Estimation of the Nucleus Size of Comet Shoemaker-Levy 9 under the Assumption of Its Step-by-Step Disintegration

Abstract

The orbital dynamics of comet Shoemaker-Levy 9 was considered. The size of the nucleus before its disintegration was estimated using positional observations of individual fragments of the comet and taking into account the time when the fragment falls on Jupiter were observed. The center of inertia of the parent body was assumed to coincide with the center of fragment H at the moment of disintegration. The diameter of the parent body was estimated under different assumptions about the moments of disintegration. Thus, if the nucleus of the comet was disintegrated at the moment when fragment H was passing the perijovion, the diameter of the nucleus is equal to 1.39 km; if the nucleus was disintegrated two hours before the perijovion passage, the estimate of the nucleus diameter must be increased up to 9.03 km. The period of revolution of the comet nucleus was estimated assuming that the comet rotated about the axis perpendicular to its orbital plane. The calculations allowed us to assume that fragmentation of the nucleus began approximately an hour before the comet passed the perijovion and the diameter of the parent nucleus was about 4 km.