Xi Cephei

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ξ Cephei
Cepheus constellation map.svg
Red circle.svg
Location of ξ Cephei (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Cepheus
Right ascension 22h 03m 47.455s[1]
Declination +64° 37′ 40.71″[1]
Apparent magnitude (V) 4.2[2] (4.45 + 4.60[3])
ξ Cephei A
Spectral type kA2.5hF2mF2(IV)[4]
ξ Cephei B
Spectral type F8V[5]
Proper motion (μ) RA: 215.46±1.14[1] mas/yr
Dec.: 91.06±0.97[1] mas/yr
Parallax (π)38.10 ± 2.81[6] mas
Distance86 ± 6 ly
(26 ± 2 pc)
Absolute magnitude (MV)+1.79[7]
Period (P)810.9 d
Eccentricity (e)0.46
Periastron epoch (T)2438529.8 JD
Argument of periastron (ω)
Semi-amplitude (K1)
7.1 km/s
Semi-amplitude (K2)
19.9 km/s
ξ Cephei Aa
Mass1.045±0.031[6] M
ξ Cephei Ab
Mass0.408±0.066[6] M
Other designations
Kurhah, 17 Cephei, BD+63°1802, CCDM J22038+2407, HIP 108917, HR 8417, SAO 19827, WDS J22038+6438
A: HD 209790
B: HD 209791
Database references

Xi Cephei (ξ Cephei, abbreviated Xi Cep, ξ Cep) is a multiple star system in the constellation of Cepheus. It is approximately 86 light-years from Earth.[6]

It consists of two binary stars, designated Xi Cephei A and B, together with a more distant companion, Xi Cephei C. A's two components are themselves designated Xi Cephei Aa (also named Kurhah[9]) and Ab.


ξ Cephei (Latinised to Xi Cephei) is the system's Bayer designation. The designations of the three constituents as ξ Cephei A, B and C, and those of A's components - ξ Cephei Aa and Ab - derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).[10]

Xi Cephei bore the traditional names Kurhah, Alkirdah or Al Kirduh,[11] the name coming from Qazvini who gave Al Ḳurḥaḥ (القرحة al-qurhah), an Arabic word Ideler translated as a white spot, or blaze, in the face of a horse. Allen indicates that Ideler felt this was not a proper name for a star, and suggested the name Al Ḳirdah (ألقردة al qírada "the Ape").[12] In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[13] to catalogue and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems.[14] It approved the name Kurhah for the component Xi Cephei Aa on 12 September 2016 and it is now so included in the List of IAU-approved Star Names.[9]

In Chinese, 天鈎 (Tiān Gōu), meaning Celestial Hook, refers to an asterism consisting of Xi Cephei, 4 Cephei, HD 194298, Eta Cephei, Theta Cephei, Alpha Cephei, 26 Cephei, Iota Cephei and Omicron Cephei.[15] Consequently, Xi Cephei itself is known as 天鈎六 (Tiān Gōu liù, English: the Sixth Star of Celestial Hook).[16]


Xi Cephei A is a double-lined spectroscopic binary system with an orbital period of 810.9 days and an eccentricity of 0.46.[8] The primary, component Aa, is a chemically peculiar Am star, a probable subgiant with an apparent magnitude of +4.29. Eight arcseconds away, Xi Cephei B is another spectroscopic binary. Xi Cephei C is a 13th magnitude star nearly two arcminutes away.[3]


  1. ^ a b c d van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357.Vizier catalog entry
  2. ^ Monet, David G.; Levine, Stephen E.; Canzian, Blaise; Ables, Harold D.; Bird, Alan R.; Dahn, Conard C.; Guetter, Harry H.; Harris, Hugh C.; Henden, Arne A.; Leggett, Sandy K.; Levison, Harold F.; Luginbuhl, Christian B.; Martini, Joan; Monet, Alice K. B.; Munn, Jeffrey A.; Pier, Jeffrey R.; Rhodes, Albert R.; Riepe, Betty; Sell, Stephen; Stone, Ronald C.; Vrba, Frederick J.; Walker, Richard L.; Westerhout, Gart; Brucato, Robert J.; Reid, I. Neill; Schoening, William; Hartley, M.; Read, M. A.; Tritton, S. B. (2003). "The USNO-B Catalog". The Astronomical Journal. 125 (2): 984. arXiv:astro-ph/0210694. Bibcode:2003AJ....125..984M. doi:10.1086/345888.
  3. ^ a b Mason, Brian D.; Wycoff, Gary L.; Hartkopf, William I.; Douglass, Geoffrey G.; Worley, Charles E. (2001). "The 2001 US Naval Observatory Double Star CD-ROM. I. The Washington Double Star Catalog". The Astronomical Journal. 122 (6): 3466. Bibcode:2001AJ....122.3466M. doi:10.1086/323920.
  4. ^ Gray, R. O; Garrison, R. F (1989). "The early F-type stars - Refined classification, confrontation with Stromgren photometry, and the effects of rotation". The Astrophysical Journal Supplement Series. 69: 301. Bibcode:1989ApJS...69..301G. doi:10.1086/191315.
  5. ^ Gray, R. O; Napier, M. G; Winkler, L. I (2001). "The Physical Basis of Luminosity Classification in the Late A-, F-, and Early G-Type Stars. I. Precise Spectral Types for 372 Stars". The Astronomical Journal. 121 (4): 2148. Bibcode:2001AJ....121.2148G. doi:10.1086/319956.
  6. ^ a b c d Farrington, C. D.; et al. (2014). "Separated Fringe Packet Observations with the CHARA Array. II. omega Andromeda, HD 178911, and xi Cephei". The Astronomical Journal. 148 (3): 48. arXiv:1407.0639. Bibcode:2014AJ....148...48F. doi:10.1088/0004-6256/148/3/48.
  7. ^ Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015.
  8. ^ a b Pourbaix, D.; Tokovinin, A. A.; Batten, A. H.; Fekel, F. C.; Hartkopf, W. I.; et al. (2004), "SB9: The ninth catalogue of spectroscopic binary orbits", Astronomy & Astrophysics, 424 (2): 727, arXiv:astro-ph/0406573, Bibcode:2004A&A...424..727P, doi:10.1051/0004-6361:20041213.
  9. ^ a b "Naming Stars". IAU.org. Retrieved 16 December 2017.
  10. ^ Hessman, F. V.; Dhillon, V. S.; Winget, D. E.; Schreiber, M. R.; Horne, K.; Marsh, T. R.; Guenther, E.; Schwope, A.; Heber, U. (2010). "On the naming convention used for multiple star systems and extrasolar planets". arXiv:1012.0707 [astro-ph.SR].
  11. ^ Islamic Crescent Project: Star names
  12. ^ Allen, R. H. (1963). Star Names: Their Lore and Meaning (Reprint ed.). New York: Dover Publications Inc. p. 159. ISBN 0-486-21079-0. Retrieved 2010-12-12.
  13. ^ IAU Working Group on Star Names (WGSN), International Astronomical Union, retrieved 22 May 2016.
  14. ^ "WG Triennial Report (2015-2018) - Star Names" (PDF). p. 5. Retrieved 2018-07-14.
  15. ^ (in Chinese) 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, ISBN 978-986-7332-25-7.
  16. ^ (in Chinese) 香港太空館 - 研究資源 - 亮星中英對照表 Archived January 29, 2011, at the Wayback Machine., Hong Kong Space Museum. Accessed on line November 23, 2010.