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This two-panel illustration shows a black hole surrounded by a disk of gas, before and after the disk is partially dispersed. In the left panel, the ball of white light above the black hole is the black hole corona, a collection of ultra-hot gas particles that forms as gas from the disk falls into the black hole. The streak of debris falling toward the disk is what remains of a star that was torn apart by the black hole's gravity. The right panel shows the black hole after the debris from the star has dispersed some of the gas in the disk, causing the corona to disappear.
Figure A is the left panel of the illustration. Figure B is the right panel.