... M13: The Great Globular Cluster in Hercules . ... A system of stars numbering in the hundreds of thousands, it is one of the brightest globular star clusters in the northern sky. At a distance of 25,000 light-years, the cluster stars crowd into a region 150 light-years in diameter, but approaching the cluster core over 100 stars would be contained in a cube just 3 light-years on a side. ... Publications with keywords: globular cluster - star cluster . ... Globular Star Cluster M3 . ...