Kasterborous

Kasterborous is the constellation in which the planet Gallifrey was located. (DW: Pyramids of Mars)

Behind the Scenes
It has been suggested that the design on the back of the TARDIS key (as worn by the Third Doctor, Fourth and Eighth Doctors) is a representation of the constellation, with Gallifrey's twin suns being the central star in the pattern.

The name Kasterborous was first mentioned in the revived series in DW: Voyage of the Damned.