| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Cetus |
| Right ascension | 02h32m 05.22884s[1] |
| Declination | −15° 14′ 40.8278″[1] |
| Apparent magnitude (V) | 4.78[2] |
| Characteristics | |
| Spectral type | F5 V[3] or F4 IV[4] |
| U−B color index | −0.03[2] |
| B−V color index | +0.45[2] |
| Astrometry | |
| Radial velocity (Rv) | −27.5±0.9[5] km/s |
| Proper motion (μ) | RA: −80.21[1] mas/yr Dec.: −146.29[1] mas/yr |
| Parallax (π) | 37.46 ± 0.25 mas[1] |
| Distance | 87.1 ± 0.6 ly (26.7 ± 0.2 pc) |
| Absolute magnitude (MV) | +2.68[3] |
| Details | |
| σ Cet A | |
| Mass | 1.21[6] M☉ |
| Radius | 1.5[7] R☉ |
| Luminosity | 7.6[8] L☉ |
| Surface gravity (log g) | 4.07±0.07[9] cgs |
| Temperature | 6,527±59[9] K |
| Metallicity [Fe/H] | −0.12±0.04[9] dex |
| Rotational velocity (v sin i) | 20[3] km/s |
| Age | 2.135[6] Gyr |
| Other designations | |
σ Cet, 76 Cet, BD−15° 449, FK5 1071, HD 15798, HIP 11783, HR 740, SAO 148445.[10] | |
| Database references | |
| SIMBAD | data |
Sigma Ceti (σ Ceti) is the Bayer designation for a star in the equatorial constellationofCetus. With an apparent visual magnitude of 4.78,[2] it can be seen with the naked eye on a dark night. Based upon an annual parallax shift of 37.46 mas,[1] it lies at an estimated distance of 87.1 light years from the Sun. It is a probable astrometric binary star system.[11]
The primary, component A, appears to be a normal F-type main sequence star with a stellar classification of F5 V.[3] However, Malaroda (1975) assigned it a classification of F4 IV,[4] which would suggest it is a more evolved subgiant star. It is estimated to have 121%[6] of the Sun's mass and around 150% of the radius of the Sun.[7] With an age of about 2.1[6] billion years, it is radiating 7.6[8] times the solar luminosity from its outer atmosphere at an effective temperature of 6,527 K.[9]
This star, along with π Cet, ε Cet and ρ Cet, was Al Sufi's Al Sadr al Ḳaiṭos, the Whale's Breast [12]
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 CetasAl Sadr al Ḳaiṭos I, this star (σ Cet) as Al Sadr al Ḳaiṭos II, ε CetasAl Sadr al Ḳaiṭos III and π CetasAl Sadr al Ḳaiṭos IV[13]
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