M13 - GREAT GLOBULAR CLUSTER IN HERCULES

Messier 13, the Great Hercules Cluster, is the most famous globular cluster in the Northern Hemisphere and one of the brightest globular clusters visible from mid-northern latitudes. Located approximately 22,200 light-years from Earth in the constellation Hercules, it contains several hundred thousand stars packed into a sphere about 145 light-years in diameter. M13 shines at an apparent magnitude of 5.8, making it just barely visible to the naked eye under excellent conditions as a faint fuzzy star. The cluster was discovered by Edmond Halley in 1714 and later cataloged by Messier in 1764. In 1974, M13 achieved a unique distinction when the Arecibo radio telescope beamed a coded message toward the cluster as part of a demonstration of the telescope's capabilities, making it the target of humanity's most famous deliberate interstellar radio transmission. The message, which encoded basic information about humanity and our solar system, will take approximately 22,000 years to reach the cluster. Through binoculars, M13 appears as a bright, round, nebulous glow. It is through telescopes that the cluster truly comes alive, with 4 inches of aperture beginning to resolve the outer stars and 8 inches or more revealing an astonishing cascade of stars spilling outward from a blazing core. Experienced observers note dark lanes and Y-shaped voids within the cluster known as the "propeller," visible in telescopes of 8 inches or larger. M13's combination of brightness, large apparent size, and high northern declination make it the go-to showpiece object for public star parties and the quintessential introduction to globular clusters for beginning astronomers.

Contains several hundred thousand stars within 145 light-years diameter at a distance of 22,200 light-years, shining at magnitude 5.8.