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KIC 12557548
KIC 12557548 is a K-type main-sequence star located in the constellation Cygnus. The star is particularly important, as measurements taken by the ''Kepler'' spacecraft indicate that the variations in the star's light curve cover a range from about 0.2% to 1.3% of the star's light being blocked. This indicates that there may be a rapidly disintegrating planet, a prediction not yet conclusively confirmed, in orbit around the star, losing mass at a rate of 1 Earth mass every billion years.〔 The planet itself is about 0.1 Earth masses, or just twice the mass of Mercury, and is expected to disintegrate in about 100〔-200 million years.〔 The planet orbits its star in just 15.7 hours,〔 at a distance only two stellar diameters away from the star's surface, and has an estimated effective temperature of about 2255 K.〔 The orbital period of the planet is one of the shortest ever detected in the history of the extrasolar planet search.
== History of detection ==
The existence of the planet was first evidenced in data collected by the ''Kepler'' spacecraft. However, the light curve of the star, a graph of its stellar flux versus time, showed that while there were regular drops in stellar flux approximately every 15 hours, the amount of light being blocked covered a wide range, from 0.2% to 1.3% of the starlight being blocked.〔 Rappaport et al. (2012) proposed various possible phenomena which may have caused the anomalies in the light curve, including two planets orbiting each other, and an eclipsing binary orbiting the star in a larger triple-star system.〔 However, the authors found the hypothetical binary planet system to be unstable〔 and the latter scenario to be poorly supported by the data collected by ''Kepler''.〔
Therefore, the authors posited that the most likely cause of the observed light curve was a closely orbiting planet, about twice the mass of Mercury, which was rapidly emitting small particles into independent orbits around the star.〔 Exactly the cause of this phenomenon could be the direct sublimation of the planetary surface and its emission into space, the intense volcanism caused by the tidal effects of orbiting extremely close to the host star, or both processes mutually reinforcing the strength of each other in a positive feedback loop.〔
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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