Messier 80 — Globular Cluster in Scorpius

M80 is a dense globular cluster located about 32,600 light-years from Earth in the constellation Scorpius, shining at magnitude 7.9. It spans about 95 light-years in diameter and contains several hundred thousand stars. M80 is one of the most densely concentrated globular clusters in the Milky Way, with a concentration class II rating. The cluster core is so dense that stellar interactions are common, producing an unusually large population of blue stragglers — stars that appear younger and bluer than they should be in such an old cluster, likely formed through stellar collisions or mergers. M80 is estimated to be about 12.5 billion years old.

Located roughly midway between the stars Antares (Alpha Scorpii) and Graffias (Beta Scorpii), about 4 degrees northwest of Antares. In binoculars, M80 appears as a bright, compact fuzzy star — it can actually be mistaken for a comet. A 4-inch telescope at 100x shows a bright, unresolved core surrounded by a faint halo. Resolving individual stars requires at least a 10-inch telescope at high power due to the cluster's extreme density. Unlike the looser globulars, M80 has an intensely brilliant, almost explosive appearance. Best observed from May through August when Scorpius is highest.

Discovered by Charles Messier on January 4, 1781. Messier described it as 'a nebula without a star, resembling the nucleus of a small comet.' William Herschel resolved it into stars in 1785. In 1860, a nova (designated T Scorpii) erupted within M80, briefly reaching magnitude 7.0 and outshining the entire cluster for several days. This was only the second nova ever observed in a globular cluster and the first to be scientifically documented. The nova was caused by a thermonuclear explosion on the surface of a white dwarf accreting matter from a companion star.