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NGC 6712
NGC 6712
	NGC 6712, by HST
Observation data (J2000 epoch)
Class	IX:
Constellation	Scutum
Right ascension	18h 53m 04.32s
Declination	–08° 42′ 21.5″
Distance	26.4 kly (8.1 kpc)<
Apparent magnitude (V)	+8.69
Apparent dimensions (V)	7.2'
Physical characteristics
Mass	9.4×104 M☉
Metallicity	= –0.94 dex
Estimated age	10.4 Gyr
Other designations	GCl 103, GC 4441
	See also: Globular cluster, List of globular clusters

NGC 6712 is a globular cluster that was probably discovered by Le Gentil on July 9, 1749 when investigating the Milky Way star cloud in Aquila. He described it as a "true nebula," in contrast to the open star cluster M11. Independently discovered by William Herschel on June 16, 1784 and cataloged as H I.47; he also first classified it as a round nebula. John Herschel was the first to describe it as a globular star cluster during his observations in the 1830s. The cluster appears to be about 12 billion years old and may have originally have been significantly more massive having undergone significant mass loss due to passes through the galactic disc.^[3] For a globular cluster, NGC 6712 is somewhat metal-rich.^[6]

NGC 6712 is home to a "black widow" pulsar named PSR J1853−0842A. Such systems involve an extremely rapidly rotating pulsar, accompanied by a low-mass star or brown dwarf. The high amounts of radiation emitted from the pulsar contributes to the evaporation of the low-mass companion, which has a mass between 0.018 and 0.036 solar masses. Although pulsars rotate more slowly with age, PSR J1853−0842A is accelerating, which would not be possible without it being within a globular cluster.^[6]

References

^ Shapley, Harlow; Sawyer, Helen B. (August 1927), "A Classification of Globular Clusters", Harvard College Observatory Bulletin, 849 (849): 11–14, Bibcode:1927BHarO.849...11S.
^ ^a ^b ^c ^d "SIMBAD Astronomical Database". Results for NGC 6712. Retrieved 2006-11-16.
^ ^a ^b Deras, D; Ferro, A Arellano; Lázaro, C; Fierro, I H Bustos; Calderón, J H; Muneer, S; Sunetra, Giridhar (22 January 2020). "NGC 6712: the variable star population of a tidally disrupted globular cluster". Monthly Notices of the Royal Astronomical Society. 493 (2): 1996–2014. arXiv:2001.08306. doi:10.1093/mnras/staa196.
^ Marks, Michael; Kroupa, Pavel (August 2010), "Initial conditions for globular clusters and assembly of the old globular cluster population of the Milky Way", Monthly Notices of the Royal Astronomical Society, 406 (3): 2000–2012, arXiv:1004.2255, Bibcode:2010MNRAS.406.2000M, doi:10.1111/j.1365-2966.2010.16813.x, S2CID 118652005. Mass is from M_PD on Table 1.
^ ^a ^b Forbes, Duncan A.; Bridges, Terry (May 2010), "Accreted versus in situ Milky Way globular clusters", Monthly Notices of the Royal Astronomical Society, 404 (3): 1203–1214, arXiv:1001.4289, Bibcode:2010MNRAS.404.1203F, doi:10.1111/j.1365-2966.2010.16373.x, S2CID 51825384.
^ ^a ^b Yan, Zhen; Pan, Zhi-Chen; Ransom, Scott M.; Lorimer, Duncan R.; Qian, Lei; Wang, Pei; Shen, Zhi-Qiang; Li, Di; Jiang, Peng; Luo, Jin-Tao; Liu, Jie; Huang, Zhi-Peng (2021). "An Eclipsing Black Widow Pulsar in NGC 6712". The Astrophysical Journal. 921 (2): 120. arXiv:2109.06754. Bibcode:2021ApJ...921..120Y. doi:10.3847/1538-4357/ac25eb. S2CID 237502882.