Editing Planetary migration (section)

{{this|planetary motion within a solar system|migration between solar systems|gravitational capture}}
{{Short description|Astronomical phenomenon}}
{{Star formation}}
'''Planetary migration''' occurs when a [[planet]] or other body in orbit around a star interacts with a disk of gas or [[planetesimal]]s, resulting in the alteration of its orbital parameters, especially its [[semi-major axis]].  Planetary migration is the most likely explanation for [[hot Jupiter]]s ([[exoplanets]] with [[Jupiter mass|Jovian mass]]es but orbits of only a few days).  The generally accepted [[Solar nebula#Formation of planets|theory of planet formation]] from a [[protoplanetary disk]] predicts that 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{{cn|date=July 2020}} that [[Terrestrial planet|terrestrial-mass planet]]s 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 to 1000 Earth masses), if those planets form via the [[Core-accretion theory|core-accretion]] mechanism.