Expert: Steve Nelson - 11/20/2010

Question
My question is concerning the nature of a Gamma Ray Burst and the speed at which it moves relative to the speed of visible light a supernova produces.

I know that gamma-rays are essentially high frequency light waves, but I would imagine their speed can be affected somewhat by gravitational forces or perhaps gas and dust clouds, however, is it known if there is a significant difference between the speed of gamma-rays from a GRB and the extremely bright, visible light that is also produced by a supernova?

Another take on this question, if a star, relatively close to our solar system, collapsed and went supernova and produced a GRB that was aimed at our system, would we have any advanced warning of the event? Would the light from the supernova reach us a significant amount of time before the gamma-rays do or are they moving at essentially the same speed?

Thank you for your time in answering my question.

Answer
No, actually, the difference in the speed of light based on frequency has strict limits placed on it by the Fermi space telescope, which my division built part of at the Naval Research Lab.  Two years ago we couldn't have definitively answered that question, but now we can.  There would be no advance warning, we would just receive the light signals and the gamma rays at the same time.