High Quality Content by WIKIPEDIA articles! Kepler-9b is one of the first planets discovered outside the solar system (exoplanets) by NASA`s Kepler Mission. It revolves around the star Kepler-9 within the constellation Lyra. Kepler-9b is the largest of three planets detected in the Kepler system by transit method; its mass is slightly smaller than the planet Saturn, and it is the largest planet in its system. Kepler-9b and Kepler-9c display a phenomenon called orbital resonance, in which gravitational pull from each planet alters and stabilizes the orbit of the other. The planet`s discovery was announced on August 26, 2010.