Tremulus Three

Tremulus Three, also referred to as the Telos system, (AUDIO: Secrets of Telos) was the star system containing the planet Telos (PROSE: Attack of the Cybermen) which was six weeks travel from Earth. The system also held the smaller planetoid Telos Minor. (AUDIO: Secrets of Telos)

Tremulus Three was located outside of Mutter's Spiral, (AUDIO: Last of the Cybermen) near Tasker's Crown, (PROSE: Attack of the Cybermen) and was a neighbour to Krelos's star system, which contained several other planets with the "-os" suffix. (AUDIO: The Fate of Krelos / Return to Telos)

The human colony Red Rocket Rising may also have been in Tremulus Three, as before Acting President Eileen Klint's message was cut off, she mentioned a world on the edge of their solar system whose name began with "Tel-." (AUDIO: Blood of the Daleks)