light elements in the coma of this comet. We obtained two high-resolution spectra of C/2015 ER61 with UVES/VLT on the nights of 2017 April 13 and 17. At the time of our observations, the comet was fading gradually following the outburst. We measured the nitrogen and carbon isotopic ratios from the CN violet (0, 0) band and found that 12C/13C = 100 ± 15, 14N/15N = 130 ± 15. In addition, we determined the 14N/15N ratio from four pairs of NH2 isotopolog lines and measured 14N/15N = 140 ± 28. The measured isotopic ratios of C/2015 ER61 do not deviate significantly from those of other comets.

Comet Halley - Chapter I in cometary exploration

International Nuclear Information System (INIS)

Newburn, R.L. Jr.

1986-01-01

The information gained on the Comet Halley by the international probe studies is presented. The new information includes data on the true size and shape of the cometary nucleus and the mass of its dust grains, the chemical composition of the nucleus, and the characteristics of the bow wave of the comet. The requirements of future missions for solving the many questions that are still open are discussed

THE NEOWISE-DISCOVERED COMET POPULATION AND THE CO + CO{sub 2} PRODUCTION RATES

Energy Technology Data Exchange (ETDEWEB)

Bauer, James M.; Stevenson, Rachel; Kramer, Emily; Mainzer, A. K.; Masiero, Joseph R.; Weissman, Paul R.; Nugent, Carrie R.; Sonnett, Sarah [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, MS 183-401, Pasadena, CA 91109 (United States); Grav, Tommy [Planetary Science Institute, 1700 East Fort Lowell, Suite 106, Tucson, AZ 85719-2395 (United States); Fernández, Yan R. [Department of Physics, University of Central Florida, 4000 Central Florida Blvd., P.S. Building, Orlando, FL 32816-2385 (United States); Cutri, Roc M.; Dailey, John W.; Masci, Frank J.; Blair, Nathan; Lucas, Andrew [Infrared Processing and Analysis Center, California Institute of Technology, Pasadena, CA 91125 (United States); Meech, Karen J. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Dr., Manoa, HI 96822 (United States); Walker, Russel [Monterey Institute for Research in Astronomy, 200 Eighth Street, Marina, CA 93933 (United States); Lisse, C. M. [Applied Physics Laboratory, Johns Hopkins University, 11100 Johns Hopkins Road Laurel, MD 20723-6099 (United States); McMillan, Robert S. [Lunar and Planetary Laboratory, University of Arizona, 1629 East University Blvd., Kuiper Space Science Bldg. 92, Tucson, AZ 85721-0092 (United States); Wright, Edward L., E-mail: bauer@scn.jpl.nasa.gov [Department of Physics and Astronomy, University of California, P.O. Box 91547, Los Angeles, CA 90095-1547 (United States); Collaboration: WISE and NEOWISE Teams

2015-12-01

The 163 comets observed during the WISE/NEOWISE prime mission represent the largest infrared survey to date of comets, providing constraints on dust, nucleus size, and CO + CO{sub 2} production. We present detailed analyses of the WISE/NEOWISE comet discoveries, and discuss observations of the active comets showing 4.6 μm band excess. We find a possible relation between dust and CO + CO{sub 2} production, as well as possible differences in the sizes of long and short period comet nuclei.

The Meteoroid Fluence at Mars Due to Comet Siding Spring

Science.gov (United States)

Moorhead, Althea V.

2014-01-01

Long-period comet C/2013 A1 (Siding Spring) is headed for a close encounter with Mars on 2014 Oct 19. A collision between the comet and the planet has been ruled out, but the comets coma may envelop Mars and its man-made satellites. We present an analytic model of the dust component of cometary comae that describes the spatial distribution of cometary dust and meteoroids and their size distribution. If the coma reaches Mars, we estimate a total incident particle fluence on the planet and its satellites of 0.01 particles per square meter. We compare our model with numerical simulations, data from past comet missions, and recent Siding Spring observations.

Comet assay optimization for assessment of DNA damage due to radiation exposure

International Nuclear Information System (INIS)

Dwi Ramadhani; Devita Tetriana; Viria Agesti Suvifan

2016-01-01

Comet assay can be used to measure the deoxyribonucleic acid (DNA) damage level caused by ionizing radiation exposure in peripheral blood lymphocytes. The principle of the comet assay is based on the amount of denatured DNA fragments that migrated out of the cell nucleus during electrophoresis. There are several aspects that must be concerned when doing the comet assay. For example the agarose concentration, duration of alkaline incubation, electrophoresis conditions (time, temperature, and voltage gradient), and the measurement parameters that used in analyze the comet. Percentage of DNA in the comet tail (% tail DNA) is strongly recommended as a parameter when analyze the comet because it can be converted to lesions per 106 base pairs (bp) using calibration curve that show relationship between the dose of ionizing radiation and % tail DNA. To obtain an accurate result, the calibration curve must be made and comet should be analyzing using image processing analysis software since it can be increase the precision and reduce the subjectivity of the measurement process. (author)

Comet 2001 Q2

Czech Academy of Sciences Publication Activity Database

Pravec, Petr; Kušnirák, Peter; Bouma, R. J.; Raymundo, P. M.

č. 7687 (2001), s. 1 ISSN 0081-0304 R&D Projects: GA ČR GA205/99/0255 Institutional research plan: CEZ:AV0Z1003909 Keywords : comet s * astrometry Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics

An analytical theory of a scattering of radio waves on meteoric ionization - II. Solution of the integro-differential equation in case of backscatter

Science.gov (United States)

Pecina, P.

