How it works
This black hole diagram, labeled part by part, shows a black hole from outside and, in the framed close-up, its middle cut open. Read the eight names, tap a part for one line about it, then quiz yourself.
Read the full guide
The view from outside
The accretion disk is a hot, bright disk of gas spinning around the black hole. The arches over and under the round middle are the far side of that disk: its light is bent around the hole. The filled-in round middle is the shadow, and the jets shoot away in opposite directions.
The close-up
The event horizon is the boundary that nothing can cross back out of, not even light. The singularity is the point at the very center. Outside the event horizon lies the photon sphere, and the corona is a very hot cloud above the inner disk.
- The black hole shadow is not the event horizon: seen from far away, the dark zone looks larger than the hole itself.
Questions and answers
What are the parts of a black hole?
The event horizon is its boundary and the singularity is the point at its center. Around it, gas forms an accretion disk with a hot corona above it, and some black holes shoot out a pair of jets.
What is the event horizon of a black hole?
The event horizon is the boundary of a black hole. Inside it, the speed needed to escape is greater than the speed of light, so nothing that crosses it can come back out.
What is at the center of a black hole?
General relativity predicts a singularity: a point at the very center where matter is crushed to infinite density. Astronomers do not yet know whether it is a physical structure or only a mathematical one.
Why can we see a black hole if no light escapes it?
The black hole itself gives off no light. Astronomers see the matter around it: gas in the accretion disk becomes hot and bright before it falls past the event horizon.