Planetary Migration

Planetary migration occurs when a planet or other stellar satellite interacts with a disk of gas or planetesimals, resulting in the alteration of the satellite's orbital parameters, especially its semi-major axis. The generally accepted theory of planet formation from a protoplanetary disk predicts such planets cannot form so close to their stars, as there is insufficient mass at such small radii and the temperature is too high to allow the formation of rocky or icy planetesimals. It has also become clear that terrestrial-mass planets may be subject to rapid inward migration if they form while the gas disk is still present. This may affect the formation of the cores of the giant planets (which have masses of the order of 10 Earth masses), if those planets form via the core accretion mechanism. Planetary migration is the most likely explanation for hot Jupiters, extrasolar planets with jovian masses and orbits of only a few days.