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.
Author/Curator:
Dr. David R. Williams, dave.williams@nasa.gov
NSSDCA, Mail Code 690.1
NASA Goddard Space Flight Center
Greenbelt, MD 20771
+1-301-286-1258
NASA Official: Dave Williams, david.r.williams@nasa.gov
Last Updated: 30 December 2004, DRW