Cygnus A was a feature of space, beyond which lay Zeta Minor. (TV: Planet of Evil) A sentence of digging ore in Cygnus A was a punishment for attempting to defraud a Federation-backed diamond franchise. (PROSE: Diamond Dogs) At some point, Cygnus A fell to the Committee. (AUDIO: The Conspiracy)
Behind the scenes[]
Cygnus A was used again, three years later, in the Terry Nation-produced series Blake's 7. This is further referenced in the novel Diamond Dogs where Cygnus A is said to be a place of punishment set up by the Federation. In the Blake's 7 episode named after the planet, it is indeed shown to be a prison under control of the Federation, the primary governing force in the show's universe.