© NASA, ESA, A.M. Koekemoer (STScI), M. Dickinson (NOAO), and the GOODS team.
As gas in the region surrounding a black hole is pulled inside the black hole's event horizon, it accelerates and heats up. The hot gas emits x-rays that can be observed with telescopes. The image above is a Chandra X-Ray Observatory observation of a supermassive black hole in a young galaxy billions of light-years from Earth. The x-ray image is superimposed on an optical image from the Hubble Space Telescope that shows nearby galaxies. The galaxy containing the black hole is obscured by dust. (Unit: 3)