M13 - The Hercules Cluster

Image: Keith Turnecliff, Long Itchington, Warwickshire

Like shiny flakes sparkling in a snow globe, over 100,000 stars whirl within the globular cluster M13, one of the brightest star clusters visible from the Northern Hemisphere. Located 25,000 light-years from Earth with an apparent magnitude of 5.8, this glittering metropolis of stars in the constellation Hercules can be spotted with a pair of binoculars most easily in July.
The English astronomer Edmond Halley, best known for recognizing the periodicity of the comet that bears his name, discovered M13 in 1714. When Charles Messier added M13 to his catalog in 1764, he was convinced that the nebulous object did not contain any stars at all. Because they are so densely packed together, the cluster’s individual stars were not resolved until 1779. Near the core of this cluster, the density of the stellar population is about a hundred times greater than the density in the neighborhood of our sun. These stars are so crowded that they can, at times, run into each other and even form a new star. The resulting “blue stragglers” appear to be younger than the other stars in their immediate vicinity and are of great scientific interest to astronomers.
Hubble’s composite image of this cluster’s core was created using observations taken between 1999 and 2006 in both visible and infrared wavelengths.

Facts about M13 by Keith Turnecliff

M13, also designated NGC 6205 and sometimes called the Great Globular Cluster in Hercules or the Hercules Globular Cluster, is a globular cluster of several hundred thousand stars in the constellation of Hercules.