| Turbulence responsible for black holes' balancing act |
 |
 |
 |
Tweet me!
| Written by Chris O'Neal | ||||
| Tuesday, 14 July 2009 17:27 | ||||
Page 1 of 2 New simulations reveal that turbulence created by jets of material ejected from the disks of the Universe’s largest black holes is responsible for halting star formation. Evan Scannapieco, an assistant professor in the School of Earth and Space Exploration in the College of Liberal Arts and Sciences at Arizona State University (ASU) and Professor Marcus Brueggen of Jacobs University in Bremen, Germany, present the new model in a paper in the journal Monthly Notices of the Royal Astronomical Society. We live in a hierarchical Universe where small structures join into larger ones. Earth is a planet in our Solar System, the Solar System resides in the Milky Way Galaxy, and galaxies combine into groups and clusters. Clusters are the largest structures in the Universe, but sadly our knowledge of them is not proportional to their size. Researchers have long known that the gas in the centres of some galaxy clusters is rapidly cooling and condensing, but were puzzled why this condensed gas did not form into stars. Until recently, no model existed that successfully explained how this was possible.  Professor Scannapieco has spent much of his career studying the evolution of galaxies and clusters. “There are two types of clusters: cool-core clusters and non-cool core clusters,” he explains. “Non-cool core clusters haven’t been around long enough to cool, whereas cool-core clusters are rapidly cooling, although by our standards they are still very hot.” X-ray telescopes have revolutionized our understanding of the activity occurring within cool-core clusters. Although these clusters can contain hundreds or even thousands of galaxies, they are mostly made up of a diffuse, but very hot gas known as the intracluster medium. This intergalactic gas is only visible to X-ray telescopes, which are able to map out its temperature and structure. These observations show that the diffuse gas is rapidly cooling into the centres of cool-core clusters. At the core of each of these clusters is a black hole, billions of times more massive than the Sun. Some of the cooling medium makes its way down to a dense disk surrounding this black hole, some of it goes into the black hole itself, and some of it is shot outward. X-ray images clearly show jet-like bursts of ejected material, which occur in regular cycles. But why were these outbursts so regular, and why did the cooling gas never drop to colder temperatures that lead to the formation of stars? Some unknown mechanism was creating an impressive balancing act. “It looked like the jets coming from black holes were somehow responsible for stopping the cooling,” says Scannapieco, “but until now no one was able to determine how exactly.” Scannapieco and Brueggen used the enormous supercomputers at ASU to develop their own three-dimensional simulation of the galaxy cluster surrounding one of the Universe’s biggest black holes. By adapting an approach developed by Guy Dimonte at Los Alamos National Laboratory and Robert Tipton at Lawrence Livermore National Laboratory, Scannapieco and Brueggen added the component of turbulence to the simulations, which was never accounted for in the past. And that was the key ingredient. |
||||
| Last Updated on Monday, 30 November 2009 16:46 |
