Cluster of galaxies in Hercules

Abell 2151, the Hercules cluster, is a small, irregular cluster, with a core membership of fewer than 100 galaxies, and no strongly dominant central galaxy. It is more than 360 million light-years away and probably contains 1000 billion solar masses of sundry materials. It contains the two peculiar systems Arp 71 (NGC6045) and Arp 272 (NGC6050+IC1179). KPNO 4-meter Mayall telescope, 1974.