AST 101 Lecture Notes - Lecture 15: Molecular Cloud, Protostar, Star Formation
Document Summary
A black hole is an object whose gravity is so powerful that not even light can escape. Some massive star supernovae can make a black hole if enough mass (>3msol) falls onto the core. You can escape from the surface of an astrophysical object (planet, star) only if you can reach speed that kinetic kinetic energy is equal or exceed initial gravitation potential energy. Smaller the object = more velocity needed. The surface of a black hole is the radius at which the escape velocity equals the speed of light. This spherical surface is known as the event horizon. Schwarzschild radius the radius of the event horizon. Nothing can escape from within event horizon because nothing can go faster than the speed of light. Spectroscopic observations can reveal binary with an unseen companion (one set of lines that moves back and forth) If unseen companion is >3 msol, it must be a black hole.
