DDP

Abstract

It is well known that a planet embedded in a protoplanetary gaseous disk migrates, generally towards the central star. If two planets are migrating in the same disk at different speeds, they may get caught in a Mean Motion Resonance. It has been shown for instance that Jupiter and Saturn in a same disk should most likely end in the 2:3 MMR. Other configurations are possible, in particular some planets could share the same orbit in 1:1 resonance. The resonance has several effects on the migration of the pair of planets. First, their eccentricities should increase. We have shown that the damping of the eccentricity of the inner planet by the inner disk can explain the eccentricities of observed systems. Second, the migration rate may be completely changed. If the outer planet is lighter than the inner one, and if the two planets in resonance lie inside a common gap, they may migrate outwards (Masset & Snellgrove, 2001). We have shown that this can proceed on the long run, towards up to ~100 AU in flared disks. This could explain the presence of the recently directly detected exo-planets, orbiting at several dozens of AU around HD8799 and Fomalhaut. In addition, under some conditions, the migration rate could be negligible over the life-time of the disk. This should apply to the outer solar system, in the frame of the Nice model (Morbidelli et al., 2007). Consequences of this idea on the Minimum Mass Solar Nebula will be presented.