Comet Publications Used in Preparing
the 2005 Triennial Report
The ADS abstract service (http://adsabs.harvard.edu/abstract_service.html)
was searched for papers appearing in refereed publications during the period
between July 2002 and June 2005, inclusive, on the term "COMET". This
returned 917 abstracts plus 37 papers published in the Comet II book that are
not considered to be refereed papers by the ADS.
From these 954 papers, 361
were selected as falling under the purview of the Physical Studies of Comets
Working Group. That is, no papers on purely meteoritic, interplanetary dust
(including cometary trails), dynamical, or astrometric
studies were included. Papers presenting
ground-based instrumentation or space instrumentation or missions for future
comet studies were not taken into consideration either. However, papers
presenting laboratory experiments for the understanding of the origin of
cometary material were included.
The 361 relevant papers were
sorted into nine categories and a brief description of the scientific results
in each category was written citing a subset of them. The titles and abstracts
for the entire list of 361 papers appear below. The order of this list is that
returned by the ADS search engine, i.e., it is not in alphabetical or
chronological order. A paper cited in the IAU Triennial Report can be located
using the browser or PDF reader’s “Find” function.
This list was prepared by D.
Bockelée-Morvan on 20 September 2005
|
Title: |
|
On the ejection velocity of meteoroids from comets |
|
Authors: |
|
|
|
Affiliation: |
|
AA( |
|
Journal: |
|
Monthly Notice of the Royal Astronomical Society, Volume 337, Issue 3, pp. 1081-1086. (MNRAS Homepage) |
|
Publication Date: |
|
12/2002 |
|
Origin: |
|
MNRAS |
|
MNRAS Keywords: |
|
comets: general, meteors, meteoroids |
|
Abstract Copyright: |
|
(c) RAS |
|
DOI: |
|
|
|
Bibliographic Code: |
|
2002MNRAS.337.1081M |
The ejection of meteoroids from comets has been discussed by many authors and is a problem that is important both for a full understanding of cometary processes and for the evolution of meteoroid streams. We reinvestigate the problem here, starting from simple physical principles, and compare the results that we obtain with those of other authors, in particular Whipple.
|
Title: |
|
Erratum: On the source of C(1D) atoms in cometary comae |
|
Authors: |
|
|
|
Journal: |
|
Monthly Notice of the Royal Astronomical Society, Volume 337, Issue 2, pp. 768-768. (MNRAS Homepage) |
|
Publication Date: |
|
12/2002 |
|
Origin: |
|
MNRAS |
|
MNRAS Keywords: |
|
errata, addenda, molecular processes, comets: individual: Comet Halley, comets: individual: Comet West, comets: individual: Comet Bradfield (1979 X) |
|
Abstract Copyright: |
|
(c) RAS |
|
DOI: |
|
|
|
Bibliographic Code: |
|
2002MNRAS.337..768S |
Not Available
|
Title: |
|
X-Ray Emission from Comet McNaught-Hartley (C/1999 T1) |
|
Authors: |
|
Krasnopolsky, V. A.; Christian, D. J.; Kharchenko, V.; Dalgarno, A.; Wolk, S. J.; Lisse, C. M.; Stern, S. A. |
|
Journal: |
|
Icarus, Volume 160, Issue 2, p. 437-447. (Icarus Homepage) |
|
Publication Date: |
|
12/2002 |
|
Origin: |
|
ELSEVIER |
|
Abstract Copyright: |
|
(c) 2002 Elsevier Science ( |
|
DOI: |
|
|
|
Bibliographic Code: |
|
2002Icar..160..437K |
Comet McNaught-Hartley was observed in five 1-h exposures on January 8-14 2001 using the advanced CCD imaging spectrometer on board the Chandra X-ray Observatory. The X-ray image of the comet does not show a crescent-like shape. The brightest region is offset from the nucleus between the sunward and comet velocity directions. The comet mean X-ray luminosity is equal to 7.8×1015 erg s-1 for photon energy E>150 eV and aperture ρ=1.5×105 km where the comet X-ray brightness exceeds 20% of the peak value. Gas production rate was 1029 s-1 during the observations, and the efficiency of X-ray excitation was equal to 4×10-14 erg AU3/2. Day-to-day variations in X-rays reached a factor of 5. The strongest short-term variation was by a factor of 1.75 for 1600 s. This variation may be explained by a decline in the solar-wind flux by the same factor in ~800 s. The comet and Earth were seeing different faces of the Sun, and time delay in the solar-wind events on the Earth and the comet was long, equal to 6 days. The best correlation between the comet X-ray luminosity and the solar-wind proton density is for the time delay of 5.5 days and may be explained by the higher velocity of heavy ions. Careful background subtraction made it possible to extract the comet spectrum from 150 to 1000 eV. No signal was detected at E>1000 eV, and a 3σ upper limit to any emission with E>1000 eV is 0.3% of the photon emission at 150-1000 eV. The best χ2-fit model to the spectrum consists of nine narrow emission features. The emission energies and intensities are in good agreement with a charge exchange spectrum calculated by us for the slow solar wind. Using this spectrum, we identify the observed emissions as (Ne7++Mg7++Mg8+) at 195 eV, (Mg8++Mg9++Si8+) at 250 eV, C5+ at 370 and 460 eV, O6+ at 560 eV, O7+ at 650, 780, and 840 eV, and Ne8+ at 940 eV. X-ray spectroscopy of comets may be used to diagnose the solar-wind composition and its interaction with comets.
|
Title: |
|
The Dust in Comet C/1999 S4 (LINEAR) during Its Disintegration: Narrow-Band Images, Color Maps, and Dynamical Models |
|
Authors: |
|
Bonev, T.; Jockers, K.; Petrova, E.; Delva, M.; Borisov, G.; Ivanova, A. |
|
Affiliation: |
|
AA(Institute of Astronomy, 72 Tsarigradsko chaussée Boulevard, Sofia, 1784 Bulgaria), AB(Max-Planck-Institut für Aeronomie, Katlenburg-Lindau, 37191, Germany), AC(Space Research Institute, Moscow Russia), AD(Institut für Weltraumforschung, Graz Austria), AE(Institute of Astronomy, 72 Tsarigradsko chaussée Boulevard, Sofia, 1784 Bulgaria), AF(Institute of Astronomy, 72 Tsarigradsko chaussée Boulevard, Sofia, 1784 Bulgaria) |
|
Journal: |
|
Icarus, Volume 160, Issue 2, p. 419-436. (Icarus Homepage) |
|
Publication Date: |
|
12/2002 |
|
Origin: |
|
ELSEVIER |
|
Abstract Copyright: |
|
(c) 2002 Elsevier Science ( |
|
DOI: |
|
|
|
Bibliographic Code: |
|
2002Icar..160..419B |
Comet C/1999 S4 was observed with
the 2m-telescopes of the Bulgarian National Observatory and Pik Terskol
Observatory, Northern Caucasus, Russia, at the time of its disintegration. Maps
of the dust brightness and color were constructed from images obtained in red
and blue continuum windows, free from cometary molecular emissions. We analyze the
dust environment of Comet C/1999 S4 (LINEAR) taking into account the observed
changes apparent in the brightness images and in plots of Afρ profiles as
function of the projected distance ρ from the nucleus. We also make use of the
syndyne-synchrone formalism and of a
|
Title: |
|
A McDonald Observatory Study of Comet 19P/Borrelly: Placing the Deep Space 1 Observations into a Broader Context |
|
Authors: |
|
|
|
Journal: |
|
Icarus, Volume 160, Issue 2, p. 398-418. (Icarus Homepage) |
|
Publication Date: |
|
12/2002 |
|
Origin: |
|
ELSEVIER |
|
Abstract Copyright: |
|
(c) 2002 Elsevier Science ( |
|
DOI: |
|
|
|
Bibliographic Code: |
|
2002Icar..160..398F |
We present imaging and spectroscopic data on Comet 19P/Borrelly that were obtained around the time of the Deep Space 1 encounter and in subsequent months. In the four months after perihelion, the comet showed a strong primary (sunward) jet that is aligned with the nucleus' spin axis. A weaker secondary jet on the opposite hemisphere appeared to become active around the end of 2001, when the primary jet was shutting down. We investigated the gas and dust distributions in the coma, which exhibited strong asymmetries in the sunward/antisunward direction. A comparison of the CN and C2 distributions from 2001 and 1994 (during times when the viewing geometry was almost identical) shows that each species is remarkably similar, indicating that the comet's activity is essentially repeatable from one apparition to the next. We also measured the dust reflectivities as a function of wavelength and position in the coma, and though the dust was very red overall, we again found variations with respect to the solar direction. We used the primary jet's appearance on several dates to determine the orientation of the rotation pole to be α=214°, δ=-5°. We compared this result to published images from 1994 to conclude that the nucleus is near a state of simple rotation. However, data from the 1911, 1918, and 1925 apparitions indicate that the pole might have shifted by 5-10° since the comet was discovered. Using our pole position and the published nongravitational acceleration terms, we computed a mass of the nucleus of 3.3×1016 g and a bulk density of 0.49 g cm-3 (with a range of 0.29<ρ<0.83 g cm-3). This result is the least model-dependent comet density known to date.
|
Title: |
|
Long-Term Evolution of Objects in the Kuiper Belt Zone-Effects of Insolation and Radiogenic Heating |
|
Authors: |
|
|
|
Affiliation: |
|
AA(Department of Geophysics and Planetary Sciences, Tel Aviv University, Ramat Aviv, 69978 Israel), AB(Department of Geophysics and Planetary Sciences, Tel Aviv University, Ramat Aviv, 69978 Israel), AC(Department of Geophysics and Planetary Sciences, Tel Aviv University, Ramat Aviv, 69978 Israel), AD(Department of Geophysics and Planetary Sciences, Tel Aviv University, Ramat Aviv, 69978, Israel) |
|
Journal: |
|
Icarus, Volume 160, Issue 2, p. 300-312. (Icarus Homepage) |
|
Publication Date: |
|
12/2002 |
|
Origin: |
|
ELSEVIER |
|
Abstract Copyright: |
|
(c) 2002 Elsevier Science ( |
|
DOI: |
|
|
|
Bibliographic Code: |
|
2002Icar..160..300C |
The Kuiper Belt zone is unique insofar as the major heat sources of objects a few tens of kilometers in size-solar radiation on the one hand and radioactive decay on the other-have comparable power. This leads to unique evolutionary patterns, with heat waves propagating inward from the irradiated surface and outward from the radioactively heated interior. A major radioactive source that is considered in this study is 26Al. The long-term evolution of several models with characteristics typical of Kuiper Belt objects is followed by means of a 1-D numerical code that solves the heat and mass balance equations on a spherically symmetric grid. The free parameters considered are radius (10-500 km), heliocentric distance (30-120 AU), and initial 26Al content (0-5×10-8 by mass). The initial composition assumed is a porous mixture of ices (H2O, CO, and CO2) and dust. Gases released in the interior are allowed to escape to the surface. It is shown that, depending on parameters, the interior may reach quite high temperatures (up to 180 K). The models suggest that Kuiper Belt objects are likely to lose the ices of very volatile species during early evolution; ices of less volatile species are retained in a surface layer, about 1 km thick. The models indicate that the amorphous ice crystallizes in the interior, and hence some objects may also lose part of the volatiles trapped in amorphous ice. Generally, the outer layers are far less affected than the inner part, resulting in a stratified composition and altered porosity distribution. These changes in structure and composition should have significant consequences for the short-period comets, which are believed to be descendants of Kuiper Belt objects.
|
Title: |
|
Spectrophotometry of the comets C/2000 WM1 (LINEAR) and C/2002 C1 (IkeyaZhang) |
|
Authors: |
|
|
|
Affiliation: |
|
AA(State Observatory, |
|
Journal: |
|
Bulletin of the Astronomical Society of India, vol. 30, p.943-950 (BASI Homepage) |
|
Publication Date: |
|
12/2002 |
|
Origin: |
|
BASI |
|
Keywords: |
|
Comet spectrophotometry, column densities and production rates |
|
Bibliographic Code: |
|
2002BASI...30..943S |
Spectrophotometric observations of the coma of the comets C/2000 WM1 (LINEAR) and C/ 2002 C1 (Ikeya-Zhang) were taken during Nov, Dec 2001 and Mar, Apr 2002 respectively with 104-cm telescope of the State Observatory, Nainital. CN (3883) and C2 swan bands (4695, 5165 and 5538) have been identified in both the comets. Na I emission was detected in comet Ikeya-Zhang. An estimate of CN and C2 abundances and their production rates have been derived. Dust production rates have also been determined.
|
Title: |
|
Fragmentation Origin of Major Sungrazing Comets C/1970 K1, C/1880 C1, and C/1843 D1 |
|
Authors: |
|
|
|
Affiliation: |
|
AA(Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109; zs@sek.jpl.nasa.gov, ), AB(Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109; zs@sek.jpl.nasa.gov, ) |
|
Journal: |
|
The Astrophysical Journal, Volume 581, Issue 2, pp. 1389-1398. (ApJ Homepage) |
|
Publication Date: |
|
12/2002 |
|
Origin: |
|
UCP |
|
ApJ Keywords: |
|
Comets: General, Comets: Individual: Alphanumeric: X/1106 C1, comets: individual (C/1843 D1, C/1880 C1), Comets: Individual: Alphanumeric: C/1882 R1, Comets: Individual: Alphanumeric: C/1887 B1, Comets: Individual: Alphanumeric: C/1945 X1, Comets: Individual: Alphanumeric: C/1963 R1, Comets: Individual: Alphanumeric: C/1965 S1, Comets: Individual: Alphanumeric: C/1970 K1, Comets: Individual: Alphanumeric: D/1993 F2, Methods: Data Analysis |
|
Abstract Copyright: |
|
(c) 2002: The American Astronomical Society |
|
DOI: |
|
|
|
Bibliographic Code: |
|
2002ApJ...581.1389S |
Following our recent successful modeling of the common origin of two of the brightest members of the Kreutz system of sungrazing comets, we now examine three other objects: C/1970 K1 (White-Ortiz-Bolelli), the most recent sungrazer discovered from Earth, C/1880 C1 (Great Southern Comet), and C/1843 D1 (Great March Comet). For White-Ortiz-Bolelli, five possible origin and orbit evolution scenarios are explored. We find that its parent was neither C/1965 S1 (Ikeya-Seki), nor C/1882 R1 (Great September Comet), nor the comet of 1106 (the presumed parent of Ikeya-Seki and the 1882 comet). The motion of C/1970 K1 is consistent with a scenario in which the parent was an unknown fragment that separated from the 1106 comet at the same time as, or shortly before, Ikeya-Seki and passed through perihelion in 1970 June-July, shortly after White-Ortiz-Bolelli. The separation of White-Ortiz-Bolelli from this fragment is found to have occurred around the mid-eighteenth century, at a heliocentric distance of about 150 AU, with a relative velocity of 3-5 m s-1 in the general direction of the Sun and to the north of the orbital plane. On the other hand, we conclude that the 1880 comet separated directly from C/1843 D1, the second brightest known sungrazer, some 100-150 days after the 1843 comet's previous perihelion passage in the eleventh century, at 2.5-3 AU from the Sun, with a relative velocity of slightly more than 7 m s-1 in the generally antisolar direction and to the south of the orbital plane. The pattern of fragmentation of the Kreutz system's members discovered from Earth begins to resemble the evolution of the system's minor fragments detected coronagraphically from aboard the SOHO spacecraft, and there is significant qualitative similarity with fragmentation of comet D/1993 F2 (Shoemaker-Levy 9).
