Asked by: Dave Gurling, Billericay
A ‘shock wave’ is the disturbance of material that’s created when a wave moves through a medium at greater than the local speed of sound. Provided there is a ‘medium’ of sufficient density through which a shock wave can travel, there is no reason why shock waves can’t form in space.
However, because most environments in space are of extremely low density, traditional shock waves involving the collision of particles, such as those that give rise to a ‘sonic boom’, are rare. But there are other kinds of shock waves that can occur in low-density environments.
For example, the shock can be propagated by photons interacting with electrons, by a distribution of high energy particles or by magnetic effects. So, shock waves are actually quite common in space. Interplanetary shock waves can occur due to solar flares. ‘Bow shocks’ are formed by the interaction of the solar wind with planetary magnetospheres. Supernovae create powerful shocks, both within the star collapsing to form the explosion and also moving through the interstellar medium itself. Interstellar shocks can also occur simply by the collision or collapse of gas clouds. Black holes, high-density objects such as pulsars, as well as merging galaxies (and even just the motion of galaxies themselves) are also known to form shock waves of various forms.