An international research team led by Silke Britzen from the MPIfR in Bonn/DE has investigated blazars, accreting supermassive black holes in the centers of galaxies. The researchers present evidence that it is in fact the precession of the jet source, either caused by the presence of a second massive black hole close to the primary one or a warped accretion disk around a single black hole, that is responsible for the observed variability in blazars. Their findings are presented in the Astrophysical Journal.
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Image: © Michal Zajaček/UTFA MUNI; Illustration showing a magnetized radio jet (yellow), precessing due to a supermassive binary black hole at the center of the galaxy. The larger supermassive black hole is shown in black at the center within the accretion disk, that contains both warmer (blue) and cooler (red) gas. The white arrow indicates the spin of the larger black hole. The second black hole is orbiting (orange) around the central supermassive black hole and the orange arrow shows the orientation of its orbital angular momentum. Due to the misalignment, the torque from the secondary drives the precession of the accretion disk as well as the launched jet (green circle and arrows). Radio emission is indicated with white curved lines. A radio telescope indicates the direction towards the observer on Earth. The two images visualize how the jet swirls around and produces the variations in radio emission. The jet in the image on the right is turning towards the observer and thus appears brighter in the sky – hence stronger radio emission is seen.