CAOSP abstracts, Volume: 36, No.: 3, year: 2006

Abstract: Through a numerical integration of the orbits of test particles representing small bodies in the outer region of a once existing proto-planetary disc, which were perturbed by a nearly passing star and Neptune, we answer the question on a possibility that the observed truncation of the Kuiper belt at 50 AU was caused just by a close encounter of the Solar System with a star. We consider a spectrum of possible encounter relative velocities, geometries, and masses of the perturbing star. Though the stellar perturbation tends to increase the number density of the classical Kuiper-belt objects (CKBOs) inside 50 AU in some cases, Neptune simultaneously reduces again this number density. The ratio of the discovery probabilities of CKBOs within 50 AU and beyond this distance appears to be comparable, for several combinations of the encounter parameters, to a critical ratio at which the truncation could be explained by a perturbative stellar passage. However, even these interesting combinations are not acceptable, because the simultaneous change of the velocity of the Sun turns out here to be so large that the Oort cloud would have been stripped and no dynamically new comets could be observed. In conclusion, no stellar encounter, with a relative velocity comparable or larger than about 5 km s^-1, could cause the truncation of the Kuiper belt after the epoch when the macroscopic bodies in the belt and a significant fraction of the Oort cloud were formed.