A Black Hole-Powered Spiral Galaxy
NGC 7742
The term "black hole" is a region of space from which nothing can return.
A black hole is a concentration of mass great enough that the force of gravity prevents anything past its event horizon from escaping it. The gravitational field is so strong that the escape velocity past its event horizon exceeds the speed of light. This implies that nothing, not even light, inside the event horizon can escape its gravity. It is, however, theorized that wormholes can let one exit a black hole. Objects in a gravitational field experience a slowing down of time, called time dilation.