NGC 6939
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| NGC 6939 | |
| AladinLite | |
| Constellation | Cepheus |
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Position equinox : J2000.0 |
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|---|---|
| Right ascension | 20 h 31 m 30.1 s |
| declination | + 60 ° 39 ′ 43 ″ |
| Appearance
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| classification | I1m |
| Brightness (visual) | 7.8 likes |
| Angular expansion | 10.0 ' |
| Physical data
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| Affiliation | Milky Way |
| distance | 3900 ly (1185 pc ) |
| history | |
| Discovered by | William Herschel |
| Discovery time | September 9, 1798 |
| Catalog names | |
| NGC 6939 • C 2030 + 604 • OCl 217 • Mel 231 • Cr 423 • GC 4590 • H VI 42 • h 2083 • | |
NGC 6939 is an open cluster of type I 1m in the constellation Cepheus the northern sky. NGC 6939 has an angular extent of 10 'x 10' and an apparent magnitude of 7.8 mag.
In general, its distance is estimated to be about 6000 light years , but the published values vary between 4000 and 9000 light years because the area between it and the solar system is heavily " polluted " by interstellar matter . At around 1.6 billion years old, NGC 6939 is one of the oldest known objects of its kind.
The object was discovered on September 9, 1798 by William Herschel , together with the spiral galaxy NGC 6946 , located just forty arc minutes to the southeast .
Web links
- Spektrum.de : Amateur recordings [1] [2] [3]
Individual evidence
- ↑ NASA / IPAC EXTRAGALACTIC DATABASE
- ↑ a b c SEDS: NGC 6939
- ↑ WEBDA
- ↑ Stars and Space September 2007 p. 70
- ↑ Seligman