2016-12-01

The integro-differential equation for the polarization vector P inside the meteor trail, representing the analytical solution of the set of Maxwell equations, is solved for the case of backscattering of radio waves on meteoric ionization. The transversal and longitudinal dimensions of a typical meteor trail are small in comparison to the distances to both transmitter and receiver and so the phase factor appearing in the kernel of the integral equation is large and rapidly changing. This allows us to use the method of stationary phase to obtain an approximate solution of the integral equation for the scattered field and for the corresponding generalized radar equation. The final solution is obtained by expanding it into the complete set of Bessel functions, which results in solving a system of linear algebraic equations for the coefficients of the expansion. The time behaviour of the meteor echoes is then obtained using the generalized radar equation. Examples are given for values of the electron density spanning a range from underdense meteor echoes to overdense meteor echoes. We show that the time behaviour of overdense meteor echoes using this method is very different from the one obtained using purely numerical solutions of the Maxwell equations. Our results are in much better agreement with the observations performed e.g. by the Ondřejov radar.

Weird comets and asteroids the strange little worlds of the sun's family

CERN Document Server

Seargent, David A J

2017-01-01

This book concentrates on some of the odd aspects of comets and asteroids. Strange behavior of comets, such as outbursts and schisms, and how asteroids can temporally act as comets are discussed, together with the possible threat of Centaurs-class objects like the Taurid complex. Recent years have seen the distinction between comets and asteroids become less prominent. Comets in "asteroid" orbits and vice versa have become almost commonplace and a clearer view of the role of small bodies in the formation of the Solar System and their effect on Earth has become apparent. Seargent covers this development in detail by including new data and information from space probes. .

The beginning heights and light curves of high-altitude meteors

Czech Academy of Sciences Publication Activity Database

Koten, Pavel; Spurný, Pavel; Borovička, Jiří; Evans, S.; Elliott, A.; Betlem, H.; Štork, Rostislav; Jobse, K.

2006-01-01

Roč. 41, č. 9 (2006), s. 1305-1320 ISSN 1086-9379 R&D Projects: GA ČR GP205/02/P038 Institutional research plan: CEZ:AV0Z10030501 Keywords : bright Leonid meteors * atmospheric trajectories Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 2.524, year: 2006

Properties of comet Halley derived from thermal models and astrometric data

International Nuclear Information System (INIS)

Hechler, F.W.; Morley, T.A.; Mahr, P.

1986-01-01

The motion of a comet nucleus is influenced by outgassing forces. The orbit determination from astrometric data of comet Halley using empiric force and observation bias models and the incorporation of thermal models developed at ESOC into the orbit determination allows to draw some conclusions on the comet Halley dynamics and physics. 21 references

The METEOR/TRANSURANUS fuel performance code

International Nuclear Information System (INIS)

Struzik, C.; Guerin, Y.

1996-01-01

The first calculations for the FUMEX exercise were performed using version 1.1 of the METEOR/TRANSURANUS code. Since then, important improvements have been implemented on several models. In its present state, the code describes fuel rod behaviour in standard PWR conditions. Its validity extends to UO 2 and MOX fuels clad in Zircaloy-4. Power transient calculations for UO 2 and Gd doped fuel calculations are possible, but further developments are in progress, and the applications will be fully qualified in version 2.0. A considerable effort is made to replace semi-empirical models with models that have a sounder physical basis. (authors). 14 refs

Encounters between degenerate stars and extrasolar comet clouds

International Nuclear Information System (INIS)

Pineault, S.; Poisson, E.

1989-01-01

Under the assumption that the presence of comet clouds around otherwise normal stars is a common occurrence in the Galaxy, the observational consequences of random penetration encounters between the general Galactic population of degenerate stars and these comet clouds is considered. The only case considered is where the compact stars is a single star. For this scenario, encounters involving neutron stars (NSs) result in impact rates 1000-10,000 times slower than in the model of Tremaine and Zytkow (1986). The rate for white dwarfs (WDs) is larger than the one for NSs by a factor of about 30 times the ratio of the degenerate star number densities. The mean impact rate is significantly increased if the number of comets in a cloud is nearly independent of the mass of the central star. It is concluded that some of the observed gamma-ray bursts may be caused by accretion of comets onto NSs and that this scenario, but with a WD as the accretor, probably contributes to the optical flash background rate. 38 refs

Detectability of Sungrazing Comet Soft X-ray Irradiance

Directory of Open Access Journals (Sweden)

Su Yeon Oh

2007-12-01

Full Text Available Originating from the Oort cloud, some comets disappear to impact against the Sun or to split up by strong gravitational force. Then they don't go back to the Oort cloud. They are called sungrazing comets. The comets are detected by sublimation of ices and ejection of gas and dust through solar heat close to the Sun. There exists the charge transfer from heavy ions in the solar wind to neutral atoms in the cometary atmosphere by interaction with the solar wind. Cometary atoms would be excited to high electronic levels and their de-excitation would result in X-ray emission, or it would be scattering of solar X-ray emission by very small cometary grains. We calculated the X-ray emission applying the model suggested by Mendis & Flammer (1984 and Cravens (1997. In our estimation, the sungrazing comet whose nucleus size is about 1 km in radius might be detectable within a distance of 3 solar radius from the sun on soft X-ray solar camera.

Detection of garlic gamma-irradiated by assay comet

Energy Technology Data Exchange (ETDEWEB)

Moreno Alvarez, Damaris L.; Miranda, Enrique F. Prieto; Carro, Sandra; Iglesias Enrique, Isora; Matos, Wilberto [Centro de Aplicaciones Tecnologicas y Desarrollo Nuclear (CEADEN), Ciudad de La Habana (Cuba)], e-mail: damaris@ceaden.edu.cu

2009-07-01

The garlic samples were irradiated in a facility with {sup 60}Co sources, at absorbed dose values of 0-0,15 kGy. The detection method utilized for the identification of the irradiated garlic was biological comet assay. The samples were classified post-irradiation several times. The irradiated samples showed high strand breaks of DNA exhibiting comets of several forms, while the not irradiated and lower dose samples showed a behavior like round shape and light comets. Significant differences were found for higher absorbed dose values at 0.06 kGy, this absorbed dose value is corresponding with the applied dose value at this food in order to avoid the germination. (author)

Rationalization of Comet Halley's periods

Science.gov (United States)

Belton, Michael J. S.

