NGC 6791
| NGC 6791 | |
|---|---|
 Detail from the Kepler image showing NGC 6791.Celestial northis to the left.a | |
| Observation data (J2000epoch) | |
| Right ascension | 19h20m53s[1] |
| Declination | +37° 46.3′[1] |
| Distance | ~13,300 ly (4078 pc) |
| Apparent magnitude(V) | +9.5[1] |
| Apparent dimensions (V) | 16'[2] |
| Physical characteristics | |
| One of the oldest knownopen clusters | |
| Other designations | C 1919+377, Cl Berkeley 46, OCl 142.0,[1]GC 4492[2] |
| Associations | |
| Constellation | Lyra |
NGC 6791is anopen star clusterin theLyra constellation.[1]It was discovered byFriedrich August Theodor Winneckein 1853. At roughly 8 billion years old, and with anirontohydrogenabundanceratio that is more than twice that of theSun,it is one of the oldest and mostmetal-richclusters in theMilky Way.This is contrary to the typicalrule-of-thumbwhere older means more metal-poor. Compounded with the fact that it has an unusually high population of stars, NGC 6791 is among the most studied clusters in the sky.[3][4]
Age studies[edit]
Among the dimmest stars in the cluster are groups of white dwarfs that are 6 billion years old and another group that appear to be 4 billion years old. The ages are out of sync with those of the cluster's normal stars, which are 8 billion years old. This seeming contradiction in age for this cluster has been studied and a solution proposed with age of about 8 billion years.[5][6][7]
The Kepler Mission[edit]
In March 2009NASAlaunched theKepler Missionspacecraft. This spacecraft was a dedicated mission to discover extrasolar planets by thetransit methodfromsolar orbit.In April 2009 the project released thefirst lightimages from the spacecraft and NGC 6791 was one of two objects highlighted.[8]
The planet hosting starKepler-19,discovered from Kepler data, is located approximately 5arcminutesnorthwest of NGC 6791.[9]The star has a differing proper motion to the cluster and is also much closer, so it is unrelated.
Notes[edit]
- Note a:The images are rotatedcounterclockwiseapproximately 130° from the detector orientation against the sky.
References[edit]
- ^abcde"NGC 6791".SIMBAD.Centre de données astronomiques de Strasbourg.Retrieved2009-05-10.
- ^abNGC online."NGC 6791".Archived fromthe originalon 2007-08-19.Retrieved2009-05-10.
- ^Chaboyer; Green, Elizabeth M.; Liebert, James (March 1999)."The Age, Extinction, and Distance of the Old, Metal-rich Open Cluster NGC 6791"(PDF).The Astronomical Journal.117(3): 1360–1374.arXiv:astro-ph/9812097.Bibcode:1999AJ....117.1360C.doi:10.1086/300794.S2CID16633286.
- ^Kaluzny; Udalski, A. (1992)."Photometric Study of the Old Open Cluster NGC 6791"(PDF).Acta Astronomica.42(1): 29–47.Bibcode:1992AcA....42...29K.
- ^Bedin; King, Ivan R.; Anderson, Jay; Piotto, Giampaolo; et al. (May 10, 2008)."Reaching the End of the White Dwarf Cooling Sequence in NGC 67911"(PDF).The Astrophysical Journal.678(2): 1279–1291.arXiv:0801.1346.Bibcode:2008ApJ...678.1279B.doi:10.1086/529370.S2CID18969486.Archived fromthe original(PDF)on March 31, 2017.RetrievedMay 10,2009.
- ^Bedin; Salaris, M.; Piotto, G.; Cassisi, S.; et al. (May 20, 2008)."The Puzzling White Dwarf Cooling Sequence in NGC 6791: A Simple Solution"(PDF).The Astrophysical Journal Letters.679(1): L29–L32.arXiv:0804.1792.Bibcode:2008ApJ...679L..29B.doi:10.1086/589151.S2CID17920160.Archived fromthe original(PDF)on March 31, 2017.RetrievedMay 10,2009.
- ^Grundahl; Clausen, J. V.; Hardis, S.; Frandsen, S. (2008). "A new standard: age and distance for the open cluster. NGC6791 from the eclipsing binary member V20".Astronomy & Astrophysics.492(1): 171–184.arXiv:0810.2407.Bibcode:2008A&A...492..171G.doi:10.1051/0004-6361:200810749.S2CID18569623.
- ^"Kepler Eyes Cluster and Known Planet".NASA.2009-04-16.Retrieved2009-05-09.
- ^"SIMBAD clickable map".
External links[edit]
