Zeta Ceti is the primary or 'A' component of a double star system designated WDS J01515-1020 (the secondary or 'B' component is HD 11366).[1] Zeta Ceti's two components are therefore designated WDS J01515-1020 Aa and Ab. Aa is also named Baten Kaitos.[21]
Nomenclature
ζ Ceti (Latinised to Zeta Ceti) is the binary pair's Bayer designation. WDS J01515-1020 A is its designation in the Washington Double Star Catalog. The designations of the two components as WDS J01515-1020 Aa and Ab derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).[2]It bore the traditional name Baten Kaitos, derived from the Arabic بطن قيطس batn qaytus "belly of the sea monster". In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[23] to catalogue and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems.[3] It approved the name Baten Kaitos for the component WDS J01515-1020 Aa on 12 September 2016 and it is now so included in the List of IAU-approved Star Names.[21]
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".[26] 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".[27][4]
In Chinese, {{lang|zh|天倉}} ({{lang|zh-Latn|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.[5] Consequently, Zeta Ceti itself is known as {{lang|zh|天倉四}} ({{lang|zh-Latn|Tiān Cāng sì}}, {{lang-en|the Second Star of Square Celestial Granary}}).[6]
Properties
Zeta Ceti is a single-lined spectroscopic binary system with an orbital period of 4.5 years and an eccentricity of 0.59.[13] The primary, Baten Kaitos, is an evolved K-type giant star with a stellar classification of {{nowrap|K0 III Ba0.1}}.[4] The suffix notation indicates this is a weak barium star, showing slightly stronger than normal lines of singly-ionized barium.[4] This star has an estimated 2.34 times the mass of the Sun and, at an estimated age of 1.24 billion years,[15] has expanded to 25 times the Sun's radius.[8]
HD 11366 (WDS J01515-1020B), of spectral type K0 III, is further away (419 parsecs, compared to WDS J01515-1020A's 72 parsecs), and is therefore not a member of the system but a chance alignment - this is referred to as an optical companion.[7]
References
1. ^{{cite web | url=http://ad.usno.navy.mil/wds/ | title=Washington Double Star Catalog |publisher=United States Naval Observatory |accessdate=23 February 2018}}
2. ^{{cite arXiv |title=On the naming convention used for multiple star systems and extrasolar planets |date=2010 |eprint=1012.0707 |class=astro-ph.SR |last1= Hessman |first1=F. V. |last2= Dhillon |first2=V. S. |last3= Winget |first3=D. E. |last4= Schreiber |first4=M. R. |last5= Horne |first5=K. |last6= Marsh |first6=T. R. |last7= Guenther |first7=E. |last8= Schwope |first8=A. |last9= Heber |first9=U. }}
3. ^{{cite web | url=https://www.iau.org/static/science/scientific_bodies/working_groups/280/wg-starnames-triennial-report-2015-2018.pdf | page=5 | title=WG Triennial Report (2015-2018) - Star Names |accessdate=2018-07-14}}
4. ^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 for reasons that are unclear.
5. ^{{zh icon}} 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}}.
6. ^{{zh icon}} 香港太空館 - 研究資源 - 亮星中英對照表 {{webarchive |url=https://web.archive.org/web/20100811014924/http://www.lcsd.gov.hk/CE/Museum/Space/Research/StarName/c_research_chinengstars_ama_b.htm |date=August 11, 2010 }}, Hong Kong Space Museum. Accessed on line November 23, 2010.
7. ^{{Cite news|url=http://simbad.u-strasbg.fr/simbad/sim-id?mescat.distance=on&Ident=@1317452&Name=HD++11366&submit=display+selected+measurements#lab_meas|title=HD 11366|access-date=2018-09-23}}
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