A black hole grows by being fed from a so-called accretion disk that supplies it with fresh matter. This disk is made up of plasma, ionized gas that orbits in continuous spirals around the black hole at high speeds. This plasma is constantly heated by internal collisions.
To an observer, however, an accretion disk won’t look like a classic disk (like, for example, Saturn’s rings). This is because a black hole generates such an unbelievably large force of gravity that radiation from the rear part of the disk becomes distorted as it moves toward the observer. Now, researchers at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, have reenacted this in impressive, mesmerizing computer simulations.