Planet (Galaxy 4)

An unnamed Earth-like planet in the Fourth Galaxy (PROSE: Galaxy Four) visited by the First Doctor was devoid of all life except plants. The planet had three suns.

After a Drahvin ship attacked a Rill ship in space, both vessels crashed onto the planet's surface. When the Rills determined that the planet was going to explode in two days' time and the Drahvins' ship was irreparable, they offered to take the Drahvins with them. The Drahvins, led by Maaga, instead attempted to steal the Rills' ship for themselves, but were defeated by the Doctor and left behind to perish when the planet exploded. (TV: Galaxy 4)

Behind the scenes
For the animated recreation of Galaxy 4, Gary Russell stated in the audio commentary for the DVD and Blu-ray release that he named the planet as Noss as a reference point. (DCOM: Galaxy 4)

Examining the album art for the vinyl release of Galaxy 4, Jon Culshaw remarked that the planet could be 55 Cancri E, a tidally-locked carbon planet with diamond mountain ranges.