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

TL;DR

Kepler-452b is a potentially rocky super-Earth exoplanet in the habitable zone of a G2 star, with a 1.6 Earth radius, orbiting every 385 days, and likely remains habitable for billions of years.

Contribution

This paper reports the discovery and validation of Kepler-452b, the longest-period small transiting exoplanet found in the habitable zone, with detailed characterization of its orbit and host star.

Findings

Kepler-452b has a radius of approximately 1.6 Earth radii.

It orbits its star every 385 days, within the habitable zone.

The planet has a high likelihood of rocky composition.

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$^{+0.23}_{-0.20}$ R$_\oplus$ planet orbits its G2 host star every 384.843$^{+0.007}_{0.012}$ 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$\pm$85 K and a log g of 4.32$\pm$0.09. At a mean orbital separation of 1.046$^{+0.019}_{-0.015}$ 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$^{+0.15}_{-0.09}$ R$_\odot$ 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.