Pi Capricorni is a triple star system in the southern constellation of Capricornus. It has the traditional star name Oculus (meaning eye in Latin);[1] Pi Capricorni is its Bayer designation, which is Latinized from π Capricorni and abbreviated Pi Cap or π Cap. This system appears blue-white in hue and is visible to the naked eye as a 5th magnitude star.[2] It is located approximately 650 light-years (200 pc) 660 light years distant from the Sun based on parallax,[3] but is drifting closer with a radial velocity of −13 km/s.[4] The proximity of this star to the ecliptic means it is subject to lunar occultation.[5]

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.[6] Consequently, the Chinese name for π Capricorni itself is 牛宿四 (Niú Su sì, English: the Fourth Star of Ox.)[7]

The primary member, component A, is a spectroscopic binary whose two components are separated by 0.1 arcseconds. The brighter of the two, component Aa, is a blue-white B-type bright giant or main sequence star with an apparent magnitude of +5.08. It is around 43 million years old with six times the mass of the Sun.[8] The star is radiating 238 times the Sun's luminosity from its photosphere at an effective temperature of 9,623 K.[9] The third member, component B, is an eighth magnitude star at an angular separation of 3.4 arcsecond from the primary.[10]

References

  1. ^ "Oculus", constellationsofwords, retrieved 2017-05-13
  2. ^ Rakos, K. D. et al. (February 1982), "Photometric and astrometric observations of close visual binaries", Astronomy and Astrophysics Supplement Series. 47: 221–235, Bibcode:1982A&AS...47..221R
  3. ^ Retrieved 2025-08-16.
  4. ^ Wilson, Ralph Elmer (1953), "General Catalogue of Stellar Radial Velocities", Carnegie Institute Washington D.C. Publication, Washington: Carnegie Institution of Washington, Bibcode:1953GCRV..C......0W
  5. ^ Evans, D. S. & Edwards, D. A. (August 1981), "Photoelectric observations of lunar occultations. XII", Astronomical Journal. 86: 1277–1287, Bibcode:1981AJ.....86.1277E. doi:10.1086/113008
  6. ^ (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.
  7. ^ (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 5 月 13 日 Archived 2011-05-22 at the Wayback Machine
  8. ^ Tetzlaff, N. et al. (January 2011), "A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun", Monthly Notices of the Royal Astronomical Society. 410 (1): 190–200, arXiv:1007.4883. Bibcode:2011MNRAS.410..190T. doi:10.1111/j.1365-2966.2010.17434.x. S2CID 118629873
  9. ^ McDonald, I. et al. (2012), "Fundamental parameters and infrared excesses of Hipparcos stars", Monthly Notices of the Royal Astronomical Society. 427 (1): 343–357, arXiv:1208.2037. Bibcode:2012MNRAS.427..343M. doi:10.1111/j.1365-2966.2012.21873.x. S2CID 118665352
  10. ^ Mason, Brian D. et al. (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
  • Kaler, James B. (November 7, 2014), "Pi Capricorni", Stars, University of Illinois, retrieved 2017-05-13