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Dark matter makes up most of the universe, it is 85 percent of the universe mass, but constitutes of dark matter are still unknown.
Scientists have made the discovery when they were viewing the simultaneous collisions of four distant galaxies at the center of the galaxy cluster which is 1.3 billion light years away from Earth.
Scientists at the Durham University, UK viewed the galaxies from the Hubble Space Telescope and the European Southern Observatory’s Very Large Telescope.
Scientist found that one dark matter clump is lagging behind the galaxy it surrounds. They said that the dark matter is lagging behind its galaxy by 5,000 light years, and it would take 90 million years to travel by the NASA’s voyager spacecraft.
The dark matter lags behind the galaxy, if it interacts very slightly with the forces other than gravity.
Computer simulations show that extra friction from collision will cause the dark matter to slow down or even lag behind.
It is believed that galaxies exist in the clumps of dark matter called dark, because it is thought to interact with gravity and making it invisible.
If there was no dark matter then the galaxies like the milky way would fling themselves apart as they spin, it is the gravity of the dark matter which is holding on to it.
Dark matter clumps can be seen by gravitational lensing, where the dark matter bends the light from the distant galaxies because of its gravitational force.
The new discovery rules out the standard theory of Cold Dark Matter which theorizes that the dark matter will only interact with gravity.
“We used to think that dark matter sits around, minding its own business, but if it slowed down during this collision, this could be the first dynamical evidence that dark matter notices the world around it. Dark matter may not be completely ‘dark’ after all,” said Dr Richard Massey, Royal Society Research Fellow, in Durham University’s Institute for Computational Cosmology, lead author of the study.
More investigation is needed to find the other effects which can bring the lag in the dark matter.
“Our observation suggests that dark matter might be able to interact with more forces than just gravity. The parallel Universe going on around us has just got interesting. The dark sector could contain rich physics and potentially complex behavior,” said, team professor Liliya Williams, of the University of Minnesota.