NORTH-EAST astronomers have shed a little more light on dark matter, the mysterious substance which makes up most of the universe.

Research involving scientists from Durham University has shown that dark matter interacts with itself even less than previously thought, narrowing down the options for what this mysterious substance might be.

Astronomers made the finding using observations from the NASA/ESA Hubble Space Telescope and NASA’s Chandra X-ray Observatory to study how dark matter in clusters of galaxies behaves when the clusters collide.

The results are published in the journal Science.

To learn more about dark matter researchers can study it in a way similar to experiments on visible matter — by watching what happens when it bumps into things.

For this reason, researchers look at vast collections of galaxies, called galaxy clusters, where collisions involving dark matter happen naturally and where it exists in vast enough quantities to see the effects of collisions.

The researchers used data from the NASA/ESA Hubble Space Telescope and NASA's Chandra X-ray Observatory to study 72 large cluster collisions. The collisions happened at different times, and are seen from different angles — some from the side, and others head-on.

The team found that, like the stars, the dark matter continued straight through the violent collisions without slowing down.

The leading theory is that dark matter is spread evenly throughout the galaxy clusters so dark matter particles frequently get very close to each other.

The reason the dark matter doesn't slow down is because not only does it not interact with visible particles, it also interacts even less with other dark matter than previously thought.

Team member Dr Richard Massey, in Durham’s Institute for Computational Cosmology, said: "A previous study had seen similar behaviour in the Bullet Cluster.

"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."

By finding that dark matter interacts with itself even less than previously thought, the team have successfully narrowed down the properties of dark matter. Particle physics theorists have to keep looking, but they now have a smaller set of unknowns to work with.