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 of about 300,000 stars in the constellation of Hercules. M13 was discovered by Edmond Halley in 1714, and catalogued by Charles Messier on June 1, 1764. It is located at right ascension 16h 41.7m and declination +36° 28′. With an apparent magnitude of 5.8, it is barely visible with the naked eye on a very clear night. Its diameter is about 23 arc minutes and it is readily viewable in small telescopes.
The Arecibo message of 1974, containing encoded information about the human race, DNA, atomic numbers, Earth’s position, and other information, was beamed towards M13 to allow it to be picked up by potential extraterrestrial civilizations in the cluster. The message will reach the cluster in 25,000 years.