Kepler-36 b

The inner rocky world in the Kepler-36 system, Kepler-36 b orbits Kepler-36 about every 14 standard days at an average distance of less than 11 million miles, while the outer hot gas sub-giant Kepler-36 c orbits once each 16 days at a distance of 12 million miles.

The two planets experience a conjunction every 97 days on average. The timing of their orbits means they'll never collide, however, the continuous close encounters cause tremendous gravitational tides that squeeze and stretch both planets.

The smaller planet is 30 percent iron, less than 1 percent atmospheric hydrogen and helium and probably no more than 15 percent water. The planets' densities differ by a factor of eight but their orbits differ by only 10 percent.