Astronomers studying a bizarre binary star system that pulses brightly every 2 minutes across almost the entire electromagnetic spectrum can’t figure it out: Either one star is lashing the other with a particle beam, or their embrace is so close that one is making the other shine. AR Scorpii, as the system is called, is made up of a white dwarf—a collapsed stellar remnant two-thirds the mass of the sun but the size of Earth—and a younger, less massive red dwarf orbiting each other every 3.6 hours. Although first spotted more than 40 years ago, its unusual broadband pulsing—from x-ray to radio waves—was only noticed last year by a group of amateur astronomers. Teaming up with professional colleagues, they used an array of orbiting and Earth-bound telescopes, including Europe’s Very Large Telescope in Chile and the Hubble Space Telescope, to study the pair. As the team describes today in Nature, the white dwarf is highly magnetized and emits a powerful beam of radiation that swings round like a lighthouse beam every 1.97 minutes. But a large chunk of the system’s pulsed emissions seem to come from the red dwarf and show signs of coming from electrons accelerated at close to the speed of light. So is the white dwarf’s beam speeding electrons toward the red dwarf, or is its highly magnetized atmosphere somehow interacting directly with its binary partner? The binary pair isn’t telling.