A Strange Glow in the Milky Way May Be Our First Glimpse of Dark Matter

A puzzling glow of gamma rays at the Milky Way’s center may finally be pointing scientists toward dark matter, the invisible substance thought to make up most of the universe.

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.

Pulsars vs. Particles: The Cosmic Coin Flip

Light emitted from reinvigorated, old neutron stars that spin quickly—called millisecond pulsars—could also explain the existing gamma ray map, measurements, and signal signature. But this millisecond pulsar theory is imperfect, the researchers said. To make those calculations work, researchers have to assume there are more millisecond pulsars in existence than what they’ve observed.

Answers may come with the construction of a huge new gamma-ray telescope called the Cherenkov Telescope Array. Researchers believe data from the higher-resolution telescope, which has the capacity to measure high-energy signals, will help astrophysicists break the paradox.

A “Smoking Gun” in the Making

The research team is planning a new experiment to test whether these gamma rays from the Milky Way have higher energies, meaning they are millisecond pulsars, or are the lower-energy product of dark matter collisions.

“A clean signal would be a smoking gun, in my opinion,” Silk said.

In the meantime, the researchers will work on predictions about where they should find dark matter in several select dwarf galaxies that circle the Milky Way. Once they’ve mapped their predictions, they can compare them to the hi-res data.

“It’s possible we will see the new data and confirm one theory over the other,” Silk said. “Or maybe we’ll find nothing, in which case it’ll be an even greater mystery to resolve.”

Reference: “Fermi-LAT Galactic Center Excess Morphology of Dark Matter in Simulations of the Milky Way Galaxy” by Moorits Mihkel Muru, Joseph Silk, Noam I. Libeskind, Stefan Gottlöber and Yehuda Hoffman, 16 October 2025, Physical Review Letters.
DOI: 10.1103/g9qz-h8wd

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