Q&A: General Astronomy and Space Science

Q:
Which theory of gravitation is correct, Einstein's theory that gravity is a property of space and time, or Newton's theory of gravitation? Could Chandra help us in any way to resolve the above?

A:
The question has already been resolved in favor of Einstein by observing (during a solar eclipse) the bending of light from background stars as it passes near the Sun, and many other observations. However, Einstein's theory has never been verified for strong gravitational fields such as are found in the vicinity of black holes, which are themselves a prediction of Einstein's theory. Chandra may help here by observing the details of the X-ray emission produced by particles orbiting very near the event horizon of a black hole. In particular, X rays from iron ions radiate at a specific energy. As the iron ions orbit a black hole this energy signal is distorted by their motion, and by the warping of space and time. The distortion due to this warping is what astronomers hope to observe with Chandra.