When the galaxy clusters collided, dark matter (blue) got ahead of regular matter (orange).
W. M. Keck Observatory/Adam Makarenko
Billions of years ago, when two massive clusters of galaxies collided, dark matter was ejected, leaving behind the gas and stars that make up the cluster remnants. Understanding this process could shed light on the nature of dark matter and its impact on the universe.
Observing the collision of galaxy clusters is difficult: to capture it accurately, we need to capture the collision at a precise angle relative to the Earth and at a precise time.