1990-01-01

The sense of long axis orientation of Comet Halley during the Vega 1 encounter must be reversed from that deduced by Sagdeev et al. (1986) in order to harmonize the comet nucleus' Vega/Giotto-observed orientations with periodicities extracted from time-series brightness data. It is also demonstrated that Vega/Giotto observations can be satisfied by either a 2.2- or 3.7-day long-axis free precession period. A novel Fourier algorithm is used to reanalyze five independent data sets; strong evidence is adduced for periods harmonically related to a 7.4-day period. The preferred candidate models for Halley's nuclear rotation are characterized by a long-axis precession period of 3.7 days.

Comet Assay in Cancer Chemoprevention.

Science.gov (United States)

Santoro, Raffaela; Ferraiuolo, Maria; Morgano, Gian Paolo; Muti, Paola; Strano, Sabrina

2016-01-01

The comet assay can be useful in monitoring DNA damage in single cells caused by exposure to genotoxic agents, such as those causing air, water, and soil pollution (e.g., pesticides, dioxins, electromagnetic fields) and chemo- and radiotherapy in cancer patients, or in the assessment of genoprotective effects of chemopreventive molecules. Therefore, it has particular importance in the fields of pharmacology and toxicology, and in both environmental and human biomonitoring. It allows the detection of single strand breaks as well as double-strand breaks and can be used in both normal and cancer cells. Here we describe the alkali method for comet assay, which allows to detect both single- and double-strand DNA breaks.

Radar observations of Comet Halley

International Nuclear Information System (INIS)

Campbell, D.B.; Harmon, J.K.; Shapiro, I.I.

1989-01-01

Five nights of Arecibo radar observations of Comet Halley are reported which reveal a feature in the overall average spectrum which, though weak, seems consistent with being an echo from the comet. The large radar cross section and large bandwidth of the feature suggest that the echo is predominantly from large grains which have been ejected from the nucleus. Extrapolation of the dust particle size distribution to large grain sizes gives a sufficient number of grains to account for the echo. The lack of a detectable echo from the nucleus, combined with estimates of its size and rotation rate from spacecraft encounters and other data, indicate that the nucleus has a surface of relatively high porosity. 33 references

Simultaneous optical and meteor head echo measurements using the Middle Atmosphere Alomar Radar System (MAARSY): Data collection and preliminary analysis

Science.gov (United States)

Brown, P.; Stober, G.; Schult, C.; Krzeminski, Z.; Cooke, W.; Chau, J. L.

2017-07-01

The initial results of a two year simultaneous optical-radar meteor campaign are described. Analysis of 105 double-station optical meteors having plane of sky intersection angles greater than 5° and trail lengths in excess of 2 km also detected by the Middle Atmosphere Alomar Radar System (MAARSY) as head echoes was performed. These events show a median deviation in radiants between radar and optical determinations of 1.5°, with 1/3 of events having radiant agreement to less than one degree. MAARSY tends to record average speeds roughly 0.5 km/s and 1.3 km higher than optical records, in part due to the higher sensitivity of MAARSY as compared to the optical instruments. More than 98% of all head echoes are not detected with the optical system. Using this non-detection ratio and the known limiting sensitivity of the cameras, we estimate that the limiting meteoroid detection mass of MAARSY is in the 10-9-10-10 kg (astronomical limiting meteor magnitudes of +11 to +12) appropriate to speeds from 30 to 60 km/s. There is a clear trend of higher peak RCS for brighter meteors between 35 and -30 dBsm. For meteors with similar magnitudes, the MAARSY head echo radar cross-section is larger at higher speeds. Brighter meteors at fixed heights and similar speeds have consistently, on average, larger RCS values, in accordance with established scattering theory. However, our data show RCS ∝ v/2, much weaker than the normally assumed RCS ∝ v3, a consequence of our requiring head echoes to also be detectable optically. Most events show a smooth variation of RCS with height broadly following the light production behavior. A significant minority of meteors show large variations in RCS relative to the optical light curve over common height intervals, reflecting fragmentation or possibly differential ablation. No optically detected meteor occurring in the main radar beam and at times when the radar was collecting head echo data went unrecorded by MAARSY. Thus there does not

Early diagenesis driven by widespread meteoric infiltration of a Central European carbonate ramp: A reinterpretation of the Upper Muschelkalk

Science.gov (United States)

Adams, Arthur; Diamond, Larryn W.

2017-12-01

Meteoric diagenesis of carbonate ramps is often difficult to interpret and can commonly be confused with other coinciding diagenetic processes. The Middle Triassic Upper Muschelkalk of Switzerland provides an insightful case in which the effects of several overprinting diagenetic environments, including matrix dolomitization, can be clearly unravelled. Previous studies suggested that diagenesis took place in connate marine waters, with later meteoric waters being invoked to explain recrystallization of dolomite. In this study, diagenetic analyses (C-O stable isotope ratios, thin-section point counting, cathodoluminescence and UV-fluorescence microscopy) of calcitic bioclastic samples have revealed that early diagenesis (pre-stylolitization) and the accompanying porosity evolution did not occur exclusively in the presence of marine fluids. Five sequential stages of diagenesis have been identified: marine, shallow burial, mixing-zone, meteoric and dolomitization. Marine diagenesis induced precipitation of bladed and inclusion-rich syntaxial cements that fluoresce strongly under UV-light. Both cements account for a mean 7.5 vol% reduction in the porosity of bioclastic beds. Shallow burial diagenesis likely induced mouldic porosity and associated fluorescent dog-tooth cementation. Based on light oxygen isotope and elevated strontium isotope ratios, matrix aragonite-calcite neomorphism is interpreted to have occurred in a mixture of marine and meteoric fluids. The combination of shallow burial and mixing-zone processes reduced porosity on average by 4.8 vol%. Evidence for subsequent meteoric diagenesis is found in abundant dog-tooth and blocky calcite cements that have mean δ18OVPDB of - 9.36‰ and no signs of recrystallization. These meteoric cements reduced porosity by a further 13.4 vol%. Percolation of meteoric water through the ramp was driven by hydraulic gradients on an adjacent basement high, which was exposed by a cycle of early Ladinian regressions

Epithelial cells as alternative human biomatrices for comet assay.

