Epsilon Ceti

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Epsilon Ceti
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Cetus
Right ascension 02h 39m 33.82853s[1]
Declination −11° 52′ 19.7132″[1]
Apparent magnitude (V) +4.84[2]
Spectral type F2V + F7/G4V[3]
U−B color index −0.02[2]
B−V color index +0.45[2]
Proper motion (μ) RA: +161.62[1] mas/yr
Dec.: −230.53[1] mas/yr
Parallax (π)35.1 ± 1.0[1] mas
Distance93 ± 3 ly
(28.5 ± 0.8 pc)
Absolute magnitude (MV)+2.68[4]
Period (P)2.6512±0.0005 yr
Semi-major axis (a)0.1063±0.0005
Eccentricity (e)0.230±0.001
Inclination (i)24.2±0.2°
Longitude of the node (Ω)90.2±0.2°
Periastron epoch (T)2012.3109±0.0005
Argument of periastron (ω)
ε Cet A
Mass1.37±0.09[3] M
Luminosity7.17[4] L
Surface gravity (log g)4.21±0.14[5] cgs
Temperature6,537±222[5] K
Metallicity [Fe/H]−0.16±0.03[4] dex
Age1.8[5] Gyr
ε Cet B
Mass1.03±0.08[3] M
Other designations
ε Cet, 83 Cet, BD−12° 501, HD 16620, HIP 12390, HR 781, SAO 148528.[6]
Database references

Epsilon Ceti, Latinized from ε Ceti, is the Bayer designation for a binary star system located in the equatorial constellation of Cetus. It is faintly visible to the naked eye with an apparent visual magnitude of +4.84.[2] Based upon an annual parallax shift of 14.58 mas,[1] it is located around 98 light years away from the Sun.

This is a line-width spectroscopic binary star system. It has an orbital period of 2.65 years and an eccentricity of 0.23. The semimajor axis is 0.11 AU, or 11% of the distance between the Sun and the Earth, and the orbital plane is inclined at an angle of 24.2°.The primary member, component A, is an F-type main sequence star with a stellar classification of F2 V. The spectrum of the secondary, component B, can not be readily separated from that of the primary, so its type can only be estimated as a main sequence star lying in the range between F7 V and G4 V.[3] The system is estimated to be 1.8 billion years old,[5] with the primary having 1.4 times the mass of the Sun and the secondary being about equal to the Sun's mass.[3]


This star, along with π Cet, ρ Cet and σ Cet, was Al Sufi's Al Sadr al Ḳaiṭos, the Whale's Breast [7]

According to the catalogue of stars in the Technical Memorandum 33-507 - A Reduced Star Catalog Containing 537 Named Stars, Al Sadr al Ḳaiṭos were the title for four stars :ρ Cet as Al Sadr al Ḳaiṭos I, σ Cet as Al Sadr al Ḳaiṭos II, this star (ε Cet) as Al Sadr al Ḳaiṭos III and π Cet as Al Sadr al Ḳaiṭos IV[8]

In Chinese, 芻蒿 (Chú Hāo), meaning Hay, refers to an asterism consisting of ε Ceti, ρ Ceti, 77 Ceti, 67 Ceti, 71 Ceti and HD 14691[9]. Consequently, ε Ceti itself is known as 芻蒿六 (Chú Hāo liù, English: the Sixth Star of Celestial Meadows.[10]


  1. ^ a b c d e f van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, 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)", Catalogue of Eggen's UBV data, SIMBAD, Bibcode:1986EgUBV........0M.
  3. ^ a b c d e f Docobo, J. A.; Andrade, M. (2013), "Dynamical and physical properties of 22 binaries discovered by W. S. Finsen", Monthly Notices of the Royal Astronomical Society, 428 (1): 321–339, Bibcode:2013MNRAS.428..321D, doi:10.1093/mnras/sts045.
  4. ^ a b c Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015.
  5. ^ a b c d David, Trevor J.; Hillenbrand, Lynne A. (2015), "The Ages of Early-Type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets", The Astrophysical Journal, 804 (2): 146, arXiv:1501.03154, Bibcode:2015ApJ...804..146D, doi:10.1088/0004-637X/804/2/146.
  6. ^ "eps Cet". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-02-04.
  7. ^ Allen, R. H. (1963). Star Names: Their Lore and Meaning (Reprint ed.). New York: Dover Publications Inc. p. 162. ISBN 0-486-21079-0. Retrieved 2010-12-12.
  8. ^ Jack W. Rhoads - Technical Memorandum 33-507-A Reduced Star Catalog Containing 537 Named Stars, Jet Propulsion Laboratory, California Institute of Technology; November 15, 1971
  9. ^ (in Chinese) 夢之大地 @ 國立成功大學 WebBBS DreamLand @ National Cheng Kung University WebBBS System
  10. ^ (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 12 日