The Ptolemy Cluster (also known as Ptolemy's Cluster, the Scorpion's Tail, Open Cluster M7, Messier Object 7, Messier 7, M7, or NGC 6475) is an open cluster in the Scorpius constellation. It was known to Ptolemy by 130 AD. M7 is a large and brilliant group, easily detected with the naked eye.
External links
