A Region Void of Irregular Satellites Around Jupiter

TL;DR

This study investigates why there is a region around Jupiter with no irregular satellites by simulating orbital dynamics, revealing that interactions with Ganymede and Callisto influence satellite stability but do not fully explain the observed void.

Contribution

The paper provides a detailed numerical analysis of the dynamical evolution of irregular satellites around Jupiter, exploring mechanisms behind the satellite-void region.

Findings

Objects near Ganymede and Callisto become unstable due to their gravitational influence.

Interactions with Ganymede and Callisto alone do not fully explain the satellite-void region.

Long-term perturbations and formation history may contribute to the observed satellite distribution.

Abstract

An interesting feature of the giant planets of our solar system is the existence of regions around these objects where no irregular satellites are observed. Surveys have shown that, around Jupiter, such a region extends from the outermost regular satellite Callisto, to the vicinity of Themisto, the innermost irregular satellite. To understand the reason for the existence of such a satellite-void region, we have studied the dynamical evolution of Jovian irregulars by numerically integrating the orbits of several hundred test particles, distributed in a region between 30 and 80 Jupiter-radii, for different values of their semimajor axes, orbital eccentricities, and inclinations. As expected, our simulations indicate that objects in or close to the influence zones of the Galilean satellites become unstable because of interactions with Ganymede and Callisto. However, these perturbations cannot account for the lack of irregular satellites in the entire region between Callisto and Themisto. It is suggested that at distances between 60 and 80 Jupiter-radii, Ganymede and Callisto may have long-term perturbative effects, which may require the integrations to be extended to times much longer than 10 Myr. The interactions of irregular satellites with protosatellites of Jupiter at the time of the formation of Jovian regulars may also be a destabilizing mechanism in this region. We present the results of our numerical simulations and discuss their applicability to similar satellite void-regions around other giant planets.