Magnificent bursts of light help scientists pinpoint the most energetic spots in the universe.
Gamma rays are the most powerful form of light in the universe. In the darkness of space, these luminous rays, which are invisible to humans but detectable by spacecraft, act as celestial beacons that alert us to some of the most extreme events and objects in the cosmos. For instance, when dying stars explode as supernovae, they emit gamma rays; so do particles being sucked into supermassive black holes; as do pulsars, the rapidly rotating stars that are as massive as our sun but only about the size of Manhattan. Since 2008, NASA’s Fermi spacecraft has observed gamma rays in the Milky Way and beyond. Plotted on a map, the locations of different sources appear as bright spots in the night sky. Watch the video to see how the spacecraft detects gamma rays.