(a torque on a planet from co-orbiting planetary disk material)
Corotation torque is a type of torque that can be
imposed on a planet by a circumstellar disk,
i.e., a gas disk in Keplerian orbit around the star.
Gravitational forces between the planet and nearby disk material
surrounding it can have a slowing affect on the planet's orbit,
given some particular characteristics of the disk.
It is a factor in planetary migration, specifically,
Type I migration, an inward migration which might help
explain cases of planets currently in orbits where models say they
would not form, such as hot Jupiters.