Black holes are often seen as ravenous monsters that consume anything and everything and cannot be satiated in any way. New evidence, however, suggests they might actually be pushing away most of the material that gets close enough to them. This discovery provides new understanding of the complex environment that surrounds black holes.
As reported in Nature, astronomers were able to trace the presence of strong winds throughout the outburst events that are produced by black holes slowly stealing material from a companion. The strong winds are actually stopping the black holes from eating too much, pushing away a significant amount of the gas that surrounds the object.
“Winds must blow away a large fraction of the matter a black hole could eat,’’ lead author Bailey Tetarenko, a University of Alberta PhD student, said in a statement. “In one of our models, the winds removed 80 percent of the black hole’s potential meal.”
The presence of these winds has been known for a long time but this is the first time that they have been witnessed as a constant of the feeding black hole, rather than an occasional event. To study the black holes, researchers used 20 years of archival data from instruments developed and used by NASA, the European Space Agency, and JAXA, their Japanese counterpart.
The team analyzed a representative sample of 21 individual outbursts produced by 12 black hole low-mass X-ray binary systems. They used Bayesian statistics to produced reasonable models for the black hole environments and they all suggest either high speeds in the disk material or strong outflows. Both these scenarios are a product of strong magnetic fields, although the outflows are more consistent with the observations.
Outflows can also be explained by the pair of objects heating up the gas in the disk surrounding the black hole, but the team is not convinced that is the case. Thermal outflows require very specific conditions and it is unclear if these systems can sustain these conditions.
“We think magnetic fields play a key role. But we’ll need to do a great deal of future investigation to understand these winds,” added Craig Heinke, associate professor of physics at the University of Alberta and co-author.