Star cluster

A star cluster was a group of stars.

Clusters
A battle during the Rutan-Sontaran War was fought in the Madillon Cluster. (TV: The Two Doctors)

According to Commander Kaagh, half the species from Earth to the Verlixix Spiral Cluster had plans to invade Earth because humans had "no guts". (TV: Enemy of the Bane)

The Jolius Cluster was home to the Okrenians. (COMIC: Pay the Piper)

The Olveron Cluster contained a million stars and a hundred million inhabited planets. (TV: The Caretaker)