Eta Ceti

η Ceti
Location of η Ceti (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Cetus
Right ascension 01h 08m 35.39133s[1]
Declination −10° 10′ 56.1519″[1]
Apparent magnitude (V) +3.446[2]
Characteristics
Evolutionary stage red clump[3]
Spectral type K2−IIIb[4]
U−B color index +1.194[2]
B−V color index +1.161[2]
Astrometry
Radial velocity (Rv)+11.74±0.30[5] km/s
Proper motion (μ) RA: +215.922 mas/yr[1]
Dec.: −139.029 mas/yr[1]
Parallax (π)27.0603 ± 0.1799 mas[1]
Distance120.5 ± 0.8 ly
(37.0 ± 0.2 pc)
Absolute magnitude (MV)+0.68[6]
Details
Mass1.84[7] M☉
Radius13.2±0.1[8] R☉
Luminosity74.0±3.7[9] L☉
Surface gravity (log g)2.5[5] cgs
Temperature4,543±24[7] K
Metallicity [Fe/H]−0.03[5] dex
Rotational velocity (v sin i)4.8[5] km/s
Age1.80[7] Gyr
Other designations
Deneb Algenubi, Algenudi, 31 Ceti, BD−10 240, FK5 40, HD 6805, HIP 5364, HR 334, SAO 147632, 2MASS J01083539-1010560[10]
Database references
SIMBADdata

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,[2] 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 120.5 light-years (36.9 parsecs).[1]

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[11] with higher-than-normal abundance of cyanogen and iron relative to other stars of its class.)[12] It is a red clump star that is generating energy through the nuclear fusion of helium at its core.[3]

Eta Ceti has 1.8 times more mass than the Sun[7] and its surface has expanded to 13 times the Sun's radius.[8] It is radiating 74[9] times as much luminosity as the Sun from its photosphere at an effective temperature of 4,356 K.[9] This heat gives the star the orange-hued glow of a K-type star.[13]

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