NASA’s Fermi telescope has detected what may be the first confirmed gamma-ray signal from a superluminous supernova — one of the most extreme explosions in the universe. Scientists believe the blast was powered by a rapidly spinning magnetar, an exotic neutron star with unbelievably strong magnetic fields. The event, called SN 2017egm, erupted 440 million light-years away and may help explain why some supernovae become extraordinarily bright.