Zeta Cephei
Star in the constellation Cepheus
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Zeta Cephei is a red supergiant star in the northern constellation of Cepheus. Its name is a Bayer designation that is Latinized from ζ Cephei, and abbreviated Zeta Cep or ζ Cep. With an apparent visual magnitude of 3.35,[2] it is a third-magnitude star that is visible to the naked eye. Based on parallax measurements, it is located about 1000 light-years away from the Earth. Zeta Cephei marks the left shoulder of Cepheus, a mythical King of Aethiopia. It is one of the fundamental stars of the MK spectral sequence, defined as type K1.5 Ib.
 | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Cepheus |
| Right ascension | 22h 10m 51.277s[1] |
| Declination | +58° 12′ 04.54″[1] |
| Apparent magnitude (V) | 3.35[2] |
| Characteristics | |
| Evolutionary stage | Red supergiant[3] |
| Spectral type | K1.5 Ib[4] |
| B−V color index | +1.55[2] |
| Astrometry | |
| Proper motion (μ) | RA: 13.359±0.148 mas/yr[1] Dec.: 5.275±0.183 mas/yr[1] |
| Parallax (π) | 3.2972±0.1456 mas[1] |
| Distance | 992.7+51.2 −46 ly (304.5+15.7 −14.1 pc)[5] |
| Absolute magnitude (MV) | −4.7[3] |
| Details | |
| Mass | 10.1±0.1[6] M☉ |
| Radius | 172.7+7.5 −8.3[7] R☉ |
| Luminosity | 10,024±1,052[7] L☉ |
| Surface gravity (log g) | 0.75[8] cgs |
| Temperature | 4,393±58[7] K |
| Metallicity [Fe/H] | +0.04[7] dex |
| Rotational velocity (v sin i) | 10.64[9] km/s |
| Other designations | |
| 21 Cephei, BD+57°2475, FK5 836, HD 210745, HIP 109492, HR 8465, SAO 34137, Gaia DR2 2199493438511811712, Gaia DR3 2199493438511811712[10] | |
| Database references | |
| SIMBAD | data |
Characteristics
Zeta Cephei has a spectral classification of K1.5Ib,[4] indicating that it is a lower luminosity red supergiant star. It is about 173 times larger than the Sun and has a surface temperature of 4,393 K.[7] The luminosity of Zeta Cephei is approximately 10,000 times that of the Sun.[7] At a distance of about 840 light-years,[11] Zeta Cephei has an apparent magnitude (m) of 3.4 and an absolute magnitude (M) of -3.7.[12] The star has a metallicity similar to the Sun.[7]
At a mass of 10.1 M☉, Zeta Cephei might end its life in a core-collapse supernova, and has been listed as a likely pre-supernova candidate by a 2022 study. It could also provide observable pre-supernova neutrino signals, just hours before the core collapses.[6]
Hekker et al. (2008) have detected a periodicity of 533 days, hinting at the possible presence of an as yet unseen companion.[13] It is listed as a candidate eclipsing binary with a very small amplitude.[14] However, spectroscopic measurements made from 1993 to 2015 do not support the presence of the companion.[12]