Science.gov (United States)

Rojas, Emilio; Lorenzo, Yolanda; Haug, Kristiane; Nicolaissen, Bjørn; Valverde, Mahara

2014-01-01

The comet assay is a valuable experimental tool aimed at mapping DNA damage in human cells in vivo for environmental and occupational monitoring, as well as for therapeutic purposes, such as storage prior to transplant, during tissue engineering, and in experimental ex vivo assays. Furthermore, due to its great versatility, the comet assay allows to explore the use of alternative cell types to assess DNA damage, such as epithelial cells. Epithelial cells, as specialized components of many organs, have the potential to serve as biomatrices that can be used to evaluate genotoxicity and may also serve as early effect biomarkers. Furthermore, 80% of solid cancers are of epithelial origin, which points to the importance of studying DNA damage in these tissues. Indeed, studies including comet assay in epithelial cells have either clear clinical applications (lens and corneal epithelial cells) or examine genotoxicity within human biomonitoring and in vitro studies. We here review improvements in determining DNA damage using the comet assay by employing lens, corneal, tear duct, buccal, and nasal epithelial cells. For some of these tissues invasive sampling procedures are needed. Desquamated epithelial cells must be obtained and dissociated prior to examination using the comet assay, and such procedures may induce varying amounts of DNA damage. Buccal epithelial cells require lysis enriched with proteinase K to obtain free nucleosomes. Over a 30 year period, the comet assay in epithelial cells has been little employed, however its use indicates that it could be an extraordinary tool not only for risk assessment, but also for diagnosis, prognosis of treatments and diseases.

Comets: Role and importance to exobiology

Science.gov (United States)

Delsemme, Armand H.

1992-01-01

The transfer of organic compounds from interstellar space to the outskirts of a protoplanetary disk, their accretion into cometary objects, and the transport of the latter into the inner solar system by orbital diffusion throw a new light on the central problem of exobiology. It suggests the existence of a cosmic mechanism, working everywhere, that can supply prebiotic compounds to ubiquitous rocky planets, in search of the proper environment to start life in many places in the Universe. Under the heading of chemistry of the cometary nucleus, the following topics are covered: radial homogeneity of the nucleus; the dust-to-ice ratio; nature of the dust grains; origin of the dust in comets; nature of the volatile fraction; the CO distribution in comet Halley; dust contribution to the volatile fraction; elemental balance sheet of comet Halley; quantitative molecular analysis of the volatile fraction; and isotopic ratios. Under the heading of exogenous origin of carbon on terrestrial planets the following topics are covered: evidence for a high-temperature phase; from planetesimals to planets; a veneer of volatile and organic material; and cometary contribution.

Asteroids, meteorites, and comets

CERN Document Server

Elkins-Tanton, Linda T

2010-01-01

Asteroids, Comets, and Meteorites provides students, researchers, and general readers with the most up-to-date information on this fascinating field. From the days of the dinosaurs to our modern environment, this book explores all aspects of these cosmic invaders.

Death of a comet

CERN Multimedia

Hawkes, N

2000-01-01

The comet Linear dissolved as it made its closest approach to the sun on July 25th. The first stages of its breakup had been witnessed by the Hubble telescope when it threw off a piece of its crust (3 paragraphs).

Nonlinear low frequency (LF) waves - Comets and foreshock phenomena

Science.gov (United States)

Tsurutani, Bruce T.

1991-01-01

A review is conducted of LF wave nonlinear properties at comets and in the earth's foreshock, engaging such compelling questions as why there are no cometary cyclotron waves, the physical mechanism responsible for 'dispersive whiskers', and the character of a general description of linear waves. Attention is given to the nonlinear properties of LF waves, whose development is illustrated by examples of waves and their features at different distances from the comet, as well as by computer simulation results. Also discussed is a curious wave mode detected from Comet Giacobini-Zinner, both at and upstream of the bow shock/wave.

Knut Lundmark, meteors and an early Swedish crowdsourcing experiment.

Science.gov (United States)

Kärnfelt, Johan

2014-10-01

Mid twentieth century meteor astronomy demanded the long-term compilation of observations made by numerous individuals over an extensive geographical area. Such a massive undertaking obviously required the participation of more than just professional astronomers, who often sought to expand their ranks through the use of amateurs that had a basic grasp of astronomy as well as the night sky, and were thus capable of generating first-rate astronomical reports. When, in the 1920s, renowned Swedish astronomer Knut Lundmark turned his attention to meteor astronomy, he was unable to rely even upon this solution. In contrast to many other countries at the time, Sweden lacked an organized amateur astronomy and thus contained only a handful of competent amateurs. Given this situation, Lundmark had to develop ways of engaging the general public in assisting his efforts. To his advantage, he was already a well-established public figure who had published numerous popular science articles and held talks from time to time on the radio. During the 1930s, this prominence greatly facilitated his launching of a crowdsourcing initiative for the gathering of meteor observations. This paper consists of a detailed discussion concerning the means by which Lundmark's initiative disseminated astronomical knowledge to the general public and encouraged a response that might directly contribute to the advancement of science. More precisely, the article explores the manner in which he approached the Swedish public, the degree to which that public responded and the extent to which his efforts were successful. The primary aim of this exercise is to show that the apparently recent Internet phenomenon of 'crowdsourcing', especially as it relates to scientific research, actually has a pre-Internet history that is worth studying. Apart from the fact that this history is interesting in its own right, knowing it can provide us with a fresh vantage point from which to better comprehend and appreciate

The Southern Argentina Agile Meteor Radar Orbital System (SAAMER-OS): An Initial Sporadic Meteoroid Orbital Survey in the Southern Sky

Science.gov (United States)

Janches, D.; Close, S.; Hormaechea, J. L.; Swarnalingam, N.; Murphy, A.; O'Connor, D.; Vandepeer, B.; Fuller, B.; Fritts, D. C.; Brunini, C.

