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Kepler-452b is an exoplanet orbiting the G-class star Kepler-452. It was identified by the ''Kepler'' space telescope, and its discovery was publicly announced by NASA on 23 July 2015. It is the first potentially rocky super-Earth〔(【引用サイトリンク】title=The Habitable Exoplanets Catalog – Planetary Habitability Laboratory @ UPR Arecibo )〕 planet discovered orbiting within the habitable zone of a star very similar to the Sun. Using the criteria of the Earth Similarity Index, it is the sixth-most Earth-like exoplanet known to date. The planet is about 1,400 light-years away from the Solar System; at the speed of the ''New Horizons'' spacecraft, about , it would take approximately 26 million years to get there. == Properties == The planet takes 385 Earth days to orbit its star. It is 60% bigger than Earth, and lies within the conservative habitable zone of its parent star. It has a probable mass five times that of Earth, and its surface gravity is twice Earth's, though calculations of mass for exoplanets are only rough estimates.〔 If it is a terrestrial planet, it is most likely a super-Earth with many active volcanoes due to its higher mass and density. The clouds on the planet would be thick and misty, covering much of the surface as viewed from space. From the surface, its star Kepler-452 would look almost identical to the Sun as viewed from the Earth.〔NASA Kepler press conference. 23 July 2015.〕 It is not known if Kepler-452b is a rocky planet or a small gas planet, but based on its small radius, Kepler-452b has a reasonable chance of being rocky.〔 It is not clear if Kepler-452b offers habitable environments. It orbits a G2V-type star, like the Sun, with nearly the same temperature and mass and 20% more luminous.〔 However, the star is six billion years old, making it 1.5 billion years older than the Sun. At this point in its star's evolution, Kepler-452b is receiving 10% more energy from its parent star than Earth is currently receiving from the Sun.〔 If Kepler-452b is a rocky planet, it may be subject to a runaway greenhouse effect similar to that seen on Venus. 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「Kepler-452b」の詳細全文を読む スポンサード リンク
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