M13: The Great Globular Cluster in Hercules

This image captures M13, the Great Globular Cluster in Hercules, one of the brightest and best-known globular clusters visible from the northern hemisphere. Lying roughly 22,000 light-years away, this tightly bound sphere of several hundred thousand stars spans about 145 light-years and is among the oldest structures in our galaxy, with an age of over 11 billion years.

The image resolves individual stars from the sparse outer halo all the way into the crowded core, while preserving their natural colors: cool, evolved red giants glow in warm orange tones, contrasting with the hotter blue stars scattered throughout the cluster. First recorded by Edmond Halley in 1714, M13 was also the target of the famous 1974 Arecibo radio message.

M13 has an apparent magnitude of 5.8 and an apparent diameter of roughly 20 arcminutes. Its stars contain only about 5% as much iron as the Sun, and they are so tightly packed that collisions sometimes create new, young stars known as blue stragglers. Charles Messier added it to his catalogue on 1 June 1764.

Stacked and processed in PixInsight.