"EXPLORING GALAXY EVOLUTION WITH HIGH ENERGY GAMMA RAYS"
The Compton Gamma Ray Observatory discovered a unique
class of extragalactic objects, "grazars," which produce intense beams
of high energy gamma rays. Grazars are powered by supermassive black
holes at the cores of active galaxies which spawn jets of plasma moving
at close to the speed of light which are pointed directly at us.
Just as a flashlight beam is dimmed when it traverses a dusty room, grazar
beams are attenuated by interactions with light produced by stars and dust
in galaxies which radiate into intergalactic space. Gamma-ray telescopes
can measure this effect to probe the amount of stellar activity occurring
at various epochs in the history of the Universe. Results are already
being obtained and will be discussed.