What is a supernova shock wave?
Raoul, in the explanation it states that the shock wave from a nearby supernova causes it to glow. What does a supernova shock wave consist of? On earth when an explosion occurs the shock wave consists of compressed waves of air, i.e. sound. In space, without air, what carries the shock wave? Is it that space is never a complete vacuum, and what little gas that does exist is what carries the shock wave? Is it the gamma rays, X-rays, etc. that creates the shock wave? Are gravity waves involved?