The primary component, ζ Cyg A is agiant star with aspectral type of G8 IIIp. Its most likely status is as ared clump giant,[citation needed] 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 itsouter atmosphere at aneffective temperature of 4,910 K. At this temperature, the star glows with the yellow hue of aG-type star.[12]
The secondary component, ζ Cyg B, is awhite dwarf of type DA4.2. The pair orbit each other every 6,489 days (17.8 years) with aneccentricity of 0.22. The white dwarf cannot be seen directly, but is estimated to have anapparent magnitude of 13.2.[3]
Zeta Cygni has an overabundance ofbarium, 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 theasymptotic giant branch (AGB) stage of itsevolution, then ejected in itsstellar 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.[9]
^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
^"The Colour of Stars",Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived fromthe original on 2013-12-03, retrieved2012-01-16
