9 Cygni
Star in the constellation Cygnus
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9 Cygni is a binary star system in the northern constellation of Cygnus. 9 Cygni is its Flamsteed designation. The two stars have a combined magnitude of 5.39,[2] so it can be seen with the naked eye under good viewing conditions. Parallax measurements made by Gaia put the star at a distance of around 590 light-years (182 parsecs) away.[1]
The two stars of 9 Cygni are a G-type giant and an A-type star. Both stars are over twice as massive as the Sun.[2] They orbit once every 4.56 years, separated with a semi-major axis of 0.030 arcseconds. However, the eccentricity is high, at 0.82.[3] The primary is a red clump giant, a star on the cool end of the horizontal branch fusing helium in its core. The secondary star has begun to evolve off the main sequence; it is sometimes classified as a giant star[2] and sometimes as a main-sequence star.[4]