A Sonic Boom (Half) as Old as Time Itself

A Sonic Boom (Half) as Old as Time Itself

By comparing different models of the shock, the authors derive a “mach number” M≈2.4, which says the clusters are colliding at 2.4 times the speed of sound. That’s quite a sonic boom, particularly given that the speed of sound in the hot plasma is around 2 million miles per hour!