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Messier 23 (NGC 6494) is an open cluster in the constellation Sagittarius.

M23 is at a distance of about 2,150 light years away from Earth, its radius is around 15-20 light years. There are some 150 identified members in this cluster. The hottest stars in M23 are of spectral type B9, the brightest star is of magnitude 9.21. The age of M23 has been estimated at 220 million years.

July 14, 2010