The impact of a close stellar encounter on the Edgeworth-Kuiper Belt

Abstract

We numerically investigate the possibility that a close stellar encounter could account for the high inclinations of the Kuiper belt, as originally proposed by Ida, Larwood and Burkert, however we consider encounters with pericenters within those explored by previous works. A star of mass 0.2 Msol entering the solar system on a nearly parabolic, low inclination, retrograde orbit with perihelion of 50 AU can scatter ~30% of the Kuiper belt into moderate inclination (i>10 degrees) and eccentricity orbits, while leaving the rest of the belt at low eccentricities and inclinations. This scenario provides a possible explanation for the dichotomy of the Kuiper belt, accounting for the scattered and classical populations, including objects with high eccentricities and inclinations. High eccentricity objects that were not placed into resonance with Neptune are more likely to be removed from the system by subsequent long timescale evolution. Consequently this scenario suggests that some Plutinos could have originally been objects in circular orbits which were scattered into resonant high eccentricity and high inclination orbits by the stellar encounter. Objects could have been placed into stable resonant regions with Neptune by the encounter. However long lived regions of dynamical stability should differ from those selected by resonance capture. This scenario predicts the presence of objects in resonances with Neptune that are unlikely to have been captured via Neptune's migration.