Messier 72 on:
[Wikipedia]
[Google]
[Amazon]
Messier 72 (also known as M72 or NGC 6981) is a globular cluster in the south west of the very mildly southern constellation of Aquarius.
Messier 72, SEDS Messier pages
Messier 72, Galactic Globular Clusters Database page
* {{DEFAULTSORT:Messier 72 Messier 072 Messier 072 072 Messier 072 Astronomical objects discovered in 1780
Observational history and guide
M72 was discovered by astronomer Pierre Méchain in 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 faintnebula
A nebula ('cloud' or 'fog' in Latin; pl. nebulae, nebulæ or nebulas) is a distinct luminescent part of interstellar medium, which can consist of ionized, neutral or molecular hydrogen and also cosmic dust. Nebulae are often star-forming regio ...
rather than a cluster. With a larger instrument, astronomer John Herschel
Sir John Frederick William Herschel, 1st Baronet (; 7 March 1792 – 11 May 1871) was an English polymath active as a mathematician, astronomer, chemist, inventor, experimental photographer who invented the blueprint and did botanical wor ...
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. The surrounding field stars become visible from a -aperture device. One of will allow measurement of an angular diameter of 2.5 . At the core is clear: its 1.25 diameter, meaning a broad spread; and small parts scarcer in stars to the south and east.
Properties
Based upon a 2011 census of variable stars, the cluster is away from the Sun. It has an estimated combined mass of 168,000solar mass
The solar mass () is a standard unit of mass in astronomy, equal to approximately . It is often used to indicate the masses of other stars, as well as stellar clusters, nebulae, galaxies and black holes. It is approximately equal to the mass ...
es () and is around 9.5 billion years old. The core region has a density of stars that is radiating 2.26 times solar luminosity () per cubic parsec. There are 43 identified variable stars in the cluster.
See also
* List of Messier objectsReferences and footnotes
External links
Messier 72, SEDS Messier pages
Messier 72, Galactic Globular Clusters Database page
* {{DEFAULTSORT:Messier 72 Messier 072 Messier 072 072 Messier 072 Astronomical objects discovered in 1780