The two galaxy clusters, known collectivity as MACS J0018.5+1626, each contain thousands of galaxies and are located billions of light-years away from Earth. As they plowed through each other, the dark matter sped ahead of the normal matter. This artist’s concept shows what happened when two massive clusters of galaxies, collectively known as MACS J0018.5+1626, collided: the dark matter in the galaxy clusters (blue) sailed ahead of the associated...
