SOME BLACK HOLES POWER THE BRIGHTEST OBJECTS IN THE UNIVERSE
In the 1960s, astronomer Allan Sandage noticed a very bright object in the distant sky. It was as bright as a nearby star, but its vast distance meant it must be emitting hundreds of times as much energy as all of the stars in the Milky Way. Dubbed quasars, these objects are among the brightest in the universe and represent actively feeding supermassive black holes. Thousands have been identified, and each blazes brightly as matter tumbles onto its accretion disc, spewing X-rays and visible light into space.