Colliding Galaxy Clusters Further Hints Existence of Dark Matter

By observing massive colliding galaxy clusters, astronomers have been able derive how dark matter behaves during these vast encounters.

Researchers carried out a new survey by the NASA/ESA Hubble Space Telescope and NASA's Chandra X-ray Observatory, focusing on 72 galactic cluster collisions from all angles and at different times during their collisions.

With the help of new survey, researchers have been able to see how dark matter interact with itself over time.

Up until now, researchers were able to study only handful of cluster smashups that allowed just snapshot of the dark matter interaction.

"We know how gas and stars react to these cosmic crashes and where they emerge from the wreckage. Comparing how dark matter behaves can help us to narrow down what it actually is," said lead author David Harvey of the école Polytechnique Fédérale de Lausanne (EPFL) in Switzerland.

Dark matter's presence is known only by its interactions with normal matter through gravity. It does not, however, interact via the electromagnetic force, which is why we cannot directly see it - it does not emit, scatter or reflect light - it is more "invisible" than "dark."

This survey helped researchers realize just how invisible the stuff is, even to itself.

"A previous study had seen similar behavior in the Bullet Cluster," said co-investigator Richard Massey of Durham University in the UK. "But it's difficult to interpret what you're seeing if you have just one example. Each collision takes hundreds of millions of years, so in a human lifetime we only get to see one freeze-frame from a single camera angle. Now that we have studied so many more collisions, we can start to piece together the full movie and better understand what is going on."

The study will be published in the journal Science.