Zeta Cygni

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Zeta Cygni
Diagram showing star positions and boundaries of the Cygnus constellation and its surroundings
Cercle rouge 100%.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] / 11.6
Spectral type G8+IIIa Ba 0.6[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) 6,389 ± 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[3] 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[3] km/s
Age 0.2[8] Gyr
ζ Cyg B
Mass 0.6[7] M
Temperature 12,000[7] K
Other designations
Zet Cyg, 64 Cygni, BD+29°4348, HD 202109, HIP 104732, HR 8115, SAO 71070.[9]
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.[2] Based upon parallax measurements, the distance to this star is about 143 light-years (44 parsecs).[1]

The primary component is a giant star with a stellar classification of G8 IIIp.[7] Its most likely status is as a core-helium fusing giant star, although it could be in transition to gianthood with a tranquil helium core.[10] This star has around three[3] times the mass of the Sun and has expanded to about 15[4] times the Sun's radius. It is radiating 112[4] times the brightness of the Sun from its outer atmosphere at an effective temperature of 4,910 K.[5] At this temperature, the star glows with the yellow hue of a G-type star.[11]

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.[3]

The secondary component of this system is a white dwarf.[7] The pair orbit each other every 6,489 days, or every 17.8 years, with an eccentricity of 0.22.[6]

See also[edit]


  1. ^ a b c d e f van Leeuwen, F. (November 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 
  2. ^ a b c d 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 c d e 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: 1105–1114, arXiv:astro-ph/0308337, Bibcode:2004A&A...413.1105Y, doi:10.1051/0004-6361:20031596 
  4. ^ a b c d e 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 e 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:1009.4688, Bibcode:2011A&A...525A..63A, doi:10.1051/0004-6361/200912356 
  6. ^ a b 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 d e 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/0010645, Bibcode:2001MNRAS.322..891B, doi:10.1046/j.1365-8711.2001.04203.x 
  8. ^ 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/0702421, Bibcode:2007A&A...468..679S, doi:10.1051/0004-6361:20065867 
  9. ^ "zet Cyg -- Spectroscopic binary", Simbad Astronomical Object Database (Centre de Données astronomiques de Strasbourg), retrieved 2012-03-02 
  10. ^ Kaler, James B., "Zeta Cygni", Stars (University of Illinois), 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