The mysterious substance known as dark matter may not be as unobservable as we thought, scientists have discovered after observing it interacting with other dark matter in a cluster that is 1.4 billion light-years away from us.

It was believed that dark matter, which makes up approximately 85 percent of the matter in the universe, does not interact with anything, but findings published in a recent paper suggest that there are some strange physics at play that are simply outside our current ideas about how it works, according to a BBC News report.

The paper, which was published in the journal Monthly Notices of the Royal Astronomical Society, found that visible matter in galaxies appears to reside within clumps of dark matter, and without the dark matter’s gravity, galaxies like the Milky Way would rip apart as they spin.

Dark matter has been extremely difficult to observe because it only appears to interact with the force of gravity.

The astronomers, from Durham University, studied a collision of four galaxies in the cluster Abell 3827, which they were able to locate using gravitational lensing, which is when light is bent, warping the view of anything on the other side of the distorting object. The dark matter in Abell 3827 was bending light from a background galaxy.

The team noticed that there was one clump of dark matter that was sitting behind the galaxy it surrounds, which would suggest that it was interacting with itself through forces other than gravity, according to the report.

This interaction indicates a sort of exotic physics that go beyond the Standard Model that we understand. It means that dark matter can be observed, just with special conditions.

The Large Hadron Collider will be delving deeper into the dark matter mystery when it begins its second run this month in Europe. The huge machine, built underneath the French-Swiss border, will begin smashing protons together again to learn more about the dark matter particles that have so far remained elusive.