images

Open cluster M21 in Sagittarius

by

V.Toporenko/DSS/Novapix

Reference

a-aou65-31002

Date

2007-03-25

The open cluster M21, or NGC 6531, in the constellation Sagittarius shows a strong central concentration and a wide range of star brightnesses, despite its limited membership of probably fewer than 60 stars. Most likely quite young (for a star cluster, that means only a few million years), its distance is uncertain. M21 is quite close on the sky to M20, the Trifid Nebula.