|
Title: |
|
Measurements of [C I] Emission from Comet Hale-Bopp |
|
Authors: |
|
Oliversen, R. J.; Doane, N.; Scherb, F.; Harris, W. M.; Morgenthaler, J. P. |
|
Affiliation: |
|
AA(NASA Goddard Space Flight Center, Greenbelt, MD 20771; ron@midnight.gsfc.nasa.gov.; Visiting Astronomer at the National Solar Observatory, operated by the Association for Research in Astronomy, under contract to the National Science Foundation.), AB(Visiting Astronomer at the National Solar Observatory, operated by the Association for Research in Astronomy, under contract to the National Science Foundation.; NASA Goddard Space Flight Center, Greenbelt, MD 20771.; Currently at Department of Astronomy, University of Wisconsin, Madison, WI 53706; doane@astro.wisc.edu.), AC(Visiting Astronomer at the National Solar Observatory, operated by the Association for Research in Astronomy, under contract to the National Science Foundation.; Department of Physics, University of Wisconsin, Madison, WI 53706; scherb@physics.wisc.edu, jpmorgen@alum.mit.edu.), AD(Space Astronomy Lab, University of Wisconsin, Madison, WI 53706; wharris@sal.wisc.edu.), AE(Department of Physics, University of Wisconsin, Madison, WI 53706; scherb@physics.wisc.edu, jpmorgen@alum.mit.edu.) |
|
Journal: |
|
The Astrophysical Journal, Volume 581, Issue 1, pp. 770-775. (ApJ Homepage) |
|
Publication Date: |
|
12/2002 |
|
Origin: |
|
UCP |
|
ApJ Keywords: |
|
Comets: Individual: Name: Hale-Bopp (C/1995 O1) |
|
Abstract Copyright: |
|
(c) 2002: The American Astronomical Society |
|
DOI: |
|
|
|
Bibliographic Code: |
|
2002ApJ...581..770O |
We present quantitative
measurements of cometary [C I] 9850 Å emission obtained during observations of
comet Hale-Bopp (C/1995 O1) in 1997 March and April. The observations were
carried out using a high-resolution (λ/Δλ~40,000) Fabry-Pérot/CCD spectrometer
at the McMath-Pierce Solar telescope on
|
Title: |
|
Common Origin of Two Major Sungrazing Comets |
|
Authors: |
|
|
|
Affiliation: |
|
AA(Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109; zs@sek.jpl.nasa.gov, ), AB(Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109; zs@sek.jpl.nasa.gov, ) |
|
Journal: |
|
The Astrophysical Journal, Volume 581, Issue 1, pp. 760-769. (ApJ Homepage) |
|
Publication Date: |
|
12/2002 |
|
Origin: |
|
UCP |
|
ApJ Keywords: |
|
Celestial Mechanics, Comets: General, Comets: Individual: Alphanumeric: X/1106 C1, comets: individual (C/1882 R1, C/1965 S1), Comets: Individual: Alphanumeric: D/1993 F2, Methods: Numerical |
|
Abstract Copyright: |
|
(c) 2002: The American Astronomical Society |
|
DOI: |
|
|
|
Bibliographic Code: |
|
2002ApJ...581..760S |
Our extensive orbital calculations show that the motion of comet C/1965 S1 (Ikeya-Seki), a major member of the Kreutz sungrazing system, can be derived from the motion of its ``sister'' comet C/1882 R1 (Great September Comet) on the assumption that the two objects are fragments of a common parent that split in the year 1106, at the time when a very bright comet appeared near the Sun according to a number of historical records. Specifically, the orbit of Ikeya-Seki derived from astrometric positions in 1965-1966 is matched with remarkably high accuracy, well within the errors of observation, by (1) integrating the motion of comet C/1882 R1 back to 1106; (2) launching from the parent a fragment some 18 days after perihelion, 0.75 AU from the Sun, with a relative velocity of about 7 m s-1 nearly in the antisolar direction; and (3) integrating the fragment's motion forward to 1965. We find that having the break-up closer to the Sun or before perihelion yields grossly inferior solutions. We conclude that the fragmentation event itself was not tidal in nature, but appears to have been due to rotational, and possibly other, forces acting on the parent comet, afflicted with cracks and fissures caused by the Sun's tidal forces a few weeks earlier. We note that the derived separation velocity is in the range established for nontidal fragmentation of minor sungrazers at large heliocentric distances and that there are obvious similarities with the behavior of comet D/1993 F2 (Shoemaker-Levy 9) following its close encounter with Jupiter in 1992 July.
|
Title: |
|
The Origin of the Solar Wind |
|
Authors: |
|
|
|
Journal: |
|
American Scientist, vol. 90, Issue 6, p.532 |
|
Publication Date: |
|
12/2002 |
|
Origin: |
|
WEB |
|
Bibliographic Code: |
|
2002AmSci..90..532W |
Nearly 1,400 years ago, Chinese astronomers noticed that comet tails always point away from the Sun. They concluded that the Sun must have <em>chi</em>—a basic life force—that blows the tails away. It wasn't until the middle of the 20th century that scientists understood that this "force" actually consisted of little pieces of the sun itself—protons and electrons—blowing out into the solar system as a "wind" at more than a million kilometers per hour. The traditional view of the solar wind's origins suggests that it originates from special regions on the Sun, called coronal holes. Woo and Habbal present new evidence showing that the wind actually emanates from all regions on the Sun.
|
Title: |
|
Production, processing and characterisation techniques for cosmic dust analogues |
|
Authors: |
|
Rotundi, A.; Brucato, J. R.; Colangeli, L.; Ferrini, G.; Mennella, V.; Palomba, E.; Palumbo, P. |
|
Affiliation: |
|
AA(Ist. di
Mat., Fis. e Appl., Università "Parthenope", Via A. De Gasperi 5,
I-80133 Napoli, Italy; rotundi@uninav.it) |
|
Journal: |
|
Meteoritics & Planetary Science, vol. 37, no. 11, pp. 1623-1635 (2002) |
|
Publication Date: |
|
11/2002 |
|
Origin: |
|
M&PS |
|
Bibliographic Code: |
|
2002M&PS...37.1623R |
The laboratory analyses of cosmic dust analogues, that in the context of this paper include interstellar, circumstellar as well as cometary dust, have a critical role in the study of circumstellar and cometary dust. The morphological, structural and chemical characterisation of these analogues are critical for comparisons of their IR and UV spectra with those obtained by astronomical observations, as well as for modelling purposes. Besides, the results from these laboratory studies are important to the success of space missions to comets when testing and calibrating the payload instruments. The interpretations of returned scientific data would benefit from the comparison with data recorded by the instruments in a laboratory setting for different classes of previously characterised analogues. We produced various types of condensed samples: (1) Mg,Fe-silicates, (olivine; pyroxene), (2) carbon-rich dust and (3) mixed carbon-silicate dust. The samples were prepared using different techniques, viz. (1) laser bombardment of solid targets in an Ar and O2 atmosphere, (2) arc discharge in an Ar and H2 atmosphere, and (3) grinding powders of natural minerals. We simulated various post-condensation processes, such as thermal annealing, UV irradiation, ion bombardment and exposure to atomic hydrogen. These processes produced compound samples of a wide range of physico-chemical properties. To identify their textures, morphologies, grain compositions and crystallographic properties we used electron microscopy and far-ultraviolet to far-infrared (millimiter range) spectroscopy.
|
Title: |
|
Low-energy helium ion irradiation-induced amorphization and chemical changes in olivine: Insights for silicate dust evolution in the interstellar medium |
|
Authors: |
|
Carrez, Philippe; Demyk, Karine; Cordier, Patrick; Gengembre, Léon; Grimblot, Jean; D'Hendecourt, Louis; Jones, Anthony P.; Leroux, Hugues |
|
Affiliation: |
|
AA(Laboratoire
de Structure et Propriétés de l'Etat Solide (ESA CNRS 8008)-Bât. C6,
Université des Sciences et Technologies de Lille, 59655 Villeneuve
d'Ascq-Cedex, |
|
Journal: |
|
Meteoritics & Planetary Science, vol. 37, no. 11, pp. 1599-1614 (2002) |
|
Publication Date: |
|
11/2002 |
|
Origin: |
|
M&PS |
|
Bibliographic Code: |
|
2002M&PS...37.1599C |
We present the results of irradiation experiments aimed at understanding the structural and chemical evolution of silicate grains in the interstellar medium (ISM). A series of He+ irradiation experiments have been performed on ultra-thin olivine, (Mg,Fe)2SiO4, samples having a high surface/volume (S/V) ratio, comparable to the expected S/V ratio of interstellar dust. The energies and fluences of the helium ions used in this study have been chosen to simulate the irradiation of interstellar dust grains in supernovae shock waves. The samples were mainly studied using Analytical Transmission Electron Microscopy (ATEM). Our results show that olivine is amorphized by low-energy ion irradiation. Changes in composition are also observed. In particular, irradiation leads to a decrease of the atomic ratios O/Si and Mg/Si as determined by X-ray Photoelectron Spectroscopy (XPS) and by X-ray Energy Dispersive Spectroscopy (EDS). This chemical evolution is due to the differential sputtering of atoms near the surfaces. We also observe a reduction process resulting in the formation of metallic iron. The use of very thin samples emphasizes the role of surface/volume ratio and thus the importance of the particle size in the irradiation-induced effects. These results allow us to account qualitatively for the observed properties of interstellar grains in different environments, i.e., at different stages of their evolution : chemical and structural evolution in the interstellar medium, from olivine to pyroxene-type and from crystalline to amorphous silicates, porosity of cometary grains as well as the formation of metallic inclusions in silicates.
|
Title: |
|
Condensation processes in astrophysical environments: The composition and structure of cometary grains |
|
Authors: |
|
Nuth, Joseph A., III; Rietmeijer, Frans J. M.; Hill, Hugh G. M. |
|
Affiliation: |
|
AA(Astrochemistry Branch, Code 691, NASA's Goddard Space Flight Center, Greenbelt, Maryland 20771, USA; nuth@gsfc.nasa.gov) |
|
Journal: |
|
Meteoritics & Planetary Science, vol. 37, no. 11, pp. 1579-1590 (2002) |
|
Publication Date: |
|
11/2002 |
|
Origin: |
|
M&PS |
|
Bibliographic Code: |
|
2002M&PS...37.1579N |
We review the results of our recent experimental studies of astrophysical dust analogs. We discuss the condensation of amorphous silicates from mixed metal vapors, including evidence that such condensates form with metastable eutectic compositions. We consider the spectral evolution of amorphous magnesium silicate condensates as a function of time and temperature. Magnesium silicate smokes anneal readily at temperatures of ~1000-1100 K. In contrast we find that iron silicates require much higher temperatures (~1300 K) to bring about similar changes on the same timescale (days to months). We first apply these results to ISO observations of crystalline magnesium silicate grains around high-mass-outflow AGB stars in order to demonstrate their general utility in a rather simple environment. Finally, we apply these experimental results to infrared observations of comets and protostars in order to derive some interesting conclusions regarding large-scale nebular dynamics, the natural production of organic molecules in protostellar nebulae and the use of crystalline magnesium silicates as a relative indicator of a comet's formation age.
|
Title: |
|
Hydrogen cyanide in comet C/1996 B2 Hyakutake |
|
Authors: |
|
Magee-Sauer, Karen; Mumma, Michael J.; DiSanti, Michael A.; Dello Russo, Neil |
|
Journal: |
|
Journal of Geophysical Research (Planets), Volume 107, Issue E11, pp. 6-1, CiteID 5096, DOI 10.1029/2002JE001863 (JGRE Homepage) |
|
Publication Date: |
|
11/2002 |
|
Origin: |
|
AGU |
|
AGU Keywords: |
|
Planetology: Solar System Objects: Comets, Planetology: Comets and Small Bodies: Composition, Planetology: Comets and Small Bodies: Atmospheres-composition and chemistry, |
|
Abstract Copyright: |
|
(c) 2002: American Geophysical |
|
DOI: |
|
|
|
Bibliographic Code: |
|
2002JGRE.107k....6M |
Spectral emission from HCN in C/1996 B2 Hyakutake was detected on UT 1996 March 24.4 (rh = 1.06 AU, Δ = 0.106 AU), using the CSHELL infrared spectrometer at the NASA Infrared Telescope Facility. A Boltzmann analysis of eight ro-vibrational lines in the ν3 band returned a rotational temperature (83 +/- 9 K) for a region centered on the nucleus. The global HCN production rate was (4.50 +/- 0.81) × 1026 molecules s-1. The HCN abundance relative to water is then (0.18 +/- 0.04)%, based on direct measurements of H2O made on the same night with the same instrument and reduced with the same data processing algorithms. The measured spatial distribution for HCN is consistent with its release at the nucleus; no significant contribution from a distributed source is required within ~600 km of the nucleus. We use these data to obtain insights regarding the origin of HCN in this comet.
|
Title: |
|
Production of ethane and water in comet C/1996 B2 Hyakutake |
|
Authors: |
|
Dello Russo, Neil Dello; Mumma, Michael J.; DiSanti, Michael A.; Magee-Sauer, Karen |
|
Journal: |
|
Journal of Geophysical Research (Planets), Volume 107, Issue E11, pp. 5-1, CiteID 5095, DOI 10.1029/2001JE001838 (JGRE Homepage) |
|
Publication Date: |
|
11/2002 |
|
Origin: |
|
AGU |
|
AGU Keywords: |
|
Planetology: Comets and Small Bodies: Atmospheres-composition and chemistry, Planetology: Comets and Small Bodies: Composition, Planetology: Comets and Small Bodies: Ice, Planetology: Comets and Small Bodies: Radiation and spectra, |
|
Abstract Copyright: |
|
(c) 2002: American Geophysical |
|
DOI: |
|
|
|
Bibliographic Code: |
|
2002JGRE.107k....5D |
Ethane (C2H6) and water (H2O) were detected in Comet C/1996 B2 Hyakutake between UT 1996 March 23.4 (Rh = 1.08 AU preperihelion) and 1996 April 12.2 (Rh = 0.64 AU preperihelion). Our long-slit infrared spectra featured both high spectral dispersion and high spatial resolution about the nucleus, permitting the extraction of rotational temperatures, production rates, and spatial distributions of species along the slit. Production rates were measured for water (on four dates) and ethane (on three dates). Their average relative abundance was C2H6/H2O = (6.2 +/- 0.7) × 10-3. The spatial distributions of C2H6 and H2O molecules in the coma were consistent with both species being released directly from the nucleus on all dates, although asymmetries about the nucleus are seen for both gas and dust.
|
Title: |
|
Experimental levitation of dust grains in a plasma sheath |
|
Authors: |
|
Sickafoose, A. A.; Colwell, J. E.; Horányi, M.; Robertson, S. |
|
Journal: |
|
Journal of Geophysical Research (Space Physics), Volume 107, Issue A11, pp. SMP 37-1, CiteID 1408, DOI 10.1029/2002JA009347 (JGRA Homepage) |
|
Publication Date: |
|
11/2002 |
|
Origin: |
|
AGU |
|
AGU Keywords: |
|
Space Plasma Physics: Laboratory studies, Space Plasma Physics: Experimental and mathematical techniques, Planetology: Solar System Objects: Dust, Planetology: Comets and Small Bodies: Dust, |
|
Abstract Copyright: |
|
(c) 2002: American Geophysical |
|
DOI: |
|
|
|
Bibliographic Code: |
|
2002JGRA.107kSMP37S |
Dust grains have been observed to levitate above the surface of the Moon and as spokes in Saturn's rings. In order to gain a better understanding of these observations, we have performed levitation experiments on dust grains in a low-density plasma. Plasma sheath potential profiles, measured by an emissive probe, are used to determine the spatial dependence of the electric force on a grain in the sheath. The observed levitation height agrees with the values calculated using orbital-motion-limited charging theory and force balance equations. Levitating grains were also exposed to an ultraviolet light source to induce photoemission. Three types of dust were investigated: polystyrene divinylbenzene microspheres 10.0 +/- 0.5 μm in diameter, glass microballoons <38 μm in diameter, and JSC-1 (lunar regolith simulant) <25 μm in diameter. Our experimental results show that (1) various types and sizes of grains can levitate in a plasma sheath above a conducting surface; (2) levitating grains of a standard size float at a height corresponding to that predicted by theory; (3) exposure to UV light causes the grain levitation height to decrease slightly as a result of less negative charge; and (4) a mechanism to inject grains into the sheath is not necessary if the electric field is sufficiently strong.
|
Title: |
|
Is the D/H Ratio in the Comet Coma Equal to the D/H Ratio in the Comet Nucleus? |
|
Authors: |
|
|
|
Affiliation: |
|
AA(Department of Geophysics and Planetary Sciences, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Ramat Aviv Israel), AB(Department of Geophysics and Planetary Sciences, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Ramat Aviv Israel), AC(Department of Geophysics and Planetary Sciences, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Ramat Aviv Israel) |
|
Journal: |
|
Icarus, Volume 160, Issue 1, p. 208-211. (Icarus Homepage) |
|
Publication Date: |
|
11/2002 |
|
Origin: |
|
ELSEVIER |
|
Abstract Copyright: |
|
(c) 2002 Elsevier Science ( |
|
DOI: |
|
|
|
Bibliographic Code: |
|
2002Icar..160..208P |
We present a simple, semianalytic model of the vaporization of H2O and HDO ice from a comet nucleus. We use this model to show that the flux of HDO relative to H2O can be much higher, at times, than would be expected from the D/H ratio in the nuclear ice itself. This effect varies with position in the comet's orbit. It is negligible sufficiently near the Sun but could lead to erroneous interpretations of the primordial D/H ratio in cometary ice if measurements are made in other parts of the cometary orbit.
