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HST and VLT Investigations of the Fragments of Comet C/1999 S4 (LINEAR)
H. A. Weaver,1*Z. Sekanina,2I. Toth,3C. E. Delahodde,4O. R. Hainaut,4P. L. Lamy,5J. M. Bauer,6M. F. A'Hearn,7C. Arpigny,8M. R. Combi,9J. K. Davies,10P. D. Feldman,1M. C. Festou,11R. Hook,12L. Jorda,5M. S. W. Keesey,2C. M. Lisse,13B. G. Marsden,14K. J. Meech,6G. P. Tozzi,15R. West12
At least 16 fragments were detected in images of comet C/1999
S4 (LINEAR) taken on 5 August 2000 with the Hubble Space Telescope(HST) and on 6 August with the Very Large Telescope
(VLT). Photometricanalysis of the fragments indicates
that the largest ones haveeffective spherical diameters of about 100 meters, which impliesthat the total mass in the observed fragments was
about 2 × 109 kilograms. The comet's dust tail,
which was the most prominentoptical feature in August, was produced
during a major fragmentationevent, whose activity peaked on UT
22.8 ± 0.2 July 2000. The massof small particles (diameters less
than about 230 micrometers)in the tail was about 4 × 108 kilograms, which is comparable to the mass contained in
a largefragment and to the total mass lost from water sublimation
after21 July 2000 (about 3 × 108 kilograms). HST
spectroscopic observations during 5 and 6 July2000 demonstrate that
the nucleus contained little carbon monoxideice (ratio of carbon
monoxide to water is less than or equal to0.4%), which suggests that
this volatile species did not playa role in the fragmentation of
C/1999 S4 (LINEAR).
1 Department of Physics and Astronomy, Johns
Hopkins University, 3400 North Charles Street, Baltimore, MD
21218-2686, USA.
2 Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109, USA.
3 Konkoly
Observatory, Post Office Box 67, Budapest H-1525, Hungary.
4 European Southern Observatory, Alonso de Cordova
3107, Santiago, Chile.
5 Laboratoire d'Astronomie
Spatiale du CNRS, BP 8, 13376 Marseille, Cedex 12, France.
6 Institute for Astronomy, University of Hawaii,
2680 Woodlawn Drive, Honolulu, HI 96822, USA.
7 Department of Astronomy, University of Maryland,
College Park, MD 20742, USA.
8 Institut
d'Astrophysique, Université de Liège, B-4000 Liège,
Belgium.
9 Space Physics Research Laboratory,
University of Michigan, 2455 Hayward Street, Ann Arbor, MI 48109-2143,
USA.
10 Joint Astronomy Centre, Hilo, HI 96720, USA.
11 Observatoire Midi-Pyrénées, 14 avenue Edouard Belin, F-31400, Toulouse, France.
12 European Southern Observatory,
Karl-Schwarzschild-Strasse 2, D-85748 Garching, Germany.
13 Space Telescope Science Institute, 3900 San
Martin Drive, Baltimore, MD 21218, USA.
14 Smithsonian Astrophysical Observatory, 60 Garden
Street, Cambridge, MA 02138, USA.
15 Osservatorio
Astrofisico di Arcetri, Largo E. Fermi 5, I-50125, Florence, Italy.
*
To whom correspondence should be addressed.
Present address: Laboratoire d'Astronomie
Spatiale du CNRS, BP 8, 13376 Marseille, Cedex 12, France.
Present address: Department of Astronomy,
University of Maryland, College Park, MD 20742, USA.
The editors suggest the following Related Resources on Science sites:
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