Orientation-dependent effects in Oort's theory of comet origin II. Anisotropies in the distribution of long-period comet orbits

The statistical significance of anisotropies in the distribution of orbital orientations among the long-period and nearly parabolic comets is evaluated. It is suggested that these anisotropies are not the result of observational selection effects. A numerical model for the distribution of orbital orientations is constructed, based on Oort's theory of comet origin and the assumption that the observed anisotropies are caused by multiple planetary perturbations over the course of many perihelion passages. The model, which is restricted to comets with peri-helion distances less than 0.3AU, does not predict any significant anisotropies.