Radio pulses from one of the stars showed that its orbital period was decreasing. In other words, the stars were spiraling toward each other, and by the exact amount predicted if the system were losing energy by radiating gravity waves. Most black holes tend to be in a consistent spinning motion as a result of the gravitational waves. The matter keeps within the event horizon until it has spun into the center where it is concentrated within the core adding to the mass. Such spinning black holes are known as Kerr black holes.
Time runs slower where gravity is stronger.
If we look at something next to a black hole, it appears to be in slow motion, and it is. The further into the hole you get, the slower time is running. However, if you are inside, you think that you are moving normally, and everyone outside is moving very fast. Some scientists think that if you enter a black hole the forces inside will transport you to another place in space and time. At the other end would be a white hole, which is theoretically a point in space that just expels matter and energy.