English: NASA's Kepler mission has discovered a new planetary system that is home to the smallest planet yet found around a star like our sun, approximately 210 light-years away in the constellation Lyra.

The line up compares the smallest known planet to the moon and planets in the solar system. Kepler-37b is slightly larger than our moon, measuring about one-third the size of Earth. Kepler-37c, the second planet, is slightly smaller than Venus, measuring almost three-quarters the size of Earth. Kepler-37d, the third planet, is twice the size of Earth.

A "year" on these planets is very short. Kepler-37b orbits its host star every 13 days at less than one-third the distance Mercury is to the sun. The other two planets, Kepler-37c and Kepler-37d, orbit their star every 21 and 40 days. All three planets have orbits lying less than the distance Mercury is to the sun, suggesting that they are very hot, inhospitable worlds.