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84 Ceti
84 Ceti is the Flamsteed designation for a binary star system〔 in the equatorial constellation of Cetus. It has an apparent visual magnitude of 5.7,〔 making it faintly visible to the naked eye from dark suburban skies. Parallax measurements with the Hipparcos spacecraft put this system at a distance of around 74 light years.〔
The primary, 84 Ceti A, is an F-type main sequence star with a stellar classification of F7V. It is slightly larger than the Sun, with 117% of the Sun's mass, 121% of the radius, and 213% of the luminosity.〔 The abundance of elements more massive than helium is 71% of the Sun's and it has a relatively high projected rotational velocity of 32 km/s.〔 This star is estimated to be less than half the age of the Sun, at 2.1 billion years.〔
The secondary component, 84 Ceti B, has a classification of K2V,〔 making it a K-type main sequence star. It lies at an angular separation of 3.3″ from the primary, which is equivalent to a physical separation of at least 74.5 AU.〔
The space velocity components of this system are: –13(U), –25(V), –2(W) km/s.〔 Based upon the position and motion, it is a candidate member of the Tucana-Horologium Association; this is a group of stars that share a similar motion through space and hence may have originated in the same molecular cloud.〔 84 Ceti is following an orbit through the Milky Way galaxy that has an eccentricity of 0.03, taking it as close as and as far as from the Galactic Center. The inclination of the orbital plane carries it as far as away from the galactic plane.〔
==References==
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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