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Alnilam
Alnilam is a large blue supergiant star some 1,340 light years distant in the constellation of Orion. It has a Bayer designation of Epsilon Orionis (ε Ori) and its Flamsteed designation is 46 Orionis. It is estimated to be 275,000 to 537,000 times as luminous as the Sun, and around 34 times as massive.
==Description==
It is the 30th brightest star in the sky (the 4th brightest in Orion) and is a blue-white supergiant. Together with Mintaka and Alnitak, the three stars make up the belt of Orion, known by many names across many ancient cultures. Alnilam is the middle star. It is slightly variable, from magnitude 1.64 to 1.74. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified. It is also one of the 58 stars used in celestial navigation. It is at its highest point in the sky around midnight on December 15. Alnilam's relatively simple spectrum has made it useful for studying the interstellar medium. Within the next million years, this star may turn into a red supergiant and explode as a supernova. It is surrounded by a molecular cloud, NGC 1990, which it illuminates to make a reflection nebula. Its stellar winds may reach up to 2000 km/s, causing it to lose mass about 20 million times more rapidly than the Sun.〔
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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