Analysis of near-separatrix motion inplanetary systems

摘要

Near-separatrix motion is a kind of motion of two planets with their relative apsidallongitude near the boundary between libration and circulation. Observed multiple planetarysystems seem to favor near-separatrix motions between neighboring planets. In this report, westudy the probability that near-separatrix motion occurs with both the linear secular systemand full three-body systems. We find that generally the ratio of near-separatrix motion is smallunless the eccentricities of the two planets differ from each other by an order of magintude,or they are in mean motion resonance. To explore the dynamical procedures causing the near-separatrix motion, we suppose a modification to scattering model by adding a mass-accretionprocess during the protoplanet growth. Statistics on the modified scattering model indicate thatthe probability of the final planet pairs in near-separatrix motion is high (~85%), which mayexplain the high occurrence of near-separatrix motions in observed planetary systems.