A black hole is a massive object whose gravitational field is so intense that nothing - not even light (electromagnetic radiation) — can escape from within its so-called event horizon. Accretion disks of hot material encircle many black holes, and this material emits X-rays and other forms of energy. Gas closer to the black hole is hotter and emits more energetic radiation. Gas at the innermost stable orbit tells astronomers whether the black hole is spinning because a rotating black hole can host material in stable orbits much closer to its event horizon. Oppositely directed jets of gas often form in the innermost zone of black hole accretion disks.
This animation depicts three hot blobs of matter orbiting a black hole. If placed in our Solar System, this black hole would appear like a dark abyss spread out nearly as wide as Mercury's orbit. And the three blobs (each as large as the Sun) would be as far out as Jupiter. They orbit the black hole in a lightning-quick 20,000 miles per second, over a tenth of the speed of light.