Messier 13 - An ultradeep exposure of the popular cluster

Astronomy Picture of the Day, September 26 2024

Messier 13 (M13), also known as the Great Hercules Cluster, is one of the most prominent and well-studied globular clusters in the northern sky. Located in the constellation Hercules, this cluster lies about 22,200 light-years from Earth and is composed of several hundred thousand stars. With an apparent magnitude of 5.8, M13 is visible to the naked eye under dark skies and can be easily observed through binoculars or a small telescope.

M13 was discovered by the French astronomer Edmond Halley in 1714, although it was later cataloged by Charles Messier in 1764 as the 13th entry in his famous list of non-cometary celestial objects. At the time, globular clusters were poorly understood, but M13’s sheer brightness and dense star population made it a significant object for early astronomers.

M13 spans approximately 145 light-years in diameter, making it one of the larger globular clusters associated with the Milky Way galaxy. Like other globular clusters, it is a densely packed sphere of old stars, gravitationally bound to each other. The core of M13 contains a high concentration of stars, making this region extremely dense compared to the cluster’s outer halo. At the cluster’s center, stars can be as close as 0.05 light-years apart—about 1/10th the distance between the Sun and its nearest stellar neighbor.

Although M13 is one of the most photographed astronomical objects, there are only a few deep images that show the numerous small background galaxies in the field. Therefore, our goal was to get the deepest possible image of the globular cluster, in which, to our surprise, even IFN clouds appeared.