Messier 21
Messier 21 Atlas Image courtesy of 2MASS / UMass / IPAC-Caltech / NASA / NSF |
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AladinLite | |
Constellation | Sagittarius |
Position equinox : J2000.0 |
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Right ascension | 18 h 04 m 13 s |
declination | −22 ° 29 ′ 24 ″ |
Appearance
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classification | I, 3, m (Trumpler), d (Shapley) |
Brightness (visual) | 5.9 likes |
Brightness (B-band) | 6.02 mag |
Angular expansion | 13 ' |
Number of stars | 57 |
Physical data
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Redshift | −49 · 10 −6 |
Radial velocity | −14.71 km / s |
distance | 4250 ly (1300 pc ) |
diameter | 16 years |
Age | 4.6 million years |
history | |
Discovered by | Charles Messier |
Discovery time | June 5, 1764 |
Catalog names | |
M 21 • NGC 6531 • C 1801-225 • OCl 26 • Mel 188 • Cr 363 • Lund 806 • ESO 521-SC019 • OCISM 3 |
Messier 21 (also known as NGC 6531 ) is a +5.9 mag bright open star cluster with an area of 13 'in the constellation Sagittarius . M21 is not easily observed in Central Europe because of its southern position.
See also: Messier catalog
Web links
Commons : Messier 21 - album with pictures, videos and audio files