Messier 72
20h 53m 27.91s, −12° 32′ 13.4″Distance | 54.57 ± 1.17 kly (16.73 ± 0.36 kpc)[3] | |
|---|---|---|
| Apparent magnitude (V) | 9.3[4] | |
| Apparent dimensions (V) | 6.6' | |
| Physical characteristics | ||
| Mass | 1.68×105[5] M☉ | |
| Metallicity | = –1.48 ± 0.03 Gyr[6] | |
| Other designations | NGC 6981, GCl 118[7] | |
![{\displaystyle {\begin{smallmatrix}\left[{\ce {Fe}}/{\ce {H}}\right]\end{smallmatrix}}}](https://wikimedia.org/api/rest_v1/media/math/render/svg/4c0821bd80891e071c08e7c7ee8e022baedf522c)
Messier 72 (also known as M72 or NGC 6981) is a
Observational history and guide
M72 was discovered by astronomer Pierre Méchain in 1780.[a] His countryman Charles Messier looked for it 36 days later, and included it in his catalog.[8] 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.[9]
It is visible in
Properties
Based upon a 2011 census of variable stars, the cluster is 54.57 ± 1.17 kly (16.73 ± 0.36 kpc) away from the Sun.[3] It has an estimated combined mass of 168,000[5] solar masses (M☉) and is around 9.5 billion years old. The core region has a density of stars that is radiating 2.26 times solar luminosity (L☉) per cubic parsec.[6] There are 43 identified variable stars in the cluster.[3]
See also
- List of Messier objects
References and footnotes
- Bibcode:1927BHarO.849...11S.
- ^ S2CID 119183070.
- ^ Bibcode:2011RMxAC..40..235F.
- ^ "Messier 72". SEDS Messier Catalog. Archived from the original on 1 July 2022. Retrieved 30 April 2022.
- ^ S2CID 118649860.
- ^ S2CID 3088769
- ^ "NGC 6981". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2006-11-16.
- ISBN 978-0521598897
- ISBN 978-0486235677
- ISBN 978-0521625562
- ^ on August 29
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
- Messier 72 on
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