1. If light cannot escape from a black hole, how can we detect X rays from such objects? 2. What is the Schwarzschild radius of a black hole, measured in kilometers, containing 3 M? 30 M? 3. If more...

1. If light cannot escape from a black hole, how can we detect X rays from such objects?

2. What is the Schwarzschild radius of a black hole, measured in kilometers, containing 3 M? 30 M?

3. If more massive stars evolve and die before less massive ones, why do some black-hole candidates have lower masses than their stellar companions?