M13 is best known as
the Great Cluster in Hercules. It is one of the brightest of the
globular clusters, visible to the naked eye.
It lies approximately 25 thousand light years away and is 100 light
years in diameter. It was first discovered by Edmund Haley in 1714
and was cataloged by Charles Messier in 1764.
Globular clusters reside
in the halo around most galaxies. They contain some of the oldest
The small spiral galaxy
at the lower left is Herschel H701-2.