M72 - NGC 6981

Messier 72 (NGC 6981) is a globular cluster located approximately 55,400 light-years from Earth in the constellation Aquarius, making it one of the more distant globular clusters in the Messier catalog. It was discovered by Pierre Mechain in 1780 and subsequently cataloged by Charles Messier. M72 is classified as a relatively loose globular cluster with a Shapley-Sawyer concentration class of IX. The cluster spans about 106 light-years in physical diameter and contains an estimated population of several hundred thousand stars, though its considerable distance makes it appear small and faint compared to closer Messier globulars. M72 has a visual magnitude of about 9.3, which combined with its distance makes it one of the more challenging Messier globulars for amateur observers. The cluster contains at least 43 known variable stars, most of which are RR Lyrae pulsators useful for distance determination. M72 also has a moderately blue horizontal branch, consistent with its intermediate metallicity. The cluster lies about 3 degrees east-southeast of the star Epsilon Aquarii, in a region of sky that is relatively sparse of bright guide stars, making it somewhat tedious to locate via star-hopping. In binoculars, M72 is visible as a very faint, tiny fuzzy spot under dark skies. A 4-inch telescope shows it as a small, round, nebulous patch, while telescopes of 8 inches or more are needed to begin resolving any individual stars at the periphery. Due to its looseness and distance, M72 never quite achieves the spectacular resolved appearance of closer globulars, but it remains a satisfying challenge for dedicated observers.

M72 spans about 106 light-years in diameter and lies approximately 55,400 light-years from Earth, making it one of the more distant Messier globulars.