Ruprecht 147 or NGC 6774 is a dispersed star cluster in the Milky Way galaxy. It is about 1,000 light years away, which is close to Earth in comparison with other such clusters. In late summer, it can be seen with binoculars in the constellation of Sagittarius. The stars, bound by gravity, are about 2.5 to 3.25 billion years old.[2]
| Ruprecht 147 | |
|---|---|
 Image of NGC 6774 from Pan-STARRS | |
| Observation data (J2000 epoch) | |
| Right ascension | 19h 16m 42s[1] |
| Declination | −16° 17′ 00″[1] |
| Distance | 1,000 ly (300 pc)[2] |
| Apparent dimensions (V) | > 60′[2] |
| Physical characteristics | |
| Radius | > 9 ly[2] |
| Other designations | NGC 6774 |
| Associations | |
| Constellation | Sagittarius |
The cluster, discovered in 1830 by John Herschel, was sometimes thought to be an asterism (a random collection of stars) due to its sparseness and location against the background of the richest part of the Milky Way, and also since the brightest stars in this old cluster perished long ago. In 1966 the Czech astronomer Jaroslav Ruprecht classified it as a type III 2 m open cluster under the Trumpler scheme.[3] It received otherwise little attention until 2012, when it was identified as a potentially important reference gauge for stellar and Galactic astrophysics research, particularly the research of Sun-like stars.[4][5]
Ruprecht 147 has five detached eclipsing binary stars that are relatively bright, and thus easy to observe.[6] Additionally, there is a transiting brown dwarf around the star EPIC 219388192 (CWW 89A),[7][8] and a transiting planet around the star K2-231.[9]
References
edit- ^ a b "NGC 6774". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 20 May 2016.
- ^ a b c d Curtis, Jason L.; Wolfgang, Angie; Wright, Jason T.; Brewer, John M.; Johnson, John Asher (2013). "Ruprecht 147: The Oldest Nearby Open Cluster as a New Benchmark for Stellar Astrophysics". The Astronomical Journal. 145 (5): 134. arXiv:1206.6533. Bibcode:2013AJ....145..134C. doi:10.1088/0004-6256/145/5/134. ISSN 1538-3881. S2CID 9983151.
- ^ Ruprecht, J. (1966). "Classification of open star clusters". Bulletin of the Astronomical Institutes of Czechoslovakia. 17: 33. Bibcode:1966BAICz..17...33R. ISSN 0004-6248.
- ^ "Nearby star cluster, long forgotten, now discovered to be useful in studies of Sun and search for planets like Earth". Phys.org. 23 June 2012.
- ^ Wright, Jason. "Ruprecht 147: The Oldest Nearby Galactic Cluster". AstroWright. PSU. Retrieved 20 May 2016.
- ^ Torres, Guillermo; Vanderburg, Andrew; Curtis, Jason L.; Kraus, Adam L.; Gaidos, Eric (2021). "Eclipsing Binaries in the Open Cluster Ruprecht 147. IV: The Active Triple System EPIC 219511354". The Astrophysical Journal. 921 (2): 133. arXiv:2108.11384. Bibcode:2021ApJ...921..133T. doi:10.3847/1538-4357/ac20d1. S2CID 237304094.
- ^ Nowak, Grzegorz; Palle, Enric; et al. (March 2017). "EPIC 219388192b—An Inhabitant of the Brown Dwarf Desert in the Ruprecht 147 Open Cluster". The Astronomical Journal. 153 (3): 131. arXiv:1610.08571. Bibcode:2017AJ....153..131N. doi:10.3847/1538-3881/aa5cb6.
- ^ Beatty, Thomas G.; Morley, Caroline V.; et al. (October 2018). "A Significant Overluminosity in the Transiting Brown Dwarf CWW 89Ab". The Astronomical Journal. 156 (4): 168. arXiv:1807.11500. Bibcode:2018AJ....156..168B. doi:10.3847/1538-3881/aad697.
- ^ Curtis, Jason Lee; Vanderburg, Andrew; et al. (April 2018). "K2-231 b: A Sub-Neptune Exoplanet Transiting a Solar Twin in Ruprecht 147". The Astronomical Journal. 155 (4): 173. arXiv:1803.07430. Bibcode:2018AJ....155..173C. doi:10.3847/1538-3881/aab49c.