Hercules Great Globular Cluster “ M13 ”

Messier 13 (M13), also designated NGC 6205 and sometimes called the Great Globular Cluster in Hercules or the Hercules Globular Cluster, is a globular cluster (opens in a new tab) of about 300,000 stars in the constellation (opens in a new tab) of Hercules (opens in a new tab).

M13 was discovered by Edmond Halley (opens in a new tab) in 1714, and catalogued by Charles Messier (opens in a new tab) on June 1, 1764.

It is barely visible with the naked eye (opens in a new tab) on a very clear night. Its diameter is about 23 arc minutes and it is readily viewable in small telescopes.

M13 is about 145 light-years in diameter (opens in a new tab), and it is composed of several hundred thousand stars (opens in a new tab), the brightest of which is the variable star (opens in a new tab) V11 with an apparent magnitude of 11.95. M13 is 25,100 light-years away from Earth (opens in a new tab) The Arecibo message (opens in a new tab) of 1974, containing encoded information about human race, DNA, atomic numbers, Earth position, was beamed there for being picked up by a potential extraterrestrial civilization (opens in a new tab). It will reach the cluster in 25,100 years.