Epsilon Ceti

Epsilon Ceti, Latinized from ε Ceti, is 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.

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]
Characteristics
Spectral type	F2V + F7/G4V[3]
U−B color index	−0.02[2]
B−V color index	+0.45[2]
Astrometry
Proper motion (μ)	RA: +161.62[1] mas/yr Dec.: −230.53[1] mas/yr
Parallax (π)	35.1±1.0 mas[1]
Distance	93 ± 3 ly (28.5 ± 0.8 pc)
Absolute magnitude (MV)	+2.68[4]
Orbit[3]
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[3] M☉
Radius	1.52[5] R☉
Surface gravity (log g)	4.21±0.14[6] cgs
Temperature	6,520[5] K
Metallicity [Fe/H]	−0.08[5] dex
Rotational velocity (v sin i)	11.5[5] km/s
Age	1.8[6] Gyr
ε Cet B
Mass	1.03±0.08[3] M☉
Radius	1.27[5] R☉
Temperature	6,370[5] K
Metallicity [Fe/H]	−0.08[5] dex
Rotational velocity (v sin i)	2.0[5] km/s
Other designations
ε Cet, 83 Cet, BD−12°501, HD 16620, HIP 12390, HR 781, SAO 148528.[7]
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°.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,^[6] with the primary having 1.4 times the mass of the Sun and the secondary being about equal to the Sun's mass.^[3]

Name

This star, along with π Cet, ρ Cet and σ Cet, was Al Sufi's Al Sadr al Ḳaiṭos, the Whale's Breast.^[8]

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.^[9]

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.^[10] Consequently, the Chinese name for ε Ceti itself is 芻蒿六 (Chú Hāo liù, English: the Sixth Star of Celestial Meadows).^[11]