As more mass is accumulated, equilibrium against gravitational collapse exceeds its breaking point. Once the star's pressure is insufficient to counterbalance gravity, a catastrophic gravitational collapse occurs within milliseconds. The escape velocity at the surface, already at least 1 ⁄ 3 light speed, quickly reaches the velocity of light. At that point no energy or matter can escape and a black hole has formed. Because all light and matter is trapped within an event horizon, a black hole appears truly black, except for the possibility of very faint Hawking radiation. It is presumed that the collapse will continue inside the event horizon.