A new Earth-sized exoplanet has been discovered with a peculiar and ultra-short orbit around its host star, completing a revolution every four hours and 20 minutes. There's a joke in there somewhere, but we don't know what it'd be. The planet is named EPIC 228813918 b, and it has the second-shortest orbital period of any planet ever discovered. The new planet has a radius 0.89 times as large as Earth's, but it's much denser than our little blue marble — about 249 times denser, giving it a mass more than twice that of Saturn. Located 310 light years from Earth, EPIC orbits an M-type red dwarf. EPIC was identified by an international team lead by Alexis Smith of the German Aerospace Center's (DLR) Institute of Planetary Research in Berlin. A paper proving that EPIC was a planet, not a small star, was published on arXiv.org on July 14. "We use its K2 light curve, radial velocities, archival images, adaptive optics imaging and a catalog of [eclipsing binary stars (EB)] to demonstrate that