|
Title: |
|
New Activity of Chiron: Results from 5 Years of Photometric Monitoring |
|
Authors: |
|
Duffard, René; Lazzaro, Daniela; Pinto, Sandro; Carvano, Jorge; Angeli, Claudia; Alvarez-Candal, Alvaro; Fernández, Silvia |
|
Affiliation: |
|
AA(Observatório
Nacional, Coordenação de Astronomía e Astrofísica, Rio de Janeiro, 20921-400,
Brazil), AB(Observatório Nacional, Coordenação de Astronomía e Astrofísica,
Rio de Janeiro, 20921-400 Brazil), AC(Observatório Nacional, Coordenação de
Astronomía e Astrofísica, Rio de Janeiro, 20921-400 Brazil), AD(Observatório
Nacional, Coordenação de Astronomía e Astrofísica, Rio de Janeiro, 20921-400
Brazil), AE(Observatório Nacional, Coordenação de Astronomía e Astrofísica,
Rio de Janeiro, 20921-400 Brazil), AF(Facultad de Matemática, Astronomía y
Física, Universidad Nacional de Córdoba, Córdoba, 5000 Argentina),
AG(Observatorio Astronómico, Universidad Nacional de Córdoba, Laprida 854,
Córdoba, 5000 Argentina) |
|
Journal: |
|
Icarus, Volume 160, Issue 1, p. 44-51. (Icarus Homepage) |
|
Publication Date: |
|
11/2002 |
|
Origin: |
|
ELSEVIER |
|
Abstract Copyright: |
|
(c) 2002 Elsevier Science ( |
|
DOI: |
|
|
|
Bibliographic Code: |
|
2002Icar..160...44D |
The results of photometric observations of Centaur object Chiron carried out at the Observatório do Pico dos Dias (OPD, Brazil), the Estación Astrofísica de Bosque Alegre (EABA, Argentina), and Complejo Astronómico El Leoncito (CASLEO, Argentina) from 1997 to 2001 are presented here. The analysis of the photometric data shows that the brightness of Chiron reached a minimum value in 1999 and began increasing again in 2000. The absolute magnitude, HV, varied from 7.26 in June 1999 to 5.78 in April 2001. The data tend to indicate that Chiron is starting a new outburst of activity which is compatible with a sporadic cometary behavior not related to heliocentric distance.
|
Title: |
|
The Jovian Stratosphere after Comet Shoemaker-Levy/9: Unusual Isotopic Ratios in Molecular Trace Constituents |
|
Authors: |
|
|
|
Affiliation: |
|
AA(Joint Astronomy Centre, 660 North A'ohōkū Place, Hilo, HI 96720; ), AB(LESIA, Observatoire de Paris, 5 Place Jules Janssen, F-92195 Meudon, France), AC(Institut de Radio Astronomie Millimétrique, 300 Rue de la Piscine, F-38406 Saint Martin d'Hères, France), AD(Institute for Astronomy, 2680 Woodlawn Drive, University of Hawaii at Manoa, Honolulu, HI 96822) |
|
Journal: |
|
The Astrophysical Journal, Volume 580, Issue 1, pp. 598-605. (ApJ Homepage) |
|
Publication Date: |
|
11/2002 |
|
Origin: |
|
UCP |
|
ApJ Keywords: |
|
Comets: Individual: Name: Shoemaker-Levy/9, Planets and Satellites: Individual: Jupiter, Submillimeter |
|
Abstract Copyright: |
|
(c) 2002: The American Astronomical Society |
|
DOI: |
|
|
|
Bibliographic Code: |
|
2002ApJ...580..598M |
Since the collision of comet Shoemaker-Levy/9 with Jupiter in 1994 July, a number of minor molecular species have been observed to persist in the stratosphere of the planet. Here we report observations acquired in 1998 September at frequencies near 350 GHz (wavelength 850 μm) of HCN and CS and their respective isotopomers H13CN, HC15N, and C34S. Through radiative transfer modeling of the observed lines, we find that the isotopic abundance ratios 12C/13C, 14N/15N, and 32S/34S are considerably elevated with respect to their terrestrial values. We speculate that this result indicates an unusual composition for comet Shoemaker-Levy/9, or that cometary grains evaporated in the collisions significantly modified the isotope ratios.
|
Title: |
|
Grain Properties of Comet C/1995 O1 (Hale-Bopp) |
|
Authors: |
|
Harker, David E.; Wooden, Diane H.; Woodward, Charles E.; Lisse, Carey M. |
|
Affiliation: |
|
AA(NASA Ames Research Center, Space Science Division, MS 245-3, Moffet Field, CA 94035-1000; National Research Council Associate.; Visiting Astronomer at the Infrared Telescope Facility, which is operated by the University of Hawaii under contract with the National Aeronautics and Space Administration.), AB(NASA Ames Research Center, Space Science Division, MS 245-3, Moffet Field, CA 94035-1000), AC(Department of Astronomy, University of Minnesota, 116 Church Street SE, Minneapolis, MN 55455), AD(Department of Astronomy, University of Maryland, College Park, MD 20742) |
|
Journal: |
|
The Astrophysical Journal, Volume 580, Issue 1, pp. 579-597. (ApJ Homepage) |
|
Publication Date: |
|
11/2002 |
|
Origin: |
|
UCP |
|
ApJ Keywords: |
|
Comets: General, comets: individual (C/1995 O1 Hale-Bopp), Infrared: Solar System |
|
Abstract Copyright: |
|
(c) 2002: The American Astronomical Society |
|
DOI: |
|
|
|
Bibliographic Code: |
|
2002ApJ...580..579H |
We present the analysis of 7.6-13.2 μm infrared (IR) spectrophotometry (R~=250) of comet C/1995 O1 (Hale-Bopp), in conjunction with concurrent observations that extend the wavelength coverage of the spectral energy distribution from near- to far-infrared wavelengths. The observations include temporal epochs preperihelion (1996 October and 1997 February UT), near perihelion (1997 April UT), and postperihelion (1997 June UT). Through the modeling of the thermal emission from small, amorphous carbon grains and crystalline and amorphous silicate grains in Hale-Bopp's coma, we find that as the comet approached perihelion, the grain size distribution (the Hanner modified power law) steepened (from N=3.4 preperihelion to N=3.7 near and postperihelion), along with an increase in the fractal porosity of larger (greater than 1 μm) grains. The peak of the grain size distribution remained constant (ap=0.2 μm) at each epoch. We attribute the emergence of the 9.3 μm peak near perihelion to crystalline orthopyroxene grains released during epochs of high jet activity. Crystalline silicates (olivine and orthopyroxene) make up about 30% (by mass) of the submicron-sized (<=1 μm) dust grains in Hale-Bopp's coma during each epoch.
|
Title: |
|
Laboratory study of annealed amorphous MgSiO3 silicate using IR spectroscopy and synchrotron X-ray diffraction |
|
Authors: |
|
Thompson, S. P.; Fonti, S.; Verrienti, C.; Blanco, A.; Orofino, V.; Tang, C. C. |
|
Affiliation: |
|
AA(Daresbury
Laboratory, Warrington, Cheshire WA4 4AD, Great Britain), AB(Dipartimento di
Fisica, Universita di Lecce, C. P. 193 - Via Arnesano, 73100 Lecce, Italy),
AC(Dipartimento di Fisica, Universita di Lecce, C. P. 193 - Via Arnesano,
73100 Lecce, Italy), AD(Dipartimento di Fisica, Universita di Lecce, C. P.
193 - Via Arnesano, 73100 Lecce, Italy), AE(Dipartimento di Fisica,
Universita di Lecce, C. P. 193 - Via Arnesano, 73100 Lecce, Italy),
AF(Daresbury Laboratory, Warrington, Cheshire WA4 4AD, Great Britain) |
|
Journal: |
|
Astronomy and Astrophysics, v.395, p.705-717 (2002) (A&A Homepage) |
|
Publication Date: |
|
11/2002 |
|
Origin: |
|
A&A |
|
A&A Keywords: |
|
methods: laboratory, comets: general, stars: circumstellar matter |
|
DOI: |
|
|
|
Bibliographic Code: |
|
2002A&A...395..705T |
We present the results of combining in situ high resolution synchrotron X-ray powder diffraction and infrared spectroscopic measurements on an amorphous pyroxene powder sample annealed in the region of 1000 K. We find using both techniques that the crystalline structure formed during annealing is Mg2SiO4 (forsterite), but that the presence of certain features in the 10 mu m band normally attributed to crystalline enstatite (MgSiO3) is contradicted by spectroscopy in the 20 mu m region (along with certain other 10 mu m band features) and X-ray diffraction. Both indicate crystalline forsterite as the only crystalline phase formed at this temperature. We discuss the possible mechanism of forsterite formation from amorphous pyroxene and identify the presence of proto-forsteritic structures in the amorphous starting material. We suggest the likely origin of the 10 mu m band ``crystalline enstatite'' features as being due to short-range improvements in the amorphous MgSiO3 network ordering which are not necessarily accompanied by the formation of crystalline enstatite structure. These results not only suggest that the formation of crystalline enstatite dust grains via annealing may be difficult to realise at this temperature, but also highlight the possibility, in the absence of additional corroborating evidence, of misidentifying the nature of the carrier of the 10 mu m ``enstatite'' features when observed in the spectra of objects such as comets. We also discuss the evolution of fine structure in the region of 15 to 16 mu m, which may serve as an observational indicator of grain processing in stellar sources.
|
Title: |
|
On the origin of comet C/1999 S4 LINEAR |
|
Authors: |
|
|
|
Affiliation: |
|
AA(Universidad Complutense de Madrid, |
|
Journal: |
|
Astronomy and Astrophysics, v.395, p.697-704 (2002) (A&A Homepage) |
|
Publication Date: |
|
11/2002 |
|
Origin: |
|
A&A |
|
A&A Keywords: |
|
minor planets, asteroids, comets: general, comets: individual: C/1994 S4 LINEAR, Kuiper belt, Oort cloud, solar system: formation |
|
DOI: |
|
|
|
Bibliographic Code: |
|
2002A&A...395..697D |
Current models of the formation of
comets in the Solar System assume that the most likely formation site for these
pristine objects is in the Uranus-Neptune zone or just beyond with subsequent
dynamical ejection by the growing protoplanets to distant orbits to form the Oort
cloud. However, the composition of the recently disintegrated comet C/1999 S4
LINEAR suggests that it was most likely formed in the Jupiter-Saturn region
(Mumma et al. 2001b; Kawakita et al. 2001). In this paper we argue that
cometesimals could easily appear inside exterior resonances resulting from gas
drag, between the orbits of Jupiter and Saturn and beyond Saturn, during the
formation of these giant planets. Then, the trapped material could evolve into
actual comets by means of collisional coagulation, followed by gravitational
instability of a layer of macroscopic bodies or two-body accretion. Properties
of these objects would be rather different from those found in classical comets
formed beyond
|
Title: |
|
Deuterium in comets-and AGB stars? |
|
Authors: |
|
|
|
Affiliation: |
|
AA(Space Science Division, MS 245-3, |
|
Journal: |
|
Planetary and Space Science, Volume 50, Issue 12-13, p. 1215-1219. (P&SS Homepage) |
|
Publication Date: |
|
10/2002 |
|
Origin: |
|
ELSEVIER |
|
Bibliographic Code: |
|
2002P&SS...50.1215R |
We discuss the deuterium chemistry of cometary comae, and show how the fractionation observed in coma molecules relates to the D/H ratios in the nuclear ices. For most molecules, we find that the fractionation is unchanged in the coma. In addition, we calculate the potential effects of degradation of D-rich polymers/organic refractory material on selected gas-phase fractionation ratios. We demonstrate that for molecules known to have an extended coma source, the observed D/H ratios may not necessarily reflect those in the nuclear ice. The recent detection of water vapour in the stellar wind of the carbon-rich red giant /IRC+10°216 has been attributed to the vaporization of a remnant population of comets surrounding this evolved star. This theory would be confirmed by the detection of deuterated molecules in this object: as deuterium is destroyed in stars, any D-bearing molecules must originate from cometary or planetary objects. We quantitatively assess the possibility of detecting HDO in this source if such comets contain similar D/H ratios to those in our solar system, and show that the 111-000 transition at 894GHz is the most promising candidate for detection.
|
Title: |
|
The magnitude distribution and evolution of short-period comets |
|
Authors: |
|
|
|
Affiliation: |
|
AA(Department of Physics and Astronomy, The University, |
|
Journal: |
|
Monthly Notice of the Royal Astronomical Society, Volume 336, Issue 2, pp. 363-372. (MNRAS Homepage) |
|
Publication Date: |
|
10/2002 |
|
Origin: |
|
MNRAS |
|
MNRAS Keywords: |
|
comets: general |
|
Abstract Copyright: |
|
(c) RAS |
|
DOI: |
|
|
|
Bibliographic Code: |
|
2002MNRAS.336..363H |
The magnitude distribution, perihelion distribution, nucleus size variation and evolution of the short-period comet population are re-assessed. Short-period comets with perihelion distances greater than 2 au have a magnitude distribution index of about 2.3, similar to that of the long-period comets. This index progressively increases for smaller perihelion distances, owing to the pronounced effects of cometary decay. The relationship between absolute magnitude and nucleus radius is investigated, as is the relationship between cometary decay rate and perihelion distance. It is estimated that 50 per cent of the known short-period comets will decay away completely in the next 2600 yr, a further 25 per cent going in the following 2300 yr.
|
Title: |
|
Variations of physical parameters in the plasma tail of comet Abe (C/1970 N1) and their connection with solar activity |
|
Authors: |
|
Shabas, N. L.; Churyumov, K. I.; Luk'yanyk, I. V.; Kravtsov, F. I. |
|
Journal: |
|
Kinematika i
Fizika Nebesnykh Tel, vol. 18, no. 5, p. 433-440. |
|
Publication Date: |
|
10/2002 |
|
Origin: |
|
KFNT |
|
Language: |
|
Russian |
|
Bibliographic Code: |
|
2002KFNT...18..433S |
More exact estimates of physical parameters in the plasma tail of comet Abe (C/1970 N1) are presented for 24 dates. The diffusion model was used. The connection between the changes of the magnetic field in the plasma tail of the comet in the period from 1970 September 30 to October 8 and in solar flares is investigated.
|
Title: |
|
Scaling of hypervelocity impact craters in ice with impact angle |
|
Authors: |
|
|
|
Journal: |
|
Journal of Geophysical Research (Planets), Volume 107, Issue E10, pp. 6-1, CiteID 5076, DOI 10.1029/2001JE001525 (JGRE Homepage) |
|
Publication Date: |
|
10/2002 |
|
Origin: |
|
AGU |
|
AGU Keywords: |
|
Planetology: Comets and Small Bodies: Ice, Planetology: Comets and Small Bodies: Impact phenomena, Planetology: Comets and Small Bodies: Surfaces and interiors, Planetology: Comets and Small Bodies: Satellites, Planetology: Solar System Objects: Comets, |
|
Abstract Copyright: |
|
(c) 2002: American Geophysical |
|
DOI: |
|
|
|
Bibliographic Code: |
|
2002JGRE.107j....6G |
Hypervelocity oblique impacts using spherical 1 mm diameter aluminum projectiles at velocities of (5.2 +/- 0.2) km s-1 were incident at angles ranging from normal (0° to the vertical) to grazing incidence (80°) onto thick polycrystalline H2O ice targets at 253 K. Data were obtained to distinguish changes in crater size and shape. The resultant craters had a deep central pit surrounded by a shallower terrace. Results on crater size showed that volume and crater depth had varying levels of dependence on obliquity for the full angular range, and terrace depth had a dependence only at angles > 45°. Length and width measurements held a strong dependence on obliquity only at angles > 50° from the normal. These results for ice show that it is hard to determine angle of impact from crater morphology. Although crater depth and volume do change with angle, it would be hard to separate this effect from the influence of an impact of a projectile of different speed, density, etc., which might also affect crater depth or crater depth/diameter ratios. Only at extreme angles > 70° do real differences in shape emerge for ice.
|
Title: |
|
Dust Grains in the Comae and Tails of Sungrazing Comets: Modeling of Their Mineralogical and Morphological Properties |
|
Authors: |
|
Kimura, Hiroshi; Mann, Ingrid; Biesecker, Douglas A.; Jessberger, Elmar K. |
|
Affiliation: |
|
AA(Institut für Planetologie, Westfälische Wilhelms-Universität, Wilhelm-Klemm-Straße 10, Münster, D-48149, Germany), AB(Institut für Planetologie, Westfälische Wilhelms-Universität, Wilhelm-Klemm-Straße 10, Münster, D-48149 Germany), AC(), AD(Institut für Planetologie, Westfälische Wilhelms-Universität, Wilhelm-Klemm-Straße 10, Münster, D-48149 Germany) |
|
Journal: |
|
Icarus, Volume 159, Issue 2, p. 529-541. (Icarus Homepage) |
|
Publication Date: |
|
10/2002 |
|
Origin: |
|
ELSEVIER |
|
Abstract Copyright: |
|
(c) 2002 Elsevier Science ( |
|
DOI: |
|
|
|
Bibliographic Code: |
|
2002Icar..159..529K |
Observations of sungrazing comets, all of which belong to the Kreutz family, provide the opportunity of studying the properties of dust in the comae and tails of the comets. On the basis of available information on cometary and interplanetary dust as well as observations of dust in the tails of sungrazers, we model dust in sungrazing comets as fluffy silicate aggregates of submicrometer sizes. To better interpret observational data, we numerically calculate the solar radiation pressure, the equilibrium temperature, and the sublimation and crystallization rates of silicate grains near the Sun. Our results show that the dust tails contain aggregates of submicrometer crystal grains, but not amorphous grains, since amorphous silicates mostly crystallize after release from the comets. The peak in the lightcurves of the dust comae observed either at 11.2 or 12.3 solar radii (Rsolar) seems to result from sublimation of fluffy aggregates consisting of crystalline or amorphous olivines, respectively. We attribute an additional enhancement in the lightcurves inside 7 Rsolar to increasing out-flow of crystalline and amorphous pyroxenes composed fluffy aggregates. According to our model, the observed lightcurves indicate a high abundance of olivine and a low abundance of pyroxene in the comets, which may bear implications about the dynamical and thermal history of the sungrazers and their progenitor.
