- Globular Star Clusters Click icon to view globular clusters of Messier's catalog Messier's Globular Clusters; Links The icon shows 47 Tucanae (NGC 104). Globular clusters are gravitationally bound concentrations of approximately ten thousand to one million stars, spread over a volume of several tens to about 200 light years in diameter. The first globular cluster discovered, but then taken ...seds.org/messier/glob.html