Messier 7 - Ptolemy's Cluster

Located against the rich starfield of the Milky Way in the direction of Scorpius, the open cluster Messier 7 stands out through its beautiful blue stars, a sign they are quite young – their age is not bigger than 200 million years. It is also known as Ptolemy’s Cluster, because he observed it since 2nd century AD, describing it as a nebula visible with the naked eye. In 1764, Charles Messier catalogued it, counting around 30 stars.
Today, we know that the cluster has around 100 stars spread over 25 light-years. These are more massive than the Sun, their total mass being 730 that of our local star.