|
Title: |
|
A comparison between the compositions of cometary and interstellar materials. I. Molecular abundances |
|
Authors: |
|
|
|
Journal: |
|
Contributions of the Astronomical Observatory Skalnaté Pleso, vol. 32, no. 2, p. 145-174. (CoSka Homepage) |
|
Publication Date: |
|
10/2002 |
|
Origin: |
|
COSKA |
|
Keywords: |
|
comets: general, Solar System: formation, ISM: clouds, ISM: molecules |
|
Bibliographic Code: |
|
2002CoSka..32..145N |
Comets were created as a by-product of planet formation from pristine interstellar material. A certain similarity between the composition of both cometary nuclei and interstellar clouds has actually be observed by several authors in few last decades. We summarize the quantitative measurements of abundances of observed molecules in both the above entities and discuss their similarities and differences. The found variety of the chemical composition of comets is practically within the range of observed molecular composition of relatively cold matter in the Galaxy. It proves that the gaseous and dusty components from which the cometary nuclei were built are primordial.
|
Title: |
|
Production, Outflow Velocity, and Radial Distribution of H2O and OH in the Coma of Comet C/1995 O1 (Hale-Bopp) from Wide-Field Imaging of OH |
|
Authors: |
|
Harris, Walter M.; Scherb, Frank; Mierkiewicz, Edwin; Oliversen, Ronald; Morgenthaler, Jeffrey |
|
Affiliation: |
|
AA(University of Wisconsin-Madison, 1150 University Avenue, Madison, WI 53706.), AB(University of Wisconsin-Madison, 1150 University Avenue, Madison, WI 53706.), AC(University of Wisconsin-Madison, 1150 University Avenue, Madison, WI 53706.), AD(Goddard Space Flight Center.), AE(University of Wisconsin-Madison, 1150 University Avenue, Madison, WI 53706.) |
|
Journal: |
|
The Astrophysical Journal, Volume 578, Issue 2, pp. 996-1008. (ApJ Homepage) |
|
Publication Date: |
|
10/2002 |
|
Origin: |
|
UCP |
|
ApJ Keywords: |
|
Comets: Individual: Name: Hale-Bopp 1995 O1 |
|
Abstract Copyright: |
|
(c) 2002: The American Astronomical Society |
|
DOI: |
|
|
|
Bibliographic Code: |
|
2002ApJ...578..996H |
Observations of OH are a useful proxy of the water production rate (QH2O) and outflow velocity (VH2O) in comets. From wide-field images taken on 1997 March 28 and April 8 that capture the entire scale length of the OH coma of comet C/1995 O1 (Hale-Bopp), we obtain QOH from the model-independent method of aperture summation and QH2O from the OH photochemical branching ratio, BROH. Using an adaptive ring summation algorithm, we extract the radial brightness distribution of OH 0-0 band emission out to cometocentric distances of up to 106 km, both as azimuthal averages and in quadrants covering different position angles relative to the comet-Sun line. These profiles are fitted using both fixed and variable velocity two-component spherical expansion models to estimate VOH with increasing distance from the nucleus. The OH coma of Hale-Bopp was more spatially extended than those of previous comets, and this extension is best matched by a variable acceleration of H2O and OH that acted across the entire coma, but was strongest within 1-2×104 km from the nucleus. Our models indicate that VOH at the edge of our detectable field of view (106 km) was ~2-3 times greater in Hale-Bopp than for a 1P/Halley class comet at 1 AU, which is consistent with the results of more sophisticated gas-kinetic models, extrapolation from previous observations of OH in comets with QH2O>1029s-1, and direct radio measurements of the outer coma Hale-Bopp OH velocity. The likely source of this acceleration is thermalization of the excess energy of dissociation of H2O and OH over an extended collisional coma. When the coma is broken down by quadrants in position angle, we find an azimuthal asymmetry in the radial distribution that is characterized by an increase in the spatial extent of OH in the region between the orbit-trailing and anti-Sunward directions. Model fits specific to this area and comparison with radio OH measurements suggest greater acceleration here, with VOH~1.5 times greater at a 106 km cometocentric distance than elsewhere in the coma. We discuss several mechanisms that may have acted within the coma to produce the observed effect.
|
Title: |
|
Observations at Nançay of the OH 18-cm lines in comets. The data base. Observations made from 1982 to 1999 |
|
Authors: |
|
Crovisier, J.; Colom, P.; Gérard, E.; Bockelée-Morvan, D.; Bourgois, G. |
|
Affiliation: |
|
AA( |
|
Journal: |
|
Astronomy and Astrophysics, v.393, p.1053-1064 (2002) (A&A Homepage) |
|
Publication Date: |
|
10/2002 |
|
Origin: |
|
A&A |
|
A&A Keywords: |
|
comets: general, radio lines: solar system, solar system: general |
|
DOI: |
|
|
|
Bibliographic Code: |
|
2002A&A...393.1053C |
Since the apparition of comet Kohoutek 1973 XII, the 18-cm lines of the OH radical have been systematically observed in a number of comets with the Nançay radio telescope. Between 1973 and 1999, 52 comets have been successfully detected. This allowed an evaluation of the cometary water production rates and their evolution with time, as well as a study of several physical processes such as the excitation mechanisms of the OH radio lines, the expansion of cometary atmospheres, their anisotropy in relation to non-gravitational forces, and the Zeeman effect in relation to the cometary magnetic field. Part of these observations and their analysis have already been published. The bulk of the results are now organized in a data base. The present paper is a general presentation of the Nançay cometary data base and a more specific description of the observations of 53 cometary apparitions between 1982 and 1999. Comets observed before 1982 are only partly incorporated in the data base. Observations of comets since 2000 have benefited from a major upgrade of the telescope; they will be presented in forthcoming publications. Appendix A, Table 2 and figures of the sum spectra are only available in electronic form at http://www.edpsciences.org The spectra and tables of the Appendix are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-in/qcat?J/A+A/393/1053
|
Title: |
|
On the Light-Absorbing Surface Layer of Cometary NucleiII. Thermal Modeling |
|
Authors: |
|
|
|
Affiliation: |
|
AA(Department of Astronomy and Space Physics, Uppsala University, Box 515, Uppsala, SE-751 20, Sweden), AB(Keldysh Institute of Applied Mathematics, Miusskaya Sq. 4, Moscow, 125047 Russia) |
|
Journal: |
|
Icarus, Volume 159, Issue 1, p. 239-258. (Icarus Homepage) |
|
Publication Date: |
|
09/2002 |
|
Origin: |
|
ELSEVIER |
|
Abstract Copyright: |
|
(c) 2002 Elsevier Science ( |
|
DOI: |
|
|
|
Bibliographic Code: |
|
2002Icar..159..239D |
The classical way to treat absorption of solar light in thermophysical modeling of cometary nuclei (and other ice-rich bodies such as jovian satellites) has been to assume complete opaqueness of the surface material. However, as shown by Davidsson and Skorov (2002, Icarus156, 223-248), substantial light penetration can occur in porous ice even if it is very dusty, implying that gradual absorption of energy in a surface layer should be accounted for. We present a thorough comparison between a surface energy absorption model and a layer energy absorption model, for various combinations of heliocentric distances, conductivities, opacities, pore sizes, and rotational periods relevant for cometary nuclei, by fully solving the coupled differential equations of heat transfer and gas diffusion. We find substantial differences between the models in terms of gas production rate, thermal lag angle, surface temperature, and the origin of coma molecules. For example, the surface energy absorption model overestimates the total gas production by a factor of 2-7, underestimates the lag angle by a factor of 2-3, and places the origin of coma molecules at the surface, instead of the near-surface interior.
|
Title: |
|
3- to 14-μm Spectroscopy of Comet C/1999 T1 (McNaught-Hartley) |
|
Authors: |
|
|
|
Journal: |
|
Icarus, Volume 159, Issue 1, p. 234-238. (Icarus Homepage) |
|
Publication Date: |
|
09/2002 |
|
Origin: |
|
ELSEVIER |
|
Abstract Copyright: |
|
(c) 2002 Elsevier Science ( |
|
DOI: |
|
|
|
Bibliographic Code: |
|
2002Icar..159..234L |
We report spectroscopy of Comet C/1991 T1 (McNaught-Hartley) at 3-13 μm on January 31.62 and February 1.7 2001 UT (delta=1.29 AU, r=1.40 AU) using the broadband array spectrograph system on the IRTF. The spectrum showed a silicate emission feature extending about 20% above the continuum. Two emission features at 10.3 and 11.2 μm appeared above the silicate band, the latter seemingly indicative of crystalline olivine. The 10.3-μm feature is only a 1-2 sigma detection but if real could indicate the presence of hydrated silicates. The color temperature at 8-13 μm was 260+/-10 K, approximately 6% above the blackbody radiative equilibrium temperature of 235 K. The magnitude at [N] was 3.13+/-0.02. On the second night, the comet had brightened slightly ([N]=2.98+/-0.02) and the two prominent emission features were absent, although the silicate emission feature maintained its trapezoidal shape with shoulders at 9.5 and 11.2 μm.
|
Title: |
|
Long- and Short-Term Photometric Behavior of Comet Hyakutake (1996 B2) |
|
Authors: |
|
|
|
Journal: |
|
Icarus, Volume 159, Issue 1, p. 210-233. (Icarus Homepage) |
|
Publication Date: |
|
09/2002 |
|
Origin: |
|
ELSEVIER |
|
Abstract Copyright: |
|
(c) 2002 Elsevier Science ( |
|
DOI: |
|
|
|
Bibliographic Code: |
|
2002Icar..159..210S |
Narrowband filter photometry observations of Comet Hyakutake (1996 B2) were used to investigate this comet's short-term variability as well as its behavior for the apparition as a whole. Utilizing measurements obtained on a total of 13 nights between February 9, 1996, and April 14, 1996, we find that the heliocentric distance (rH) dependence of the production rates of OH and NH were much shallower than those for either the carbon-bearing species or the visible dust. Based on the OH measurements, the derived water rH-dependence was also significantly less steep than expected from a basic water vaporization model and required an effective active surface area of about 29 km2 at rH=1.8 AU, 16 km2 at rH=1 AU, and only 13 km2 at rH=0.6 AU. This decrease in active area may be due to seasonally induced variations of a heterogeneous surface, or due to a decreasing contribution of gas from icy grains in the innermost coma. The relative abundances of the minor gas species place Hyakutake into the ``typical'' category of comets in the A'Hearn et al. (1995, Icarus118, 223-270) taxonomic classification system. The spectrum is generally redder at shorter wavelengths throughout the apparition; however, the dust color progressively changes from being significantly reddened (37%/1000 Å) at large rH to near-solar at small rH. This change of color with distance implies a significant change in grain sizes or a changing proportion between two or more grain populations. A major outburst was initiated near March 19.9, just prior to the comet's close approach to Earth. The characteristic recovery from the outburst differed among the observed species, with OH recovering most rapidly, essentially returning to its baseline values by March 25. The spatial radial fall-off of OH throughout this interval was consistent with the expected nominal spatial distribution, while CN and C2 displayed fall-offs consistent with a distributed source, and the dust fall-off was significantly less steep than 1/ρ, possibly due to fragmenting grains. Rotational lightcurve amplitudes were largest for the OH, NH, and dust, again consistent with the carbon-bearing species primarily originating from a distributed source. Significant variations were observed in the lightcurve amplitude and phase shifts as functions of aperture size. Finally, a refined value for the rotation period of 0.2614+/-0.0003 day was determined.
|
Title: |
|
Solitary potentials in cometary dusty plasmas |
|
Authors: |
|
|
|
Journal: |
|
Geophysical Research Letters, Volume 29, Issue 18, pp. 17-1, CiteID 1870, DOI 10.1029/2002GL015219 (GeoRL Homepage) |
|
Publication Date: |
|
09/2002 |
|
Origin: |
|
AGU |
|
AGU Keywords: |
|
Space Plasma Physics: Electrostatic structures, Space Plasma Physics: Nonlinear phenomena, Planetology: Solar System Objects: Comets, Space Plasma Physics: General or miscellaneous, |
|
Abstract Copyright: |
|
(c) 2002: American Geophysical |
|
Bibliographic Code: |
|
2002GeoRL..29r..17M |
Recent observations reveal that plasmas in cometary tails contain charged dust grains of positive and negative polarities. Our objective here is to show that such a two-component dusty plasma supports dust-Langmuir and dust-acoustic waves. The latter in the nonlinear regime propagate in the form of localized negative potentials. The role of large amplitude potential structures for trapping the positive dust grains and for the formation of dust layers of opposite polarity is discussed.
|
Title: |
|
A Search for N+2 in Spectra of Comet C/2002 C1 (Ikeya-Zhang) |
|
Authors: |
|
|
|
Affiliation: |
|
AA(Department of Astronomy, University of Texas at Austin, RLM 15.308, C-1400, Austin, TX 78712-1083 anita@barolo.as.utexas.edu) |
|
Journal: |
|
The Astrophysical Journal, Volume 576, Issue 2, pp. L165-L168. (ApJ Homepage) |
|
Publication Date: |
|
09/2002 |
|
Origin: |
|
UCP |
|
ApJ Keywords: |
|
Comets: Individual: Ikeya-Zhang (C/2002 C1), Solar System: Formation |
|
Abstract Copyright: |
|
(c) 2002: The American Astronomical Society |
|
DOI: |
|
|
|
Bibliographic Code: |
|
2002ApJ...576L.165C |
We report low- and high-resolution
spectra of comet C/2002 C1 (Ikeya-Zhang) from the McDonald Observatory. The
comet has a well-developed ion tail including CO+, CO+2,
CH+, and H2O+. We used our high-resolution
spectra to search for N+2. None was detected, and we
placed upper limits on N+2/CO+ of 5.4×10-4.
N+2 was detected in the low-resolution spectra, but we
show that this emission was probably telluric in origin (if cometary, we derive
N+2/CO+=5.5×10-3, still very low).
We discuss the implications for the conditions in the early solar nebula of the
nondetection of N+2. These depend on whether the H2O
ice was deposited in the amorphous or crystalline form. If H2O was
deposited in its crystalline form, the detection of
|
Title: |
|
A Search for Argon and O VI in Three Comets Using the Far Ultraviolet Spectroscopic Explorer |
|
Authors: |
|
Weaver, H. A.; Feldman, P. D.; Combi, M. R.; Krasnopolsky, V.; Lisse, C. M.; Shemansky, D. E. |
|
Affiliation: |
|
AA(Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218; weaver@pha.jhu.edu, pdf@pha.jhu.edu.; Current address: Space Department, Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723-6099 .), AB(Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218; weaver@pha.jhu.edu, pdf@pha.jhu.edu.), AC(Department of Atmospheric, Oceanic, and Space Sciences, 1417A Space Research Building, University of Michigan at Ann Arbor, 2455 Hayward Street, Ann Arbor, MI 48109-2143 mcombi@engin.umich.edu.), AD(Department of Physics, Catholic University of America, 620 Michigan Avenue, NE, Washington, DC 20064; vkrasn@verizonmail.com.), AE(Department of Astronomy, University of Maryland, College Park, MD 20742; lisse@astro.umd.edu.), AF(Department of Aerospace Engineering, University of Southern California, 854 West 36th Place, Los Angeles, CA 90089-1191 dons@hippolyta.usc.edu.) |
|
Journal: |
|
The Astrophysical Journal, Volume 576, Issue 1, pp. L95-L98. (ApJ Homepage) |
|
Publication Date: |
|
09/2002 |
|
Origin: |
|
UCP |
|
ApJ Keywords: |
|
Comets: General, Comets: Individual: Alphanumeric: C/1999 T1, Comets: Individual: Alphanumeric: C/2000 WM1, Comets: Individual: Alphanumeric: C/2001 A2, Ultraviolet: Solar System |
|
Abstract Copyright: |
|
(c) 2002: The American Astronomical Society |
|
DOI: |
|
|
|
Bibliographic Code: |
|
2002ApJ...576L..95W |
We conducted a sensitive search for the resonance lines of Ar I (λλ1048.22, 1066.66) and O VI (λλ1031.93, 1037.62) in the spectra of three long-period comets observed with the Far Ultraviolet Spectroscopic Explorer (FUSE). Argon emission was not detected from C/1999 T1 (McNaught-Hartley), C/2001 A2 (LINEAR), or C/2000 WM1 (LINEAR). Compared with the solar value, the [Ar/O] ratio is depleted in C/A2 by at least a factor of 10 and in C/WM1 by at least a factor of 13. The [Ar/O] upper limit for C/T1 is essentially the solar value, as our measurement was much less sensitive for that case. We also detected CO, which has a volatility similar to that of argon, during the FUSE observations. C/T1 was CO-rich ([CO/H2O] ~ 13%), while both C/A2 and C/WM1 were CO-poor ([CO/H2O] ~ 0.7% for C/A2 and ~0.4% for C/WM1). The argon and CO depletions in C/A2 and C/WM1 suggest formation temperatures >~60 K for both of these comets. The high CO abundance and upper limit on the argon abundance in C/T1 suggest that its formation temperature was in the range of ~40-50 K. No O VI emission was detected from comets C/T1 or C/A2, but the stronger line was marginally detected in C/WM1.
