If we could watch a star collapse into a black hole, it might look like the
It emits will be shifted progressively more and more to the red as they lose energyĮscaping from the huge gravitational field. It predicts that time viewed from the outside will slow toĪ standstill as we watch something collapse into the event horizon, and that the photons The influence of gravity on light is included in this theory. Of how objects move it would also slightly modify our calculation of Theory of gravity, Einstein's General Theory of Relativity is needed to make calculations Only a few tens of km, even smaller than a neutron star. So black hole with a stellar type mass will have a "radius" of This R is called the Schwarzschild radius it defines the position ofįor an object with M = 6 M, R = 18 kilometers! M = the mass of the central object R = distance of orbiting objectĪt what R does the escape velocity = c, the speed of light? We can estimate the size of the event horizon from the escape velocity That happens inside the event horizon can be detected from outside, since no light (orĪnything else) can get out to show that something took place!! Star gets still closer, no light gets out - it is then inside the event horizon. It does - just a little that happens to be emitted directly outward can get away. Light captured goes up further as the star approaches closer, until in (d), nearly all of In (c), the star is muchĬloser and this bending is so strong that fully half the light is captured. In (b), the star is close enough that theĪmount of light captured is increased because of the strong gravitational field of theīlack hole that bends the paths of the photons inward toward it. In (a), only a small portion of the light is directedĬlose enough to the black hole to be captured. This picture shows the light trajectories as a star getsĬloser and closer to the black hole. Object whose escape velocity near its "surface" approaches the speed of light.Īnything inside this distance.