Near-parabolic cometary flux in the outer solar system

The flux of near-parabolic comets in the outer planetary region is calculated by adopting the regularized equation of motion which incorporates planetary and galactic perturbations. It is found that the flux is similar to the case of a strong comet shower, derived on the presumption that the Galactic tidal force is not operative. The flux so calculated, together with the capture probability of short-period (SP) comets, makes it possible to estimate the supply rate of SP comets. The estimated rate is 0.002/yr, which is at least one order of magnitude less than that required by observation. Possible sources of SP comets are discussed such as a disintegration of a giant comet, an inner extension of the observed Oort cloud, or the Kuiper belt.