|
Title: |
|
Far Ultraviolet Spectroscopic Explorer Observations of CO and H2 Emission in Comet C/2001 A2 (LINEAR) |
|
Authors: |
|
|
|
Affiliation: |
|
AA(Department of Physics and Astronomy, Johns Hopkins University, Charles and 34th Street, Baltimore, MD 21218; pdf@pha.jhu.edu), AB(Department of Physics and Astronomy, Johns Hopkins University, Charles and 34th Street, Baltimore, MD 21218; pdf@pha.jhu.edu; Current address: Space Department, Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723-6099.), AC(Department of Physics and Astronomy, Johns Hopkins University, Charles and 34th Street, Baltimore, MD 21218; pdf@pha.jhu.edu) |
|
Journal: |
|
The Astrophysical Journal, Volume 576, Issue 1, pp. L91-L94. (ApJ Homepage) |
|
Publication Date: |
|
09/2002 |
|
Origin: |
|
UCP |
|
ApJ Keywords: |
|
Comets: Individual: Alphanumeric: C/2001 A2, Ultraviolet: Solar System |
|
Abstract Copyright: |
|
(c) 2002: The American Astronomical Society |
|
DOI: |
|
|
|
Bibliographic Code: |
|
2002ApJ...576L..91F |
Observations of comet C/2001 A2 (LINEAR) were made with the Far Ultraviolet Spectroscopic Explorer beginning 2001 July 12.58 and coinciding with a photometric increase of ~1.5 mag. Spectra were obtained in the 905-1180 Å range at 0.25 Å spectral resolution using the 30''×30'' aperture. Several new cometary emissions were identified, particularly the (0,0) bands of the CO Hopfield-Birge systems C-X and B-X at 1088 and 1151 Å, respectively, O I (1D-1D) at 1152 Å, and three lines of the H2 Lyman system at 1071.6, 1118.6, and 1166.8 Å, pumped by solar Lyβ fluorescence. Also detected were O I multiplets at 989, 1027, and 1040 Å and several lines of the H I Lyman series. The rotational envelopes of the CO bands are resolved and appear to consist of both ``cold'' and ``hot'' components, the cold component accounting for 70% of the flux and with a rotational temperature of 55+/-5 K. The hot component may be indicative of a CO2 source. The CO bands, H2 lines, and O I λ1152 all decreased by a factor of 2 over the 7.5 hr observation. The derived time-averaged production rates are Q(CO)=1.3×1027 molecules s-1 and Q(H2O)=2.1×1029 molecules s-1. These values may be uncertain by as much as a factor of 2 because of uncertainties in the solar flux and the electron impact contribution to the excitation.
|
Title: |
|
Runaway Fragmentation of Sungrazing Comets Observed with the Solar and Heliospheric Observatory |
|
Authors: |
|
|
|
Affiliation: |
|
AA(Jet Propulsion Laboratory, California Institute of
Technology, |
|
Journal: |
|
The Astrophysical Journal, Volume 576, Issue 2, pp. 1085-1089. (ApJ Homepage) |
|
Publication Date: |
|
09/2002 |
|
Origin: |
|
UCP |
|
ApJ Keywords: |
|
Comets: General, Methods: Data Analysis |
|
Abstract Copyright: |
|
(c) 2002: The American Astronomical Society |
|
DOI: |
|
|
|
Bibliographic Code: |
|
2002ApJ...576.1085S |
The observed clustering of the
Solar and Heliospheric Observatory (SOHO) sungrazing comets is a product of
runaway fragmentation that occurs throughout their orbits about the Sun. Since
the sungrazers in tight pairs occasionally appear simultaneously in the field
of view of the
|
Title: |
|
An advanced physical model of cometary activity |
|
Authors: |
|
Rodionov, A. V.; Crifo, J.-F.; Szegő, K.; Lagerros, J.; Fulle, M. |
|
Affiliation: |
|
AA(Central Research Institute on Machine Building (TsNIIMASH), Pionyerskaya St., 4, Korolev, 141070, Moscow Region, Russia), AB(Service d'Aéronomie du CNRS, BP 3, F 91371 Cedex, Verrières le Buisson, France), AC(KFKI Research Institute for Particles and Nuclear Physics, PO Box 49, H 1525, Budapest, Hungary), AD(Uppsala Observatory, Box 515, S 75120, Uppsala, Sweden), AE(Osservatorio Astronomico di Trieste, Via Tiepolo, 11, I-34131, Trieste, Italy) |
|
Journal: |
|
Planetary and Space Science, Volume 50, Issue 10-11, p. 983-1024. (P&SS Homepage) |
|
Publication Date: |
|
08/2002 |
|
Origin: |
|
ELSEVIER |
|
Bibliographic Code: |
|
2002P&SS...50..983R |
We describe the present state of an advanced physical model aimed at the simulation of the environment of active cometary nuclei. The model can handle the complicated shapes of real cometary nuclei, and is ready to handle alternative assumptions concerning the nucleus composition and structure; its present version is based on the simple, but hitherto highly successful, Whipple (1950) paradigm: at small heliocentric distances, strong sublimation theory is used to compute the surface gas production, taking into account the time-dependent heat flow in the nucleus interior; at large distances, different types of gas molecules may be assumed to dominate the gas production. Any size and shape distribution of dust can be assumed. The nucleus spin motion is modelled with allowance for the outgassing and solar tidal torques. The gas outflow is computed by solving quasistationary flow equations (Euler, or Navier-Stokes), hence the extent of the coma which can be modelled is limited either by the breakdown of the fluid approximation, or by that of the steady-state approximation. The dust outflow is computed by solving quasi-stationary ``zero-temperature'' multifluid Eulerian equations in the gas-dust interaction region, and from a ``Keplerian fountain model'' beyond it: the extent of the dust distribution which can be modelled is only limited by computer resources limitations. In addition to the detailed gas and dust coma structure, the resulting net nucleus mass loss, net sublimation recoil force, net sublimation torque, and net thermal emission are computed. We mention the past applications of the model to comets P/Halley and C/Hyakutake, and indicate some of the future steps of development of the model.
|
Title: |
|
Theoretical aspects and interpretation of thermal measurements concerning the subsurface investigation of a cometary nucleus |
|
Authors: |
|
|
|
Affiliation: |
|
AA(Institut für Planetologie, Westfälische Wilhelms-Universität Münster, Wilhelmstr. 10, D-48149, Münster, Germany), AB(Institut für Planetologie, Westfälische Wilhelms-Universität Münster, Wilhelmstr. 10, D-48149, Münster, Germany) |
|
Journal: |
|
Planetary and Space Science, Volume 50, Issue 9, p. 929-937. (P&SS Homepage) |
|
Publication Date: |
|
08/2002 |
|
Origin: |
|
ELSEVIER |
|
Bibliographic Code: |
|
2002P&SS...50..929K |
Part of the lander payload for the comet rendezvous mission Rosetta is the thermal probe multi-purpose sensors for surface and subsurface science (MUPUS). In this paper, we discuss the relationship of the expected MUPUS data to structural and textural parameters of the near-surface layers of the cometary nucleus. Such properties could be crucial parameters concerning the formation and evolution of the nucleus. Thus, we calculate the thermal conductivity of a porous material in terms of microstructural parameters, using a geometrical model with a solid matrix, a surrounding pore space and a distinct contact area between different particles. We include the possibility that a significant amount of heat may be transported by pore filling vapour in addition to heat conducted via the matrix. Furthermore, we consider that the heat is transmitted through only a fraction of the grains and these are organized into a chain-like structure. These chains-and not the single grains-should be regarded as the basic unit of structure. Applying our model to measured thermal conductivities of porous water ice, we interpret the material in terms of microparameters and estimate the effective size of the contact area and the effective pore radius. The results are in good agreement with our knowledge of the prepared samples. Contrary, we can also show that popular models used in cometary research do not fit with laboratory data at all.
|
Title: |
|
Polarimetric study of levitating dust aggregates with the PROGRA2 experiment |
|
Authors: |
|
Hadamcik, E.; Renard, J. B.; Levasseur-Regourd, A. C.; Worms, J. C. |
|
Affiliation: |
|
AA(CNRS Aéronomie, BP3, 91371, Verriéres-le-Buisson, France), AB(LPCE-CNRS, 3A avenue de la Recherche Scientifique, 45071, Cedex 2, Orléans, France), AC(CNRS Aéronomie, BP3, 91371, Verriéres-le-Buisson, France), AD(ESSC-ESF, c/o ENSPS-Parc d'Innovation, Boulevard S. Brandt, 67400, Illkirch France) |
|
Journal: |
|
Planetary and Space Science, Volume 50, Issue 9, p. 895-901. (P&SS Homepage) |
|
Publication Date: |
|
08/2002 |
|
Origin: |
|
ELSEVIER |
|
Bibliographic Code: |
|
2002P&SS...50..895H |
In order to interpret polarimetric remote observations of solar system dust clouds (e.g. cometary coma dust), laboratory measurements are needed. Three samples composed of aggregates are studied: crystallized enstatite, pyrogenic alumina and titanium oxide. The new version of the PROGRA2 instrument allows to obtain polarimetric images of the samples under levitation. The dependence of polarization with phase angle and particle size is studied, as well as the effect of the porosity of the particles. Values of polarization at small phase angles are also discussed. The polarization near /90° decreases when the agglomerate size increases and when the porosity increases.
|
Title: |
|
Dielectric properties of comet analog refractory materials |
|
Authors: |
|
|
|
Affiliation: |
|
AA(Laboratoire de Planétologie de Grenoble, UJF/CNRS, Grenoble, France), AB(Centre de Recherche sur les Trés Basses Temperature, CNRS,, Grenoble, France), AC(Laboratoire de Planétologie de Grenoble, UJF/CNRS, Grenoble, France), AD(Laboratoire de Planétologie de Grenoble, UJF/CNRS, Grenoble, France) |
|
Journal: |
|
Planetary and Space Science, Volume 50, Issue 9, p. 857-863. (P&SS Homepage) |
|
Publication Date: |
|
08/2002 |
|
Origin: |
|
ELSEVIER |
|
Bibliographic Code: |
|
2002P&SS...50..857H |
Ground penetrating radio waves or
radar provide a promising technique for the study of sub-surface planetary or
cometary material. The comet nucleus sounding experiment by radiowave
transmission (CONSERT) will be the only experiment on board the ROSETTA mission
to provide information on the interior of the comet Wirtanen. Other projects planned
or under development are Marsis/Mars Express and GPR for Net Lander. The aim is
to perform a radar tomography, and the necessary data inversion of the measured
permittivity requires knowledge of the complex dielectric permittivities of
probable sub-surface materials, so laboratory studies of the dielectric
properties of analog geological materials have become necessary. In connection
with the Rosetta mission, we have characterized the dielectric permittivity of
dunite, montmorillonite and kaolinite. We used granular materials identical to
those of the KOSI comet simulation experiment conducted at DLR in
|
Title: |
|
Modelling the astronomical silicate features - I. On the spectrum subtraction method |
|
Authors: |
|
|
|
Affiliation: |
|
AA(National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China; Princeton University Observatory, Peyton Hall, Princeton, NJ 08544, USA; Theoretical Astrophysics Program, University of Arizona, Tucson, AZ 85719, USA), AB(Raymond and Beverly Sackler Laboratory for Astrophysics, University of Leiden, Postbus 9504, 2300 RA Leiden, the Netherlands), AC(National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China) |
|
Journal: |
|
Monthly Notices of the Royal Astronomical Society, Volume 334, Issue 4, pp. 840-846. (MNRAS Homepage) |
|
Publication Date: |
|
08/2002 |
|
Origin: |
|
MNRAS |
|
Abstract Copyright: |
|
(c) RAS |
|
DOI: |
|
|
|
Bibliographic Code: |
|
2002MNRAS.334..840L |
The assumption of additive absorptivity by different components in compound particles is a widely used method applied in the literature to the analysis of the chemical and structural properties of astronomical (circumstellar, interstellar, protostellar and cometary) silicates as well as other materials. The errors intrinsic in this additivity assumption, which, in application to astronomical spectra, amounts in some cases to spectrum subtraction, have not always been adequately considered in previous works on silicate mineralogy. The failings in the `spectrum subtraction method' (intrinsically the same as the additive absorptivity assumption) are discussed here in terms of silicate core-ice mantle grains with various shapes. It is shown that these assumptions result in substantial errors for spherical grains. For spheroidal grains, the errors are less significant and the spectrum subtraction method can be used to remove the ice mantle effects. It is demonstrated that there is no significant improvement by considering a distribution of spheroidal shapes. It is further shown that the presence of additional organic mantles substantially modifies the silicate mineralogy interpretation.
|
Title: |
|
On the source of C(1D) atoms in cometary comae |
|
Authors: |
|
|
|
Affiliation: |
|
AA(Department of Mathematics & Astronomy, |
|
Journal: |
|
Monthly Notices of the Royal Astronomical Society, Volume 334, Issue 3, pp. 563-568. (MNRAS Homepage) |
|
Publication Date: |
|
08/2002 |
|
Origin: |
|
MNRAS |
|
MNRAS Keywords: |
|
molecular process; comets: individual: Comet Halley; comets: individual: Comet West; comets: individual: Comet Bradfield (1979 X) |
|
Abstract Copyright: |
|
(c) 2002 Blackwell Science Ltd |
|
DOI: |
|
|
|
Bibliographic Code: |
|
2002MNRAS.334..563S |
The two mechanisms known for the production of cometary C(1D) atoms, namely the dissociative electron recombination of CO+ ions and the photodissociation of CO molecules, have been examined to ascertain whether these mechanisms can produce the observed brightnesses of the comae of Comet 1P/Halley, Comet C/1975 V1 (Comet West 1976 VI) and Comet C/1979 Y1 (Comet Bradfield 1979 X) in the CI (1D-1Po) line at 1931Å on specific dates. The brightnesses computed from these mechanisms for the respective comets are compared with those quoted in the literature. It is found that the latter of the above two mechanisms can account for the observed brightnesses of these comets in the CI (1D-1Poh) line. A valid, hitherto undiscussed reaction mechanism not involving COH for the production of cometary C(1D) atoms is suggested.
|
Title: |
|
Unidentified Bands in Comet Ikeya-Zhang (C/2002 C1): The Correlation between Unidentified Bands and H2O+ |
|
Authors: |
|
|
|
Affiliation: |
|
AA(Gunma Astronomical Observatory, 6860-86 Nakayama,
Takayama, Gunma 377-0702, |
|
Journal: |
|
The Astrophysical Journal, Volume 574, Issue 2, pp. L183-L185. (ApJ Homepage) |
|
Publication Date: |
|
08/2002 |
|
Origin: |
|
UCP |
|
ApJ Keywords: |
|
Comets: General, Comets: Individual: Ikeya-Zhang (C/2002 C1), Molecular Data |
|
Abstract Copyright: |
|
(c) 2002: The American Astronomical Society |
|
DOI: |
|
|
|
Bibliographic Code: |
|
2002ApJ...574L.183K |
We report the results of the low-dispersion spectroscopic observations of comet Ikeya-Zhang (C/2002 C1) performed from 2002 March 10 to 20. The unidentified molecular bands that have been recognized in the plasma tail of several comets are detected in an antisunward coma of the comet Ikeya-Zhang. Our observations show the flux of unidentified bands at 5310 Å is correlated to the flux of H2O+ as reported for three comets by S. Wyckoff et al. The observed column density ratio between H2O+ and CO+, and the flux ratio between the unidentified bands and CO+ varied day by day, by a factor of ~2 in our observations. However, it appears that the ratios are proportional to each other. We conclude that a parent of unidentified bands is produced from or generates H2O+ directly or indirectly. We propose the hypothesis that H2O+ is the parent of the unidentified bands since similar structures of emission bands are recognized in some laboratory studies on charge transfer collisions between neutral water and Ar+ or N+2.
