Wiktionary
n. (context astronomy English) A group of gravitationally bound stars and other material (such as nebulae and planets), conventionally with one generation of similarly aged stars from the same pre-stellar nebula.
Wikipedia
Star clusters or star clouds are groups of stars. Two types of star clusters can be distinguished: globular clusters are tight groups of hundreds or thousands of very old stars which are gravitationally bound, while open clusters, more loosely clustered groups of stars, generally contain fewer than a few hundred members, and are often very young. Open clusters become disrupted over time by the gravitational influence of giant molecular clouds as they move through the galaxy, but cluster members will continue to move in broadly the same direction through space even though they are no longer gravitationally bound; they are then known as a stellar association, sometimes also referred to as a moving group.
Star clusters visible to the naked eye include Pleiades, Hyades and the Beehive Cluster.
Usage examples of "star cluster".
It was quite a surprise, then, when the 'Sibwarra' arrived at the Ssi-ruuvi star cluster and found a half - beaten foe.
Since the Hapans hadn't yet fallen to the Empire, the smugglers had been using an outpost in neutral territory near the borders of the Hapan star cluster, hoping that their proximity to the Hapans would keep the Empire off their back.
Nothing like this had happened in three years of surveying in this star cluster.
As xenophobic as the Yevetha, having evolved under similar circumstances in the heart of an isolated star cluster, the reptilian aliens had only just been driven back by the New Republic with the unexpected assistance of the Chiss.
The star cluster is over two weeks distant at warp seven, but Jaza advises that if one star-jelly school was found this far from it—.