Dr. Ed Thommes
CITA

University of Florida Astronomy Colloquium - Jan 25th, 2006

Planet formation, migration and survival

In the first few million years of a planetary system's life, (proto-) planets are subject to strong interactions with the protostellar gas disk, resulting in their inward migration. For bodies not massive enough to open a gap in the disk, migration rate is proportional to mass, and the time to spiral into the parent star is much shorter than the accretion timescale for bodies of order 10 Earth masses. This poses a problem for the standard model of giant planet formation, in which the solid core must accrete first. I will present models of "survival strategies" which allow giant planets to outlast this hazardous period. Even in the worst-case scenario, a window of opportunity for the emergence of jovian planets opens up as the gas disk dissipates. The process becomes easier when the disk contains a magnetohydrodynamic "dead zone", which acts as a migration bottleneck. Whichever the mechanism, the first gas giant to form then itself becomes a barrier to migration, and so facilitates the formation of subsequent planets. Finally, I will discuss how a system's giant planets can produce a large-scale dynamical shake-up as the gas disk disperses, thus driving the final stage of terrestrial planet formation.