* Astronomy

Messier 21 (also M21, ESO 521-SC19, NGC 6531 and OCL 26) is a magnitude +6.5 open star cluster located 4,250 light-years away in the constellation Sagittarius.
M21 contains about 57 stars, mainly small dim stars. The brightest stars are bluegiants of spectral type B0. On this basis, it is estimated that the cluster is a relatively young cluster, only 4.6 million years old and belongs to the OB1 stellar association.
The cluster was discovered by French astronomer Charles Messier on the 5th June 1764.

Right Ascension 18h 04m 36.0s, Declination -22° 30' 00.0"

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