Dynamical lifetime of the Oort Cloud new comets under planetary perturbation

We describe the result of our numerical simulations that trace the dynamical evolution of the Oort Cloud new comets that fall down to the planetary region. These comets approach the planetary region (such as inside Neptune’s orbit) through the galactic tide and encounter with nearby stars, stay in the planetary region for a while, and eventually get scattered away. We combine two dynamical models (analytic and numerical) to follow the dynamical paths of the comets that leave the Oort Cloud during two different periods: One is the 1 billion years that include the present time when the outer comet cloud is likely nearly isotropic, and the other is the 1 billion years in the early solar system presumably with the comet cloud confined in a flat disk. Here are two major conclusions derived from our numerical result: (1) Typical dynamical lifetime of the comets is O(10⁷) years. After traversing the planetary region for this timespan, most of the comets get scattered and ejected out of the system. (2) When orbital inclination of the comets is small, the so-called “planet barrier” works effectively, preventing the comets from penetrating into the terrestrial planetary region. Transition probabilities of the comets into other minor body populations, such as Centaurs or Jupiter-family comets, are also discussed.