Astronomy:Messier 12

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Short description: Globular cluster in the constellation Ophiuchus
Messier 12
M12 Adam Block.jpg
Globular cluster Messier 12 in Ophiuchus
Observation data (J2000 epoch)
ClassIX[1]
ConstellationOphiuchus
Right ascension 16h 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[math]\displaystyle{ \begin{smallmatrix}\left[\ce{Fe}/\ce{H}\right]\end{smallmatrix} }[/math] = –1.14[6] dex
Estimated age13.8 ± 1.1 Gyr[3]
Other designationsNGC 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

  • The Central Part of Messier 12. Credit: ESO

  • Map showing the location of M12

See also

Notes

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

References

  1. ↑ 1.0 1.1 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 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. et al. (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. doi:10.1093/mnras/stab2756. 
  4. ↑ "Messier 12". https://messier.seds.org/m/m012.html. 
  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, doi:10.1111/j.1365-2966.2010.16813.x, Bibcode: 2010MNRAS.406.2000M.  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, doi:10.1111/j.1365-2966.2010.16373.x, Bibcode: 2010MNRAS.404.1203F. 
  7. ↑ "M 12". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=M+12. 
  8. ↑ 8.0 8.1 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, https://books.google.com/books?id=ymt9nj_uPhwC&pg=PA137. 
  9. ↑ 9.0 9.1 Monks, Neale (2010), Go-To Telescopes Under Suburban Skies, Patrick Moore's Practical Astronomy Series, Springer, p. 118, ISBN 978-1441968500, https://books.google.com/books?id=waO6tUtfblsC&pg=PA118. 
  10. ↑ 10.0 10.1 O'Meara, Stephen James; Levy, David H. (1998), Deep-Sky Companions: The Messier Objects, Cambridge University Press, p. 68, ISBN 978-0521553322, https://books.google.com/books?id=jis4evHuuzUC&pg=PA68. 
  11. ↑ "Messier 12: Gumball Globular | Messier Objects". 11 March 2015. http://www.messier-objects.com/messier-12-gumball-globular/. 
  12. ↑ How to Steal a Million Stars?, ESO, February 7, 2006, http://www.eso.org/outreach/press-rel/pr-2006/pr-04-06.html. 

External links

Coordinates: Sky map 16h 47m 14.52s, −01° 56′ 52.1″



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