  | |
| Observation data EpochJ2000.0 EquinoxJ2000.0 (ICRS) | |
|---|---|
| Constellation | Cetus[1] |
| Right ascension | 01h 51m 27.631s[2] |
| Declination | −10° 20′ 06.112″[2] |
| Apparent magnitude (V) | 3.742[3] |
| Characteristics | |
| Spectral type | K0 III Ba0.1[4] |
| U−Bcolor index | +1.076[3] |
| B−Vcolor index | +1.131[3] |
| Variable type | Suspected[5] |
| Astrometry | |
| Radial velocity (Rv) | +10.86±0.64[6] km/s |
| Proper motion (μ) | RA: +39.752mas/yr[2] Dec.: −40.956mas/yr[2] |
| Parallax (π) | 12.8770±0.2100 mas[2] |
| Distance | 253 ± 4 ly (78 ± 1 pc) |
| Absolute magnitude (MV) | −0.54[1] |
| Orbit[7] | |
| Period (P) | 1,652 d |
| Eccentricity (e) | 0.59 |
| Longitude of the node (Ω) | 85° |
| Periastronepoch (T) | 2414377 JD |
| Semi-amplitude (K1) (primary) | 3.3 km/s |
| Details[6] | |
| ζ Cet A | |
| Mass | 2.34[8] 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[8] Gyr |
| Other designations | |
| Baten Kaitos,ζ Cet,55 Cet,BD−11°359,FK5 62,HD 11353,HIP 8645,HR 539,SAO 148059,WDS J01515-1020A[9] | |
| Database references | |
| SIMBAD | data |
Zeta Ceti is abinary star system in the equatorialconstellation ofCetus. Its name is aBayer designation that isLatinized fromζ Ceti, and abbreviatedZeta Cet orζ Cet. The system has a combinedapparent visual magnitude of 3.74,[3] which is bright enough to be seen with thenaked eye as a point of light. Based uponparallax measurements, it is approximately 253light-years (78 pc) distant from theEarth.[2] The system is drifting further from the Sun with a line of sight velocity component of +11 km/s.[6]
Zeta Ceti is the primary or 'A' component of adouble star system designated WDS J01515-1020 (the secondary or 'B' component is HD 11366).[10] Zeta Ceti's two components are therefore designated WDS J01515-1020 Aa and Ab. Aa is officially namedBaten Kaitos/ˈbeɪtənˈkeɪtɒs/, the traditional name of the entire system.[11][12]
ζ Ceti (Latinised toZeta Ceti) is the binary pair'sBayer designation. WDS J01515-1020 A is its designation in theWashington 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) formultiple star systems, and adopted by theInternational Astronomical Union (IAU).[13]
It bore the traditional nameBaten Kaitos, derived from theArabic بطن قيطسbatn qaytus "belly of the sea monster". In 2016, theInternational Astronomical Union organized aWorking Group on Star Names (WGSN)[14] to catalogue and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entiremultiple systems.[15] It approved the nameBaten 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.[12]
In the catalogue of stars in theCalendarium ofAl Achsasi al Mouakket, this star was designatedRabah al Naamat رابع ألنعامةraabi3 al naʽāmāt, which was translated intoLatin asQuarta Struthionum, meaning "the fourth ostrich".[16] This star, along withEta Ceti (Deneb Algenubi),Theta Ceti (Thanih Al Naamat),Tau Ceti (Thalath Al Naamat), andUpsilon Ceti, formedAl Naʽāmāt ('ألنعامة), "the Hen Ostriches".[17][18]
InChinese,天倉 (Tiān Cāng), meaningSquare Celestial Granary, refers to anasterism consisting of Zeta Ceti,Iota Ceti, Theta Ceti, Eta Ceti, Tau Ceti and57 Ceti.[19] Consequently, theChinese name for Zeta Ceti itself is天倉四 (Tiān Cāng sì, English:the Fourth Star of Square Celestial Granary).[20]
Zeta Ceti is a single-linedspectroscopic binary system with anorbital period of 4.5 years and aneccentricity of 0.59.[7] The primary, Baten Kaitos, is anevolvedK-typegiant star with astellar classification ofK0 III Ba0.1.[4] The suffix notation indicates this is a weakbarium star, showing slightly stronger than normal lines of singly-ionized barium.[4] This star has an estimated 2.34 times themass of the Sun and, at an estimated age of 1.24 billion years,[8] has expanded to 25 times theSun's radius.[6]
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.[21]
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