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.
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]
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.