Celestial Objects
Messier 21
Star Clusters
Citation Formats
General Reference
APA Style
BibTeX
Messier 21, also known as M21, NGC 6531 or Webb's Cross, is a young, tightly packed open cluster of stars in the constellation Sagittarius, discovered and catalogued by Charles Messier on 5 June 1764. It contains a few blue giant stars amid mostly small, dim stars, forms part of the Sagittarius OB1 association, and lies near the Trifid Nebula without being physically associated with it.
Reader Challenges (0 open reader challenges)
No disputes yet. Spotted an error or a better source? Open the first one.
Sign in to dispute this or suggest a correction.
View At A Past Year
The atlas records no dated fact of its own for this entry, so there is no other year to choose.