What are the orbital parameters of the comet?
Comet Shoemaker-Levy 9 is actually in a temporary orbit of Jupiter, which is most unusual: comets usually just orbit the Sun. Only two comets have ever been known to orbit a planet (Jupiter in both cases), and this was inferred in both cases by extrapolating their motion backwards to a time before they were discovered. S-L 9 is the first comet observed while orbiting a planet. Shoemaker-Levy 9’s previous closest approach to Jupiter (when it broke up) was on July 7, 1992; the distance from the center of Jupiter was about 96,000 km, or about 1.3 Jupiter radii. The comet is thought to have reached apojove (farthest from Jupiter) on July 14, 1993 at a distance of about 0.33 Astronomical Units from Jupiter’s center. The orbit is very elliptical, with an eccentricity of over 0.998. Computations by Paul Chodas, Zdenek Sekanina, and Don Yeomans, suggest that the comet has been orbiting Jupiter for 20 years or more, but these backward extrapolations of motion are highly uncertain. See “elements
