The Central Engine

If matter disappears forever when it falls through the event horizon of a black hole, how does a black hole power an AGN? As we have already seen, the answer is that as matter is swept into an accretion disk around the rotating hole, it is strongly accelerated and only part of it ends up falling through the event horizon.

The accelerated matter radiates strongly before it reaches the event horizon. Further, because of the rotation and magnetic fields, part of the matter is ejected in high-speed jets on the polar axes of the rotating black hole. These processes tap the rotational and gravitational energy of the black hole to provide the engine powering the AGN.