This labeled diagram separates features that are often blended together: the event horizon is a boundary, the black-hole shadow is an apparent dark region, and the glowing accretion disk is matter outside the hole. The singularity is a prediction of classical general relativity, not something astronomers can directly observe.
The exact radii below apply to a non-rotating Schwarzschild black hole where stated. Real astrophysical black holes can spin, which changes the geometry.
| Feature | What it is | What an observer sees | Important distinction |
|---|---|---|---|
| Singularity | A breakdown point predicted by classical general relativity inside the hole. | Not directly observable. | Its true quantum-scale structure is unknown. |
| Event horizon | The causal boundary beyond which signals cannot return to the outside universe. | Not a glowing or solid surface. | For a Schwarzschild black hole, radius rs = 2GM/c². |
| Black-hole shadow | An apparent dark region produced by captured and strongly lensed light paths. | The central brightness depression seen in horizon-scale images. | The shadow appears larger than the event horizon itself. |
| Photon sphere / photon rings | The photon sphere is a region of unstable circular light orbits; photon rings are thin image features made by highly lensed light. | Nested, increasingly thin ring features in idealized images. | For a Schwarzschild hole, the photon-sphere radius is 1.5 rs; the observed ring is not the event horizon. |
| Accretion disk | Hot orbiting matter outside the black hole. | Bright radio, optical, UV, and X-ray emission depending on the system. | Not every black hole has a bright disk; the disk's inner edge depends on spin and flow physics. |
There is no single official four-part list. Introductory diagrams commonly label the event horizon, black-hole shadow, accretion disk, and singularity. More detailed diagrams may add the photon sphere or photon rings, a corona, and jets.
No. At the same distance, an object feels the same gravitational pull from a black hole as it would from any other object with the same mass. The extreme one-way behavior appears at the event horizon.
The EHT reconstructed radio emission around M87* and Sagittarius A*. The images show a bright ring surrounding a central black-hole shadow consistent with general relativity; they are not direct photographs of a solid event horizon or the singularity.
Real images (like the Event Horizon Telescope's) are blurry, radio-wavelength composites — this diagram exaggerates and labels features for clarity, the same "illustration, not photograph" distinction covered elsewhere on this site.
A black hole with nothing nearby to pull in has no accretion disk and emits no light at all — it's detected only through its gravity's effect on nearby stars.
See which stars can end their lives as stellar-mass black holes.
Separate observations, processed data, simulations, and artist concepts before interpreting a black-hole image.
Place stellar and supermassive black holes in the larger cosmic scale.