Stability of co-orbital ring material with applications to the Janus-Epimetheus system

Abstract

An analytical model that describes the evolution of ring particles that are co-orbital with two larger bodies on near-circular and near-planar orbits has been formulated. This can be used to estimate the lifetime of the particles within the ring. All the examples investigated, such as the Janus-Epimetheus (JE) system, indicate that the particles should be removed from the co-orbital region within half a synodic period (∼4 years for JE). Numerical modelling confirms the predictions of the model. When the masses are on eccentric orbits the particles remain within the co-orbital system for longer. Our results suggest that the ring associated with Janus and Epimetheus must be continually fed with material, probably by meteoroid impacts on the two satellites.