Messier 21

Messier 21
M21 taken from Wikisky.org
Observation
Constellation	Sagittarius
Declination	−22° 29′ 24″
Distance	3,930 ly
Apparent magnitude (V)	6.5
Physical characteristics
Miscellaneous info
Other names	M21, NGC 6531, Cr 363, OCl 26.0

Messier 21 or M21, also designated NGC 6531, is an open cluster of stars in the constellation of Sagittarius. It was discovered and catalogued by Charles Messier on June 5, 1764. This cluster is relatively young and tightly packed. A few blue giant stars have been identified in the cluster, but Messier 21 is composed mainly of small dim stars. With a magnitude of 6.5, M21 is not visible to the naked eye; however, with the smallest binoculars it can be easily spotted on a dark night. The cluster is positioned near the Trifid nebula (NGC 6514), but is not associated with that nebulosity. It forms part of the Sagittarius OB1 association.