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Galaxy cluster collisions offer clues about dark matter

Scientists have claimed that the dark matter may not be part of a "dark sector" of particles as suggested by physicists in the past. The new claim has been made by the scientists studying collisions of galaxy clusters.

The scientists said that after the collision of the clusters of galaxies, the hot gas that fills the space between the stars in those galaxies also collides and splatters in all directions with a motion akin to splashes of water. Around 90 percent of the matter in galaxy clusters is made of dark matter but the question is does it splatter like water as well?

But the new study has found that dark matter does not splatter when clusters of galaxies collide, and this finding limits the kinds of particles that can make up dark matter. Specifically, the authors of the new research say it is unlikely that dark matter is part of an entire "dark sector."

Our Milky Way galaxy is made up of hundreds of billions of stars, and there are hundreds of billions of galaxies in the observable universe. The space between the stars and the galaxies is filled with a lot of gas and dust. But all of those stars, galaxies, gas and dust make up only about 10 to 15 percent of the matter in the universe.

"Galaxy cluster mergers are incredibly messy. You've got the stars, the highest densities of dark matter and hot gas all swirling together," David Harvey, a postdoctoral researcher at the Swiss Federal Institute of Technology Lausanne, said.