Icarus 137, 84–121 (1999) Article ID icar.1998.6040, available online at http://www.idealibrary.com on The Evolution of Long-Period Comets Paul Wiegert Department of Physics and Astronomy, York University, Toronto, Ontario M3J 1P3, Canada E-mail:
[email protected] and Scott Tremaine Princeton University Observatory, Peyton Hall, Princeton, New Jersey 08544-1001 Received May 16, 1997; revised September 29, 1998 the length of time over which routine telescopic observations We study the evolution of long-period comets by numerical in- have been taken—the sample of comets with longer periods is tegration of their orbits, a more realistic dynamical approach than much less complete; (iii) the planetary perturbations suffered the Monte Carlo and analytic methods previously used to study by comets with periods longer than 200 yr are uncorrelated on this problem. We follow the comets from their origin in the Oort successive perihelion passages. The orbits of typical Halley- cloud until their final escape or destruction, in a model solar sys- type and Jupiter-family comets are further distinguished by tem consisting of the Sun, the four giant planets and the Galactic (i) their inclinations, which are much larger for Halley-type tide. We also examine the effects of nongravitational forces as well comets; (ii) their Tisserand invariants T , which are typically as the gravitational forces from a hypothetical solar companion greater than 2 for Jupiter-family comets (Carusi and Valsecchi or circumsolar disk. We confirm the conclusion of Oort and other investigators that the observed distribution of long-period comet 1992; Levison 1996).