Physical law · Astrophysics
The Schwarzschild Radius
Cosmology & UniverseEstablished Science
Definition
The radius to which a mass must be compressed for its escape velocity to reach the speed of light — the size of a non-rotating black hole's event horizon.
Scientific overview
Derived by Karl Schwarzschild in 1916 from Einstein's equations, it is proportional to mass: about 3 km per solar mass. Compress any mass within its Schwarzschild radius and it becomes a black hole.
Rests on
Related topics
Knowledge connections
- Related toThe Event Horizon
- Depends onEscape Velocity
- Related toThe Event Horizon
- Related toBlack Hole
- Depends onGeneral Relativity
- Related toEscape Velocity
- Required byBlack Hole
- Required byStellar-Mass Black Hole
- Associated withThe Photon Sphere
- Associated withThe Innermost Stable Circular Orbit
Sources & references
The primary and reference sources this topic draws on.
- NASANational Aeronautics and Space Administration
Mission data, planetary science, space telescopes, and public-domain imagery.
Most NASA-produced imagery is in the public domain; individual items are checked for usage terms before publication.