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Artist impression of the surface of Kepler 452b. With a radius 60% larger than Earth, the planet has a better than even chance of having a rocky composition, and is likely to have a thick atmosphere and a significant amount of water. Because we can’t yet measure the mass of Kepler 452b, astronomers rely on models to estimate a range of possible masses, with the most likely being 5 times that of Earth. Such a massive rocky planet would likely still have active volcanism. Kepler 452b is orbiting a close cousin of our Sun, but one that is 1.5 billion years older.  In the scenario depicted here, the planet is just entering a runaway greenhouse phase of its climate history.  The increasing energy from its aging sun could be evaporating any oceans, leaving behind large lakes ringed with mineral deposits. Kepler 452b could be giving us a preview of what the Earth will undergo more than a billion years from now, as the Sun ages and grows brighter. Danielle Futselaar/SETI Institute
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