Great Hercules Cluster

A Milky Way globular cluster, the Great Hercules Cluster, also known as M13, measures 150 light years across and contains several hundreds of thousands of stars; possibly more than a million. Towards its center, stars are about 500 times more concentrated than in a typical galactic solar neighborhood; in the core upwards of 100 stars can be contained in a cube just 3 light-years on a side.

The age of M13 has been determined as 14 billion years.

M13 is peculiar in containing one young blue star, Barnard No. 29, of spectral type B2. The membership of such a star is strange for an old cluster - apparently it is a captured field star.

There are four apparently star-poor regions in M13.