The researchers studied X-ray polarimetry data from black hole jets obtained by the IXPE satellite.
Scientists have used IXPE to monitorBlazar Markarian 501 in the constellation Hercules. This active black hole system is at the center of a large elliptical galaxy. The satellite observed the object twice for three days with a break of two weeks in March 2022. In parallel with this observation, astrophysicists used ground-based telescopes to collect data in other electromagnetic wave bands: optical, infrared, and radio.
Artistic illustration of the study. The IXPE satellite collects X-ray polarization data. Image: NASA, Pablo Garcia
The combined data allowedto answer a question that has remained unresolved for 40 years: how particles in black hole jets accelerate to such high energies. Scientists have found that X-ray light is more polarized than optical light, which in turn is more polarized than radio. But the direction of the polarized light was the same for all observed wavelengths of light, and also coincided with the direction of the jet.
After comparing their information with theoreticalUsing models, the researchers found that the data most closely matched the scenario in which the shock wave accelerated the particles of the jet. A shock wave occurs when something moves faster than the speed of sound of the surrounding material, such as when a supersonic plane flies through our Earth's atmosphere, the authors explain.
The study was not designed to studythe origin of shock waves, which still remain a mystery. But scientists suggest that the perturbation of the flow of the jet leads to the fact that part of it becomes supersonic. This may be the result of high-energy particles colliding within the jet, or sudden changes in pressure at the jet boundary. The authors of the paper believe that new studies will help to establish the exact nature of the shock waves.
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On the cover: an artistic illustration of a blazar. Image: NASA