NGC 6791 explained

NGC 6791
Epoch:J2000
Constellation:Lyra
Dist Ly:~13,300 ly
Dist Pc:4078 pc
Appmag V:+9.5
Size V:16'[1]
Notes:One of the oldest known open clusters
Names:C 1919+377, Cl Berkeley 46, OCl 142.0, GC 4492

NGC 6791 is an open star cluster in the Lyra constellation.[2] It was discovered by Friedrich August Theodor Winnecke in 1853. At roughly 8 billion years old, and with an iron to hydrogen abundance ratio that is more than twice that of the Sun, it is one of the oldest and most metal-rich clusters in the Milky Way. This is contrary to the typical rule-of-thumb where 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

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

See main article: article and Kepler Mission.

In March 2009 NASA launched the Kepler Mission spacecraft. This spacecraft was a dedicated mission to discover extrasolar planets by the transit method from solar orbit. In April 2009 the project released the first light images from the spacecraft and NGC 6791 was one of two objects highlighted.[8]

The planet hosting star Kepler-19, discovered from Kepler data, is located approximately 5 arcminutes northwest of NGC 6791.[9] The star has a differing proper motion to the cluster and is also much closer, so it is unrelated.

Notes

External links

Notes and References

  1. Web site: NGC 6791 . NGC online . 2009-05-10 . dead . https://web.archive.org/web/20070819155822/http://www.seds.org/~spider/ngc/ngc.cgi?n6791 . 2007-08-19.
  2. NGC 6791 . 2009-05-10 .
  3. Chaboyer. The Age, Extinction, and Distance of the Old, Metal-rich Open Cluster NGC 6791. The Astronomical Journal. 117. 3. 1360–1374. March 1999. 10.1086/300794. Green. Elizabeth M.. Liebert. James. 1999AJ....117.1360C. astro-ph/9812097 . 16633286.
  4. Kaluzny. Photometric Study of the Old Open Cluster NGC 6791. Acta Astronomica. 1992. 42. 1. 29–47. 1992AcA....42...29K. Udalski. A. .
  5. The Astrophysical Journal . Reaching the End of the White Dwarf Cooling Sequence in NGC 67911 . Bedin . 678 . 2 . 1279–1291 . May 10, 2008 . 10.1086/529370 . 4 . King . Ivan R. . Anderson . Jay . Piotto . Giampaolo . Salaris . Maurizio . Cassisi . Santi . Serenelli . Aldo . 2008ApJ...678.1279B . 0801.1346 . 18969486 . May 10, 2009 . https://web.archive.org/web/20170331141423/http://hubblesite.org/pubinfo/pdf/2008/25/pdf1.pdf . March 31, 2017 . dead.
  6. The Astrophysical Journal Letters . The Puzzling White Dwarf Cooling Sequence in NGC 6791: A Simple Solution . Bedin . 679 . 1 . L29–L32 . May 20, 2008 . 10.1086/589151 . 4 . Salaris . M. . Piotto . G. . Cassisi . S. . Milone . A. P. . Anderson . J. . King . I. R. . 2008ApJ...679L..29B . 0804.1792 . 17920160 . May 10, 2009 . https://web.archive.org/web/20170331141435/http://hubblesite.org/pubinfo/pdf/2008/25/pdf2.pdf . March 31, 2017 . dead.
  7. Astronomy & Astrophysics. A new standard: age and distance for the open cluster. NGC6791 from the eclipsing binary member V20. Grundahl. 492. 1. 171–184. 2008. 10.1051/0004-6361:200810749. Clausen. J. V.. Hardis. S.. Frandsen. S.. 2008A&A...492..171G. 0810.2407 . 18569623.
  8. Web site: Kepler Eyes Cluster and Known Planet. NASA. 2009-04-16. 2009-05-09.
  9. Web site: SIMBAD clickable map .

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