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| Paper: |
Analysis of Preimpact Hubble Space Telescope Images to Determine the Nature of Comet Shoemaker--Levy 9 Fragments |
| Volume: |
107, Completing the Inventory of the Solar System |
| Page: |
309 |
| Authors: |
Rettig, T. W.; Mumma, M. J.; Disanti, M.; Sobczak, G. J.; Hahn, J. M. |
| Abstract: |
We obtained Hubble Space Telescope (HST) Wide Field Planetary Camera images of comet Shoemaker--Levy 9 (S--L 9) prior to impact with Jupiter in 1994 to observe the effects of the Jovian gravitational field on the approaching fragments. The HST images were used to monitor the absolute brightness in the central regions of the comae, changes in the surface brightness profiles, and general morphological changes in the fragments as they approached final impact with Jupiter. S--L 9 most likely came apart under the influence of the Jovian tidal force near perijove in 1992 ({Scotti and Melosh,} 1993; {Asphaug and Benz,} 1994a; {Solem,} 1994; Sekanina {\it et al.,} 1994) into approximately 20 fragments ({Scotti,} 1993; { Luu and Jewitt,} 1993; {Weaver et al.,} 1994). In contrast to condensed or solid fragments, we suggested that after perijove, the breakup debris condensed initially as swarms of particles ({Rettig et al.,} 1994a; {Olson and Mumma,} 1994) and if interparticle collisions were infrequent, some of these swarm-like subnuclei might have remained extended throughout the 2-year orbit. In this paper we discuss a simple analytical model to demonstrate how after the original nucleus came apart, the debris cloud formed 14--20 fragments. We also present temporal magnitudes of all fragments obtained from the HST images from January through July 1994 and an analysis of the preimpact images for four S--L 9 condensations T(4), Q2(7b), P1(8a), and K(12) which suggests that not all of the central subnuclei were consistent with solid objects. The temporal magnitudes and surface brightness profiles of several S--L 9 fragments are consistent with tidal dispersal at distances much greater than the classical $\sim 2R_J$ Roche limit. |
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