Behold! Stunning images of a cosmic shock wave 60 times larger than the Milky Way

A relic from a billion-year-old collision.

Galaxies are often spread apart from each other by millions of light years.

But sometimes gravity draws together clusters of hundreds to thousands of galaxies in a close formation.

Valerio Pardi / 500px/500Px Plus/Getty Images

And when entire galaxy clusters get too close to each other, gravity can wind them in tighter until they’re unable to escape.

This results in extremely powerful collisions whose aftermath we can still observe today.