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Messier 72
M72 from Hubble Space Telescope; 3.44′ view
Observation data (J2000 epoch)
Class	IX
Constellation	Aquarius
Right ascension	20 53 27.70
Declination	–12° 32′ 14.3″
Distance	54.57 ± 1.17 kly (16.73 ± 0.36 kpc)
Apparent magnitude (V)	9.3
Apparent dimensions (V)	6.6'
Physical characteristics
Mass	1.68×10 M☉
Metallicity	${\displaystyle {\begin{smallmatrix}\left\end{smallmatrix}}}$ = –1.48 ± 0.03 dex
Estimated age	9.5 Gyr
Other designations	NGC 6981, GCl 118
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.

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 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 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.

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. It has an estimated combined mass of 168,000 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. There are 43 identified variable stars in the cluster.

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. ^ 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, arXiv:1008.2755, Bibcode:2010AJ....140.1830G, doi:10.1088/0004-6256/140/6/1830, S2CID 119183070.
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, vol. 40, pp. 235–236, Bibcode:2011RMxAC..40..235F.
4. "Messier 72". SEDS Messier Catalog. Archived from the original on 1 July 2022. Retrieved 30 April 2022.
5. ^ Boyles, J.; et al. (November 2011), "Young Radio Pulsars in Galactic Globular Clusters", The Astrophysical Journal, 742 (1): 51, arXiv:1108.4402, Bibcode:2011ApJ...742...51B, doi:10.1088/0004-637X/742/1/51, S2CID 118649860.
6. ^ 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, arXiv:0801.4511, Bibcode:2008A&A...481..701S, doi:10.1051/0004-6361:20079082, S2CID 3088769
7. "NGC 6981". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2006-11-16.
8. Garfinkle, Robert A. (1997), Star-Hopping: Your Visa to Viewing the Universe, Cambridge University Press, p. 266, ISBN 978-0521598897
9. Burnham, Robert (1978), Burnham's Celestial Handbook: An Observer's Guide to the Universe Beyond the Solar System, Dover Books on Astronomy Series, vol. 1 (2nd ed.), Courier Dover Publications, pp. 188–189, ISBN 978-0486235677
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

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

• Astronomy
• Stars
• Outer space

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
Category Commons Portal

v t e Constellation of Aquarius
Aquarius in Chinese astronomy Aquarius Stream List of stars in Aquarius
Stars	Bayer α (Sadalmelik) β (Sadalsuud) γ (Sadachbia) δ (Skat) ε (Albali) ζ η θ (Ancha) ι κ (Situla) λ (Hydor) μ ν ξ (Bunda) ο π ρ σ τ τ υ φ χ ψ (91) ψ ψ ω ω A A b b b c c c d e f g g h i i i k α PsA C Flamsteed 1 4 5 7 8 9 10 11 12 14 15 16 17 18 19 20 21 24 26 28 29 30 32 35 36 37 39 40 41 42 44 45 47 49 50 51 54 56 58 60 61 64 65 67 70 72 74 75 77 78 81 82 84 85 87 94 96 97 100 Variable R U AE DV EP EW EZ FO HK IL HU IZ LL LP HR 8017 8056 8121 8263 8363 8453 8500 8507 8581 8612 8629 8645 8716 8783 8836 8856 8879 8924 9014 HD 206610 (Bosona) 210277 212771 (Lionrock) 215152 219617 220466 220689 222093 222582 Other 2MASS J21392676+0220226 BD−22 5866 Gliese 849 K2-21 K2-28 K2-58 K2-72 K2-138 LS IV-14 116 Sneden's Star TRAPPIST-1 WASP-6 (Márohu) WASP-47 WASP-69 WASP-75
Exoplanets ψ Aquarii b Gliese 849 b Gliese 876 b c d e HD 206610 b HD 210277 b HD 212771 b (Victoriapeak) HD 221416 b HD 222582 b K2-66b 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 Nebula Saturn Nebula
Galaxies	NGC 6975 7001 7010 7047 7051 7065 7069 7077 7081 7184 7222 7252 7257 7301 7302 7393 7492 7585 7592 7600 7606 7723 7727 7759 Other Aquarius Dwarf ESO 603-G21 Lyman-alpha blob 1 PGC 1228197 PHL 293B SMM J2135-0102 WISE J224607.57−052635.0 J2345-0449
Galaxy clusters Abell 2597 RXC J2211.7-0350 XMMXCS 2215-1738
Astronomical events SN 2213-1745
Category

• Globular clusters
• Aquarius (constellation)
• Messier objects
• NGC objects
• Astronomical objects discovered in 1780
• Discoveries by Pierre Méchain