|
Title: |
|
Radio continuum observations of Comet C/1999 S4 (LINEAR) before, during, and after break-up of its nucleus |
|
Authors: |
|
Altenhoff, W. J.; Bertoldi, F.; Menten, K. M.; Sievers, A.; Thum, C.; Kreysa, E. |
|
Affiliation: |
|
AA(Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany wja@mpifr-bonn.mpg.de), AB(Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany fbertoldi@mpifr-bonn.mpg.de), AC(Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany ekreysa@mpifr-bonn.mpg.de), AD(Institute for Radio Astronomy at Millimeter Wavelengths (IRAM) Avenida Divina Pastora 7, 18012 Granada, Spain sievers@iram.es), AE(Institute for Radio Astronomy at Millimeter Wavelengths (IRAM) Domaine Universitaire de Grenoble, 300 rue de la piscine, 38406 St. Martin d'Hères, France thum@iram.fr), AF(Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany kmenten@mpifr-bonn.mpg.de) |
|
Journal: |
|
Astronomy and Astrophysics, v.391, p.353-360 (2002) (A&A Homepage) |
|
Publication Date: |
|
08/2002 |
|
Origin: |
|
A&A |
|
A&A Keywords: |
|
comets: general, comets: individual: C/1999 S4, radio continuum: solar system |
|
DOI: |
|
|
|
Bibliographic Code: |
|
2002A&A...391..353A |
We observed radio continuum emission from Comet C/1999 S4 before, during, and after break-up of its nucleus. The detections before break-up indicate a photometric diameter of 4.7 km, from which we estimate that the nuclear diameter was about 0.9 km. We derive a dust production rate of ~ 9*E4 g s-1, corresponding to 0.03 g s-1 per square meter of the nuclear surface area, which is comparable to the values found for comets 1P/Halley and C/1995 O1 (Hale-Bopp). The implied gas-to-dust mass production ratio was between 2 and 5. The high daily erosion rate and the continuous fragmentation over months, as derived from water production rates, could not be confirmed. The low radio emission of the fragments directly after the break-up and their low cometary activity may be explained by their low surface temperatures. The published optical and most radio data support that the main nuclear decay started July 23, 2000. Our upper limits on the flux density obtained after the nuclear disintegration put an upper bound on the particulate dust mass released during that event. A scenario in which most of the nucleus disintegrated into many big boulders and part of it into a dust cloud is consistent with our observations.
|
Title: |
|
On the Return of Comet Grigg-Skjellerup |
|
Authors: |
|
|
|
Affiliation: |
|
AA(Kazan State University, Kremlevskaya ul. 18, Kazan, 420008 Tatarstan, Russia), AB(Chelyabinsk Agro-Technical University, Chelyabinsk, Russia), AC(Southern Urals State University, pr. Lenina 76, Chelyabinsk, 454080 Russia) |
|
Journal: |
|
Solar System Research, v. 36, Issue 4, p. 348-352 (2002). |
|
Publication Date: |
|
07/2002 |
|
Origin: |
|
KLUWER |
|
Abstract Copyright: |
|
(c) 2002 Kluwer Academic Publishers |
|
Bibliographic Code: |
|
2002SoSyR..36..348K |
Comet Grigg-Skjellerup must return to its perihelion on November 29, 2002. Before that, it will pass by Jupiter at a distance of 0.5 AU. A simulation of the meteor swarm that is related to this comet in origin has been made for 19 perihelia since 1907. Particles ejected from the nucleus at velocities +/-40 m/s in the direction perpendicular to its radius vector are concentrated around the comet and do not approach the Earth, while for particles ejected at velocities +/-60 m/s, conditions for the encounter with Jupiter are different; they approach Jupiter to a distance of 0.1 AU, then pass near the Earth's orbit at a distance of 0.01 AU. However, these particles have substantially different radiant coordinates and hardly form a flow of sufficient density.
|
Title: |
|
Multi-transitional observations of methanol in Comet Hale-Bopp (1995 O1) |
|
Authors: |
|
Ikeda, M.; Kawaguchi, K.; Takakuwa, S.; Sakamoto, A.; Sunada, K.; Fuse, T. |
|
Affiliation: |
|
AA(Nobeyama Radio Observatory, Nobeyama, Minamimaki, Minamisaku, Nagano 384-1305, Japan), AB(Nobeyama Radio Observatory, Nobeyama, Minamimaki, Minamisaku, Nagano 384-1305, Japan), AC(Nobeyama Radio Observatory, Nobeyama, Minamimaki, Minamisaku, Nagano 384-1305, Japan), AD(Nobeyama Radio Observatory, Nobeyama, Minamimaki, Minamisaku, Nagano 384-1305, Japan), AE(Nobeyama Radio Observatory, Nobeyama, Minamimaki, Minamisaku, Nagano 384-1305, Japan), AF(Subaru Telescope, National Astronomical Observatory of Japan 650 North A'ohoku Place, Hilo, Hawaii 96720, USA) |
|
Journal: |
|
Astronomy and Astrophysics, v.390, p.363-367 (2002) (A&A Homepage) |
|
Publication Date: |
|
07/2002 |
|
Origin: |
|
A&A |
|
A&A Keywords: |
|
comets: general, comets: individual: C/1995 O1(Hale-Bopp), ISM: abundances |
|
DOI: |
|
|
|
Bibliographic Code: |
|
2002A&A...390..363I |
We have observed 9 rotational
lines of methanol in comet Hale-Bopp (1995 O1) using the 45-m radio telescope
at Nobeyama Radio Observatory in the frequency range 36-104 GHz. The observed
transitions have upper state rotational energy levels of Eu = 7-159
K. Assuming the Haser model for density distribution, we estimated the
excitation temperature and the production rate to be
|
Title: |
|
Radial mixing in protoplanetary accretion disks. III. Carbon dust oxidation and abundance of hydrocarbons in comets |
|
Authors: |
|
|
|
Affiliation: |
|
AA(Institut für Theoretische Astrophysik, Universität
Heidelberg, Tiergartenstraße 15, 69121 |
|
Journal: |
|
Astronomy and Astrophysics, v.390, p.253-265 (2002) (A&A Homepage) |
|
Publication Date: |
|
07/2002 |
|
Origin: |
|
A&A |
|
A&A Keywords: |
|
accretion, accreation disks, molecular processes, solar system: formation, comets: general |
|
DOI: |
|
|
|
Bibliographic Code: |
|
2002A&A...390..253G |
The oxidation of carbon dust and its conversion into CO and some hydrocarbon compounds as intermediate products is studied for protoplanetary accretion discs. The disc model is based on the one-zone alpha -disc approximation. The radial mixing of the combustion products into the cold outer disc region by turbulent diffusion is considered in the transport-diffusion-reaction equations for the chemistry. It is shown that considerable amounts of CH_4 and C_2H_2 formed as by-products of carbon oxidation are mixed into cold disc regions beyond a distance of 10 AU where they can be included into the ice mixture of cometary nuclei formed in that region. This may explain the high abundance of these gases recently observed in comets Hyakutake (C/1996 B2) and Hale-Bopp (C/1995 O1). This mixing of hydrocarbons from carbon oxidation cannot, however, explain the high abundance of some other molecular species like C2H6 or CH3OH, which have to be formed by different processes.
|
Title: |
|
Large-scale disturbance of the solar wind by a comet |
|
Authors: |
|
|
|
Affiliation: |
|
AA(Max-Planck-Institut für Astrophysik, 85748 |
|
Journal: |
|
Astronomy and Astrophysics, v.389, p.1039-1046 (2002) (A&A Homepage) |
|
Publication Date: |
|
07/2002 |
|
Origin: |
|
A&A |
|
A&A Keywords: |
|
comets: general, Sun: solar wind |
|
DOI: |
|
|
|
Bibliographic Code: |
|
2002A&A...389.1039W |
Model calculations for the interaction of the solar wind with a comet are presented that extend 30 million km into the tail. It is shown that the disturbance of the interplanetary magnetic field (IMF) (the draping) is limited to timescales of 10 to 50 hours and length scales of 10 to 50 million km. This is supported by a theoretical argument about the acceleration of the cometary ions. The distribution of ions and protons at the end of the model tails agrees with measurements made by Ulysses far in the tail of comet Hyakutake. It is shown that the ion tail is concentrated in the current sheet between two flux lobes as long as the draping persists. The far tail, however, is flat and concentrated in a plane parallel to the IMF.
|
Title: |
|
Solar system objects in the ISOPHOT 170 mu m serendipity survey |
|
Authors: |
|
|
|
Affiliation: |
|
AA(Max-Planck-Institut für extraterrestrische Physik, Giessenbachstraße, 85748 Garching, Germany; ISO Data Centre, Astrophysics Division, Space Science Department of ESA, Villafranca, PO Box 50727, 28080 Madrid, Spain (until Dec. 2001)), AB(ISOPHOT Data Centre, Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany), AC(ISOPHOT Data Centre, Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany) |
|
Journal: |
|
Astronomy and Astrophysics, v.389, p.665-679 (2002) (A&A Homepage) |
|
Publication Date: |
|
07/2002 |
|
Origin: |
|
A&A |
|
A&A Keywords: |
|
minor planets, asteroids, comets: general, planets and satellites: general, infrared: solar system, surveys |
|
DOI: |
|
|
|
Bibliographic Code: |
|
2002A&A...389..665M |
The ISOPHOT Serendipity Survey
(ISOSS) covered approximately 15% of the sky at a wavelength of 170 mu m while
the ISO satellite was slewing from one target to the next. By chance, ISOSS slews
went over many solar system objects (SSOs). We identified the comets, asteroids
and planets in the slews through a fast and effective search procedure based on
N-body ephemeris and flux estimates. The detections were analysed from a
calibration and scientific point of view. Through the measurements of the
well-known asteroids Ceres, Pallas, Juno and Vesta and the planets Uranus and
|
Title: |
|
Colors of Minor Bodies in the Outer Solar System. A statistical analysis |
|
Authors: |
|
|
|
Affiliation: |
|
AA(European Southern Observatory, Casilla 19001, Santiago, Chile), AB(European Southern Observatory, Casilla 19001, Santiago, Chile; Observatoire de Paris-Meudon, 5 place Jules Janssen, 92195 Meudon Cedex, France) |
|
Journal: |
|
Astronomy and Astrophysics, v.389, p.641-664 (2002) (A&A Homepage) |
|
Publication Date: |
|
07/2002 |
|
Origin: |
|
A&A |
|
A&A Keywords: |
|
comets: general, Kuiper Belt, solar system: general, methods: statistical |
|
DOI: |
|
|
|
Bibliographic Code: |
|
2002A&A...389..641H |
We present a compilation of all available colors for 104 Minor Bodies in the Outer Solar System (MBOSSes); for each object, the original references are listed. The measurements were combined in a way that does not introduce rotational color artifacts. We then derive the slope, or reddening gradient, of the low resolution reflectance spectra obtained from the broad-band color for each object. A set of color-color diagrams, histograms and cumulative probability functions are presented as a reference for further studies, and are discussed. In the color-color diagrams, most of the objects are located very close to the ``reddening line'' (corresponding to linear reflectivity spectra). A small but systematic deviation is observed toward the I band indicating a flattening of the reflectivity at longer wavelengths, as expected from laboratory spectra. A deviation from linear spectra is noticed toward the B for the bluer objects; this is not matched by laboratory spectra of fresh ices, possibly suggesting that these objects could be covered with extremely evolved/irradiated ices. Five objects (1995 SM55, 1996 TL66, 1999 OY_3, 1996 TO66 and (2060) Chiron) have almost perfectly solar colors; as two of these are known or suspected to harbour cometary activity, the others should be searched for activity or fresh ice signatures. In the color-color diagrams, 1994 ES_2, 1994 EV_3, 1995 DA_2 and 1998 HK151 are located very far from the main group of objects; it is suspected that this corresponds to inaccurate measurements and not intrinsically strange objects. The color distributions were analyzed as functions of the orbital parameters of the objects and of their absolute magnitude. No significant correlation is observed, with the following exceptions: Cubewanos with low orbital excitation (low i, e and/or E = sqrt(e2 + sin 2 i)), and therefore experiencing on average fewer and less violent collisions have significantly redder colors; Cubewanos with faint absolute magnitude M(1,1) tend to be redder than the others, while Plutinos present the opposite trend. The color distribution of the various MBOSS classes are analyzed and compared using generic statistic tools. The comets were found to be significantly bluer than the other MBOSSes. Finally, we compare the various 1D and 2D color distributions to simple models, in order to throw some light on the question of the bimodality of MBOSS color distributions. It is found that with the current data set, all color distributions are compatible with simple, continuous distribution models, while some color distributions are not compatible with simple bimodal distribution models. Table 1 is also available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/389/641, and the tables and complete set of figures corresponding the up-to-date database are available on the web at http://www.sc.eso.org/~ohainaut/MBOSS. Table 1 is also available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/389/641 Tables 3, 5, 6 and the list of papers are only available in electronic form at http://www.edpsciences.org
|
Title: |
|
The Deep Space 1 Encounter with Comet 19p/Borrelly |
|
Authors: |
|
Boice, D. C.; Soderblom, L. A.; Britt, D. T.; Brown, R. H.; Sandel, B. R.; Yelle, R. V.; Buratti, B. J.; Hicks; Nelson; Rayman; Oberst, J.; Thomas, N. |
|
Affiliation: |
|
AA( Southwest Research Institute, Space Science and Engineering Division, P.O. Drawer 28510, San Antonio, Texas 78228-0510, USA dboice@swri.edu ), AB( United States Geological Survey, 2255 North Gemini Drive, Flagstaff, Arizona 86001, USA ), AC( University of Tennessee, Department of Geological Sciences, Knoxville, Tennessee 37996, USA ), AD( University of Arizona, Department of Planetary Sciences, Lunar and Planetary Laboratory, Tucson, Arizona 85721, USA ), AE( University of Arizona, Department of Planetary Sciences, Lunar and Planetary Laboratory, Tucson, Arizona 85721, USA ), AF( University of Arizona, Department of Planetary Sciences, Lunar and Planetary Laboratory, Tucson, Arizona 85721, USA ), AG( Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA ), AH( Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA ), AI( Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA ), AJ( Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA ), AK( DLR Institute of Space Sensor Technology and Planetary Exploration, Rutherfordstrasse 2, D-12489 Berlin, Germany ), AL( Max-Planck-Institut für Aeronomie, Max-Planck-Strasse 2, D-37191 Katlenburg-Lindau, Germany ) |
|
Journal: |
|
Earth, Moon, and Planets, v. 89, Issue 1, p. 301-324 (2002). (EM&P Homepage) |
|
Publication Date: |
|
00/2002 |
|
Origin: |
|
KLUWER |
|
Keywords: |
|
Coma, comets, Deep Space 1, nucleus, spacecraft exploration |
|
Bibliographic Code: |
|
2002EM&P...89..301B |
NASA's Deep Space 1 (DS1) spacecraft successfully encountered comet 19P/Borrelly near perihelion and the Miniature Integrated Camera and Spectrometer (MICAS) imaging system onboard DS1 returned the first high-resolution images of a Jupiter-family comet nucleus and surrounding environment. The images span solar phase angles from 88° to 52°, providing stereoscopic coverage of the dust coma and nucleus. Numerous surface features are revealed on the 8-km long nucleus in the highest resolution images (47-58 m pixel). A smooth, broad basin containing brighter regions and mesa-like structures is present in the central part of the nucleus that seems to be the source of jet-like dust features seen in the coma. High ridges seen along the jagged terminator lead to rugged terrain on both ends of the nucleus containing dark patches and smaller series of parallel grooves. No evidence of impact craters with diameters larger than about 200-m are present, indicating a young and active surface. The nucleus is very dark with albedo variations from 0.007 to 0.035. Short-wavelength, infrared spectra from 1.3 to 2.6 μm revealed a hot, dry surface consistent with less than about 10% actively sublimating. Two types of dust features are seen: broad fans and highly collimated ``jets'' in the sunward hemisphere that can be traced to the surface. The source region of the main jet feature, which resolved into at least three smaller ``jets'' near the surface, is consistent with an area around the rotation pole that is constantly illuminated by the sun during the encounter. Within a few nuclear radii, entrained dust is rapidly accelerated and fragmented and geometrical effects caused from extended source regions are present, as evidenced in radial intensity profiles centered on the jet features that show an increase in source strength with increasing cometocentric distance. Asymmetries in the dust from dayside to nightside are pronounced and may show evidence of lateral flow transporting dust to structures observed in the nightside coma. A summary of the initial results of the Deep Space 1 Mission is provided, highlighting the new knowledge that has been gained thus far.
|
Title: |
|
Comet Grains: Their IR Emission and Their Relation to ISm Grains |
|
Authors: |
|
|
|
Affiliation: |
|
AA( |
|
Journal: |
|
Earth, Moon, and Planets, v. 89, Issue 1, p. 247-287 (2002). (EM&P Homepage) |
|
Publication Date: |
|
00/2002 |
|
Origin: |
|
KLUWER |
|
Keywords: |
|
Amorphous carbon, CP IDPs, crystals, dust, Hale-Bopp, silicates |
|
Bibliographic Code: |
|
2002EM&P...89..247W |
Comets and the chondritic porous
interplanetary dust particles (CP IDPs) that they shed in their comae are
reservoirs of primitive solar nebula materials. The high porosity and fragility
of cometary grains and CP IDPs, and anomalously high deuterium contents of
highly fragile, pyroxene-rich Cluster IDPs imply these aggregate particles
contain significant abundances of grains from the interstellar medium (ISM). IR
spectra of comets (3-40 μm) reveal the presence of a warm (near-IR) featureless
emission modeled by amorphous carbon grains. Broad and narrow resonances near
10 and 20 microns are modeled by warm chondritic (50% Fe and 50% Mg) amorphous
silicates and cooler Mg-rich crystalline silicate minerals, respectively.
