Tau Ceti was a star roughly 11.9 light years away from Sol. Its star system had at least four inhabited planets: Diplos, Ogros, (TV: The Stones of Blood) Zygor (PROSE: The Bodysnatchers) and Cornucopia. (COMIC: Hunters of the Burning Stone) It was located in the Western Spiral Arm of Mutter's Spiral. (PROSE: Come One, Come All, to The Greatest Show in the Galaxy! [+]Gareth Roberts, Gary Russell and Philip Murphy, Doctor Who Live fiction (BBC Worldwide, 2010).)
Nocturne was located "smack in the middle" between Tau Ceti and Zeta Reticuli. (AUDIO: Nocturne)