Kepler is a roughly 1-meter-diameter telescope that is staring at 150,000 Sun-like stars in the constellations Cygnus and Lyra. It will watch those stars for about three and a half years continuously, without ever closing its eyes. Kepler will look for events called transits, in which a planet briefly passes in front of its parent star, blocking a little bit of the star’s light.The goal is to find Earth-size planets around Sun-like stars.