Close Encounters of Comets and Planets

Abstract

Distributions are formed of the results of close planet-comet encounters when 109 hypothetical random parabolic comets interact with the solar system. Attention is paid to the rare close encounters wherein the comet is captured to a new period in the range of 240 years. The encounter trajectory is solved using a new conic matching procedure that agrees well with exact calculations. Multiple encounters are not treated. Distributions (whose absolute scale factor is specified) are plotted for various orbital elements of the captured comets, including period, inclination, argument of perihelion, and perihelion distance. These distributions do not agree with those for the known short-period comets, even after allowing for observational selection. The capture event is rare. Taking into account the actual flux of long-period comets entering the solar system, it is estimated that only once in 7000 years will such a comet of absolute magnitude 11.9 or brighter be captured by Jupiter to a new period of less than 21 years with a new perihelion distance less than 2 astronomical units.