2015-01-01

We present an initial survey in the southern sky of the sporadic meteoroid orbital environment obtained with the Southern Argentina Agile MEteor Radar (SAAMER) Orbital System (OS), in which over three-quarters of a million orbits of dust particles were determined from 2012 January through 2015 April. SAAMER-OS is located at the southernmost tip of Argentina and is currently the only operational radar with orbit determination capability providing continuous observations of the southern hemisphere. Distributions of the observed meteoroid speed, radiant, and heliocentric orbital parameters are presented, as well as those corrected by the observational biases associated with the SAAMER-OS operating parameters. The results are compared with those reported by three previous surveys performed with the Harvard Radio Meteor Project, the Advanced Meteor Orbit Radar, and the Canadian Meteor Orbit Radar, and they are in agreement with these previous studies. Weighted distributions for meteoroids above the thresholds for meteor trail electron line density, meteoroid mass, and meteoroid kinetic energy are also considered. Finally, the minimum line density and kinetic energy weighting factors are found to be very suitable for meteoroid applications. The outcomes of this work show that, given SAAMERs location, the system is ideal for providing crucial data to continuously study the South Toroidal and South Apex sporadic meteoroid apparent sources.

DNA comet assay for rice seeds treated with low energy electrons ('soft-electrons')

International Nuclear Information System (INIS)

Todoriki, Setsuko; Hayashi, Toru

1999-01-01

As rice seeds are sometimes contaminated with phytopathogenic organisms such as blast disease fungi and nematodes, a novel non-chemical disinfection method for rice seeds is highly required. In order to develop a disinfection method, the effect of low energy electron ('soft-electrons') on seed DNA was examined by using the neutral comet assay. Rice seeds (whole grain) were treated with electrons of different acceleration voltages (180 kV to 1 MV) at a dose of 5 kGy. Nucleus suspensions were prepared from whole brown rice and subjected to electrophoresis. DNA from un-irradiated (control) seeds relaxed and produced comets with a short tail, most of the comets distributed within the range of comet length between 30 μm to 70 μm. In the case of seeds treated with electrons at acceleration voltages up to 190 kV, cells without seed coats were not damaged and the frequency histograms of comet length showed almost the same pattern as that for control. At acceleration voltages higher than 200 kV, the cells were distributed into two categories; DNA comets with a short tail (with little DNA damages, less than 70 μm in the comet length) and DNA comets with long tails (with sever strand breaks, more than 130 μm in the comet length). The ratios of damaged cells increased with increasing acceleration voltage. The growths of rice seedlings were not affected by the treatment with electrons at up to 200 kV. On the contrary, the cells of gamma-irradiated seed showed small variations in the comet length, and which were depending on radiation dose. The individual cells of gamma-irradiated seeds at 1 kGy showed shorter comet than the damaged cells with soft electron, seed treated with gamma rays (1-5 kGy) did not shoot nor root. (author)

Measurement of plasma and energetic charged particles in the proximity of Halley's comet

International Nuclear Information System (INIS)

Erdoes, Geza; Gombosi, Tamas; Kecskemety, Karoly; Somogyi, Antal; Tatrallyay, Mariella; Varga, Andras

1987-01-01

The instrumentation aboard the space probe VEGA for the exploration of Halley's comet contained the particle analyzers PLAZMAG and TUENDE-M. PLAZMAG was used for the measurement of the interaction between the low-energy solar plasma and the heavy ions from the comet. From the energy spectra measured near the nucleus of the comet the density distribution of ion groups can also be determined. TUENDE-M recorded the distribution of energetic heavy ions from the comet. The properties of various plasma regions within the 10 million km range from the comet's nucleus are discussed in detail. (R.P.)

Evaluation of irradiation in foods using DNA comet assay

International Nuclear Information System (INIS)

Khawar, Affaf; Bhatti, Ijaz Ahmad; Khan, Q.M.; Ali, T.; Khan, A.I.; Asi, M.R.

2011-01-01

Comet assay is a rapid, inexpensive and sensitive biological technique to detect DNA damage in food stuffs by irradiation. In this study the Comet assay is applied on foods of plant and animal origins. Samples were irradiated by using 60 Co gamma-radiation source. The applied doses were 2, 6 and 10 kGy for food of plant origin and 0.5, 1 and 2 kGy for meat items. The un-irradiated and irradiated samples were clearly differentiated on the basis of DNA fragmentation. During the electrophoresis study, it was found that in un-irradiated cells DNA remained intact and appeared as Comets without tail whereas in irradiated cells Comets with tails were visible due to stretching of fragmented DNA. Moreover, it was also revealed that the DNA tail length was dose dependent. Dry food stuffs (seeds) showed good results as compared to moist foods (meat, fruits and vegetables) due to the absence of background damage. (author)

COMETARY VOLATILES AND THE ORIGIN OF COMETS

International Nuclear Information System (INIS)

A'Hearn, Michael F.; Feaga, Lori M.; Sunshine, Jessica M.; Besse, Sebastien; Bodewits, Dennis; Farnham, Tony L.; Kelley, Michael S.; Keller, H. Uwe; Kawakita, Hideyo; Hampton, Donald L.; Kissel, Jochen; Klaasen, Kenneth P.; Yeomans, Donald K.; McFadden, Lucy A.; Meech, Karen J.; Schultz, Peter H.; Thomas, Peter C.; Veverka, Joseph; Groussin, Olivier; Lisse, Carey M.

