Zeta Cygni

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Zeta Cygni
Cygnus constellation map.svg
Red circle.svg

Location of ζ Cygni (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Cygnus
Right ascension 21h 12m 56.18594s[1]
Declination +30° 13′ 36.8957″[1]
Apparent magnitude (V) 3.26[2]
Spectral type G8IIIa + DA4.2[3]
U−B color index +0.77[2]
B−V color index +0.98[2]
Radial velocity (Rv) +15.85 ± 0.26[4] km/s
Proper motion (μ) RA: +6.51[1] mas/yr
Dec.: –68.21[1] mas/yr
Parallax (π) 22.79 ± 0.35[1] mas
Distance 143 ± 2 ly
(43.9 ± 0.7 pc)
Absolute magnitude (MV) –0.01[5]
Period (P) 6,489 ± 31 days
Semi-major axis (a) 0.19"[7]
Eccentricity (e) 0.22 ± 0.03
Periastron epoch (T) 40,712 ± 178 MJD
Argument of periastron (ω)
41 ± 10°
Semi-amplitude (K1)
3.31 ± 0.12 km/s
ζ Cyg A
Mass 3.05[8] M
Radius 15[4] R
Luminosity 112[4] L
Surface gravity (log g) 2.41[5] cgs
Temperature 4,910[5] K
Metallicity [Fe/H] –0.04[5] dex
Rotational velocity (v sin i) 0.4 ± 0.5[8] km/s
Age 0.2[9] Gyr
ζ Cyg B
Mass 0.6[7] M
Temperature 12,000[7] K
Other designations
Zeta Cyg, 64 Cygni, BD+29°4348, HD 202109, HIP 104732, HR 8115, SAO 71070[10]
Database references

Zeta Cygni (ζ Cyg) is a binary star system in the northern constellation of Cygnus, the swan. It has an apparent visual magnitude of 3.26 and, based upon parallax measurements, is about 143 light-years (44 parsecs) away.

The primary component, ζ Cyg A is a giant star with a spectral type of G8 IIIp. Its most likely status is as a core-helium fusing red clump star, an evolved star that has begun core helium fusion. It has around three times the mass of the Sun and has expanded to about 15 times the Sun's radius. It is radiating 112 times the brightness of the Sun from its outer atmosphere at an effective temperature of 4,910 K. At this temperature, the star glows with the yellow hue of a G-type star.[11]

The secondary component, ζ Cyg B, is a white dwarf of type DA4.2. The pair orbit each other every 6,489 days (17.8 years) with an eccentricity of 0.22. The white dwarf cannot be seen directly, but is estimated to have an apparent magnitude of 13.2.[3]

Zeta Cygni has an overabundance of barium, as well as other heavy chemical elements in its atmosphere, making it a so-called "mild" barium star. These elements were synthesized by the other member of the system as it passed through the asymptotic giant branch (AGB) stage of its evolution, then ejected in its stellar wind and accreted onto the current primary component. Prior to acquiring this additional mass, Zeta Cygni had about 2.5 times the mass of the Sun, while the more evolved AGB star had three solar masses.[8]

See also[edit]


  1. ^ a b c d e van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752free to read, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357 
  2. ^ a b c Fernie, J. D. (May 1983), "New UBVRI photometry for 900 supergiants", Astrophysical Journal Supplement Series, 52: 7–22, Bibcode:1983ApJS...52....7F, doi:10.1086/190856 
  3. ^ a b Holberg, J. B.; Oswalt, T. D.; Sion, E. M.; Barstow, M. A.; Burleigh, M. R. (2013). "Where are all the Sirius-like binary systems?". Monthly Notices of the Royal Astronomical Society. 435 (3): 2077. arXiv:1307.8047free to read. Bibcode:2013MNRAS.435.2077H. doi:10.1093/mnras/stt1433. 
  4. ^ a b c Massarotti, Alessandro; et al. (January 2008), "Rotational and Radial Velocities for a Sample of 761 HIPPARCOS Giants and the Role of Binarity", The Astronomical Journal, 135 (1): 209–231, Bibcode:2008AJ....135..209M, doi:10.1088/0004-6256/135/1/209 
  5. ^ a b c d Allen, D. M.; Porto de Mello, G. F. (January 2011), "Mn, Cu, and Zn abundances in barium stars and their correlations with neutron capture elements", Astronomy and Astrophysics, 525: A63, arXiv:1009.4688free to read, Bibcode:2011A&A...525A..63A, doi:10.1051/0004-6361/200912356 
  6. ^ Griffin, R. F.; Keenan, P. C. (August 1992), "Spectroscopic binary orbits from photoelectric radial velocities. Paper 105: zeta Cygni", The Observatory, 112: 168–182, Bibcode:1992Obs...112..168G 
  7. ^ a b c Barstow, M. A.; et al. (April 2001), "Resolving Sirius-like binaries with the Hubble Space Telescope", Monthly Notices of the Royal Astronomical Society, 322 (4): 891–900, arXiv:astro-ph/0010645free to read, Bibcode:2001MNRAS.322..891B, doi:10.1046/j.1365-8711.2001.04203.x 
  8. ^ a b c Yushchenko, A. V.; Gopka, V. F.; Kim, C.; Liang, Y. C.; Musaev, F. A.; Galazutdinov, G. A. (January 2004), "The chemical composition of the mild barium star HD 202109", Astronomy and Astrophysics, 413 (3): 1105–1114, arXiv:astro-ph/0308337free to read, Bibcode:2004A&A...413.1105Y, doi:10.1051/0004-6361:20031596 
  9. ^ Smiljanic, R.; Porto de Mello, G. F.; da Silva, L. (June 2007), "Abundance analysis of barium and mild barium stars", Astronomy and Astrophysics, 468 (2): 679–693, arXiv:astro-ph/0702421free to read, Bibcode:2007A&A...468..679S, doi:10.1051/0004-6361:20065867 
  10. ^ "zet Cyg -- Spectroscopic binary", Simbad Astronomical Object Database, Centre de Données astronomiques de Strasbourg, retrieved 2012-03-02 
  11. ^ "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, retrieved 2012-01-16