Xi Cephei Explained

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.

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 (officially named Kurhah, the traditional name of the system)[1] and Ab.

Nomenclature

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).[2]

Xi Cephei bore the traditional names Kurhah, Alkirdah or Al Kirduh,[3] 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").[4] In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems.[5] 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.[1]

In Chinese, Chinese: 天鈎 (Chinese: 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.[6] Consequently, the Chinese name for Xi Cephei itself is Chinese: 天鈎六 (Chinese: Tiān Gōu liù, English: the Sixth Star of Celestial Hook).[7]

Properties

Xi Cephei A is a double-lined spectroscopic binary system with an orbital period of 810.9 days and an eccentricity of 0.46. 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.

Notes and References

  1. Web site: Naming Stars . IAU.org . 16 December 2017.
  2. On the naming convention used for multiple star systems and extrasolar planets . 2010 . 1012.0707 . astro-ph.SR . Hessman . F. V. . Dhillon . V. S. . Winget . D. E. . Schreiber . M. R. . Horne . K. . Marsh . T. R. . Guenther . E. . Schwope . A. . Heber . U. .
  3. Web site: Islamic Crescent Project: Star names . 2010-12-08 . 2008-02-02 . https://web.archive.org/web/20080202163504/http://www.icoproject.org/star.html . dead .
  4. Book: Allen, R. H. . 1963 . Richard Hinckley Allen . Star Names: Their Lore and Meaning . 2010-12-12 . Reprint . Dover Publications Inc . New York . 0-486-21079-0 . 159 . registration .
  5. Web site: WG Triennial Report (2015-2018) - Star Names . 5 . 2018-07-14.
  6. 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, .
  7. 香港太空館 - 研究資源 - 亮星中英對照表, Hong Kong Space Museum. Accessed on line November 23, 2010.