Messier 12

Messier 12
M12 core by HST, 3.18′ view
Observation data (J2000 epoch)
Class	IX
Constellation	Ophiuchus
Right ascension	16h 47m 14.52s[1]
Declination	-01° 56′ 52.1″[1]
Distance	16.0 kly (4.9 kpc)
Apparent magnitude (V)	+7.68[1]
Apparent dimensions (V)	16′.0
Physical characteristics
Radius	37.2 ly[NB 1]
Other designations	NGC 6218[1]
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 Charles Messier on May 30, 1764.

Located roughly 3° in the sky from the cluster M10, M12 is about 16,000 light-years from Earth and has a spatial diameter of about 75 light-years. The brightest stars of M12 are of 12th magnitude. 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.

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 the gravitational influence of the Milky Way.^[2]

• 

  Messier 12, from 2MASS

• 

  M12 with amateur telescope

• 

  The Central Part of Messier 12. Credit: ESO

Notes

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

References

1. ^ ^{a b c d} "SIMBAD Astronomical Database". Results for NGC 6218. http://simbad.u-strasbg.fr/Simbad. Retrieved 2006-11-15. 
2. ^ ESO, "How to Steal a Million Stars?", 7 February 2006 (eso0604 — Photo Release)

External links

• Messier 12, SEDS Messier pages
• Messier 12, Galactic Globular Clusters Database page
• 'Stolen' stars article at Universe Today
• Messier 12 on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images

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