Quasars over 1000 times brighter than Milky Way stars

Washington: Powered by massive black holes at the center of most known galaxies, quasars can emit enormous amounts of energy, up to a thousand times the total output of the hundreds of billions of stars in our entire Milky Way. Dartmouth astrophysicists Ryan Hickox and Kevin Hainline and colleagues have detailed their discoveries based upon observations of 10 quasars. They documented the immense power of quasar radiation, which reaches out for many thousands of light years to the limits of the quasar`s galaxy. "For the first time, we are able to see the actual extent to which these quasars and their black holes can affect their galaxies, and we see that it is limited only by the amount of gas in the galaxy," Hainline, a Dartmouth postdoctoral research associate, said. "The radiation excites gas all the way to the margins of the galaxy and stops only when it runs out of gas," he said. The radiation released by a quasar covers the entire electromagnetic spectrum, from radio waves and microwaves at the low-frequency end through infrared, ultraviolet, and X-rays, to high-frequency gamma rays. A central black hole, also called an active galactic nucleus, may grow by swallowing material from the surrounding interstellar gas, releasing energy in the process. This leads to the creation of a quasar, emitting radiation that illuminates the gas present throughout the galaxy. "If you take this powerful, bright radiation source in the center of the galaxy and blast the gas with its radiation, it will get excited in just the same way the neon gets excited in neon lamps, producing light," Hickox, an assistant professor in the Department of Physics and Astronomy at Dartmouth, said. "The gas will produce very specific frequencies of light that only a quasar can produce. This light functioned as a tracer that we were able to use to follow the gas excited by the black hole out to large distances," he said.

The study is set to be published in The Astrophysical Journal. ANI