Gamma rays from far, far away

At least 7.6 billion years ago – when the universe was less than half its current 13.8-billion-year age – a superbright galaxy known as a blazar spewed two powerful jets of light, X-rays, radio waves and other radiation, including gamma rays. These gargantuan jets were emitted as a supermassive black hole at the galaxy’s heart sucked in huge amounts of gas and dust. One of those jets was aimed at Earth. It slammed into Earth’s atmosphere last April 25. It was detected by various orbiting and ground-based observatories, including the world’s most sensitive, high-energy gamma-ray observatory, VERITAS, the Very Energetic Radiation Imaging Telescope Array System in southern Arizona. Dave Kieda – a U professor of physics and astronomy and dean of the graduate school – leads the U’s research group in the multi-institution VERITAS collaboration. He can discuss the latest findings, published last month, about blazar PKS 1441+25’s gamma ray blast from the distant past. One is that the universe is much more transparent to the passage of radiation than was thought, given that the gamma rays reached Earth despite the “fog” of light from other objects in the universe. Second, the gamma rays originated much farther from the heart of the supermassive black hole than was expected, about the 4-light-year distance between our sun and the nearest star. Third, the gamma-ray measurements confirmed theories about the number and brightness of stars and galaxies that emit gamma rays.
David Kieda, office 801-581-6926, cell 801-518-2548, dave.kieda@utah.edu


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