But instead of destruction, the cosmic crash is causing the birth of thousands of millions of new stars.
The merger of the Antennae galaxies, in the constellation of Corvus the crow, was photographed by Hubble’s Advanced Camera for Surveys, high above the Earth.
It sent back the best ever colour picture of the galaxies, given their name because of long filaments that stretch from them like the antennae of an insect.
Astronomers say the two spiral galaxies began to merge around 500 million years ago. It is the closest and youngest such collision seen in the sky. Hubble reveals that their coming together has produced countless clusters of new stars, shining bright blue within a pink cloud of hydrogen gas.
The European Space Agency, which jointly runs Hubble with Nasa, says our own Milky Way will collide with the neighbouring Andromeda galaxy in around six billion years.