Science doi:10.1126/science.1195778 (2010)

Two planets roughly the size of Saturn have been discovered orbiting a star similar to the Sun 650 parsecs away. As they zip around their parent star in 19.2 and 38.9 days, respectively, the duo tug on each other gravitationally. As a result, the first planet is speeding up by 4 minutes per orbit, whereas the second is slowing by 39 minutes per orbit.

Using the Kepler satellite, Matthew Holman of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, and his colleagues spotted telltale dips in the intensity of the host star's light, revealing each planet as it passed in front of the star. The team says that in the long term, the number of orbits for the pair will average out so that one planet circles almost exactly twice as often as the other.