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Webb’s Cross

M21, NGC 6531

Proper NameWebb's Cross
Messier NumberM21
NGC/IC NumberNGC 6531
Right Ascension18h 4m 13s
Declination-22° 29' 24"
Distancec.3,900 light years
c.1,200 parsecs
MagnitudeApparent: +5.9
Absolute: -4.5
DiameterApparent: 14'
Actual: 16 light years
Number of Starsc. 100
Optimum VisibilityJuly

A very young cluster of hot blue stars. It lies in Sagittarius, in a dense region of the Milky Way that it shares with the Trifid and Lagoon Nebulae.


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