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Epsilon Tauri (abbreviated ε Tauri or ε Tau) is the Bayer designation of an orange giant star, spectral type of K0 III, located approximately 45 parsecs or 147 light-years away from the Sun in the constellation of Taurus.〔 It has the traditional name Ain (Arabic عين for "eye") and was given the name Oculus Boreus (Latin for "Northern eye") by John Flamsteed. It is claimed to be the heaviest among planet-harboring stars with reliable initial masses〔 although the star HD 13189 is potentially more massive.〔(【引用サイトリンク】 work=The Extrasolar Planets Encyclopaedia )〕 It is a member of the Hyades open cluster. As such its age is well constrained at 625 million years.〔 Given its large mass, this star was formerly a member of spectral type A that has now evolved off the main sequence into the giant phase. It is regarded as a red clump giant; that is, a core-helium burning star.〔 Since Epsilon Tauri lies near the plane of the ecliptic, it is sometimes occulted by the Moon and (very rarely) by planets. It has an 11th magnitude companion 182 arcseconds from the primary. == Planetary system == In 2007 a massive extrasolar planet was reported orbiting the star with a period of 1.6 years in a somewhat eccentric orbit. Its discoverers claimed it was the first planet ever discovered in an open cluster.〔 The planet is one of those selected by the International Astronomical Union as part of their public process for giving proper names to exoplanets.〔(NameExoWorlds: An IAU Worldwide Contest to Name Exoplanets and their Host Stars ). IAU.org. 9 July 2014〕〔(NameExoWorlds ).〕 The process involves public nomination and voting for the new name, and the IAU plans to announce the new name in mid-November 2015.〔(NameExoWorlds ).〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Epsilon Tauri」の詳細全文を読む スポンサード リンク
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