Jupiter: Its Captured Satellites

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Science  27 Aug 1971:
Vol. 173, Issue 3999, pp. 812-813
DOI: 10.1126/science.173.3999.812


Because of the small size and irregular orbits of the seven outer satellites of Jupiter, it is often assumed that they were derived by capture. The conditions whereby Jupiter can capture satellites have therefore been examined. Relationships derived on the basis of the three-body problem for planets in elliptical orbits enable the dimensions of the capture orbits around Jupiter to be calculated. It is found that Jupiter may capture satellites through the inner Lagrangian point when at perihelion or at aphelion. Captures at perihelion should give rise to satellites in direct orbits of 11.48 x 106 kilometers and capture at aphelion to retrograde orbits of 21.7 x 106 kilometers. The correspondence with the seven outer satellites suggests that Jupiter VI, VIl, and X in direct orbits at 11.47, 11.74, and 11.85 x 106 kilometers were captured at Jupiter perihelion, whereas Jupiter VIII, IX, XI, and XII in retrograde orbits of 23.5, 23.7, 22.5, and 21.2 x 106 kilometers were captured when Jupiter was at aphelion. Examination of the precapture orbits indicates that the seven outer satellites were derived from the asteroid belt.