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Epsilon Pegasi
Epsilon Pegasi (ε Peg, ε Pegasi) is the brightest star in the northern constellation of Pegasus. It has the traditional name Enif (EE-nif). The name Enif is derived from the Arabic word for ''nose'', due to its position as the muzzle of Pegasus. With an apparent visual magnitude of 2.4,〔 this is a second-magnitude star that is readily visible to the naked eye. The distance to this star can be estimated using parallax measurements from the Hipparcos astrometry satellite,〔〔 yielding a value of around .〔
Other traditional names for the star include ''Fom al Feras'', Latinised to ''Os Equi''. In Chinese, (), meaning ''Rooftop (asterism)'', refers to an asterism consisting of ε Pegasi, α Aquarii and θ Peg.〔 ''中國星座神話'', written by 陳久金. Published by 台灣書房出版有限公司, 2005, ISBN 978-986-7332-25-7.〕 Consequently, ε Pegasi itself is known as (, (英語:the Third Star of Rooftop).)〔 (香港太空館 - 研究資源 - 亮星中英對照表 ), Hong Kong Space Museum. Accessed on line November 23, 2010.〕
==Properties==
This is an evolved star that has entered the supergiant stage, as indicated by the stellar classification of K2 Ib.〔 It is estimated to be 12〔 times the Sun's mass. The measured angular diameter of this star, after correction for limb darkening, is .〔 At the estimated distance of this star, this yields an enormous physical size of about 185 times the radius of the Sun.〔 From this expanded envelope, it is radiating roughly 12,250〔 times the luminosity of the Sun at an effective temperature of 4,337 K.〔 This temperature is cooler than the Sun, giving it the orange-hued glow of a K-type star.〔
Enif probably only has a few million years left to go, although it is unknown whether it will explode in a supernova or die off as a rare neon-oxygen white dwarf, due to its mass straddling the dividing line between stars destined to explode or not. Enif has been observed to brighten radically upon a few occasions, giving rise to the theory that it (and possibly other supergiants) erupt in massive flares that dwarf those of our own Sun.〔 It is a type LC slow irregular variable star that varies from +0.7 to +3.5 in magnitude.〔 The spectrum shows an overabundance of the elements strontium and barium, which may be the result of the S-process of nucleosynthesis in the outer atmosphere of the star.〔 It has a relatively high peculiar velocity of .〔
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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