A New Source of Gamma Rays

摘要

Relativistic outflows or "jets" are collimated streams of high-energy electrons that emit synchrotron radiation at radio wavelengths and have bulk velocities that are a substantial fraction of the speed of light. Jets have been known since Curtis observed a "curious straight ray" from the nucleus of the radio galaxy M87 in 1918. It is now clear that these jets trace the outflow of enormous amounts of energy and matter from a central supermassive black hole. The outflows are probably powered by the gravitational potential energy of the matter that crosses the event horizon and falls into the black hole; there may also be some contribution from the spin energy of the black hole if it is rapidly rotating.