Astronomers don't know exactly how high-energy X-rays are produced near a black hole. Here's what the think: Material from a large torus of gas and dust is pulled toward a black hole. Most of the infalling gas is concentrated in a rapidly rotating disk, and a hot atmosphere or corona where temperatures can climb to billions of degrees. Collisions of low-energy optical, ultraviolet and X-ray photons from the disk with the hot electrons in the corona boost the energy of the photons up to the high-energy X-ray range. Credit: NASA/CXC/D.Schwartz & S.Virani; Illustration: CXC/M.Weiss
