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SLAC study sheds light on black holes

Most of the gamma rays produced by black holes are created much farther from the bodies than expected, according to a study by Stanford and SLAC National Accelerator Laboratory scientists. Data from more than 20 telescopes showed that the jets of particles that stream out of bright galaxies function differently than researchers previously thought.

The recent work by scientists at the Kavli Institute for Particle Astrophysics and Cosmology, jointly located at SLAC and Stanford University, may help theorists better explain some of the keys to the universe, such as how its biggest accelerators operate.

Above the Milky Way, galaxies called blazars prevail in the gamma-ray filled sky. At the center of a blazer is a black hole. When matter falls into such a black hole, some energy is spit back out into the universe in the form of jets of particles.

Earlier theories have suggested that tendrils of magnetic field hold these jets together, while the light is produced when the particles revolve around these tendrils. However, the details of that process have been poorly understood.

During more than a year of observation, researchers witnessed a 20-day-long flare in gamma rays from a blazar jet located in the constellation Virgo, in concurrence with a change in the directionality of the jet’s optical light.

Previous theories suggested that gamma rays are created where the matter entering the black hole loses its energy, near the point of entry.

This new data suggests that both types of light are created in the same geographical region of the jet. If gamma rays are created farther from the black hole than previously thought, magnetic field lines must help energy travel outward from the black hole.

- Tyler Brown and Margaret Rawson