It was discovered by the Scottish astronomer James Dunlop on May 13, 1826, who described it as "a small, well-defined rather bright nebula, about 20″ in diameter".

[2] This is one of the most massive and luminous globular clusters in the Milky Way, with an estimated 1.6 million solar masses of stars.

[6] This cluster has an abnormally large number of RR Lyrae variables—68 candidates as of 2006, and their periods are longer than is typical for their respective metallicities.

[10] Examination of the red giant branch section of the color-magnitude diagram suggests that there are at least two and possibly three distinct populations in the cluster.

The brightest and higher temperature members of the red clump stars are more concentrated toward the center of the cluster.