2012-01-01

We describe recent results on the CO/CO 2 /H 2 O composition of comets together with a survey of older literature (primarily for CO/H 2 O) and compare these with models of the protoplanetary disk. Even with the currently small sample, there is a wide dispersion in abundance ratios and little if any systematic difference between Jupiter-family comets (JFCs) and long-period and Halley-type comets (LPCs and HTCs). We argue that the cometary observations require reactions on grain surfaces to convert CO to CO 2 and also require formation of all types of comets in largely, but not entirely, overlapping regions, probably between the CO and CO 2 snow lines. Any difference in the regions of formation is in the opposite direction from the classical picture with the JFCs having formed closer to the Sun than the LPCs. In the classical picture, the LPCs formed in the region of the giant planets and the JFCs formed in the Kuiper Belt. However, these data suggest, consistent with suggestions on dynamical grounds, that the JFCs and LPCs formed in largely overlapping regions where the giant planets are today and with JFCs on average forming slightly closer to the Sun than did the LPCs. Presumably at least the JFCs passed through the scattered disk on their way to their present dynamical family.

COMETARY VOLATILES AND THE ORIGIN OF COMETS

Energy Technology Data Exchange (ETDEWEB)

A' Hearn, Michael F.; Feaga, Lori M.; Sunshine, Jessica M.; Besse, Sebastien; Bodewits, Dennis; Farnham, Tony L.; Kelley, Michael S. [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States); Keller, H. Uwe [Institute for Geophysics and Extraterrestrial Physics, Technische Universitaet Braunschweig, D-38106 Braunschweig (Germany); Kawakita, Hideyo [Department of Physics, Kyoto Sangyo University, Kamigamo JP Kita-ku, Kyoto 603-8555 (Japan); Hampton, Donald L. [Geophysical Institute, University of Alaska Fairbanks, 903 Koyukuk Drive, Fairbanks, AK 99775 (United States); Kissel, Jochen [Max-Planck-Institut for Solar System Research, Max-Planck-Strasse 2, D-37191 Katlenburg-Lindau (Germany); Klaasen, Kenneth P.; Yeomans, Donald K. [Jet Propulsion Laboratory/Caltech, Pasadena, CA 91109 (United States); McFadden, Lucy A. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Meech, Karen J. [Institute for Astronomy, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Schultz, Peter H. [Department of Geological Sciences, Brown University, Providence, RI 02912 (United States); Thomas, Peter C.; Veverka, Joseph [Department of Astronomy, Cornell University, Ithaca, NY 14853 (United States); Groussin, Olivier [Laboratoire d' Astrophysique de Marseille, Universite d' Aix-Marseille and CNRS, UMR7326, 38 rue F. Joliot-Curie, F-13388 Marseille Cedex 13 (France); Lisse, Carey M., E-mail: ma@astro.umd.edu [Space Department, JHU-APL, 11100 Johns Hopkins Road, Laurel, MD 20723 (United States); and others

2012-10-10

We describe recent results on the CO/CO{sub 2}/H{sub 2}O composition of comets together with a survey of older literature (primarily for CO/H{sub 2}O) and compare these with models of the protoplanetary disk. Even with the currently small sample, there is a wide dispersion in abundance ratios and little if any systematic difference between Jupiter-family comets (JFCs) and long-period and Halley-type comets (LPCs and HTCs). We argue that the cometary observations require reactions on grain surfaces to convert CO to CO{sub 2} and also require formation of all types of comets in largely, but not entirely, overlapping regions, probably between the CO and CO{sub 2} snow lines. Any difference in the regions of formation is in the opposite direction from the classical picture with the JFCs having formed closer to the Sun than the LPCs. In the classical picture, the LPCs formed in the region of the giant planets and the JFCs formed in the Kuiper Belt. However, these data suggest, consistent with suggestions on dynamical grounds, that the JFCs and LPCs formed in largely overlapping regions where the giant planets are today and with JFCs on average forming slightly closer to the Sun than did the LPCs. Presumably at least the JFCs passed through the scattered disk on their way to their present dynamical family.

Asteroid-comet continuum objects in the solar system.

Science.gov (United States)

Hsieh, Henry H

2017-07-13

In this review presented at the Royal Society meeting, 'Cometary science after Rosetta', I present an overview of studies of small solar system objects that exhibit properties of both asteroids and comets (with a focus on so-called active asteroids). Sometimes referred to as 'transition objects', these bodies are perhaps more appropriately described as 'continuum objects', to reflect the notion that rather than necessarily representing actual transitional evolutionary states between asteroids and comets, they simply belong to the general population of small solar system bodies that happen to exhibit a continuous range of observational, physical and dynamical properties. Continuum objects are intriguing because they possess many of the properties that make classical comets interesting to study (e.g. relatively primitive compositions, ejection of surface and subsurface material into space where it can be more easily studied, and orbital properties that allow us to sample material from distant parts of the solar system that would otherwise be inaccessible), while allowing us to study regions of the solar system that are not sampled by classical comets.This article is part of the themed issue 'Cometary science after Rosetta'. © 2017 The Author(s).

Comet assay as a cold chain control tool

International Nuclear Information System (INIS)

Duarte, Renato Cesar

2009-01-01

Bearing in mind an ever more demanding market regarding the quality of food, it has been necessary to develop processes that meet the demands of consumers. Within the existing processes the cold chain and irradiation stand out. The cold chain comprises all the stages of conserving food from production, cooling, freezing, storing and transportation to the final consumer. Irradiation, as a means of conserving food, prolongs the shelf life, inhibits budding and reduces pathogenic contamination among other benefits. Is very important the identification of food degradation in function of failure on the processes which they were subjected. The comet assay is a screening test widely studied, considerate fast and with low cost. By the fact of the test identify breaks on the DNA, may be possible use the comet test on the control of cold chain failures that degrade de food. The labels and stamp, do not consider the previous food situation and indicate failures from the moment where they be placed in contact with the product. With the comet assay is possible to check the degradation that has occurred in liver chicken samples until the moment of comet's test realization. (author)

Comet Dust: The Diversity of Primitive Particles and Implications

Science.gov (United States)

John Bradley; Zolensky, Michael E.

