Paper Announcing Kepler186f Available for Download
by Franck Marchis, Senior Scientist
The article announcing the discovery of Kepler-186f, led by Elisa Quintana and included the work of several other SETI Institute scientists, is now available on astro-ph.
This article reports on the discovery of a Earth-size planet (1.1x the diameter of Earth) around a M-type star (T=3788 K) named Kepler-186, made using the Kepler NASA spacecraft data from the first 3 years of observation. Four other planets designated Kepler-186b-e (all smaller than 1.5 times Earth) were reported previously from the first 2 years of Kepler data, This fifth planet, named Kepler-186f, was seen on the third year of observation. The team is confident at 99% that this exoplanet is real, having used adaptive optics follow-up observations on Gemini and Keck telescopes. The composition and the density of the planet are unknown, but evolutionary models of the star ruled out a H/He gas envelop for the exoplanet (aka a mini-Neptune). Consequently this exoplanet could be made of iron, silicate rock or water with a mass from 3.8 to 1.4 times the mass of the Earth
Kepler spacecraft data has revealed several Earth-size planets in the past, but in less favorable orbits. Kepler-186f is located in the outer portion of the star's habitable zone and far enough from the star not to be tidally locked (always keeping the same face toward its star). The SETI Institute scientists concluded that this exoplanet probably has the properties required to host liquid water on its surface, making Kepler-186f the first Earth-size exoplanet located in the habitable zone of its star.