Cometary amorphous silicates resonances are well matched by IR spectra of CP
IDPs dominated by GEMS (0.1 μm silicate spherules) that are thought to be the
interstellar Fe-bearing amorphous silicates produced in AGB stars. Acid-etched
ultramicrotomed CP IDP samples, however, show that both the carbon phase
(amorphous and aliphatic) and the Mg-rich amorphous silicate phase in GEMS are
not optically absorbing. Rather, it is Fe and
|
Title: |
|
Physico-Chemistry of Comets: Models and Laboratory Experiments |
|
Authors: |
|
|
|
Affiliation: |
|
AA( Leiden Observatory, P.O. Box 9513, 2300 RA Leiden, The Netherlands ), AB( Astrobiology Laboratory, Leiden Institute of Chemistry, P.O. Box 9502, 2300 RA Leiden, The Netherlands ), AC( Space Science Division, NASA Ames Research Center, MS 245-3, Moffett Field, CA 94035, USA ) |
|
Journal: |
|
Earth, Moon, and Planets, v. 89, Issue 1, p. 221-246 (2002). (EM&P Homepage) |
|
Publication Date: |
|
00/2002 |
|
Origin: |
|
KLUWER |
|
Keywords: |
|
Comet C/1995 O1 Hale-Bopp, comets, laboratory studies, physico-chemsitry |
|
Bibliographic Code: |
|
2002EM&P...89..221E |
Until cometary matter can be studied in-situ or cometary samples are brought back to Earth for analysis, theoretical models and laboratory studies remain a crucial tool for revealing the nature of cometary matter. Constraints on the nature of the primordial material available for incorporation into comets and other solar system material comes from analysis of data from space-based and ground-based observatories. The structure of the nuclear ice component, which may have coexisting amorphous/crystalline phases and include clathrates and other trapped guest molecules, strongly influences the cometary outgassing properties. This paper reviews laboratory work on ice and carbonaceous compounds and discusses their significance for cometary chemistry. Special emphasis will be given to studies on the thermal processing of ices and their implications for the structure changes and subsequent release of volatiles. We also describe the preliminary results of a model of nuclear outgassing, and discuss how such models can be used to infer the chemical structure of the nuclear ices. Furthermore, we confront cometary data with the analysis of carbonaceous meteorites. Recent laboratory results on volatile compounds and the macromolecular structure of carbonaceous meteorites allow us to investigate the link of small bodies in the Solar System. Until ROSETTA will land on comet Wirtanen and study directly the nuclear composition, laboratory measurements of ice and refractory analogs will - together with the analysis of meteorites - significantly improve our knowledge on the origin and structure of comets.
|
Title: |
|
New Experimental and Theoretical Techniques for Studying Photochemical reactions of Cometary Atmospheres |
|
Authors: |
|
Jackson, William M.; Xu, Dadong; Huang, Jianhua; Price, Roosevelt J.; Volman, David H. |
|
Affiliation: |
|
AA( Chemistry Department, University of California, Davis, One Shields Ave, Davis, CA 95616, USA wmjackson@ucdavis.edu), AB( Chemistry Department, University of California, Davis, One Shields Ave, Davis, CA 95616, USA), AC( Chemistry Department, University of California, Davis, One Shields Ave, Davis, CA 95616, USA), AD( Chemistry Department, University of California, Davis, One Shields Ave, Davis, CA 95616, USA), AE( Chemistry Department, University of California, Davis, One Shields Ave, Davis, CA 95616, USA) |
|
Journal: |
|
Earth, Moon, and Planets, v. 89, Issue 1, p. 197-220 (2002). (EM&P Homepage) |
|
Publication Date: |
|
00/2002 |
|
Origin: |
|
KLUWER |
|
Keywords: |
|
Carbon disulfide, cometary atmosphere, ion imaging, photochemical reaction, sulfur branching ratio |
|
Bibliographic Code: |
|
2002EM&P...89..197J |
New experimental methods for studying photochemical reactions are given and the strength and weakness are briefly discussed. References and bibliographies for these photochemical studies are presented. A case study of carbon disulfide (CS2) that uses vacuum ultraviolet lasers, time-of-flight mass spectrometry, molecular beams and ion velocity imaging to measure and characterize the products is described. These results are compared with previous studies and the difficulties involved in understanding these results are pointed out.
|
Title: |
|
Composition of Comets: Observations and Models |
|
Authors: |
|
|
|
Affiliation: |
|
AA(Southwest Research Institute, P. O. Drawer 28510, |
|
Journal: |
|
Earth, Moon, and Planets, v. 89, Issue 1, p. 179-195 (2002). (EM&P Homepage) |
|
Publication Date: |
|
00/2002 |
|
Origin: |
|
KLUWER |
|
Keywords: |
|
Comets, composition |
|
Bibliographic Code: |
|
2002EM&P...89..179H |
We analyze the chemical composition and abundances of comets based on in situ measurements of Comet 1P/Halley and remote sensing observations of several recent bright comets including Hale-BOPP (C/1995 O1) and Hyakutake (C/1996 B2), in light of the elemental abundances of the solar system. Nitrogen is underabundant in comets relative to the solar system because nitrogen tends to be in N2, which is chemically relatively inert. While many details remain uncertain, some gross features are emerging. The abundance of water : silicates: carbonaceous molecules (CO, CO2, and hydrocarbons) by mass is approximately 1 : 1 : 1. Furthermore, the mass abundance of ice : dust (silicates and hydrocarbon polycondensates) is about 1 : 1. We compare a list of identified comet molecules with molecules detected in the interstellar medium, although a comparison with their relative abundances, particularly in the ice phase, would be more meaningful. However, ice-phase abundances are not yet available. One can expect a variation of the abundances of carbon-bearing molecules in comets to be associated with their place of origin in the solar nebula. However, we also note that comets are heterogeneous. Thus, observed differences may be related to the place of origin, heterogeneity of the nucleus, or acquired through evolution. The molecular and elemental compositions of the coma are most likely not the same as those in the nucleus. This is particularly true for volatile ices and their gases and for the dust-to-ice and dust-to-gas ratios. Analyses must carefully consider the three sources of gas: Water from the surface of the nucleus, gases more volatile than water from the interior of the nucleus, and gases from the sublimation of the dust distributed in the coma. Topography on the surface of the nucleus may cause important evolutionary differences in the dust-to-gas mass ratio. Relatively inactive areas on the surface of the nucleus are probably associated with convex topography. Gas sublimated from convex areas (hills and mountains) diverges more strongly relative to gas sublimated from concave areas, which can entrain dust more efficiently. Thus, the entrainment of dust from convex areas is poor and dust may fall back to the surface of the nucleus creating a dust mantle, which further inhibits outgassing.
|
Title: |
|
Sublimation Mechanisms of Comet Nuclei |
|
Authors: |
|
|
|
Affiliation: |
|
AA(CNR, IASF,
Area di Ricerca di Tor Vergata, v. del Fosso del Cavaliere, 100 - 00133 Rome,
Italy) |
|
Journal: |
|
Earth, Moon, and Planets, v. 89, Issue 1, p. 161-178 (2002). (EM&P Homepage) |
|
Publication Date: |
|
00/2002 |
|
Origin: |
|
KLUWER |
|
Keywords: |
|
Comet, nucleus, sublimation |
|
Bibliographic Code: |
|
2002EM&P...89..161C |
In this paper the sublimation mechanisms of parent molecules from nuclei will be reviewed from the point of view of theoretical models, and the results of models will be compared with the results of the extensive observation campaign of C/1995 O1 Hale-Bopp. The simple model of a mixture of ices in which each gas sublimates independently from the others when the right temperature has been reached is in many cases inadequate to explain the observations. Many minor volatiles can be trapped in the amorphous water ice and released in a complex way when particular ranges of temperature are reached. The presence of sublimating icy grains in the inner coma of comets, suggested many years ago, seems now to be proven, at least for Hale-Bopp. From these grains a significant amount of water and other volatiles could contribute to the total flux measured in the coma. The unprecedented coverage of Hale-Bopp's gas production curve for such a long time and with so many instruments has offered to modellers a wonderful occasion to test and compare observation results with the predictions of sublimation models, demonstrating that current models are able to explain observed results.
|
Title: |
|
Rotational Properties of Cometary Nuclei |
|
Authors: |
|
|
|
Affiliation: |
|
AA( Laboratoire
d'Astrophysique de Marseille, BP 8, 13376 Marseille Cedex 12, France ), AB( Instituto de Astrofísica de Andalucía, c/ Camino Bajo de
Huétor, 24, Apartado 3004, 18080 Granada, Spain ) |
|
Journal: |
|
Earth, Moon, and Planets, v. 89, Issue 1, p. 135-160 (2002). (EM&P Homepage) |
|
Publication Date: |
|
00/2002 |
|
Origin: |
|
KLUWER |
|
Keywords: |
|
C/1995 O1 (Hale-Bopp), 19P/Borrelly, 46P/Wirtanen, comets, modeling, nucleus, observations, rotation |
|
Bibliographic Code: |
|
2002EM&P...89..135J |
We review several techniques used to retrieve rotational parameters from observations. The spin period of a dozen of comets retrieved with these techniques are summarized. We describe how the spin period of comet Hale-Bopp (C/1995 O1) has been calculated with a high accuracy (11.30-11.34 h). Although several authors converged to a spin axis orientation at (α,δ) = (275 +/- 15°, -55 +/- 5°), detailed studies indicate that the dust jets morphology in 1996-1997 may be incompatible with this orientation. Comet 19P/Borrelly has been recently observed by the Deep Space 1 spacecraft. At the same time, its spin axis orientation and period have been determined by several authors to be respectively (α,δ) = (225 +/- 15°, -10 +/- 10°) and 26h. These two comets are likely to be in (or close to) a principal axis spin state. We discuss new modeling of the spin state of comet 46P/Wirtanen, the target of the Rosetta mission. The model involves a three-dimensional shape and thermal model, from which the torque of the nongravitational force is calculated at each time step. The moments of inertia are computed for each irregular shape. The results from numerical integrations show that this comet can remain in a principal axis spin state during more than 10 orbits if the spin period does not get above ~6 h. If the spin period increases, its nucleus gets rapidly into excited spin states. It shows that even small and very active short-period comets are not necessarily in nonprincipal axis spin states. In the last section, the consequences of recent observations and modeling of the rotational parameters of comet nuclei are discussed, and unsolved problems are presented.
|
Title: |
|
Observational Constraints On Surface Characteristics Of Comet Nuclei |
|
Authors: |
|
|
|
Affiliation: |
|
AA( Physics Department, University of Central Florida, Orlando, Florida 32816-2385, USA. campins@physics.ucf.edu ), AB( University of Hawaii, 2680 Woodlawn Drive, Honolulu, Hawaii 96822, USA ) |
|
Journal: |
|
Earth, Moon, and Planets, v. 89, Issue 1, p. 117-134 (2002). (EM&P Homepage) |
|
Publication Date: |
|
00/2002 |
|
Origin: |
|
KLUWER |
|
Keywords: |
|
Comets, nuclei, surfaces |
|
Bibliographic Code: |
|
2002EM&P...89..117C |
Direct observations of the nuclear surfaces of comets have been difficult; however a growing number of studies are overcoming observational challenges and yielding new information on cometary surfaces. In this review, we focus on recent determinations of the albedos, reflectances, and thermal inertias of comet nuclei. There is not much diversity in the geometric albedo of the comet nuclei observed so far (a range of 0.025 to 0.06). There is a greater diversity of albedos among the Centaurs, and the sample of properly observed TNOs (2) is still too small. Based on their albedos and Tisserand invariants, Fernández et al. (2001) estimate that about 5% of the near-Earth asteroids have a cometary origin, and place an upper limit of 10%. The agreement between this estimate and two other independent methods provide the strongest constraint to date on the fraction of objects that comets contribute to the population of near-Earth asteroids. There is a diversity of visible colors among comets, extinct comet candidates, Centaurs and TNOs. Comet nuclei are clearly not as red as the reddest Centaurs and TNOs. What Jewitt (2002) calls ultra-red matter seems to be absent from the surfaces of comet nuclei. Rotationally resolved observations of both colors and albedos are needed to disentangle the effects of rotational variability from other intrinsic qualities. New constraints on thermal inertia of comets are consistent with previous independent estimates. The thermal inertia estimates for Centaurs 2060 Chiron and 8405 Asbolus are significantly lower than predicted by thermal models, and also lower than the few upper limits or constraints known for active, ordinary nuclei.
|
Title: |
|
Comet Splitting - Observations and Model Scenarios |
|
Authors: |
|
|
|
Affiliation: |
|
AA(European Southern Observatory ESO, Alonso de Cordova 3107, Santiago de Chile) |
|
Journal: |
|
Earth, Moon, and Planets, v. 89, Issue 1, p. 91-115 (2002). (EM&P Homepage) |
|
Publication Date: |
|
00/2002 |
|
Origin: |
|
KLUWER |
|
Keywords: |
|
Appearance, boulders, classification, comet evolution, disappearing comets, double nuclei, dynamics, fragmentation models, Kreutz group comets, split comets, striae |
|
Bibliographic Code: |
|
2002EM&P...89...91B |
Splitting events affect cometary nuclei to a different level of severity ranging from complete disruption of the nucleus (e.g., C/1999 S4 LINEAR) to separation of major fragments (e.g., 73P/Schwassmann-Wachmann 3) and spill-offs of smaller boulders (e.g., C/2001 A2 LINEAR). Fragmentation of comets produces secondary products over a wide range of sizes (from cometesimals to sub-micron dust). It is detectable through the presence of fragments (with own comae and tails) in the coma of the parent nucleus, through outbursts in its activity and through arc-lets (``coma wings'') associated with fragments. The secondaries have different lifetimes and show different non-gravitational forces. Nucleus splitting is also considered to generate whole families of comets (Kreutz group) or - if gravitational bound - multiple nuclei (e.g., C/1995 O1 Hale-Bopp). It may explain the striae phenomena seen in dust tails of bright comets (C/1995 O1 Hale-Bopp) and the detection of chains of impact craters on other bodies in the solar system. As process of significant mass loss it is relevant for the scenario of nucleus extinction, at the same time it also plays a role for the number statistics of existing (observable) comets and for the size distribution of comet nuclei. Various model scenarios for nucleus splitting are proposed: tidal disruption, rotational splitting, break-up due to internal gas pressure, fragmentation due to collision with other bodies. Only in one case, Comet D/1993 F1 Shoemaker-Levy 9, the physical process of fragmentation could be undoubtedly identified. In any case, comet splitting provides important insights in the internal structure, surface layering and chemistry of comet nuclei.
|
Title: |
|
Hale-Bopp: What Makes a Big Comet Different? Coma Dynamics: Observations and Theory |
|
Authors: |
|
|
|
Affiliation: |
|
AA(Department of Atmospheric, Oceanic and Space Sciences, |
|
Journal: |
|
Earth, Moon, and Planets, v. 89, Issue 1, p. 73-90 (2002). (EM&P Homepage) |
|
Publication Date: |
|
00/2002 |
|
Origin: |
|
KLUWER |
|
Keywords: |
|
Comet C/1995 O1 (Hale-Bopp), comets, dynamics, molecular processes |
|
Bibliographic Code: |
|
2002EM&P...89...73C |
Comet Hale-Bopp was the largest comet by almost any definition, observed at least since the advent of modern observing techniques. In a more typical comet both the chemical and dynamical influences of collisional processes are limited by the short time a parcel of gas sublimated from the nucleus remains in the dense part of the coma. The resulting large size of the collisional coma in comet Hale-Bopp had important consequences on the dynamics of the coma, which in turn has important consequences on how observations are interpreted with standard models. Measured velocities of typical gas species (mostly the observed radicals) as well as dust were larger than normal comets. Conversely, velocities of superthermal atomic hydrogen were smaller than normal because of the same collisional processes. Furthermore, as a consequence, dust particles, which are dragged by the outflowing gas, were also accelerated to larger velocities. Such larger velocities are not simply an interesting curiosity in their own right, because nearly all observations of dust and gas are interpreted with models of the coma that depend directly on some measurement or assumption with regard to velocity. In this presentation both observations and theory regarding the dynamical conditions in the coma of comet Hale-Bopp are summarized.
|
Title: |
|
Lessons of Comet Hale-Bopp for Coma Chemistry: Observations and Theory |
|
Authors: |
|
|
|
Affiliation: |
|
AA( Observatoire de Paris, F-92195 Meudon, France), AB( Observatoire de Paris, F-92195 Meudon, France ) |
|
Journal: |
|
Earth, Moon, and Planets, v. 89, Issue 1, p. 53-71 (2002). (EM&P Homepage) |
|
Publication Date: |
|
00/2002 |
|
Origin: |
|
KLUWER |
|
Keywords: |
|
Astrochemistry, Comet C/1995 O1 (Hale-Bopp), comets, molecular processes, molecules |
|
Bibliographic Code: |
|
2002EM&P...89...53B |
Many new cometary molecules - both parents and daughters - were detected in the exceptionally productive comet C/1995 O1 (Hale-Bopp). The space distribution of several of these species could be investigated from radio interferometry or from long-slit spectroscopy in the infrared. The distinction between parent species - directly sublimated from nucleus ices - and secondary species - resulting from chemical processing in the coma or produced by a secondary source - is not always clear. It is important to assess whether or not observed minor species (HCOOCH3, HCOOH ... ) could be synthesized by chemical reactions favoured by the high density of the coma of comet Hale-Bopp. Chemical modelling by Rodgers and Charnley suggests that this is not the case. CO and H2CO are abundant cometary species which partly come from distributed sources. The nature of these sources is still a mystery. A special case, now well documented, is that of HNC, for which the abundance evolution with heliocentric distance could be observed in comet Hale-Bopp and which was observed in several much less productive comets.
