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, it is a third-magnitude star that is visible to the naked eye. Based on parallax measurements, it is located about 1,000 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.
Characteristics Zeta Cephei has a spectral classification of K1.5Ib, indicating that it is a lower luminosity red supergiant star. It is about 172 times larger than the Sun and has a surface temperature of 4,393 K. The luminosity of Zeta Cephei is approximately 10,000 times that of the Sun. At a distance of about 840 light-years, Zeta Cephei has an apparent magnitude (m) of 3.4 and an absolute magnitude (M) of -3.7. The star has a metallicity similar to the Sun.
At a mass of , 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.
Hekker et al. (2008) have detected a periodicity of 533 days, hinting at the possible presence of an as yet unseen companion. It is listed as a candidate eclipsing binary with a very small amplitude. However, spectroscopic measurements made from 1993 to 2015 do not support the presence of the companion.
References Vizier catalog entry
Zeta Cephei's database entry at VizieR.
Data about this star can be seen here.