KY Cygni

KY Cygni
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Cygnus
Right ascension 20h 25m 58.05s[1]
Declination +38° 21′ 07.6″[1]
Apparent magnitude (V) 11.14[2] (10.60 - 11.74[3])
Characteristics
Spectral type M3-4I[4] (M3.5Ia[5])
U−B color index +2.91[2]
B−V color index +3.39[2]
Variable type LC[5]
Astrometry
Distance~5,000 ly
(1,580[2] pc)
Absolute magnitude (MV)−8.18[4]
Details
Radius1,420 (2,850?)[4] R☉
Luminosity (bolometric)138,000[2] - 270,000[4] L☉
Surface gravity (log g)−1.0 (−0.5?)[4] cgs
Temperature3,500[4] K
Other designations
KY Cyg, GSC 03152-01140, IRAS 20241+3811, IRC+40415, TYC 3152-1140-1, RAFGL 2575, UCAC2 45230193, 2MASS J20255805+3821076
Database references
SIMBADdata

KY Cygni is a red supergiant ofspectral class M3.5Ia) located in the constellation Cygnus. It is one of the largest stars known, with an estimated radius of 1,420 times that of the Sun and is also one of the most luminous, with about 300,000 or more times the Sun's luminosity. It is approximately 5,000 light-years away.

Observations

KY Cyg lies near the bright open cluster NGC 6913, but is not thought to be a member. The location is close to the bright star γ Cygni.[6] It was identified as a variable star in 1930,[7] and later named as KY Cygni.[8] The spectrum was given the MK classfication of M3 Ia, with only minor adjustments since.[9]

KY Cygni is heavily reddened due to interstellar extinction, losing an estimate 7.75 magnitudes at visual wavelengths. It would be a naked eye star If no light was lost.[4]

Properties

Comparison of KY Cygni to Betelgeuze

KY Cygni is a large luminous cool supergiant with a strong stellar wind. It is losing mass at one of the highest rates known for a red supergiant and has been described as a cool hypergiant.[2][10] The properties are uncertain, but the temperature is around 3,500 K and the luminosity over 100,000 L☉.[4][2]

KY Cygni is a variable star with a large amplitude but no clear periodicity. At times it varies rapidly, at others it is fairly constant for long periods.[6] The photographic magnitude range is given as 13.5 - 15.5,[5] while a visual range is 10.60 - 11.74.[3]

References

  1. 1 2 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). "VizieR Online Data Catalog: 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)". VizieR On-line Data Catalog: II/246. Originally published in: University of Massachusetts and Infrared Processing and Analysis Center 2246: 0. Bibcode:2003yCat.2246....0C.
  2. 1 2 3 4 5 6 7 Mauron, N.; Josselin, E. (2011). "The mass-loss rates of red supergiants and the de Jager prescription". Astronomy and Astrophysics 526: A156. arXiv:1010.5369. Bibcode:2011A&A...526A.156M. doi:10.1051/0004-6361/201013993.
  3. 1 2 Alfonso-Garzón, J.; Domingo, A.; Mas-Hesse, J. M.; Giménez, A. (2012). "The first INTEGRAL-OMC catalogue of optically variable sources". Astronomy & Astrophysics 1210: arXiv:1210.0821. arXiv:1210.0821 [astro-ph.IM]. Bibcode:2012arXiv1210.0821A. doi:10.1051/0004-6361/201220095.
  4. 1 2 3 4 5 6 7 8 Levesque, Emily M.; Massey, Philip; Olsen, K. A. G.; Plez, Bertrand; Josselin, Eric; Maeder, Andre; Meynet, Georges (2005). "The Effective Temperature Scale of Galactic Red Supergiants: Cool, but Not As Cool As We Thought". The Astrophysical Journal 628 (2): 973. arXiv:astro-ph/0504337. Bibcode:2005ApJ...628..973L. doi:10.1086/430901.
  5. 1 2 3 KY Cyg, database entry, The combined table of GCVS Vols I-III and NL 67-78 with improved coordinates, General Catalogue of Variable Stars, Sternberg Astronomical Institute, Moscow, Russia. Accessed on line November 12, 2010.
  6. 1 2 Romano, G. (1969). "Researches with the Schmidt telescopes. III. Variable stars in the field of gamma Cygni". Memorie della Società Astronomia Italiana 40: 375. Bibcode:1969MmSAI..40..375R.
  7. ↑ Hoffmeister, Cuno (1930). "Relative Koordinaten, Oerter und Karten neuer Veraenderlicher". Mitteilungen der Sternwarte zu Sonneberg 17: 1. Bibcode:1930MiSon..17....1H.
  8. ↑ Ahnert, P.; Van Schewick, H.; Hoffmeister, C. (1941). "Die Veraenderlichen Sterne der noerdlichen Milchstrasse. Teil II". Kleine Veroeffentlichungen der Universitaetssternwarte zu Berlin Babelsberg 6: 4.1. Bibcode:1941KVeBB...6....4A.
  9. ↑ White, N. M.; Wing, R. F. (1978). "Photoelectric two-dimensional spectral classification of M supergiants". Astrophysical Journal 222: 209. Bibcode:1978ApJ...222..209W. doi:10.1086/156136.
  10. ↑ Stickland, D. J. (1985). "IRAS observations of the cool galactic hypergiants". The Observatory 105: 229. Bibcode:1985Obs...105..229S.

External links

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