Messier 72

Short description: Globular cluster in the constellation Aquarius

Messier 72

M72 from Hubble Space Telescope; 3.44′ view

Observation data (J2000 epoch)
Class| IX[1]
Constellation| Aquarius
Right ascension|  20h 53m 27.70s[2]
Declination| –12° 32′ 14.3″[2]
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| [Fe/H] = –1.48 ± 0.03[3] dex
Estimated age| 9.5 Gyr[6]
Other designations| NGC 6981, GCl 118[7]
See also: Globular cluster, List of globular clusters

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.

## Contents

* 1 Observational history and guide
* 2 Properties
* 3 See also
* 4 References and footnotes
* 5 External links

## Observational history and guide

M72 was discovered by astronomer Pierre Méchain in 1780.[lower-alpha 1] 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 a good night sky as a faint nebula in a telescope with a 6 cm (2.4 in) aperture. The surrounding field stars become visible from a 15 cm (5.9 in)-aperture device. One of 25 cm (9.8 in) will allow measurement of an angular diameter of 2.5 ′. At 30 cm (12 in) the core is clear: its 1.25 ′ diameter, meaning a broad spread; and small parts scarcer in stars to the south and east.[10]

## 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 (Template:Lo) per cubic parsec.[6] There are 43 identified variable stars in the cluster.[3]

Map showing location of M72

## See also

* List of Messier objects

## References and footnotes

1. ↑ Shapley, Harlow; Sawyer, Helen B. (August 1927), "A Classification of Globular Clusters", Harvard College Observatory Bulletin 849 (849): 11–14, Bibcode: 1927BHarO.849...11S.
2. ↑ 2.0 2.1 Goldsbury, Ryan et al. (December 2010), "The ACS Survey of Galactic Globular Clusters. X. New Determinations of Centers for 65 Clusters", The Astronomical Journal 140 (6): 1830–1837, doi:10.1088/0004-6256/140/6/1830, Bibcode: 2010AJ....140.1830G.
3. ↑ 3.0 3.1 3.2 3.3 Figuera Jaimes, R. et al. (October 2011), Henney, W. J.; Torres-Peimbert, S., eds., "XIII Latin American Regional IAU Meeting: (item) The Globular Cluster NGC 6981: Variable stars population, physical parameters and astrometry", Revista Mexicana de Astronomía y Astrofísica, Serie de Conferencias 40: pp. 235–236, Bibcode: 2011RMxAC..40..235F.
4. ↑ "Messier 72". https://messier.seds.org/m/m072.html.
5. ↑ 5.0 5.1 Boyles, J. et al. (November 2011), "Young Radio Pulsars in Galactic Globular Clusters", The Astrophysical Journal 742 (1): 51, doi:10.1088/0004-637X/742/1/51, Bibcode: 2011ApJ...742...51B.
6. ↑ 6.0 6.1 Sollima, A. et al. (April 2008), "The correlation between blue straggler and binary fractions in the core of Galactic globular clusters", Astronomy and Astrophysics 481 (3): 701–704, doi:10.1051/0004-6361:20079082, Bibcode: 2008A&A...481..701S
7. ↑ "NGC 6981". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=NGC+6981.
8. ↑ Garfinkle, Robert A. (1997), Star-Hopping: Your Visa to Viewing the Universe, Cambridge University Press, p. 266, ISBN 978-0521598897, https://books.google.com/books?id=40JzBYGREL0C&pg=PA266
9. ↑ Burnham, Robert (1978), Burnham's Celestial Handbook: An Observer's Guide to the Universe Beyond the Solar System, Dover Books on Astronomy Series, 1 (2nd ed.), Courier Dover Publications, pp. 188–189, ISBN 978-0486235677, https://books.google.com/books?id=xq9MGuJvh8gC&pg=PA188
10. ↑ Luginbuhl, Christian B.; Skiff, Brian A. (1998), Observing Handbook and Catalogue of Deep-Sky Objects (2nd ed.), Cambridge University Press, p. 25, ISBN 978-0521625562, https://books.google.com/books?id=MwCyjQpGU7UC&pg=PA25

1. ↑ 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 WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images

Coordinates:  20h 53m 27.91s, −12° 32′ 13.4″

* v
* t
* e

Astronomical catalogs

Messier|

* M63
* M64
* M65
* M66
* M67
* M68
* M69
* M70
* M71
* M72
* M73
* M74
* M75
* M76
* M77
* M78
* M79
* M80
* M81

NGC|

* Astronomy:NGC 6976
* Astronomy:NGC 6977
* Astronomy:NGC 6978
* Astronomy:NGC 6979
* Astronomy:NGC 6980
* NGC 6981
* Astronomy:NGC 6982
* Astronomy:NGC 6983
* Astronomy:NGC 6984
* Astronomy:NGC 6985
* Astronomy:NGC 6986

