The Hercules Cluster was discovered by Edmund Halley in 1714 and cataloged by Charles Messier in 1764. It is about 25,000 light years from earth and about 150 light years in diameter, containing several hundred thousand stars. It can be seen with the naked eye as a small, fuzzy patch in the summer constellation Hercules on clear, moonless nights from locations significantly free of light pollution.

The stars comprising globular clusters are believed to all be approximately the same age, and among the oldest objects in the universe. Current theories indicate that they are held in proximity to each other by a black hole at the center. M13 is one of about 200 globular clusters in the vicinity of our galaxy, though like the others it is not part of our galaxy. Globular clusters orbit the Milky Way, caught in it's gravitation field.