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One of the biggest misconceptions about black holes is that they indiscriminately suck up everything around them. A black hole is incredibly small, and so gas on a collision course with a black hole would need to have incredibly precise aim in order to directly hit the black hole. Instead gas starts orbiting around the black hole, eventually creating what we call an ‘accretion disc’. As gas funnels closer and closer to the black hole, the gravitational potential energy that the gas had is released. This then dissipates in the form of heat, radiation, massive outflows and sometimes jets of particles moving at close to the speed of light. One question we want to answer is: where does all of the X-ray emission come from around a black hole?
High-energy X-rays are ubiquitous in accreting black holes, and yet we don’t understand the mechanism that produces them. The idea is that some extremely hot region surrounds the black hole, referred to as the ‘corona’, causing some photons to get boosted to X-ray energies. How the corona is formed, and how it remains hot for so long, is still a mystery – although we recently witnessed, in real time, the destruction and reformation of a black hole corona.
Astronomers also have evidence to believe the power output from supermassive black holes can affect how their host galaxy evolves. Not only are black holes these exotic, mysterious objects where the laws of physics break down, they are also incredibly important for understanding why our universe looks the way it does.