HST and VLT Investigations of the Fragments of Comet C/1999 S4 (LINEAR)

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Science  18 May 2001:
Vol. 292, Issue 5520, pp. 1329-1333
DOI: 10.1126/science.1058606

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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). Photometric analysis of the fragments indicates that the largest ones have effective spherical diameters of about 100 meters, which implies that the total mass in the observed fragments was about 2 × 109 kilograms. The comet's dust tail, which was the most prominent optical feature in August, was produced during a major fragmentation event, whose activity peaked on UT 22.8 ± 0.2 July 2000. The mass of 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 large fragment and to the total mass lost from water sublimation after 21 July 2000 (about 3 × 108 kilograms). HST spectroscopic observations during 5 and 6 July 2000 demonstrate that the nucleus contained little carbon monoxide ice (ratio of carbon monoxide to water is less than or equal to 0.4%), which suggests that this volatile species did not play a role in the fragmentation of C/1999 S4 (LINEAR).

  • 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.

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