Pi Capricorni

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π Capricorni
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Capricornus
Right ascension 20h27m19.2s
Declination −18°12′42″
Apparent magnitude (V) +5.08
Distance 670 ± 110 ly
(204 ± 33 pc)
Spectral type B8II-III
Other designations
Okul, 10 Capricorni, HR 7814, HD 194636, BD−18°5685, HIP 100881, SAO 163592, GC 28442, ADS 13860, CCDM J20273-1813

Pi Capricorni (π Cap, π Capricorni) is a double star in the constellation Capricornus. It also has the traditional star name Okul or Oculus (meaning eye in Latin).[1] It is approximately 670 light years from Earth.

In Chinese, 牛宿 (Niú Su), meaning Ox (asterism), refers to an asterism consisting of π Capricorni, β Capricorni, α2 Capricorni, ξ2 Capricorni, ο Capricorni and ρ Capricorni.[2] Consequently, π Capricorni itself is known as 牛宿四 (Niú Su sì, English: the Fourth Star of Ox.)[3]

The primary component, π Capricorni A, is a blue-white B-type bright giant with an apparent magnitude of +5.08. It is a spectroscopic binary whose two components are separated by 0.1 arcseconds. The third component, π Capricorni B, is an eighth magnitude star 3.4 arcseconds from the primary.[4]


  1. ^ "Oculus". 
  2. ^ (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.
  3. ^ (Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 5 月 13 日
  4. ^ 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.