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Observation data
Epoch J2000      Equinox J2000
Constellation Cygnus
Right ascension 19h 35m 08.577s[1]
Declination +45° 01′ 06.58″[1]
Apparent magnitude (V) 11.349[2]
Spectral type B9-A0V[3]
B−V color index 0.204[2]
Mass 2.71+0.19
[3] M
Radius 2.93 ± 0.14[3] R
Luminosity 77.3 ± 9.6[3] L
Temperature 10000[3] K
Other designations
KIC 8823868, 2MASS J19350857+4501065, GSC2.3 N2K9001230

KOI-81 is an eclipsing binary star in the constellation of Cygnus. The primary star is a late B-type or early A-type main-sequence star with a temperature of 10,000 K (9,700 °C; 17,500 °F). It lies in the field of view of the Kepler Mission and was determined to have an object in orbit around it which is smaller and hotter than the main star.[4]


KOI-81b is a hot compact object orbiting KOI-81. It was discovered in 2010 by the Kepler Mission and came to attention because of its small size and high temperature of 17,000 K (16,700 °C; 30,100 °F).[4] The orbit of KOI-81b around the main star takes 23.8776 days to complete. Analysis of relativistic effects in the Kepler light curve suggests that it is a low-mass white dwarf of approximately 0.3 solar masses, produced by a previous stage of mass transfer during the object's giant phase.[3]

See also[edit]


  1. ^ a b Cutri R.M., Skrutskie M.F., Van Dyk S., Beichman C.A., Carpenter J.M., Chester T., Cambresy L., Evans T., Fowler J., Gizis J., Howard E., Huchra J., Jarrett T., Kopan E.L., Kirkpatrick J.D., Light R.M, Marsh K.A., McCallon H., Schneider S., Stiening R., Sykes M., Weinberg M., Wheaton W.A., Wheelock S., Zacarias N. (2003). "2MASS J19350857+4501065". 2MASS All-Sky Catalog of Point Sources. Retrieved 2010-06-19. 
  2. ^ a b "GSC2.3 N2K9001230". Guide Star Catalog 2.3. Retrieved 2010-06-19. 
  3. ^ a b c d e f van Kerkwijk, Marten H.; Rappaport, Saul A.; Breton, René P.; Justham, Stephen; Podsiadlowski, Philipp; Han, Zhanwen (2010). "Observations of Doppler Boosting in Kepler Light Curves". The Astrophysical Journal 715 (1): 51–58. arXiv:1001.4539. Bibcode:2010ApJ...715...51V. doi:10.1088/0004-637X/715/1/51. 
  4. ^ a b Rowe, Jason F.; Borucki, William J.; Koch, David; Howell, Steve B.; Basri, Gibor; Batalha, Natalie; Brown, Timothy M.; Caldwell, Douglas; Cochran, William D.; Dunham, Edward; Dupree, Andrea K.; Fortney, Jonathan J.; Gautier, Thomas N.; Gilliland, Ronald L.; Jenkins, Jon; Latham, David W.; Lissauer, Jack J.; Marcy, Geoff; Monet, David G.; Sasselov, Dimitar; Welsh, William F. (2010). "Kepler Observations of Transiting Hot Compact Objects". The Astrophysical Journal Letters 713 (2): L150–L154. arXiv:1001.3420. Bibcode:2010ApJ...713L.150R. doi:10.1088/2041-8205/713/2/L150. 

Coordinates: Sky map 19h 35m 08.57s, +45° 01′ 06.6″