Kasterborous

Kasterborous (Cas-TER-bor-os) was the constellation in which the planet Gallifrey was located. (DW: Pyramids of Mars) When explaining where he was from, the Doctor sometimes mentioned that Gallifrey was located in Kasterborous. (DW: Attack of the Cybermen, Voyage of the Damned) The Doctor's parents owned a summer house in the constellation. (PDA: The Infinity Doctors)

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