Black-hole physics · 1.5 Schwarzschild radii
The Photon Sphere
The radius around a non-rotating black hole — one and a half Schwarzschild radii — at which gravity bends light so strongly that photons can orbit in unstable circles. It sets the size of the black hole's 'shadow' and the bright ring seen in the Event Horizon Telescope images of M87* and Sgr A*.
Highlights
- ›Where light orbits — defining the black-hole shadow
Classes, physics & objects
Knowledge connections
- Associated withBlack Hole
- Associated withThe Event Horizon
- Associated withThe Schwarzschild Radius
- Associated withEvent Horizon Telescope (EHT)
- Associated withM87*
Sources
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.