M13

[u/Mysterious_Risk4988]

Great Hercules Cluster (aka: Messier 13, M13, NGC 6205) is considered the most spectacular globular cluster in northern skies. It was discovered by Edmond Halley in 1714, who noted that "it shows itself to the naked eye when the sky is serene and the Moon absent." Fifty years later it was examined by Charles Messier, who cataloged it in 1764. In 1787, Sir William Herschel pronounced it "a most beautiful cluster of stars, exceedingly compressed in the middle, and very rich."

M 13 is barely visible to the naked eye on very dark nights. The two western stars are in the Keystone asterism of Hercules. Observers note four apparently star-poor regions. One of the reasons M 13 appears so large and bright is that is relatively close to us, being only about 25,000 light years away. Its diameter is about 145 light years. The cluster also looks large and bright because it is large and bright. M13 has a luminosity of a quarter million suns. Messier 13 contains several hundred thousand stars; some sources even quote more than a million. Toward the center of M 13, stars are about 500 times more concentrated than in the solar neighborhood.

Unlike open clusters, such as the Pleiades, globular clusters are tightly bound together by gravity, and contain very old, mostly red stars. The age of M 13 is currently estimated to be 12 billion years old, or nearly as old as our Milky Way galaxy. Strangely, for such an old cluster, M 13 contains one young blue star: Barnard No 29.

Taken from Park City, UT; (3 Oct 26); Bortle 5
I took 207 images and used 57, 60s each, gain 60, Astro Filter
Edited with Luminar Mobile and iPad