sentences:  On 2011, a density of 55 Cancri e was calculated which turned out to be similar to Earth's.At the size of about 2 Earth radii, it was the largest planet until 2014 which was determined to lack a significant hydrogen atmosphere.On 20 December 2011, the Kepler team announced the discovery of the first Earth-size exoplanets, Kepler-20e and Kepler-20f, orbiting a Sun-like star, Kepler-20.