Steady-state injection of short-period comets from the trans-Neptunian cometary belt

To examine the scenario of the existence of a trans-Neptunian comet belt as an important source region of the short-period comets, the dynamical perturbation on a system of such icy planetesimals by a few Mars- to Earth-sized planetoids in highly eccentric orbits is considered. In the context of our planetoid-scattering model with three or four large planetoids orbiting in highly eccentric orbits, the total mass of the trans-Neptunian comet belt between the orbit of Neptune and 200 AU could be on the order of 0.002 M_⊕, at the present time, and the total number of the trans-Neptunian belt objects should be on the order of 1-3 × 10⁸ with about 10⁶ of them orbiting between Saturn and Uranus. Because of the strong gravitational scattering by the hypothetical planetoids, the number of the trans-Neptunian belt comets so derived should be regarded as a lower limit. It is quite possible that in the absence of such large planetoids, a much larger population (i.e., a factor of 100) of the trans-Neptunian belt comets might exist.