2016-01-01

Comet dust is primitive and shows significant diversity. Our knowledge of the properties of primitive particles has expanded significantly through microscale investigations of cosmic dust samples (IDPs and AMMs) and of comet dust samples (Stardust and Rosetta's COSIMA), as well as through remote sensing (spectroscopy and imaging) via Spitzer and via spacecraft encounters with 103P/Hartley 2 and 67P/Churyumov-Gerasimenko. Microscale investigations show that comet dust and cosmic dust are particles of unequilibrated materials, including aggregates of materials unequilibrated at submicron scales. We call unequilibrated materials "primitive" and we deduce they were incorporated into ice-­-rich (H2O-, CO2-, and CO-ice) parent bodies that remained cold, i.e., into comets, because of the lack of aqueous or thermal alteration since particle aggregation; yet some Stardust olivines suggest mild thermal metamorphism. Primitive particles exhibit a diverse range of: structure and typology; size and size distribution of constituents; concentration and form of carbonaceous and organic matter; D-, N-, and O- isotopic enhancements over solar; Mg-, Fe-contentsof thesilicate minerals; the compositions and concentrations of sulfides, and of less abundant mineral species such as chondrules, CAIs and carbonates. The unifomity within a group of samples points to: aerodynamic sorting of particles and/or particle constituents; the inclusion of a limited range of oxygen fugacities; the inclusion or exclusion of chondrules; a selection of organics. The properites of primitive particles imply there were disk processes that resulted in different comets having particular selections of primitive materials. The diversity of primitive particles has implications for the diversity of materials in the protoplanetary disk present at the time and in the region where the comets formed.

Initial results from SKiYMET meteor radar at Thumba (8.5°N, 77°E): 2. Gravity wave observations in the MLT region

Science.gov (United States)

Kumar, Karanam Kishore; Antonita, T. Maria; Shelbi, S. T.

2007-12-01

In the present communication, allSKy interferometric METeor (SKiYMET) radar observations of gravity wave activity in the mesosphere lower thermosphere (MLT) region over Thumba (8.5°N, 77°E) are presented. The present meteor radar system provides hourly zonal and meridional winds in the MLT region, which can be readily used for studying the tides, planetary waves, gravity waves of periods 2-6 hours, and other long period oscillations in this region. However, these hourly winds are not sufficient for studying short period gravity waves having periods less than an hour, which demand high temporal resolution measurements. Even though the winds are estimated on an hourly basis, information such as zenith angle, azimuth angle, and radial velocity of each detected meteor are archived. Using these details of the meteor, an algorithm is developed to obtain the 15-min temporal resolution wind data. The output of the algorithm is compared with hourly wind data, and it showed a good agreement during the high meteor shower periods. Most of the times high meteor counts are observed during late night and early morning hours (local) over this latitude. Continuous wind measurements during the high meteor shower periods are used for studying the gravity wave activity in the MLT region. As the wave activity is intermittent and nonstationary, wavelet analysis has been used for delineating the wave features. The results showed the upward propagating intermittent gravity waves with periods 1-2 and 4-5 hours. The new aspect of the present communication is the usage of meteor radar for gravity wave studies for the first time over this latitude and studying their seasonal variability.

Modelling the motion of meteors in the Earth's atmosphere

International Nuclear Information System (INIS)

Rodrigues, Hilário

2013-01-01

This work discusses the motion of meteors in the Earth's atmosphere. The equations of motion of the projectile are presented and a simplified numerical approach to solve them is discussed. An algorithm for solving the equations of motion is constructed, and implemented in a very simple way using Excel software. The paper is intended as an example of the application of Newton's laws of motion at undergraduate level. (paper)

Disruption of microtubule network rescues aberrant actin comets in dynamin2-depleted cells.

Directory of Open Access Journals (Sweden)

Yuji Henmi

Full Text Available A large GTPase dynamin, which is required for endocytic vesicle formation, regulates the actin cytoskeleton through its interaction with cortactin. Dynamin2 mutants impair the formation of actin comets, which are induced by Listeria monocytogenes or phosphatidylinositol-4-phosphate 5-kinase. However, the role of dynamin2 in the regulation of the actin comet is still unclear. Here we show that aberrant actin comets in dynamin2-depleted cells were rescued by disrupting of microtubule networks. Depletion of dynamin2, but not cortactin, significantly reduced the length and the speed of actin comets induced by Listeria. This implies that dynamin2 may regulate the actin comet in a cortactin-independent manner. As dynamin regulates microtubules, we investigated whether perturbation of microtubules would rescue actin comet formation in dynamin2-depleted cells. Treatment with taxol or colchicine created a microtubule-free space in the cytoplasm, and made no difference between control and dynamin2 siRNA cells. This suggests that the alteration of microtubules by dynamin2 depletion reduced the length and the speed of the actin comet.

