[Image of Comet P/Shoemaker-Levy 9]

The Comet

Comet P/Shoemaker-Levy 9 was discovered by Carolyn and Gene Shoemaker and David Levy in a photograph taken on March 18, 1993 with the 0.4-meter Schmidt telescope at Mt. Palomar. The comet was in orbit around Jupiter with a period of about 2 years, and last made a close approach to Jupiter on July 7, 1992, at a distance of approximately 0.38 Jupiter radii (71,400 km) above the cloud tops. Approximately 1.5 to 2.2 hours after closest approach, the comet (which was presumably a single body at the time) was broken apart by tidal forces into at least 21 pieces. It is believed that the parent body has been in orbit about Jupiter for at least 2 decades. The pieces continued to orbit Jupiter with a period of approximately 2 years, and an apo-Jove of about 50 million km. Due to gravitational forces from the Sun which changed the orbits slightly, on the next approach to Jupiter the pieces impacted the planet. The pieces were spread out in a string, with the discernable pieces designated with letters from A to W (excluding I and O), A being the first piece which impacted Jupiter (on July 16, 1994) and W being the last (on July 22, 1994). The brightest, and presumably largest piece in the string was Q. The composition of these pieces is unknown, and the density is not well constrained, so that the parent object may have been an asteroid, which would imply a higher density, despite its designation as a comet. The diameters of the pieces are not well constrained, but they appeared to be larger than 1 km and no larger than 5 km. Images from the Hubble telescope indicate the largest fragments to be approximately 2 to 3 km in diameter, which would indicate a parent body of approximately 8 km diameter. The string of fragments was enveloped by a dust cloud and may have included smaller fragments which were not discernable from Earth. Estimates of the relative brightness of some of the fragments have been made by Olivier Hainaut and Richard West of the European Southern Observatory.

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Dr. David R. Williams, dave.williams@nasa.gov
NSSDC, Mail Code 690.1
NASA Goddard Space Flight Center
Greenbelt, MD 20771

NASA Official: Ed Grayzeck, edwin.j.grayzeck@nasa.gov
Last Updated: 30 December 2004, DRW