NGC_6218 Latitude and Longitude:
Sky map 16h 47m 14.52s, −01° 56′ 52.1″
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Messier 12
Globular cluster Messier 12 in Ophiuchus
Observation data ( J2000 epoch)
ClassIX [1]
Constellation Ophiuchus
Right ascension16h 47m 14.18s [2]
Declination–01° 56′ 54.7″ [2]
Distance16.44 ± 0.16  kly (5.04 ± 0.05  kpc) [3]
Apparent magnitude (V)6.7 [4]
Apparent dimensions (V)16.0′
Physical characteristics
Mass8.7×104 [5]  M☉
Radius37.2 ly [NB 1]
Metallicity = –1.14 [6] dex
Estimated age13.8 ± 1.1  Gyr [3]
Other designations NGC 6218 [7]
See also: Globular cluster, List of globular clusters

Messier 12 or M 12 (also designated NGC 6218) is a globular cluster in the constellation of Ophiuchus. It was discovered by the French astronomer Charles Messier on May 30, 1764, who described it as a "nebula without stars". [8] In dark conditions this cluster can be faintly seen with a pair of binoculars. Resolving the stellar components requires a telescope with an aperture of 8 in (20 cm) or greater. [9] In a 10 in (25 cm) scope, the granular core shows a diameter of 3′ ( arcminutes) surrounded by a 10′ halo of stars. [8]

M12 is roughly 3° [9] northwest from the cluster M10 and 5.6° east southeast from star Lambda Ophiuchi. It is also located near the 6th magnitude 12 Ophiuchi. [10] The cluster is about 16,400 light-years (5,000 parsecs) [3] from Earth and has a spatial diameter of about 75 light-years. The brightest stars of M12 are of 12th magnitude. M10 and M12 are only a few thousand light-years away from each other and each cluster would appear at about magnitude 4.5 from the other. [10] With a Shapley-Sawyer rating of IX, [1] it is rather loosely packed for a globular and was once thought to be a tightly concentrated open cluster. Thirteen variable stars have been recorded in this cluster. M12 is approaching us at a velocity of 16 km/s. [11]

A study published in 2006 concluded that this cluster has an unusually low number of low-mass stars. The authors surmise that they were stripped from the cluster by passage through the relatively matter-rich plane of the Milky Way. [12]

  • Messier 12 core by HST
    Messier 12 core by HST
  • The Central Part of Messier 12. Credit: ESO
    The Central Part of Messier 12. Credit: ESO
  • Map showing the location of M12
    Map showing the location of M12

See also

Notes

  1. ^ distance × sin( diameter_angle / 2 ) = 37.2 ly radius

References

  1. ^ a b 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. ^ a b 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. ^ a b c Gontcharov, George A.; Khovritchev, Maxim Yu; Mosenkov, Aleksandr V.; Il'In, Vladimir B.; Marchuk, Alexander A.; Savchenko, Sergey S.; Smirnov, Anton A.; Usachev, Pavel A.; Poliakov, Denis M. (2021). "Isochrone fitting of Galactic globular clusters – III. NGC 288, NGC 362, and NGC 6218 (M12)". Monthly Notices of the Royal Astronomical Society. 508 (2): 2688–2705. arXiv: 2109.13115. doi: 10.1093/mnras/stab2756.
  4. ^ "Messier 12". SEDS Messier Catalog. Archived from the original on 1 July 2022. Retrieved 27 April 2022.
  5. ^ 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 MPD on Table 1.
  6. ^ 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.
  7. ^ "M 12". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2006-11-15.
  8. ^ a b Thompson, Robert Bruce; Thompson, Barbara Fritchman (2007), Illustrated guide to astronomical wonders, DIY science O'Reilly Series, O'Reilly Media, Inc., p. 137, ISBN  978-0596526856.
  9. ^ a b Monks, Neale (2010), Go-To Telescopes Under Suburban Skies, Patrick Moore's Practical Astronomy Series, Springer, p. 118, ISBN  978-1441968500.
  10. ^ a b O'Meara, Stephen James; Levy, David H. (1998), Deep-Sky Companions: The Messier Objects, Cambridge University Press, p. 68, ISBN  978-0521553322.
  11. ^ "Messier 12: Gumball Globular | Messier Objects". www.messier-objects.com. 11 March 2015. Retrieved 2015-08-17.
  12. ^ How to Steal a Million Stars?, ESO, February 7, 2006, archived from the original on February 8, 2007.

External links

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