Gamma Cygni
Yellow-white supergiant at the heart of the Northern Cross.
Gamma Cygni is a star in the northern constellation Cygnus, marking the intersection of the Northern Cross asterism. It is officially named Sadr and is approximately 1,800 light-years from the Sun. This star forms the primary component of a multiple star system designated WDS J20222+4015.
Quick Facts
- Traditional name
- Sadr
- Apparent visual magnitude
- 2.23
- Stellar classification
- F8 Iab
- Mass
- 14.5 times the Sun's mass
- Radius
- about 180 times the Sun's radius
- Luminosity
- over 33,000 times the Sun's luminosity
Facts from the source article.
Nomenclature
Gamma Cygni is the Bayer designation for this star, Latinised from γ Cygni. In the Washington Double Star Catalog it is listed as WDS J20222+4015A. The traditional name Sadr, also rendered Sadir or Sador, derives from the Arabic ṣadr, meaning chest, the same root as Schedar. The IAU Working Group on Star Names approved Sadr for Gamma Cygni on 21 August 2016. In the Calendarium of Al Achsasi al Mouakket it was called Sadr al Dedjadjet, Latinised as Pectus Gallinǣ, the hen's chest. In Chinese astronomy, Gamma Cygni is part of the Celestial Ford asterism.
Properties
Gamma Cygni has an apparent visual magnitude of 2.23 and a stellar classification of F8 Iab, indicating a supergiant stage. Its spectrum has served as a stable anchor point for stellar classification since 1943. The star has 14.5 times the Sun's mass and about 180 times its radius, emitting over 33,000 times the Sun's energy at an effective temperature of 5,790 K, giving it a yellow-white hue. Its estimated age is about 12 million years, and it has sufficient mass to explode as a supernova. The spectrum shows unusual dynamic features, including radial velocity variations on a timescale of 100 days or more, and it lies close to the instability strip on the Hertzsprung–Russell diagram. The star is surrounded by the diffuse nebula IC 1318.
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