An international team of astronomers among whom Sera Markoff and Chiara Ceccobello of the UvA, has determined the distance traveled by particles before they are launched as a visible stream of plasma by a black hole. The results are published in Nature Astronomy.
Black holes do not just eat everything that comes in their way. A small fraction of the material is ejected back into the universe as powerful hot plasma jets. These jets are launched from near the black hole via magnetic fields, which collimate and accelerate the particles up to energies millions of times higher than is possible at CERN. The scientists have now determined how far the particles have traveled before they are accelerated fast enough to become a visible stream of plasma.
This was possible by studying two so-called X-ray binary systems in our Milky Way, systems comprised of a black hole orbited by a normal star. They used the NASA NuSTAR space telescope for the X-ray measurements and the fast-readout ULTRACAM on the Dutch-English-Spanish owned William Herschell telescope on La Palma.
The researchers noticed that the visible light was emitted a tenth of a second later than the X-ray emission. This suggests that the ejecting black hole’s ‘runway’ is only about 30.000 kilometers long.
Prof. Sera Markoff, co-author of the publication in Nature Astronomy, is excited about the results: 'I model black holes with the computer and these observations are in line with my earlier predictions.'
The publication was made possible by years of preparation, collaboration and coordination. The researchers had to aim the instruments simultaneously at the same X-ray binary stars during an outburst.
Markoff: ' We need these types of precision observations to produce accurate models. Having this information about the lag, or “runway" will help us better explain the connection between the plasma in the jets and the process accelerating the particles.'