A blazar is one of the brightest objects in the sky. Basically, they are supermassive black holes fed by material swirling around them in disks, which produce two powerful jets each perpendicular to the disk.
Scientists estimate there are 40 billion billions black holes in the known universe. Of course, the exact number is hard to come by. What we know about them is mostly theory. This is because black holes are some of the most elusive and mysterious cosmic objects. Shrouded in mystery, scientists only recently managed to photograph a black hole, and they did so by snapping an image of its accretion disk. Black holes are very difficult to spot since they have such a powerful gravitational pull that nothing, not even light, can escape.
Blazing in the sky
Black holes do, however, love to show off even though they emit no visible light. It is believed that blazars are some of the brightest objects in the sky. These enigmatic objects consist of a supermassive black hole grazing on the material swirling around it in a disk. A powerful jet can be generated perpendicular to the disk on each side as a result. Blazars can get pretty bright. And the reason behind this is that the jets emitted by black holes are sometimes pointed directly at us. Together, jets, black holes, and the material that feeds these cosmic monsters have been at the center of scientific debate for years.
The question has intrigued scientists for decades: how are particles in these jets accelerated to such high energies? To find out, NASA launched a mission called the Imaging X-Ray Polarimetry Explorer, or IXPE, which has gathered some crucial insight. Using data gathered by IXPE, scientists may have finally found answers for how these jets are accelerated.
Markarian 501
IXPE was used to identify the blazar Markarian 501 within the constellation Hercules. There is an active black hole system inside a very large elliptical galaxy at its center. A three-day observation of Markarian 501 by IXPE was conducted in early March of 2022 and then another two weeks later. Astronomers used radio, optical, and X-ray telescopes to observe the blazar and gather information about it. Scientists have previously looked at the polarization of lower-energy light from blazars. Still, this study gives them a better understanding of the X-rays produced closer to the acceleration source.
Shock Waves
In the end, the observations paid off. In contrast to radio and optical light, X-ray light has a higher degree of polarization than optical. The polarized light, however, was aligned with the jet’s direction no matter what wavelength of light was observed. Based on a comparison between their data and theoretical models, the team of astronomers concluded that the data best described a scenario in which shock waves accelerate the jet particles. Essentially, shock waves are produced when an object moves fast than the speed of sound of its surrounding material. This can be best explained by a fighter jet flying in Earth’s atmosphere. As it reaches speeds that surpass the speed of sound, it creates a shock wave.
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