Messier Index/M21

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Messier 21
Observation data (J2000.0 epoch)
Right ascension18h 04.6m
Declination−22° 30′
Distance4.25 kly (1.3 kPc)
Apparent magnitude (V)6.5
Apparent dimensions (V)13.0′
Other designationsNGC 6531

Messier 21 or M21 (also designated NGC 6531) is an w:open cluster of w:stars in the w:constellation of Sagittarius. It was discovered and catalogued by w:Charles Messier on w:June 5, w:1764.

M21 is a relatively young cluster of a mere 4.6 million w:years of age. It is tightly packed but contains about 57 w:stars. 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.

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