Using supercomputers, researchers recreated the galaxy’s history and mapped where dark matter should gather and collide. The results matched real gamma-ray observations, suggesting the mysterious light could be produced by dark matter particles colliding rather than by dying stars.

Clues in the Cosmic Mystery of Dark Matter
Scientists may have uncovered one of the most promising hints yet in the search to confirm the existence of dark matter.

At the heart of the Milky Way, a faint and widespread glow of gamma rays has puzzled astronomers for decades. The light could be the result of dark matter particles colliding, or it might come from fast-spinning neutron stars known as millisecond pulsars.

According to a new study published October 16 in Physical Review Letters, both explanations currently appear equally possible. If the gamma-ray glow is not produced by dying stars, it could mark the first real evidence that dark matter exists.

Scientists on the Hunt for Hidden Matter
“Dark matter dominates the universe and holds galaxies together. It’s extremely consequential and we’re desperately thinking all the time of ideas as to how we could detect it,” said co-author Joseph Silk, a professor of physics and astronomy at Johns Hopkins and a researcher at the Institute of Astrophysics, Sorbonne University, and CNRS. “Gamma rays, and specifically the excess light we’re observing at the center of our galaxy, could be our first clue.”

Silk and an international team of researchers, led by Moorits Muru with the Leibniz Institute for Astrophysics Potsdam (AIP), used supercomputers to create maps of where dark matter should be located in the Milky Way, taking into account for the first time the history of how the galaxy formed.

Galactic Collisions and a Cosmic Match
Today, the Milky Way is a relatively closed system, without materials coming in or going out of it. But this hasn’t always been the case. During the first billion years, many smaller galaxy-like systems made of dark matter and other materials entered and became the building blocks of the young Milky Way. As dark matter particles gravitated toward the center of the galaxy and clustered, the number of dark matter collisions increased.

When the researchers factored in more realistic collisions, their simulated maps matched actual gamma-ray maps taken by the Fermi Gamma-ray Space Telescope.

These matching maps round out a triad of evidence that suggests excess gamma rays in the center of the Milky Way could originate from dark matter. Gamma rays coming from dark matter particle collisions would produce the same signal and have the same properties as those observed in the real world, the researchers said—though it’s not definitive proof.