Using data from NASA's Fermi Gamma-ray Space Telescope and other facilities, an international team of scientists has found the first gamma-ray binary in another galaxy and the most luminous one ever seen. The dual-star system, dubbed LMC P3, lies within the expanding debris of a supernova explosion located in the Large Magellanic Cloud, a small nearby galaxy about 163,000 light-years away. The system contains a massive star and a crushed stellar core that interact to produce a flood of gamma rays, the highest-energy form of light. In gamma-ray binaries, outflows from both stars collide and accelerate electrons to near the speed of light. When these particles collide with the star's visible light, it receives a boost up to gamma-ray levels. Fermi observations show gamma-ray output from LMC P3 changes as the companion orbits the star. This variation lets astronomers study many of the emission processes common to other gamma-ray sources in unique detail. Watch the video to learn more.