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Pi Scorpii is a triple star〔 system in the southern constellation Scorpius. With a combined apparent magnitude of 2.9,〔 it can be easily seen with the naked eye. Parallax measurements yield an estimated distance of around from the Earth.〔 The name Pi Scorpii was assigned to this star by the German astronomer Johann Bayer in 1603. In 1712, it received the catalogue identifier 6 Scorpii with the publication of the star catalogue of English astronomer John Flamsteed. The binary nature of this star remained unknown until 1899, when it was announced by American astronomer Edward Charles Pickering. Two years later, an orbital period of 1.571 days was found by American astronomer Solon Irving Bailey, but it would not be until 1927 that the orbit of this spectroscopic binary was determined by Russian astronomer Otto Struve and American astrophysicist Christian T. Elvey.〔 The main components of this system form an eclipsing binary of the Beta Lyrae type.〔 Both its members are hot, B-type main sequence stars with a blue-white hue. They display an ellipsoidal variation of 0.03 in magnitude.〔 The two stars are rotating rapidly, with projected rotational velocities of 108 and 87 km s−1, respectively.〔 Their orbital period is 1.57 days and they are separated by an estimated distance of only 15 solar radii along a circular orbit.〔 The binary system is orbited by a smaller, more distant companion, which has an apparent magnitude of +12.2. This component is separated from the pair by 50 arcseconds, putting it at least 7000 Astronomical Units away. The Pi Scorpii system is a kinematic member of the Upper Scorpius subgroup of the Scorpius-Centaurus Association, a group of thousands of young stars with mean age 11 million years at distance 470 light years (145 parsecs). A recent analysis〔 of the HR diagram position for the primary star Pi Scorpii A estimates its effective temperature to be 25,230 Kelvin with a luminosity of 21,900 Suns, consistent with an isochronal age of 12-14 million years and an estimated mass of 12-13 solar masses. == References == 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「Pi Scorpii」の詳細全文を読む スポンサード リンク
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