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HD 102365
HR 4523 (66 G. Centauri) is a binary star system that is located in the northeastern part of the Centaurus constellation, at a distance of about from the Solar System. The larger member of the system is a G-type star that is smaller than the Sun but of similar mass. It has a common proper motion companion that was discovered by W. J. Luyten in 1960.〔 This M-type star appears to be in a wide orbit around the primary at a current separation of about 211 astronomical units (AU),〔 (or 211 times the separation of the Earth from the Sun). By comparison, Neptune orbits at an average distance of 30 AU.
The stellar classification for the primary star in this system is G2V;〔 the same as the Sun. That of the red dwarf companion is M4V.〔 The primary star has an estimated 86%〔 to 89% the mass of the Sun, 96% of the Sun's radius,〔 and 85% of the Sun's luminosity.〔 It is a slow rotator, with a projected rotational velocity of 0.5 km/s.〔 Age estimates range from 4.5–5.7 billion years (Gyr)〔 up to 7.1 Gyr〔 or 9.48 Gyr.〔 Compared to the Sun, it only has about 52%〔 of the abundance of elements other than hydrogen and helium; what astronomers term the metallicity of a star.
This star system has a relatively large proper motion.〔 The HR 4523 system is a member of the Epsilon Indi Moving Group, although it is most likely an interloper. (The star is older and has a different composition than the other group members.)〔 It has space velocity components = .〔
== Planetary system ==
The primary star is believed to be orbited by a Neptune-like planet with a mass 16 times that of the Earth. The orbital period of this planet is 122.1 days. No other planets have been discovered orbiting this star.〔 An examination of this system in the infrared did not reveal an excess emission that would otherwise suggest the presence of a circumstellar debris disk.〔
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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