Zeta Ceti

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Zeta Ceti
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Cetus
Right ascension 01h 51m 27.63482s[1]
Declination −10° 20′ 06.1289″[1]
Apparent magnitude (V) 3.742[2]
Spectral type K0 III Ba0.1[3]
U−B color index +1.076[2]
B−V color index +1.131[2]
Variable type Suspected[4]
Radial velocity (Rv) +10.86±0.64[5] km/s
Proper motion (μ) RA: +40.80[1] mas/yr
Dec.: −37.25[1] mas/yr
Parallax (π) 13.88 ± 0.57[1] mas
Distance 235 ± 10 ly
(72 ± 3 pc)
Period (P) 1,652 d
Eccentricity (e) 0.59
Longitude of the node (Ω) 85°
Periastron epoch (T) 2414377 JD
Semi-amplitude (K1)
3.3 km/s
ζ Cet A
Mass 2.34[7] M
Radius 25 R
Luminosity 240 L
Surface gravity (log g) 2.4 cgs
Temperature 4,581±14 K
Metallicity [Fe/H] −0.13 dex
Rotational velocity (v sin i) 3.2 km/s
Age 1.24[7] Gyr
Other designations
ζ Cet, 55 Cet, BD−11° 359, FK5 62, HD 11353, HIP 8645, HR 539, SAO 148059.[8]

Zeta Ceti (ζ Ceti, abbreviated Zeta Cet, ζ Cet), also named Baten Kaitos,[9] is a binary star in the equatorial constellation of Cetus. It has a combined apparent visual magnitude of 3.74,[2] which is bright enough to be seen with the naked eye. Based upon an annual parallax shift of 13.88 mas,[1] it is around 235 light years from the Sun.

This is a single-lined spectroscopic binary system with an orbital period of 4.5 years and an eccentricity of 0.59.[6] The primary, component A, is an evolved K-type giant star with a stellar classification of K0 III Ba0.1.[3] The suffix notation indicates this is a weak barium star, showing slightly stronger than normal lines of singly-ionized barium.[3] This star has an estimated 2.34 times the mass of the Sun and, at an estimated age of 1.24 billion years,[7] has expanded to 25 times the Sun's radius.[5]


ζ Ceti (Latinised to Zeta Ceti) is the star's Bayer designation. It bore the traditional name Baten Kaitos, derived from the Arabic بطن قيتوس batn qaytus "belly of the sea monster". In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[10] to catalogue and standardize proper names for stars. The WGSN approved the name Baten Kaitos for this star on 12 September 2016 and it is now so entered in the IAU Catalog of Star Names.[9]

In the catalogue of stars in the Calendarium of Al Achsasi al Mouakket, this star was designated Rabah al Naamat رابع ألنعامة raabi3 al naʽāmāt, which was translated into Latin as Quarta Struthionum, meaning "the fourth ostrich".[11] This star, along with Eta Ceti (Deneb Algenubi), Theta Ceti (Thanih Al Naamat), Tau Ceti (Thalath Al Naamat), and Upsilon Ceti, formed Al Naʽāmāt (ألنعامة), "the Hen Ostriches".[12][13]

In Chinese, 天倉 (Tiān Cāng), meaning Square Celestial Granary, refers to an asterism consisting of Zeta Ceti, Iota Ceti, Theta Ceti, Eta Ceti, Tau Ceti and 57 Ceti.[14] Consequently, Zeta Ceti itself is known as 天倉四 (Tiān Cāng sì, English: the Second Star of Square Celestial Granary.)[15]


  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:0708.1752Freely accessible, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357. 
  2. ^ a b c d Jennens, P. A.; Helfer, H. L. (September 1975), "A new photometric metal abundance and luminosity calibration for field G and K giants", Monthly Notices of the Royal Astronomical Society, 172: 667–679, Bibcode:1975MNRAS.172..667J, doi:10.1093/mnras/172.3.667. 
  3. ^ a b c Lu, Phillip K. (1991), "Taxonomy of barium stars", Astronomical Journal (ISSN 0004-6256), 101: 2229, Bibcode:1991AJ....101.2229L, doi:10.1086/115845. 
  4. ^ Samus, N. N.; Durlevich, O. V.; et al. (2007), Combined General Catalogue of Variable Stars (GCVS4.2), retrieved 2016-09-30. 
  5. ^ a b c 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. ^ a b Pourbaix, D.; et al. (2004), "SB9: The ninth catalogue of spectroscopic binary orbits", Astronomy & Astrophysics, 424 (2): 727, arXiv:astro-ph/0406573Freely accessible, Bibcode:2004A&A...424..727P, doi:10.1051/0004-6361:20041213. 
  7. ^ a b c Luck, R. Earle (September 2015), "Abundances in the Local Region. I. G and K Giants", The Astronomical Journal, 150 (3): 23, arXiv:1507.01466Freely accessible, Bibcode:2015AJ....150...88L, doi:10.1088/0004-6256/150/3/88, 88. 
  8. ^ "zet Cet -- Spectroscopic binary", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg, retrieved 2017-02-04. 
  9. ^ a b IAU Division C Working Group on Star Names (November 18, 2016), IAU Catalog of Star Names, retrieved 2017-02-05. 
  10. ^ IAU Working Group on Star Names (WGSN), International Astronomical Union, retrieved 22 May 2016. 
  11. ^ Knobel, E. B. (June 1895), "Al Achsasi Al Mouakket, on a catalogue of stars in the Calendarium of Mohammad Al Achsasi Al Mouakket", Monthly Notices of the Royal Astronomical Society, 55: 429, Bibcode:1895MNRAS..55..429K, doi:10.1093/mnras/55.8.429. 
  12. ^ 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. 
  13. ^ Eta Ceti as Aoul al Naamat or Prima Struthionum (the first ostrich), Theta Ceti as Thanih al Naamat or Secunda Struthionum (the second ostrich), Tau Ceti as Thalath al Naamat or Tertia Struthionum (the third ostrich), and Zeta Ceti as Rabah al Naamat or Quarta Struthionum (the fourth ostrich). Upsilon Ceti should be Khamis al Naamat or Quinta Struthionum (the fifth ostrich) consistently, but Al Achsasi Al Mouakket designated the title "the fifth ostrich"' to Gamma Andromedae with uncleared consideration.
  14. ^ (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.
  15. ^ (Chinese) 香港太空館 - 研究資源 - 亮星中英對照表 Archived August 11, 2010, at the Wayback Machine., Hong Kong Space Museum. Accessed on line November 23, 2010.