Zeta Cephei

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Zeta Cephei
Cepheus constellation map.svg
Red circle.svg
Location of ζ Cephei (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Cepheus
Right ascension 22h 10m 51.277s[1]
Declination +58° 12′ 04.55″[1]
Apparent magnitude (V) 3.35[2]
Spectral type K1.5 Ib[3]
B−V color index +1.55[2]
Variable type Eclipsing binary?[4]
Proper motion (μ) RA: 13.52 ± 0.10[1] mas/yr
Dec.: 5.24 ± 0.09[1] mas/yr
Parallax (π)3.90 ± 0.10[1] mas
Distance840 ± 20 ly
(256 ± 7 pc)
Absolute magnitude (MV)−4.7[5]
Radius230[6] R
Diameter230[6] D
Luminosity5,660[7] L
Surface gravity (log g)0.75[7] cgs
Temperature4,000[2] K
Metallicity [Fe/H]+0.22[7] dex
Rotational velocity (v sin i)10.64[8] km/s
Other designations
21 Cephei, HR 8465, BD+57°2475, HD 210745, GCTP 5139.00, SAO 34137, FK5 836, HIP 109492
Database references

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 an orange 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,[1] 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.[9] 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]


  1. 1.0 1.1 1.2 1.3 1.4 1.5 van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics 474 (2): 653–664. arXiv:0708.1752. Bibcode 2007A&A...474..653V. doi:10.1051/0004-6361:20078357. http://www.aanda.org/articles/aa/full/2007/41/aa8357-07/aa8357-07.html.Vizier catalog entry
  2. 2.0 2.1 2.2 Levesque, Emily M.; Massey, Philip; Olsen, K. A. G.; Plez, Bertrand; Josselin, Eric; Maeder, Andre; Meynet, Georges (2005). "The Effective Temperature Scale of Galactic Red Supergiants: Cool, but Not As Cool As We Thought". The Astrophysical Journal 628 (2): 973. arXiv:astro-ph/0504337. Bibcode 2005ApJ...628..973L. doi:10.1086/430901.
  3. Morgan, W. W.; Keenan, P. C. (1973). "Spectral Classification". Annual Review of Astronomy and Astrophysics 11: 29. Bibcode 1973ARA&A..11...29M. doi:10.1146/annurev.aa.11.090173.000333.
  4. 4.0 4.1 Samus, N. N.Expression error: Unrecognized word "etal". (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007–2013)". VizieR On-line Data Catalog: B/gcvs. Originally published in: 2009yCat....102025S 1: 02025. Bibcode 2009yCat....102025S.
  5. Luck, R. E. (1982). "The chemical composition of late-type supergiants. IV - Homogeneous abundances and galactic metallicity trends". Astrophysical Journal 256: 177. Bibcode 1982ApJ...256..177L. doi:10.1086/159895.
  6. 7.0 7.1 7.2 Mallik, Sushma V. (December 1999), "Lithium abundance and mass", Astronomy and Astrophysics 352: 495–507, Bibcode 1999A&A...352..495M
  7. Hekker, S.; Meléndez, J. (2007). "Precise radial velocities of giant stars. III. Spectroscopic stellar parameters". Astronomy and Astrophysics 475 (3): 1003. arXiv:0709.1145. Bibcode 2007A&A...475.1003H. doi:10.1051/0004-6361:20078233.
  8. Hekker (2008). "Precise radial velocities of giant stars. IV. A correlation between surface gravity and radial velocity variation and a statistical investigation of companion properties". Astronomy and Astrophysics 480 (1): 215–222. arXiv:0801.0741. Bibcode 2008A&A...480..215H. doi:10.1051/0004-6361:20078321.

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