Rogue planet
From Tardis Wiki, the free Doctor Who reference
A rogue planet was a planet which wandered through space instead of orbiting a star.
Mondas became a rogue planet when it left the vicinity of the star Sol; however, following an indeterminate amount of time it returned to the area of space it had left. (TV: The Tenth Planet, AUDIO: Spare Parts)
Skardal was a rogue planet which threatened to collide with both Skaro and Mechanus. (COMIC: The Rogue Planet, Impasse)
Voga became a rogue planet when most of it was destroyed by the Cybermen. It eventually settled into an orbit around Jupiter. (TV: Revenge of the Cybermen)
Vortis became a rogue planet when the Zarbi Supremo set it on a course to the solar system. (PROSE: The Lair of Zarbi Supremo)
