Messier 12

Messier 12
Globular cluster Messier 12 in Ophiuchus
Observation data (J2000 epoch)
ClassIX[1]
ConstellationOphiuchus
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 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
    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
  1. ^ a b Cite error: The named reference hcob849_11 was invoked but never defined (see the help page).
  2. ^ a b Cite error: The named reference aj140_6_1830 was invoked but never defined (see the help page).
  3. ^ a b c Cite error: The named reference Gontcharov was invoked but never defined (see the help page).
  4. ^ "Messier 12". SEDS Messier Catalog. Retrieved 21 July 2024.
  5. ^ Cite error: The named reference mnras406_3_2000 was invoked but never defined (see the help page).
  6. ^ Cite error: The named reference mnras404_3_1203 was invoked but never defined (see the help page).
  7. ^ Cite error: The named reference simbad was invoked but never defined (see the help page).
  8. ^ a b Cite error: The named reference thompson_thompson2007 was invoked but never defined (see the help page).
  9. ^ a b Cite error: The named reference monks2010 was invoked but never defined (see the help page).
  10. ^ a b Cite error: The named reference OMeara1998 was invoked but never defined (see the help page).
  11. ^ "Messier 12: Gumball Globular | Messier Objects". www.messier-objects.com. 11 March 2015. Retrieved 2015-08-17.
  12. ^ Cite error: The named reference eso2006 was invoked but never defined (see the help page).


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