Eta Ceti
Eta Ceti (η Cet, η Ceti) is a star in the equatorial constellation of Cetus. It has the traditional name Deneb Algenubi or Algenudi. The apparent visual magnitude of this star is +3.4, making it the fourth-brightest star in this otherwise relatively faint constellation. The distance to this star can be measured directly using the parallax technique, yielding a value of 123.9 light-years (38.0 parsecs).
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Cetus |
| Right ascension | 01h 08m 35.39148s |
| Declination | −10° 10′ 56.1570″ |
| Apparent magnitude (V) | +3.446 |
| Characteristics | |
| Evolutionary stage | red clump |
| Spectral type | K2−IIIb |
| U−B color index | +1.194 |
| B−V color index | +1.161 |
| Astrometry | |
| Radial velocity (Rv) | +11.74±0.30 km/s |
| Proper motion (μ) | RA: +215.61 mas/yr Dec.: −139.02 mas/yr |
| Parallax (π) | 26.32 ± 0.14 mas |
| Distance | 123.9 ± 0.7 ly (38.0 ± 0.2 pc) |
| Absolute magnitude (MV) | +0.68 |
| Details | |
| Mass | 1.84 M☉ |
| Radius | 15.10±0.10 R☉ |
| Luminosity | 74.0±3.7 L☉ |
| Surface gravity (log g) | 2.5 cgs |
| Temperature | 4,543±24 K |
| Metallicity [Fe/H] | −0.03 dex |
| Rotational velocity (v sin i) | 4.8 km/s |
| Age | 1.80 Gyr |
| Other designations | |
| Database references | |
| SIMBAD | data |
This is a giant star that has been chosen a standard for the stellar classification of K2−IIIb. It has exhausted the hydrogen at its core and evolved away from the main sequence of stars like the Sun. (The classification is sometimes listed as K1.5 IIICN1Fe0.5, indicating a strong CN star with higher-than-normal abundance of cyanogen and iron relative to other stars of its class.) It is a red clump star that is generating energy through the nuclear fusion of helium at its core.
Eta Ceti may have slightly more mass than the Sun and its outer envelope has expanded to 15 times the Sun's radius. It is radiating 74 times as much luminosity as the Sun from its outer atmosphere at an effective temperature of 4,356 K. This heat gives the star the orange-hued glow of a K-type star.