Messier 72 (also known as M72 or NGC 6981) is a globular cluster in the south west of the southern constellation of Aquarius.

Observational history

M72 was discovered by astronomer Pierre Méchain on August 29 1780. His countryman Charles Messier looked for it 36 days later, and included it in his catalog. Both opted for the then-dominant of the competing terms for such objects, considering it a faint nebula rather than a cluster. With a larger instrument, astronomer John Herschel called it a bright "cluster of stars of a round figure". Astronomer Harlow Shapley noted a similarity to Messier 4 and 12.

It is visible in a good night sky as a faint nebula in a telescope with a aperture.

Properties

Based upon a 2011 census of variable stars, the cluster is away from the Sun. It has an estimated combined mass of 168,000 solar masses (), and is around 9.5billion years old. There are 43 identified variable stars in the cluster.

See also

• List of Messier objects

References and footnotes

External links

• Messier 72, SEDS Messier pages

• Messier 72, Galactic Globular Clusters Database page

• Messier 72, LRGB CCD image based on two hours total exposure

• M-72 Information