Kepler-37b. Computer illustration of the newly-discovered tiny planet Kepler-37b, which lies in the Kepler-37 system, around 210 light-years from Earth in the constellation Lyra. This planet is one of the smallest yet found and is slightly larger than the Moon, measuring about one-third the size of Earth. It orbits its host star every 13 days at less than one-third the distance that Mercury is to the sun. Click image for full caption and larger size.