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Webb’s Cross

M21, NGC 6531

Proper NameWebb's Cross
Messier NumberM21
NGC/IC NumberNGC 6531
ConstellationSagittarius
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
NotesThis young cluster of stars is estimated to be no more than seven million years old. It has a dense and prominent nucleus, with fainter stars seeming to extend outwards in linear strands, especially to the north and west of the central grouping. These strands form the very approximate shape of a cross, giving the cluster its common name of 'Webb's Cross'.

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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