Before discussing gravitational radiation, let’s talk gravitational waves, as they play a huge role in gravitational radiation. Gravitational waves are created when there is a disturbance in space and time, which creates curvature that radiates outward from the center of accelerated masses. Mass is what causes these waves to curve outward from the source, and the more mass within a certain volume of space then there is more curvature seen in the waves seen at the boundary of space and time.
These curves change as the objects (white dwarfs, neutron stars, or black holes collisions) move around reflecting that the objects have moved. Sometimes, when objects accelerate, the curve will also move outward at the speed of light in a wave-like manner. These activities are referred to as gravitational waves.
Everything creates energy, regardless of what it is, and in this case, these waves create energy. When massive bodies move quickly, radiant energy is created, but because gravity is weak, it can only be detected when intense astrophysical events occur, i.e. black holes colliding and supernovae. The energy that is produced by these waves that occur when massive bodies collide is referred to as gravitational radiation.
Gravitational radiation are waves that cause disturbances in the curvature of time and space. They are generated, or caused, by accelerated masses, meaning things that take up space. They come in waves in an outward motion from the source and come at the speed of light. They can be described as an invisible ripple in space. That means they can't be seen but they are certainly there. There are ways to know they are there that scientists rely upon.
They are proven and they are real. They have been known about for many years, over one hundred years, in fact. But they are not known to just everyone. Still...they are there. They are very, very fast too and perplexing at the same time. It is speculated that they will eventually usher in a whole new type of astronomy. We shall see about that.