NGC 6642
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Globular cluster NGC 6642 |
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|---|---|
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| Image of the center by the Hubble Space Telescope | |
| AladinLite | |
| Constellation | Sagittarius |
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Position equinox : J2000.0 , epoch : J2000.0 |
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| Right ascension | 18 h 31 m 54.2 s |
| declination | -23 ° 28 ′ 34 ″ |
| Appearance | |
| Concentration class | IV |
| Brightness (visual) | 8.9 likes |
| Brightness (B-band) | 11.3 mag |
| Angular expansion | 5.8 ' |
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Color excess E (BV) (redness) |
0.42 ± 0.03 |
| Physical data | |
| Affiliation | Milky Way, Bulge |
| Integrated spectral type | F8 |
| Redshift | −0.000191 ± 0.000018 |
| Radial velocity | −57.2 ± 5.4 km / s |
| distance | 23,000 ± 2,000 years |
| Core radius | 6.2 ″ |
| Tidal radius | 10 ′ |
| Concentration lg (r t / r c ) | approx. 2.0 |
| history | |
| discovery | Wilhelm Herschel |
| Discovery date | August 7, 1784 |
| Catalog names | |
| NGC 6642 • C 1828-235 • GCl 97 • ESO 522-SC32 • Mel 203 • GC 4414 • Cr 381, Bennett 112a, II 205, h 2012, h 3749 | |
NGC 6642 is a globular cluster in the constellation Sagittarius on the ecliptic . It has an apparent magnitude of 10.4 mag and an angular diameter of 48 " . The cluster is about 25,000 light years from the Sun towards the central region of the Milky Way . It is located about 1 degree northwest of M 22 .
The object was discovered by Wilhelm Herschel on August 7, 1784 .
Web links
- astronews.com: Picture of the day December 12, 2011
Individual evidence
- ↑ NASA / IPAC EXTRAGALACTIC DATABASE
- ↑ a b c SEDS : NGC 6642
- ↑ Steve O'Meara: Herschel 400 Observing Guide . Cambridge University Press, June 14, 2007, ISBN 978-0-521-85893-9 , pp. 234-.
- ↑ Seligman