Transiting planets in Kepler-47 circumbinary system

Kepler-47 b (the "inner planet") has an orbital period of 49.5 days and a radius of about 3 R_{Earth}_. Kepler-47 c (the "outer planet") has an orbital period of 303.2 days and a radius of about 4.7 R_{Earth}_.

Here we report the discovery of a third planet, Kepler-47 d (the "middle planet"), which has an orbital period of 187.4 days and a radius of about 7 R_{Earth}_. The presence of the middle planet allows us to place much better constraints on the masses of all three planets, where the 1{sigma} ranges are less than 26 M_{Earth}_, between 7-43 M_{Earth}_, and between 2-5 M_{Earth}_ for the inner, middle, and outer planets, respectively.