Discovery and Validation of Kepler-452b: A 1.6 R ⨁ Super Earth Exoplanet in the Habitable Zone of a G2 Star

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}_\oplus planet orbits its G2 host star every {384.843}_-0.012^+0.007 days, the longest orbital period for a small ({R}_{{P}}< 2 {R}_\oplus ) 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 {log}g 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.