NASA’s Kepler space probe has discovered the smallest planet yet orbiting a Sun-like star. Dubbed Kepler-37b, the exoplanet orbits the star Kepler-37 about 210 light-years from Earth in the constellation Lyra. It’s only one-third the size of Earth and smaller than Mercury, which makes it not only the smallest planet yet found outside the Solar System, but the smallest planet ever discovered.