|
Title: |
|
Modeling the Comet Nucleus Interior |
|
Authors: |
|
|
|
Affiliation: |
|
AA(Department of Geophysics and Planetary Sciences, |
|
Journal: |
|
Earth, Moon, and Planets, v. 89, Issue 1, p. 27-52 (2002). (EM&P Homepage) |
|
Publication Date: |
|
00/2002 |
|
Origin: |
|
KLUWER |
|
Keywords: |
|
Comet C/1995 O1 Hale-Bopp, comets, interiors, modelling |
|
Bibliographic Code: |
|
2002EM&P...89...27P |
Numerical simulation of the structure and evolution of a comet nucleus is reviewed both from the mathematical and from the physical point of view. Various mathematical procedures and approximations are discussed, and different attempts to model the physical characteristics of cometary material, such as thermal conductivity, or permeability to gas flow, are described. The evolution and activity of comets is shown to depend on different classes of parameters: Defining parameters, such as size and orbit, structural parameters, such as porosity and composition, and initial parameters, such as temperature and live radioisotope content. The latter are related to the formation of comets. Despite the large number of parameters, general conclusions, or common features, appear to emerge from the numerous model calculations - for different comets - performed to date. Thus, the stratified structure of comet nuclei, volatile depletion, and the role of crystallization of ice in cometary outbursts are discussed. Finally, an evolution model applied to comet C/1995 O1 Hale-Bopp - using different assumptions - is described and analysed in the light of observations.
|
Title: |
|
The Nucleus of Comet Hale-Bopp (C/1995 O1): Size and Activity |
|
Authors: |
|
|
|
Affiliation: |
|
AA(University of Hawaii, Institute for Astronomy, 2680 Woodlawn Drive, Honolulu, HI 96822, USA yan@ifa.hawaii.edu) |
|
Journal: |
|
Earth, Moon, and Planets, v. 89, Issue 1, p. 3-25 (2002). (EM&P Homepage) |
|
Publication Date: |
|
00/2002 |
|
Origin: |
|
KLUWER |
|
Keywords: |
|
Comets, Hale-Bopp |
|
Bibliographic Code: |
|
2002EM&P...89....3F |
A review of our current understanding of Comet Hale-Bopp's nuclear size is presented. Currently the best constraints on the effective radius are derived from late-1996 mid-IR data and near-perihelion radio data. Unfortunately the two regimes give differing answers for the radius. A possible reconciliation of the two datasets is presented that would place the radius at around 30 km. This is a large cometary radius compared to the others that are known, and this motivates a discussion of what makes a large comet different. From several possible large-comet properties, Hale-Bopp's activity is analyzed, focusing on the production rates, coma jet features, dust optical depth, and relationship with the interplanetary dust environment. The optical depth is particularly important since an optically-thick inner coma could complicate attempted measurements of the ``nucleus''.
|
Title: |
|
Cosmic Roulette: Comets In The |
|
Authors: |
|
|
|
Affiliation: |
|
AA( Campion College and Department of Physics, The University of Regina, Regina, SK, Canada ), AB( Department of Physics, The University of Regina, Regina, SK, Canada ) |
|
Journal: |
|
Earth, Moon, and Planets, v. 88, Issue 4, p. 211-221 (2000). (EM&P Homepage) |
|
Publication Date: |
|
00/2002 |
|
Origin: |
|
KLUWER |
|
Keywords: |
|
Asteroid impacts, Comet 28P/Neujmin 1, cometary nuclei, cometary outbursts |
|
Bibliographic Code: |
|
2002EM&P...88..211B |
We have produced top ten ranked lists of impact velocity, main belt asteroid region dwell times and impact probabilities for a selection of short period comets. The comet with the combined highest ranking with respect to impact probability and impact velocity is Comet C/1766 G1 Helfenzrieder. Since it is not clear that this comet still exists, the highest ranked, presently active, comet with respect to the likelihood of suffering impacts from meter-sized objects while in the main belt asteroid region is Comet 28P/Neujmin 1. We find no evidence to support the existence of a distinctive sub-set of the short period comets liable to show repeated outburst or splitting behaviours due to small body, meter-sized, asteroid impacts.
|
Title: |
|
Estimating The Dust Particle Size Of Comet Hale-Bopp By Studying The Motion Of The Ejecta On September 10-11, 1996 |
|
Authors: |
|
|
|
Affiliation: |
|
AA(National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China ), AB(National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China ), AC(National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China ) |
|
Journal: |
|
Earth, Moon, and Planets, v. 88, Issue 2, p. 61-74 (2002). (EM&P Homepage) |
|
Publication Date: |
|
00/2002 |
|
Origin: |
|
KLUWER |
|
Keywords: |
|
Comet Hale-Bopp, kinematics, outburst |
|
Bibliographic Code: |
|
2002EM&P...88...61Q |
We report the observation of an outburst of comet Hale-Bopp (C/1995 O1) happened on September 10-11, 1996, carried by the 1.56 m telescope of Shanghai Astronomical Observatory. Two ejecta were found in CCD images during the outburst. According to the positions of ejecta, we discuss the motion of the ejecta considering dust particles are subjected to the gravity and the Solar radiation pressure, and conclude that the mean radii of dust grains in the ejecta were about submicron-sized. So the observed X-ray emission are most likely produced by small size particles scattering the Solar X-ray.
|
Title: |
|
The shell of Comet Hale-Bopp |
|
Authors: |
|
|
|
Affiliation: |
|
AA( |
|
Journal: |
|
Chinese Astronomy and Astrophysics, Volume 26, Issue 3, p. 348-353. (ChA&A Homepage) |
|
Publication Date: |
|
00/2002 |
|
Origin: |
|
ELSEVIER |
|
Keywords: |
|
Comet Hale, Bopp, shell, jet |
|
Bibliographic Code: |
|
2002ChA&A..26..348Y |
A film showing the shells in the coma of Comet Hale-Bopp, taken on March 4, 1997, is digitized and measured by means of a PDS. The method of fitting leads to the following results: (1)The first shell (innermost one), derived from a jet formation, is seen as an Archimedean spiral and the velocity of the ejecta from the cometary nucleus is 1.6 km/sec; (2)All of the 2nd, 3rd and 4th shells are parabolas or catenaries.
|
Title: |
|
Five main tail streamers of Comet Halley |
|
Authors: |
|
Zhao, Hai-Bin; Hu, Zhong-Wei; Wang, Jian-Zhong; Hou, Zhen-Yu |
|
Affiliation: |
|
AA(Department of Astronomy, Nanjing University, Nanjing 210093, China), AB(Department of Astronomy, Nanjing University, Nanjing 210093, China), AC(Department of Astronomy, Nanjing University, Nanjing 210093, China), AD(Department of Astronomy, Nanjing University, Nanjing 210093, China) |
|
Journal: |
|
Chinese Astronomy and Astrophysics, Volume 26, Issue 3, p. 339-347. (ChA&A Homepage) |
|
Publication Date: |
|
00/2002 |
|
Origin: |
|
ELSEVIER |
|
Keywords: |
|
comet Halley, main tail streamer, aberration angle, photometry |
|
Bibliographic Code: |
|
2002ChA&A..26..339Z |
It is of much interest that Comet Halley displayed long and straight main tails (tail streamers) even at large heliocentric distances. Streamers are usually thought to be plasma in nature. However, a dust streamer may be seen superimposed on the main tail when the Earth is close to the comet's orbital plane. Because of the broad sensitive wave range of the photographic plate and of projection effect, both plasma and dust streamers may be superimposed in the image. In this paper, photometric and geometric measurements of five main tail streamers of Comet 1P/Halley at different heliocentric distances are made and compared. The brightness profiles along streamer axes, the full widths at half maximum (FWHMs) of several transverse cuts, the apparent and actual aberration (or lag) angles of the axes as well as the tail lengths are obtained. Among the streamers recorded on blue plates, two before the perihelion passage are definitely plasma streamers. The similarity of the photometry and geometric features of the five streamers and other lines of evidence suggest that the other three streamers are also mainly plasma streamers, while any contamination by dust would be secondary.
|
Title: |
|
Evolution of Comets into Asteroids |
|
Authors: |
|
|
|
Journal: |
|
Asteroids III, W. F. Bottke Jr., A. Cellino, P. Paolicchi, and R. P. Binzel (eds), University of Arizona Press, Tucson, p.669-686 |
|
Publication Date: |
|
00/2002 |
|
Origin: |
|
LPI |
|
Bibliographic Code: |
|
2002aste.conf..669W |
In the past decade, new observations and new research tools have afforded us a better understanding of the interrelationships between comets and asteroids. The extensive automated surveys for near-Earth objects (NEOs) have serendipitously discovered many objects in comet-like orbits. Dynamical simulation codes have improved to the point where we can simulate the detailed orbital behavior of large swarms of test particles as they move out from various storage reservoirs, such as the Oort cloud and the Kuiper belt. Physical studies of both comets and asteroids have given us a far better understanding of the nature of these bodies and have identified possible discriminators to be used in comparing them. As a result, we can now identify likely dormant or extinct comet candidates among the asteroid population. It appears that ~6 ± 4% (or perhaps more) of the NEO population is derived from Jupiter-family comets. Also, it is highly likely that many asteroids in eccentric orbits with large semimajor axes and large inclinations are derived from the Oort cloud. However, we must also recognize that some small fraction of the Oort cloud population is likely to consist of asteroidal bodies ejected there during the clearing of the planetary zones in the early solar system. Additional physical and dynamical studies are required to continue improving our knowledge of the interrelationships between comets and asteroids and to help identify likely extinct comet candidates.
|
Title: |
|
Photodegradation of hexamethylenetetramine by VUV and its relevance for CN and HCN extended sources in comets |
|
Authors: |
|
Cottin, Hervé; Bachir, Souleyman; Raulin, François; Gazeau, Marie-Claire |
|
Affiliation: |
|
AA(Laboratoire Interuniversitaire des Systèmes Atmosphériques (LISA), UMR 7583 CNRS, Université Paris 7 and Paris 12, C.M.C., 61 Avenue du Général de Gaulle, 94010 Créteil Cedex, France) |
|
Journal: |
|
Advances in Space Research, Volume 30, Issue 6, p. 1481-1488. (AdSpR Homepage) |
|
Publication Date: |
|
00/2002 |
|
Origin: |
|
ELSEVIER |
|
Abstract Copyright: |
|
(c) 2002 Elsevier Science B.V. All rights reserved. |
|
Bibliographic Code: |
|
2002AdSpR..30.1481C |
This paper presents our first experimental results on the photodegradation at 147 and 122 nm of hexamethylenetetramine (HMT). This molecule, suspected to be present on cometary grains, could be responsible for extended sources of CN and HCN in comets. We show that if HMT is quite resistant to direct photolysis under vacuum, interactions with water vapor photoproducts, which could happen in inner comae, lead to a much more efficient degradation with formation of HCN, NH3 and other N bearing molecules. Thus HMT could act as a parent or grand parent molecule for observed extended sources. However, additional source with greater degradation efficiency is certainly required to account observations in outer comae.
|
Title: |
|
Are organic molecules produced by nebular Fischer-Tropsch processes preserved in comets? |
|
Authors: |
|
|
|
Journal: |
|
Advances in Space Research, Volume 30, Issue 6, p. 1469-1472. (AdSpR Homepage) |
|
Publication Date: |
|
00/2002 |
|
Origin: |
|
ELSEVIER |
|
Abstract Copyright: |
|
(c) 2002 Elsevier Science B.V. All rights reserved. |
|
Bibliographic Code: |
|
2002AdSpR..30.1469L |
Chondritic porous interplanetary dust particles, thought to be of cometary origin, contain solid phases that were likely produced by gas-grain reactions in nebular environments. In the course of laboratory simulations addressed to reproduce under nebular conditions such distinctive mineralogies, simple organic molecules are formed through Fischer-Tropsch-type processes, suggesting that part of the organic volatiles in comets may have had a nebular origin. On the basis of these experiments, the relative abundances of homologous volatile hydrocarbons and the implications for the possible existence of thiols and sulfonic acids in comets are discussed.
|
Title: |
|
Biomolecules in the interstellar medium and in comets |
|
Authors: |
|
|
|
Affiliation: |
|
AA(Space Science Division, MS 245-3, NASA Ames Research Center, Moffett Field CA 94035-1000, USA), AB(Space Science Division, MS 245-3, NASA Ames Research Center, Moffett Field CA 94035-1000, USA), AC(Space Science Division, MS 245-3, NASA Ames Research Center, Moffett Field CA 94035-1000, USA), AD(Space Science Division, MS 245-3, NASA Ames Research Center, Moffett Field CA 94035-1000, USA) |
|
Journal: |
|
Advances in Space Research, Volume 30, Issue 6, p. 1419-1431. (AdSpR Homepage) |
|
Publication Date: |
|
00/2002 |
|
Origin: |
|
ELSEVIER |
|
Abstract Copyright: |
|
(c) 2002 Elsevier Science B.V. All rights reserved. |
|
Bibliographic Code: |
|
2002AdSpR..30.1419C |
We review recent studies of organic molecule formation in dense molecular clouds and in comets. We summarise the known organic inventories of molecular clouds and recent comets, particularly Hale-Bopp. The principal chemical formation pathways involving gas phase reactions, as well as formation by catalytic reactions on grain surfaces or through dust fragmentation, are identified for both dense clouds and cometary comae. The processes leading to organic molecules with known biological function, carbon chains, deuterium fractionation, HNC and S-bearing compounds are described. Observational searches for new interstellar organics are outlined and the connection between observed interstellar organics and those detected in comets Hale-Bopp and Hyakutake are discussed.
|
Title: |
|
Production of organic molecules in interstellar ices |
|
Authors: |
|
|
|
Affiliation: |
|
AA(Raymond and Beverly Sackler Laboratory for Astrophysics
(SLA), |
|
Journal: |
|
Advances in Space Research, Volume 30, Issue 6, p. 1409-1417. (AdSpR Homepage) |
|
Publication Date: |
|
00/2002 |
|
Origin: |
|
ELSEVIER |
|
Abstract Copyright: |
|
(c) 2002 Elsevier Science B.V. All rights reserved. |
|
Bibliographic Code: |
|
2002AdSpR..30.1409S |
Complex organic species are readily created when astrophysical ice analogs containing molecules like CO, H2CO and CH3OH are exposed to energetic processes like warm-up, UV photolysis and irradiation with energetic ions. We review the organic products that have been identified in such experiments and discuss the possible relevance of these results for the origin the organic molecules that are observed in comets and in the hot cores of star-forming regions.
|
Title: |
|
Neutral sodium tails in comets |
|
Authors: |
|
|
|
Affiliation: |
|
AA(Osservatorio
Astronomico, vic. Osservatorio 5, 35122 Padova, Italy), AB(Osservatorio
Astronomico, vic. Osservatorio 5, 35122 Padova, Italy), AC(Osservatorio
Astronomico, vic. Osservatorio 5, 35122 Padova, Italy), AD(Osservatorio
Astronomico, vic. Osservatorio 5, 35122 |
|
Journal: |
|
Advances in Space Research, Volume 29, Issue 8, p. 1187-1197. (AdSpR Homepage) |
|
Publication Date: |
|
00/2002 |
|
Origin: |
|
ELSEVIER |
|
Abstract Copyright: |
|
(c) 2002 Elsevier Science B.V. All rights reserved. |
|
Bibliographic Code: |
|
2002AdSpR..29.1187C |
Not Available
|
Title: |
|
The emission of gas and dust from comets |
|
Authors: |
|
|
|
Affiliation: |
|
AA(DLR Institute of Space Sensor Technology and Planetary
Exploration, Rutherfordstreet 2, 12489 |
|
Journal: |
|
Advances in Space Research, Volume 29, Issue 8, p. 1177-1186. (AdSpR Homepage) |
|
Publication Date: |
|
00/2002 |
|
Origin: |
|
ELSEVIER |
|
Abstract Copyright: |
|
(c) 2002 Elsevier Science B.V. All rights reserved. |
|
Bibliographic Code: |
|
2002AdSpR..29.1177B |
Not Available
|
Title: |
|
Chemistry of O(1D) atoms in the coma: implications for cometary missions |
|
Authors: |
|
|
|
Affiliation: |
|
AA(Space Physics Laboratory, Vikram Sarabhai Space Centre,
|
|
Journal: |
|
Advances in Space Research, Volume 29, Issue 5, p. 745-750. (AdSpR Homepage) |
|
Publication Date: |
|
00/2002 |
|
Origin: |
|
ELSEVIER |
|
Abstract Copyright: |