DISCOVERY AND VALIDATION OF Kepler-452b: A 1.6<i>R</i>_⨁SUPER EARTH EXOPLANET IN THE HABITABLE ZONE OF A G2 STAR

Abstract

We report on the discovery and validation of Kepler-452b, a transiting planet identified by a search through the 4 years of data collected by NASA's Kepler Mission. This possibly rocky 1.63 0.20 0.23 -+ R planet orbits its G2 host star every 384.843 0.012 0.007 -+ days, the longest orbital period for a small (R 2 P < R ) transiting exoplanet to date. The likelihood that this planet has a rocky composition lies between 49% and 62%. The star has an effective temperature of 5757 85 K and a g log of 4.32 0.09. At a mean orbital separation of 1.046 0.015 0.019 -+ AU, this small planet is well within the optimistic habitable zone of its star (recent Venus/early Mars), experiencing only 10% more flux than Earth receives from the Sun today, and slightly outside the conservative habitable zone (runaway greenhouse/maximum greenhouse). The star is slightly larger and older than the Sun, with a present radius of 1.11 0.09 0.15 -+ R and an estimated age of 6 Gyr. Thus, Kepler-452b has likely always been in the habitable zone and should remain there for another 3 Gyr.