Researchers observe energy consumption in quasars

The quasars are the brightest lighthouses in the universe. shining with magnitudes brighter than whole galaxies and the stars they contain. The researchers think that the center of this light, in the heart of a quasar, is a devouring black hole.

For the first time, researchers observed the accelerated rate of interstellar fuel consumption by eight quasars to feed their black holes. They published their results on September 4th. Nature.

"As the brightest stable beacons of the universe, the quasars would be powered by an accreting disk around the central black hole," said Hongyan Zhou, author of the newspaper and faculty member of the University of Science and Technology of China. Zhou is also affiliated with the SOA Key Laboratory for Polar Science of the Polar Research Institute of China.

Zhou compared the black hole to a hungry dragon.

"The supermassive black hole in the center of the quasar engulfs a huge amount of nearby materials, which dazzle and shine when they constitute an accretion disk before finally slipping into the black hole," Zhou said. "Outside the accretion disk, materials are pumped continuously from all directions to the center by gravity to feed the black hole with an endless appetite."

An accretion disk is a mass of spiral material centered around a monumental source of interstellar matter consuming gravity – which the researchers theorized as being a black hole. Much like the way the water gets empty of a bathtub, the material rotates much faster as it gets closer to the drain.

"We think that this paradigm of black holes in the center of the quasars is accurate, but fundamental questions remain unanswered: is the accretion disk powered by external mass? If so, how?" Said Zhou.

The interstellar gas can not be observed directly because its radiation signature is submerged by the brightness of the accretion disk. Instead, researchers monitor the presence of gas in the accretion disk that can cross their field of vision. The gas forms a kind of eclipse between the Earth and the accretion disk, projecting lines on the radiation spectrum of the disk.

The researchers used the Doppler effect to measure these lines and observe the speed of the gas entering the disc, towards the black hole. A classic example of a Doppler effect is the sound drop of a police siren. Astronomers call this step of passing the "downward shift" when measuring the rate at which the gases move toward an object far away from the Earth.

Zhou and his team measured speeds of 5,000 kilometers per second. For comparison, a jet plane travels less than a thousand kilometers at the hour.

"Such a high speed can only be accelerated by the severity of the central black hole," Zhou said. "It's comparable to the fact that, under a meteor shower, the more meteors approach the ground, the faster they fall."

In the quasars observed by Zhou, the accretion disks were fed by a rapidly falling external mass from the surrounding space. The discs themselves then create entries in the black hole.

Then, Zhou and his team plan to explore precisely how these quasar dragons organize and differentiate the outer mass of accretion disks to feed incoming flows. According to Zhou, an elucidation of this process could lead to a better understanding of how quasars are formed, how long they last, when and how they end.

Provided by
University of Science and Technology of China