Gamma ray observations of a microquasar demonstrate electron shock acceleration

Observations of gamma rays, emitted by relativistic jets in a microquasar system, demonstrate the acceleration of electrons by a shock front, reports a new study. The microquasar SS 433 is a binary system made up of a compact object, probably a black hole, and a supergiant star. The black hole pulls material off the star and ejects plasma jets, which move at close to the speed of light. The High Energy Stereoscopic System (H.E.S.S.) is an array of five telescopes in Namibia that observe gamma rays. The H.E.S.S. Collaboration used the array to observe SS 433, finding that the highest energy gamma rays do not appear close to the black hole, but further out in the jet. By modeling the gamma ray emission, they show that electrons are being accelerated at a shock front within the jet, shedding light on how it reaches such high energies. In a related Perspective, Valentí Bosch-Ramon discusses how the findings could explain the origin of the most energetic cosmic rays produced within the Milky Way.