A closer look at the center of a spiral galaxy reveals a pair of black holes locked in a death spiral. When they merge, a massive amount of energy is released in the form of jets.
A black hole is a massive object whose gravitational field is so intense that no light (electromagnetic radiation) can escape it. When two orbiting black holes merge, a massive amount of energy is released in the form of jets. Meanwhile, the movement of these massive bodies disturbs the fabric of space-time around them, sending ripples of gravitational waves radiating outward. These waves are predicted by Einstein's theory of general relativity, but have yet to be directly detected.