Butterfly Cluster

The Butterfly Cluster (M 6) is a beautiful open cluster situated within the boundaries of the southern ecliptic constellation of Scorpius. Its name derives from the vague resemblance of its shape to a butterfly. The Trumpler classification of II 3 r encodes it is rich in stars, ranks II out of IV for disparateness and greatly mixes bright with faint components. It is 3.5° to the northwest of Messier 7, both north of the tail of Scorpius. The first astronomer to record the Butterfly Cluster's existence was Giovanni Battista Hodierna in 1654. However, Robert Burnham Jr. has proposed that the 1st century astronomer Ptolemy may have seen it with the naked eye while observing its neighbor the Ptolemy Cluster (M7). This capture includes BM Sco.