Effect of Jupiter's mass growth on satellite capture

The prograde case

¹ Grupo de Dinâmica Orbital & Planetologia - Unesp, CP 205 CEP 12.516-410 Guaratinguetá, SP, Brazil e-mail: [ernesto;ocwinter]@feg.unesp.br
² Universidade Estadual Paulista - IGCE - DEMAC, CP 178 CEP 13.500-970 Rio Claro, SP, Brazil e-mail: tadashi@ms.rc.unesp.br

Received: 16 July 2004
Accepted: 3 November 2005

Abstract

We study the effects of Jupiter mass growth in order to permanently capture prograde satellites. Adopting the restricted three-body problem, Sun-Jupiter-Particle, we performed numerical simulations backward in time while considering the decrease in Jupiter's mass. We considered the particle's initial conditions to be prograde, at pericenter, in the region 100R_♃ ≤ a ≤ 400R_♃ and 0 ≤ e ≤ 0.5. The results give Jupiter's mass at the moment when the particle escapes from the planet. Such values give an indication of the conditions that are necessary for capture. An analysis of these results shows that prograde satellite capture is more complex than a retrograde one. It occurs in a two-step process. First, when the particles get inside about 0.85 R_Hill (Hills' radius), they become weakly bound to Jupiter. Then, they keep migrating toward the planet with a strong decrease in eccentricity, while the planet is growing. The radial oscillation of the particles reduces significantly when they reach a radial distance that is less than about 0.45 R_Hill from the planet. Three-dimensional simulations for the known prograde satellites of Jupiter were performed. The results indicate that Leda, Himalia, Lysithea, and Elara could have been permanently captured when Jupiter had between 50% and 60% of its present mass.