International Summer Institute for Modeling in Astrophysics

Motivated by recent observations of retrograde planets, we investigated the orbital decay of a retrograde planet embedded in a protoplanetary disk. We treated both gravitational and hydrodynamic drag, and found the migration time scale ranges from 10³ to 10⁵ years for planet masses between 10^-3 to 10¹ Jupiter masses. We also found that a highly inclined orbit can increase this time scale by a factor of 10 and that due to inclination damping, the final inclination is unlikely to be greater than 50 degrees.