Astronomy & space · Advanced university
Black holes, horizons and observable environments · revision notes
For a nonrotating uncharged black hole, the horizon radius is rs=2GM/c². Rotation and charge require a different spacetime description.
Key ideas and conditions
Schwarzschild model
For a nonrotating uncharged black hole, the horizon radius is rs=2GM/c². Rotation and charge require a different spacetime description.
Horizon
The horizon is a causal boundary, not the bright accretion disk or a solid shell. Signals from inside do not reach distant outside observers.
Evidence
Motion of nearby matter, accretion emission, gravitational waves and horizon-scale imaging constrain models through different observations.
Limits
A simple horizon-radius calculation does not describe the complete interior, accretion flow, jet or quantum-gravity problem.
Explain without looking
- Using rs≈3 km per solar mass as a stated rough scale, estimate rs for 10 solar masses.
- Name two independent observational approaches to studying black-hole systems.
Further reading and review references
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