01
Event Horizon
The event horizon is a causal boundary. For an isolated nonrotating black hole, the Schwarzschild radius is:
r_s = 2GM/c²
Once inside the event horizon, no future-directed signal can reach distant external observers.
02
Accretion
Matter spiraling toward a black hole can form a hot accretion flow. Friction, magnetic fields, and relativistic processes can transform gravitational energy into intense radiation.
03
Black-Hole Mergers
When compact objects such as black holes merge, the accelerating quadrupolar mass distribution generates gravitational waves that propagate through spacetime.