Epsilon Ceti
Binary star system in the constellation Cetus
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Epsilon Ceti is a binary star system located in the equatorial constellation of Cetus. Its name is a Bayer designation that is Latinized from ε Ceti and abbreviated Epsilon Cet or ε Cet. This system is faintly visible to the naked eye as a point of light with an apparent visual magnitude of +4.84.[3] Based upon an annual parallax shift of 41.43 mas,[4] it is located around 79 light-years away from the Sun.
 | |
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Cetus[1] |
| Right ascension | 02h 39m 33.79741s[2] |
| Declination | −11° 52′ 19.5516″[2] |
| Apparent magnitude (V) | +4.84[3] |
| Characteristics | |
| Evolutionary stage | main sequence |
| Spectral type | F2V + F7/G4V[4] |
| U−B color index | −0.02[3] |
| B−V color index | +0.45[3] |
| Astrometry | |
| Radial velocity (Rv) | 15.49±0.19[5] km/s |
| Proper motion (μ) | RA: +167.071 mas/yr[2] Dec.: −251.104 mas/yr[2] |
| Parallax (π) | 41.43±0.68 mas[4] |
| Distance | 79 ± 1 ly (24.1 ± 0.4 pc) |
| Absolute magnitude (MV) | +2.68[1] |
| Orbit[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) | 2,012.3109±0.0005 |
| Argument of periastron (ω) (secondary) | 40.8±0.2° |
| Details | |
| ε Cet A | |
| Mass | 1.37±0.09[4] M☉ |
| Radius | 1.52[6] R☉ |
| Surface gravity (log g) | 4.21±0.14[7] cgs |
| Temperature | 6,520[6] K |
| Metallicity [Fe/H] | −0.08[6] dex |
| Rotational velocity (v sin i) | 11.5[6] km/s |
| Age | 1.8[7] Gyr |
| ε Cet B | |
| Mass | 1.03±0.08[4] M☉ |
| Radius | 1.27[6] R☉ |
| Temperature | 6,370[6] K |
| Metallicity [Fe/H] | −0.08[6] dex |
| Rotational velocity (v sin i) | 2.0[6] km/s |
| Other designations | |
| ε Cet, 83 Cet, BD−12°501, GJ 9091, GJ 105.4, HD 16620, HIP 12390, HR 781, SAO 148528[8] | |
| Database references | |
| SIMBAD | data |
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° to the plane of the sky.
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.[4] The system is estimated to be 1.8 billion years old,[7] with the primary having 1.4 times the mass of the Sun and the secondary being about equal to the Sun's mass.[4]
Name
This star, along with π Cet, ρ Cet and σ Cet, was Al Sufi's Al Sadr al Ḳaiṭos, the Whale's Breast.[9]
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.[10]
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.[11] Consequently, the Chinese name for ε Ceti itself is 芻蒿六 (Chú Hāo liù, English: the Sixth Star of Celestial Meadows).[12]