* v
* t
* e

Messier objects

List|

* M1
* M2
* M3
* M4
* M5
* M6
* M7
* M8
* M9
* M10
* M11
* M12
* M13
* M14
* M15
* M16
* M17
* M18
* M19
* M20
* M21
* M22
* M23
* M24
* M25
* M26
* M27
* M28
* M29
* M30
* M31
* M32
* M33
* M34
* M35
* M36
* M37
* M38
* M39
* M40
* M41
* M42
* M43
* M44
* M45
* M46
* M47
* M48
* M49
* M50
* M51
* M52
* M53
* M54
* M55
* M56
* M57
* M58
* M59
* M60
* M61
* M62
* M63
* M64
* M65
* M66
* M67
* M68
* M69
* M70
* M71
* M72
* M73
* M74
* M75
* M76
* M77
* M78
* M79
* M80
* M81
* M82
* M83
* M84
* M85
* M86
* M87
* M88
* M89
* M90
* M91
* M92
* M93
* M94
* M95
* M96
* M97
* M98
* M99
* M100
* M101
* M102
* M103
* Added
* M104
* M105
* M106
* M107
* M108
* M109
* M110

See also|

* Caldwell catalogue
* Catalogue of Nebulae and Clusters of Stars
* Herschel 400 Catalogue
* Index Catalogue
* New General Catalogue
* Revised New General Catalogue

* Book
* Category
* Commons
* Portal

* v
* t
* e

Constellation of Aquarius

* Aquarius in Chinese astronomy
* Aquarius Stream
* List of stars in Aquarius

Stars|

| Bayer|

* α
* β
* γ
* δ
* ε
* ζ
* η
* θ
* ι
* κ
* λ
* μ
* ν
* ξ
* ο
* π
* ρ
* σ
* τ1
* τ2
* υ
* φ
* χ
* ψ2
* ψ3
* ω1
* ω2

|

Flamsteed|

* 1
* 3
* 4
* 5
* 7
* 8
* 9
* 10
* 11
* 12
* 14
* 15
* 16
* 17
* 18
* 19
* 20
* 21
* 24
* 25
* 26
* 28
* 29
* 30
* 32
* 35
* 36
* 37
* 38
* 39
* 40
* 41
* 42
* 44
* 45
* 47
* 49
* 50
* 51
* 53
* 54
* 56
* 58
* 60
* 61
* 64
* 65
* 66
* 67
* 68
* 70
* 72
* 74
* 75
* 77
* 78
* 81
* 82
* 83
* 84
* 85
* 86
* 87
* 88
* 89
* 91
* 94
* 96
* 97
* 98
* 99
* 100
* 101
* 103
* 104
* 106
* 107
* 108

Variable|

* R
* U
* AE
* DV
* EW
* EZ
* FO
* HK
* HU
* IZ
* LP

HD|

* 199442
* 200375
* 202259
* 205765
* 208177
* 210277
* 210434
* 211392
* 211575
* 213429
* 214448
* 214810
* 215114
* 215152
* 216718
* 218061
* 219279
* 220035
* 220466
* 220689
* 220766
* 221148
* 222093
* 222582
* 223311

Other|

* 2MASS J21392676+0220226
* BD−22 5866
* Fomalhaut C
* Gliese 849
* Gliese 876
* K2-28
* K2-72
* K2-138
* LS IV-14 116
* Sneden's Star
* TRAPPIST-1
* WASP-6
* WASP-47

| Exoplanets|

* 91 Aquarii b
* Gliese 849 b
* Gliese 876 b
* c
* d
* e
* HD 206610 b
* HD 210277 b
* HD 212771 b
* HD 222582 b
* K2-21b
* c
* K2-72b
* c
* d
* e
* K2-138b
* TRAPPIST-1b
* c
* d
* e
* f
* g
* h
* WASP-6b

|

| Star clusters|

* Messier 2
* Messier 72
* Messier 73

|

| Nebulae|

* Helix
* Saturn

|

Galaxies|

| NGC|

* 6975
* 7001
* 7010
* 7047
* 7051
* 7065
* 7069
* 7077
* 7081
* 7184
* 7252
* 7257
* 7301
* 7302
* 7600
* 7606
* 7723
* 7727
* 7759

|

Other|

* Aquarius Dwarf
* Lyman-alpha blob 1
* SMM J2135-0102
* WISE J224607.57−052635.0

| Galaxy clusters|

* Abell 2597
* XMMXCS 2215-1738

|

| Astronomical events|

* SN 2213-1745

|

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