Black Holes
-
- Matter contracts to singularity.
- Gravity so strong, not even light can escape.
- Star appears to get dimmer and redder.
- Event Horizon
-
- surface where escape velocity = speed of light.
- Outside Event Horizon can escape, inside can not.
V(escape) = c = (2GM/R)1/2
R = 2GM/c2
Black Hole only effects surroundings by long range
forces - gravity and electric.
- Hence, can only determine mass, charge and rotation of a black hole.
-
- Black hole has no hair.
Photons escaping from vicinity of a black
hole lose energy, are redshifted.
- To distant observer, time appears to slow down near
Event Horizon
Gas falling into a black hole gets very hot and
emits x-rays,
- similar to neutron star.
- Can only distinguish black hole from neutron star by its mass.
- If mass > neutron star mass limit, must be a black hole.
Mini black holes can evaporate.
- Tidal forces pull apart particle-antiparticle pairs
created by quantum fluctuations outside event horizon.
- Pull one into black hole, other can escape.
