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K. Tsiganis, A. Morbidelli (Observatoire de la Cote d' Azur, France), H. F. Levison (Southwest Research Institute, USA), R. S. Gomes (Observatoire de la Cote d' Azur, France)
We study the migration of the four outer planets of the solar system, interacting with a planetesimals disk of 50 Earth masses, truncated at 30 AU. The four planets are set initially on almost circular and co-planar orbits. Contrary to previous models, we assume a more compact configuration (within 15 AU). In our simulations, a slow migration begins, due to particles that leak out of the disk and encounter Neptune. As the system slowly stretches, a pair of planets is forced to cross an orbital resonance. Then, the planetary orbits become eccentric, the inner part of the disk is destabilised. The mass flow, towards the planetary region, increases and the planets are extracted from the resonance. A second, fast, migration phase begins, typically accompanied by a phase of encounters among the planets. This instability is suppressed in 65% of the cases studied. The disk is cleared within 200 Myrs and the planets end up on mildly eccentric and inclined orbits at 5.0-5.1, 9.2-9.8, 18-20 and 29-32 AU. If the first, slow, migration phase lasted for about 600 Myrs after the formation of the planets, the effects of this two-phase migration would have been very similar to those attributed to the Late Heavy Bombardment of the Moon.
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Bulletin of the American Astronomical Society, 36 #2
© 2004. The American Astronomical Soceity.