Four cometary belts associated with the orbits of giant planets: a new view of the outer solar system's structure emerges from numerical simulations

Using numerical simulations, we examine the structure of a cometary populat ion near a massive planet, such as a giant planet of the Solar system, star ting with one-planet approximation (the Sun plus one planet). By studying t he distributions of comets in semimajor axis, eccentricity, pericenter, and apocenter distances, we have revealed several interesting features in thes e distributions. The most remarkable ones include (i) spatial accumulation of comets near the planetary orbit (which we call the 'cometary, belt') and (ii) avoidance of resonant orbits by comets. Then we abandon one-planet ap proximation and examine as to how a cometary belt is modified when the infl uence of all the four giant planets is taken into consideration. To this en d, we simulate a stationary distribution of comets, which results from the gravitational scattering of the Kuiper belt objects on the four giant plane ts and accounts for the effects of mean-motion resonances. In our simulatio ns, we deal with the stationary distributions computed, at different initia l conditions, as 36 runs for the dynamical evolution of comets, which start from the Kuiper belt and are typically traced until the comets are ejected from the Solar system. Accounting for the influence of four giant planets makes the cometary belts overlapping, but nevertheless keeping almost all t heir basic features found in one-planet approximation. In particular, the b elts maintain the gaps in the (a,e)- and (a, i)-space similar to the Kirkwo od gaps in the main asteroid belt. We conclude that the large-scale structu re of the Solar system is featured by the four cometary belts expected to c ontain 20-30 millions of scattered comets, and only a tiny fraction of them is currently visible as Jupiter, Saturn, etc. family comets. (C) 2000 Else vier Science Ltd. All rights reserved.