Lesson Three : Black Holes
Quasars and radio galaxies are two examples of active galaxies, which includes any galaxy that emits extremely large amounts of electromagnetic radiation from its center. Active galaxies have a large energy output from a small source at their centers.Astronomers hypothesize that the center of these galaxies contains a supermassive black hole. These black holes are much more massive than regular black holes and are millions of times more massive than our Sun. The gravity near a black hole is so strong that nothing can escape its pull, including light and other forms of electromagnetic radiation. Black holes will often collect matter from nearby objects forming a swirling whirlpool of matter known as an accretion disk. As matter falls into a supermassive black hole, it will emit the tremendous amount of radiation in the form of radio jets.
Many astronomers believe that these supermassive black holes exist within the centers of normal galaxies like our own and provide enough gravity to hold the galaxy together.
Accretion disk around a black hole
NASA - GSFC
NASA - GSFC