Messier 23
The open star cluster Messier 23 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 | 17 h 57 m |
declination | −18 ° 59 ′ |
Appearance
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classification | III, 1, m (Trumpler), d (Shapley) |
Brightness (visual) | 5.5 mag |
Brightness (B-band) | 6.03 mag |
Angular expansion | 27 ' |
Number of stars | 150 |
Brightest star | 9.21 mag |
Physical data
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distance | 2150 ly (660 pc ) |
diameter | 15 years |
Age | 220 million years |
history | |
Discovered by | Charles Messier |
Discovery time | June 20, 1764 |
Catalog names | |
M 23 • NGC 6494 • C 1753-190 • OCl 30 • Mel 184 • Cr 356 • Lund 793 • ESO 589-SC22 • |
Messier 23 (M23, also known as NGC 6494 ) is one of the six brightest open star clusters in the summer constellation Sagittarius (Sagittarius). It has a brightness of +5.5 mag and an angular extent of 27 '. The cluster is about 2000 light years away, halfway between the sun and the Sagittarius arm of our galaxy. The analysis of the color-brightness diagram of Messier 23 shows an age of around 300 million years.
A few degrees to the east - almost in the center of the Milky Way - lies the small Sagittarius cloud (M24) and the star cluster Messier 25, which is comparable to M23 .
Web links
Commons : Messier 23 - album with pictures, videos and audio files