[a] It was discovered by the French astronomer Charles Messier in 1764, who described it as a circular nebula without a star.

In the New General Catalogue, compiled during the 1880s, it was described as a "remarkable globular, bright, large, slightly oval."

It can be easily viewed with a pair of 10×50 binoculars,[10] forming a patch of hazy light some 4 arcminutes wide that is slightly elongated along the east–west axis.

[6] The cluster is following a retrograde orbit (against the general flow) through the inner galactic halo, suggesting that it was acquired from a satellite galaxy rather than forming within the Milky Way.

[3] A process of mass segregation may have caused the central region to gain a greater proportion of higher mass stars, creating a color gradient with increasing blueness toward the middle of the cluster.