In the Norma cluster, the nearest rich galaxy cluster to us, astronomers have spotted a shock wave. It arose when one cluster plowed into another, like the bow wave of a ship cutting through water. This wave compressed and heated the gas between the galaxies.
Two galaxies sit right behind the wave front. For the first, ESO 137-001, gas is being stripped away in a stream, like leaves blown from a tree in a strong wind. The wave intensified this stripping, stretching out the brightest known gas tail behind the galaxy. For the second, ESO 137-007, there is a radio tail more than half a million light-years long. The wave twisted its jet and curled it into a ring, much like a smoke ring.
Such waves change the lives of galaxies: they blow away the gas needed for star formation and twist their tails. In Norma, the wave may have also disrupted the cluster's core, leaving only a remnant to the southeast.
The tail of galaxy ESO 137-001 stretches 70,000 light-years — that's like the distance from the Sun to the center of the Milky Way.