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Beta Ceti
Beta Ceti (β Cet, β Ceti) is the brightest star in the constellation Cetus. Although it has the Bayer designation "beta", it is actually brighter than Alpha Ceti. It has the traditional names Deneb Kaitos and Diphda. This orange giant is easy to identify due to its location in an otherwise dark section of the celestial sphere. Based on parallax measurements, it lies at an estimated distance of from Earth.〔
== Properties ==
Deneb Kaitos has an apparent visual magnitude of 2.02,〔 making it the brightest star in Cetus. The stellar classification of this star is K0 III,〔 although some sources list a classification of G9.5 III〔 indicating that it lies along the dividing line separating G-type from K-type stars. The luminosity class of 'III' means that it is a giant star that has consumed the hydrogen at its core and evolved away from an A-type main sequence star.〔 After passing through the red giant stage, it underwent the helium flash event and is generating energy through the thermonuclear fusion of helium at its core.〔 Beta Ceti will remain in this mode for over 100 million years.〔
The effective temperature of the star's outer envelope is about 4,797 K,〔 giving it the characteristic orange hue of a K-type star.〔 In spite of its cooler temperature, Deneb Kaitos is much brighter than the Sun with a bolometric luminosity of about 145 times the luminosity of the Sun,〔 resulting from a radius 18〔 times as large as the Sun and a mass that is 2.8 times the Sun's mass.〔
This star displays flaring activity that results in random outbursts that increase the luminosity of the star over intervals lasting several days. This is a much longer duration than for comparable solar flare activity on the Sun, which typically last for periods measured in hours.〔 In 2005, a relatively high rate of X-ray emission was detected with the XMM-Newton space observatory.〔 It is emitting about 2,000 times the X-ray luminosity of the Sun, allowing the star to be imaged with the Chandra X-ray Observatory.〔
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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