Gamma Eridani

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γ Eridani
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Eridanus
Right ascension 03h 58m 01.76695s[1]
Declination −13° 30′ 30.6698″[1]
Apparent magnitude (V) 2.91[2] (2.88 - 2.96[3])
Spectral type M0III-IIIb[4]
U−B color index +1.96[2]
B−V color index +1.58[2]
Variable type Lb?[3]
Radial velocity (Rv) 60.81±0.25[5] km/s
Proper motion (μ) RA: +61.57[1] mas/yr
Dec.: −113.11[1] mas/yr
Parallax (π) 16.04 ± 0.58[1] mas
Distance 203 ± 7 ly
(62 ± 2 pc)
Radius 80[5] R
Luminosity 1,259[5] L
Surface gravity (log g) 1.0[5] cgs
Temperature 3,811[5] K
Rotational velocity (v sin i) 3.8[5] km/s
Other designations
Zaurac, Gamma Eridani, Gamma Eri, γ Eridani, γ Eri, 34 Eridani, 34 Eri, HD 25025, HIP 18543, HR 1231.[6]

Gamma Eridani (γ Eridani, abbreviated Gamma Eri, γ Eri), also named Zaurak,[7] is a star in the constellation of Eridanus. It is visible to the naked eye with an apparent visual magnitude of 2.91[2] and lies at a distance of about 203 light years from the Sun, as determined by the Hipparcos astrometry satellite. This is an evolved red giant star that is currently on the asymptotic giant branch of the Hertzsprung–Russell diagram.[8] It is a slow irregular variable with a peak magnitude of 2.88.[3]


Gamma Eridani is the star's Bayer designation. It has the traditional name Zaurak, alternatively spelled Zaurac, which is Arabic for 'boat'.[9] In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[10] to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016[11] included a table of the first two batches of names approved by the WGSN; which included Zaurak for this star.

In Chinese, 天苑 (Tiān Yuàn), meaning Celestial Meadows, refers to an asterism consisting of γ Eridani, δ Eridani, π Eridani, ε Eridani, ζ Eridani, η Eridani, π Ceti, τ1 Eridani, τ2 Eridani, τ3 Eridani, τ4 Eridani, τ5 Eridani, τ6 Eridani, τ7 Eridani, τ8 Eridani and τ9 Eridani.[12] Consequently, γ Eridani itself is known as 天苑一 (Tiān Yuàn yī, English: the First [Star] of Celestial Meadows.)[13]

USS Zaurak (AK-117) was a United States Navy Crater class cargo ship named after the star.


  1. ^ a b c d e van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752free to read, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357. 
  2. ^ a b c d Mermilliod, J.-C. (1986), Compilation of Eggen's UBV data, transformed to UBV (unpublished), SIMBAD, Bibcode:1986EgUBV........0M. 
  3. ^ a b c Samus, N. N.; Durlevich, O. V.; et al. (2007), Combined General Catalogue of Variable Stars (GCVS4.2), retrieved 2016-09-30. VizieR On-line Data Catalog: B/gcvs. 
  4. ^ Keenan, P.; McNeil, R. (October 1989), "The Perkins catalog of revised MK types for the cooler stars", Astrophysical Journal Supplement Series, 71: 245–266, Bibcode:1989ApJS...71..245K, doi:10.1086/191373. 
  5. ^ a b c d e f Massarotti, Alessandro; et al. (January 2008), "Rotational and radial velocities for a sample of 761 HIPPARCOS giants and the role of binarity", The Astronomical Journal, 135 (1): 209–231, Bibcode:2008AJ....135..209M, doi:10.1088/0004-6256/135/1/209. 
  6. ^ "gam Eri -- Long Period Variable candidate", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg, retrieved 2016-10-09. 
  7. ^ "IAU Catalog of Star Names". Retrieved 28 July 2016. 
  8. ^ Eggen, O. J. (1992), "Asymptotic giant branch stars near the sun", The Astronomical Journal, 104: 275, Bibcode:1992AJ....104..275E, doi:10.1086/116239. 
  9. ^ Allen, R. H. (1963), Star Names, Dover, p. 218, retrieved 2016-10-09. 
  10. ^ IAU Working Group on Star Names (WGSN), IAU, retrieved 2016-05-22 
  11. ^ Bulletin of the IAU Working Group on Star Names, No. 1 (PDF), retrieved 2016-07-28. 
  12. ^ (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.
  13. ^ (Chinese) 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.