Comet 81P/Wild 2 under a microscope

Energy Technology Data Exchange (ETDEWEB)

Brownlee, D; Tsou, P; Aleon, J; Alexander, C; Araki, T; Bajt, S; Baratta, G A; Bastien, R; Bland, P; Bleuet, P; Borg, J; Bradley, J P; Brearley, A; Brenker, F; Brennan, S; Bridges, J C; Browning, N; Brucato, J R; Bullock, E; Burchell, M J; Busemann, H; Butterworth, A; Chaussidon, M; Cheuvront, A; Chi, M; Cintala, M J; Clark, B C; Clemett, S J; Cody, G; Colangeli, L; Cooper, G; Cordier, P; Daghlian, C; Dai, Z R; D' Hendecourt, L; Djouadi, Z; Dominguez, G; Duxbury, T; Dworkin, J P; Ebel, D; Economou, T E; Fairey, S J; Fallon, S; Ferrini, G; Ferroir, T; Fleckenstein, H; Floss, C; Flynn, G; Franchi, I A; Fries, M; Gainsforth, Z; Gallien, J; Genge, M; Gilles, M K; Gillet, P; Gilmour, J; Glavin, D P; Gounelle, M; Grady, M M; Graham, G A; Grant, P G; Green, S F; Grossemy, F; Grossman, L; Grossman, J; Guan, Y; Hagiya, K; Harvey, R; Heck, P; Herzog, G F; Hoppe, P; Horz, F; Huth, J; Hutcheon, I D; Ishii, H; Ito, M; Jacob, D; Jacobsen, C; Jacobsen, S; Joswiak, D; Kearsley, A T; Keller, L; Khodja, H; Kilcoyne, A D; Kissel, J; Krot, A; Langenhorst, F; Lanzirotti, A; Le, L; Leshin, L; Leitner, J; Lemelle, L; Leroux, H; Liu, M; Luening, K; Lyon, I; MacPherson, G; Marcus, M A; Marhas, K; Matrajt, G; Meibom, A; Mennella, V; Messenger, K; Mikouchi, T; Mostefaoui, S; Nakamura, T; Nakano, T; Newville, M; Nittler, L R; Ohnishi, I; Ohsumi, K; Okudaira, K; Papanastassiou, D A; Palma, R; Palumbo, M E; Pepin, R O; Perkins, D; Perronnet, M; Pianetta, P; Rao, W; Rietmeijer, F; Robert, F; Rost, D; Rotundi, A; Ryan, R; Sandford, S A; Schwandt, C S; See, T H; Schlutter, D; Sheffield-Parker, J; Simionovici, A; Simon, S; Sitnitsky, I; Snead, C J; Spencer, M K; Stadermann, F J; Steele, A; Stephan, T; Stroud, R; Susini, J; Sutton, S R; Taheri, M; Taylor, S; Teslich, N; Tomeoka, K; Tomioka, N; Toppani, A; Trigo-Rodriguez, J M; Troadec, D; Tsuchiyama, A; Tuzolino, A J; Tyliszczak, T; Uesugi, K; Velbel, M; Vellenga, J; Vicenzi, E; Vincze, L; Warren, J; Weber, I; Weisberg, M; Westphal, A J; Wirick, S; Wooden, D; Wopenka, B; Wozniakiewicz, P; Wright, I; Yabuta, K; Yano, H; Young, E D; Zare, R N; Zega, T

2006-10-12

The Stardust spacecraft collected thousands of particles from comet 81P/Wild 2 and returned them to Earth for laboratory study. The preliminary examination of these samples shows that the nonvolatile portion of the comet is an unequilibrated assortment of materials that have both presolar and solar system origin. The comet contains an abundance of silicate grains that are much larger than predictions of interstellar grain models, and many of these are high-temperature minerals that appear to have formed in the inner regions of the solar nebula. Their presence in a comet proves that the formation of the solar system included mixing on the grandest scales. Stardust was the first mission to return solid samples from a specific astronomical body other than the Moon. The mission, part of the NASA Discovery program, retrieved samples from a comet that is believed to have formed at the outer fringe of the solar nebula, just beyond the most distant planet. The samples, isolated from the planetary region of the solar system for billions of years, provide new insight into the formation of the solar system. The samples provide unprecedented opportunities both to corroborate astronomical (remote sensing) and sample analysis information (ground truth) on a known primitive solar system body and to compare preserved building blocks from the edge of the planetary system with sample-derived and astronomical data for asteroids, small bodies that formed more than an order of magnitude closer to the Sun. The asteroids, parents of most meteorites, formed by accretion of solids in warmer, denser, more collisionally evolved inner regions of the solar nebula where violent nebular events were capable of flash-melting millimeter-sized rocks, whereas comets formed in the coldest, least dense region. The samples collected by Stardust are the first primitive materials from a known body, and as such they provide contextual insight for all primitive meteoritic samples. About 200 investigators

Comet Dust: The Story of Planet Formation as Told by the Tiniest of Particles

Science.gov (United States)

Wooden, D. H.

2005-01-01

Our planetary system formed out of a gas-rich disk-shaped nebula with the early Sun at its center. Many small icy bodies were consumed by the formation of the giant planets. However, many km-size icy bodies were tossed out of the giant-planet region to the cold, distant reaches of our solar system. Comets remained in their places of cold storage until perturbed into orbits that carry them into the inner solar system where they pass relatively close to the Sun. Comets are warmed by the Sun and shed material from their outer layers. The ices and gases shed by comets reveal simple and complex organic molecules were present at the time and in the region of the formation of the giant planets. Where the Earth was forming was too hot and had too intense sunlight for many of these ices and molecules to survive. The dust shed by comets tells us that some stardust survived unaltered but much of the dust was heated and crystallized before becoming part of the comet. Therefore, comet dust grains tell of large radial migrations from the cold outer reaches near Neptune into the hot regions near the forming Sun, and then back out to the cold regions where icy comets were accreting and forming. On 2005 July 4, the NASA Deep Impact Mission hit a comet and ejected primitive materials fiom its interior. These materials were not released into the comet s coma during normal activity. Despite the many passages of this comet close to the Sun, these primitive volatile gases and dust grains survived in its interior. Comet dust grains show that cold and hot materials were mixed into the same tiny particle very early in the formation of the solar system, and these aggregate dust grains never saw high temperatures again. The survival of primitive materials in comet nuclei suggests comets could have delivered organic molecules and primitive dust grains to early Earth.