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Xi Aquilae
Xi Aquilae (ξ Aql, ξ Aquilae) is the Bayer designation for a star in the equatorial constellation of Aquila. It is a red clump giant star with an apparent magnitude of 4.7〔 and is located at a distance of from Earth.〔 As of 2008, an extrasolar planet has been confirmed in orbit around the star.〔
==Properties==
This star has an apparent visual magnitude of 4.722,〔 which, according to the Bortle Dark-Sky Scale, is bright enough to be viewed with the naked eye from dark suburban skies. The orbital motion of the Earth causes this star to undergo an annual parallax shift of 17.77 milliarcseconds. From this measurement, the distance to this star can be determined, yielding an estimate of approximately 184 light years with a 2% margin of error.〔 The magnitude of the star is diminished by 0.09 from the extinction caused by interstellar gas and dust.〔
The spectrum of this star matches a stellar classification of G9 III,〔 where the G9 means that it belongs to the category of G-type stars while the luminosity class of III indicates that, at an estimated age of nearly five billion years,〔 is an evolved star that has reached the giant stage. It is in the red clump,〔 meaning it is generating energy through the fusion of helium into carbon at its core.
Xi Aquilae has an estimated 116% of the Sun's mass,〔 while its outer atmosphere has expanded to more than ten times the radius of the Sun.〔 It is radiating 49 times the Sun's luminosity at an effective temperature of 4,783 K,〔 giving it the golden-hued glow of a G-type star.〔 The possibility of a binary stellar companion can been ruled out based upon observations with the CHARA array.〔
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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