M53

Messier 53, commonly abbreviated M53, is a globular cluster located in the northern constellation Coma Berenices. It is one of the fainter globular clusters in Messier's catalog, with an apparent visual magnitude around 7.7, and it can be seen with small telescopes under dark skies. Estimates place M53 at a distance of about 55,000 to 60,000 light-years from Earth, placing it in the outer regions of the Milky Way’s halo. The cluster appears to span roughly 250 to 300 light-years in diameter, corresponding to an angular size on the sky of about 16 to 18 arcminutes.

Near M53 lies a second globular cluster, NGC 5053; together they form a loose pair in the Milky Way halo and are often studied for insights into cluster–cluster interactions and halo structure.

Messier 53 was discovered by Charles Messier in 1775 and was later included in his catalog. It is a relatively metal-poor and ancient system, with an estimated age of about 12 to 13 billion years and a global metallicity around [Fe/H] ≈ -2.0. The cluster contains hundreds of thousands of stars, including a population of blue horizontal-branch stars and RR Lyrae variables, which have been used to probe distances and cluster evolution.

As with other globular clusters, M53 serves as a laboratory for studying stellar dynamics, stellar evolution in low-metallicity environments, and the assembly history of the Milky Way.