- Type of star cluster found in the arms of spiral galaxies, containing between a few dozen and a few hundred stars. The Pleiades, a galactic cluster of several hundred stars, visible to the naked eye in Taurus, are the best-known example. (Only a few stars are visible to the naked eye.) The stars of galactic clusters appear to have the same composition as other stars in spiral arms and are less tightly packed than those in the globular clusters.
- synonymopen cluster