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Keywords_120
Short-Period Comets: Origin and Terrestrial Impact Hazard
V. V. Emel'yanenko
Institute of Astronomy of RAS, Moscow, Russia
Abstract:
A model of the Solar System cometary cloud is developed to explain the observed orbital distributions and numbers of both Jupiter-family and Halley-type short-period comets. The model is consistent with the basic observed distributions of near-parabolic comets, short-period comets, Centaurs and high-eccentricity trans-Neptunian objects.This model requires that initial objects in the early Solar System are concentrated to the outer planetary region, and the physical lifetime of comets in the inner planetary region at the present epoch is an increasing function of initial perihelion distances. The mean physical lifetime of active comets does not exceed 200 revolutions in the region q < 1.5 AU.The uncertain physical behaviour of comets leads to large uncertainties in estimates of a cometary contribution to the terrestrial impact hazard.

Key words:
Very Long Baseline Interferometry (VLBI), Near Earth Objects (NEOs), short-period comets, terrestrial impact hazard, Solar System cometary orbital distributions, Jupiter-family short-period comets, Halley-type short-period comets, near-parabolic comets, Centaurs, high-eccentricity trans-Neptunian objects, initial objects in the early Solar System, outer planetary region, inner planetary region, physical lifetime of comets, function of initial perihelion distances, the mean physical lifetime of active comets, uncertain physical behaviour of comets.