A team of astronomers has found evidence of another planet orbiting Proxima Centauri, the closest star to the sun. Weighing a quarter of Earth’s mass, this is the lightest exoplanet ever found. The planet has been named Proxima d and was found using a very large telescope at the European Southern Observatory in Chile. Proxima Centauri is the closest star to our sun, lying just over four light-years away.