The Capture of Halley-Type and Jupiter-Family Comets From the Near-Parabolic Flux

We have considered the transfer of comets from the near-parabolic flux to short-period orbits under the perturbations of Jupiter, Saturn, Uranus, and Neptune for 5 Gyr. We have developed a combined analytical and numerical scheme which includes all essential features of the dynamical evolution. Secular resonances are amongst the most important factors causing large changes in perihelion distances. We have studied the evolution of about 10 5 randomly oriented near-parabolic orbits with initial inclinations i uniformly distributed in cos i and perihelia q distributed in all the planetary region. The main contribution to Halleytype comets comes from q < 2 AU where the probability of the capture is 0.02. The number of Halley-type objects arising from the observed near-parabolic cometary flux of all inclinations and absolute magnitudes brighter than H 10 = 7, is hundreds of times larger than the number of known Halley-type comets. In contrast with Halley-type comets, the majority of observable Jupiter-family comets originate from orbits with q > 10 AU. The flux of comets in high-eccentricity orbits may be the dominant source of the observed Jupiter family.