Zeta Cephei

Zeta Cephei

Location of ζ Cephei (circled)
Observation data Equinox J2000.0]] (ICRS)
Constellation	Cepheus
Right ascension	22h 10m 51.279s[1]
Declination	+58° 12′ 04.53″[1]
Apparent magnitude (V)	3.35[2]
Characteristics
Spectral type	K1.5 Ib[3]
Variable type	Eclipsing binary?[4]
Astrometry
Proper motion (μ)	RA: 12.654 ± 0.4618[1] mas/yr Dec.: 5.989 ± 0.835[1] mas/yr
Parallax (π)	3.2972 ± 0.1456[5] mas
Distance	990 ± 40 ly (300 ± 10 pc)
Absolute magnitude (MV)	−4.7[6]
Details
Radius	94[7] R☉
Luminosity	2,228 - 2,249[7] L☉
Surface gravity (log g)	0.75[8] cgs
Temperature	4,072±170[7] K
Metallicity [Fe/H]	+0.22[8] dex
Rotational velocity (v sin i)	10.64[9] km/s
Other designations
21 Cephei, HR 8465, BD+57°2475, HD 210745, GCTP 5139.00, SAO 34137, FK5 836, HIP 109492
Database references
SIMBAD	data

Zeta Cephei (ζ Cep, ζ Cephei) is a star in the constellation of Cepheus. Zeta Cephei marks the left shoulder of Cepheus, the King of Joppa (Ethiopia).^{[clarification needed]} It is one of the fundamental stars of the MK spectral sequence, defined as type K1.5 Ib.

Zeta Cephei is a red supergiant star with a surface temperature of 3,853 K and eight times more massive than the Sun. The luminosity of Zeta Cephei is approximately 3,600 times that of the Sun. At a distance of about 840 light-years,^[10] Zeta Cephei has an apparent magnitude (m) of 3.4 and an absolute magnitude (M) of -4.7. The star has a metallicity approximately 1.6 times that of the Sun; i.e., it contains 1.6 times as much heavy-element material as the Sun.

Hekker et al. (2008) have detected a periodicity of 533 days, hinting at the possible presence of an as yet unseen companion.^[11] It is listed as a possible eclipsing binary with a very small amplitude.^[4]

At the edge of the 8 to 10 solar mass (M_☉) limit at which stars develop iron cores and then explode as supernovae, Zeta Cephei's most likely fate is to produce a very massive white dwarf near the Chandrasekhar limit (1.4 M_☉) at which such dense remnants can survive. If Zeta Cephei is a binary star; i.e., if there is a stellar companion, and it is close enough to feed sufficient matter to the white-dwarf-to-be, it is marginally possible that the limit could be overflowed, resulting in the white dwarf's collapse and a Type Ia supernova explosion.^{[citation needed]}

References

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