Epoch J2000.0 Equinox J2000.0
|Right ascension||20h 18m 03.3s|
|Declination||−12° 32′ 41″|
|Apparent magnitude (V)||+3.58|
|Absolute magnitude (V)||++0.07
|Spectral type||G8 IIIb|
Alpha² Capricorni (α² Capricorni, abbreviated Alpha² Cap, α² Cap), also named Algedi, is a star in the constellation of Capricornus. It is a yellow G-type giant with an apparent magnitude of +3.58 and is approximately 109 light years from the Sun. It forms part of the double star Alpha Capricorni along with α¹ Capricorni.
It bore the traditional names Secunda Giedi or Algiedi Secunda and shared the name Algedi (from the Arabic الجدي al-jadii 'the goat') with α¹ Capricorni. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars. The WGSN approved the name Algedi for α² Capricorni on 21 August 2016 and it is now so entered in the IAU Catalog of Star Names.
In Chinese, 牛宿 (Niú Su), meaning Ox (asterism), refers to an asterism consisting of α² Capricorni, Beta Capricorni, ξ² Capricorni, Pi Capricorni, Omicron Capricorni and Rho Capricorni. Consequently, α² Capricorni itself is known as 牛宿二 (Niú Su èr, English: the Second Star of Ox.)
- Carney, Bruce W.; et al. (March 2008), "Rotation and Macroturbulence in Metal-Poor Field Red Giant and Red Horizontal Branch Stars", The Astronomical Journal, 135 (3): 892–906, arXiv:, Bibcode:2008AJ....135..892C, doi:10.1088/0004-6256/135/3/892
- "IAU Catalog of Star Names". Retrieved 28 July 2016.
- IAU Working Group on Star Names (WGSN), International Astronomical Union, retrieved 22 May 2016.
- (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.
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- Kaler, Jim (2005). "Algedi". Retrieved July 27, 2005.
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