DPS 34th Meeting, October 2002
Session 23. Other (than Io and Europa) Planetary Satellites

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[23.04] The Irregular Satellites of Jupiter


Jupiter's irregular satellites are thought to be captured bodies that were originally moving in heliocentric orbits. Currently there is no known efficient mechanism by which gravitational capture can occur. The irregular satellites probably were acquired at a very early epoch, when Jupiter was still growing and sustained a bloated gas envelope hundreds of times its present size.

We are undertaking a sensitive new survey of Jupiter's Hill sphere using wide field optical cameras on Mauna Kea. The purpose is to identify large numbers of irregular satellites in the hope that the systematics of the population can be discerned. We will then be in a position to test the capture hypotheses, and may be able to place constraints on processes operative in the first few million years after Jupiter's accretion.

Our survey has so far revealed 21 new irregular satellites plus the rediscovery of the lost object S/1975 J1. This more than triples the number of irregular satellites known around Jupiter. The satellites form at least 3 distinct dynamical groupings in a-i space with possible subgroupings. Most likely each group results from the disruption of a parent body either through the capture process or possibly later during a collision. Our initial results suggest there are about 100 irregular satellites of Jupiter with diameters greater than 1 km.

We will discuss the survey strategy, the properties of the new objects, prospects for future discoveries, the relations to other irregular satellites in the Solar System and the physical constraints on the formation epoch that we expect to be able to place.

Work supported by NASA.



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