Stability in the most external region of the Oort Cloud: evolution of the ejected comets

Abstract

In this paper, we present a study of the dynamical effects of the Galaxy on the external region of the Oort Cloud. Theaimsofthispaperare: (i) to determine an outer limit for the Oort Cloud; and (ii) to analyse the dynamical behaviour of the most external objects of the Oort Cloud and how they are ejected from the Solar system. To achieve these aims, we follow the temporal evolution of massless test particles in the Galactic environment of the solar neighbourhood. We show that the effect of the perturbations from the Galactic tide in the particles is similar to that found for the evolution of the population of wide binary stars. Moreover, in the Oort Cloud, we find a dynamical structure around 105 au conformed by objects unbound from the Sun. This structure allows us to define a transition region of stability and an outer boundary for the Oort Cloud, and it is also in agreement with previous results about the disruption of wide binary stars.