A 15 Year Study May Have Just Captured the First Glimpse of Dark Matter

It's one of the biggest mysteries in this universe.

Everything you see around you—your phone, your cat, the Earth, the stars—makes up just 15% of the mass in the universe. The remaining 85% is a ghost. We can’t see it, touch it, or sense it in any way. We only know it’s there because we can notice its gravity pulling on the things we can see. This ghost is, of course, dark matter.

We know it holds our galaxy together, yet for nearly a century, it has stayed hidden in the shadows. But now, a researcher from the University of Tokyo believes he has finally caught a glimpse.

In a potentially groundbreaking new study, Professor Tomonori Totani has identified a mysterious “excess” of gamma rays glowing in the halo of the Milky Way. This signal matches the theoretical fingerprints of dark matter annihilation. If this finding holds up against the barrage of skepticism currently heading its way, it would force us to rewrite the Standard Model of particle physics.

How to Hunt for Dark Matter

For years, astronomers obsessed over the Galactic Center. It makes sense: that’s where the density of stuff (stars, gas, and presumably dark matter) is highest. But it’s also a chaotic, noisy mess of pulsars and cosmic rays that screams over any subtle signals. Because that’s where the most stuff is, it’s also one of the hardest places to study.

Totani took a different approach. He turned his gaze outward, to the “halo.”

The dark matter halo is a vast, spherical cloud that envelops our galaxy, extending far beyond the visible disk of stars. While the signal there is weaker, the background noise is significantly quieter. But the dark matter halo is a hypothetical structure; models suggest it exists and that it may contain clumps of dark matter, but this is far from fully understood.

To look for dark matter, Totani analyzed data collected by the Fermi Large Area Telescope (LAT). He utilized a massive dataset spanning 15 years, from August 2008 to August 2023. To ensure he wasn’t just seeing the glow of our own galaxy’s main engine, he rigorously masked out the galactic disk, ignoring everything within 10 degrees of the galactic plane.

This process stripped away the known sources of light, like point sources and cosmic ray interactions. What was left afterwards was a “halo-like excess” that shouldn’t be there.

The 20 GeV Smoking Gun

The signal detected by Totani has very distinct characteristics. The signal peaks sharply at a photon energy of roughly 20 GeV (gigaelectronvolts). The flux vanishes below 2 GeV and disappears again above 200 GeV. It’s also remarkably symmetric.

“We detected gamma rays with a photon energy of 20 gigaelectronvolts (or 20 billion electronvolts, an extremely large amount of energy) extending in a halolike structure toward the center of the Milky Way galaxy. The gamma-ray emission component closely matches the shape expected from the dark matter halo,” said Totani.

The fact that it’s exactly at 20 GeV matters a lot, because it fits the predictions from the annihilation of WIMPs.

WIMPs, or Weakly Interacting Massive Particles, are the leading theoretical candidates for dark matter. The theory goes that when two WIMPs crash into each other, they annihilate, transforming their mass into pure energy in the form of gamma rays. We don’t know what dark matter is made from, but WIMPs, particles with a mass around 500 times higher than that of a proton, are a top candidate.

“If this is correct, to the extent of my knowledge, it would mark the first time humanity has ‘seen’ dark matter. And it turns out that dark matter is a new particle not included in the current standard model of particle physics. This signifies a major development in astronomy and physics,” said Totani.

The Healthy Skepticism

Extraordinary claims require extraordinary evidence. As far as space observation goes, this is about as extraordinary as it gets. So, let’s not pop the champagne corks just yet.

Science rarely fits together perfectly on the first try, and this finding creates a “tension” with other observations.

If dark matter glows with gamma rays in the Milky Way halo, it should also glow in the dwarf spheroidal galaxies that orbit us. But current observations of dwarf galaxies have set strict upper limits on how bright dark matter annihilation can be. The signal Totani found is stronger than those limits allow.

Totani argues that our estimates of the Milky Way’s density profile are fraught with uncertainty. We don’t actually know exactly how dense the dark matter is in the halo. If the Milky Way’s halo is slightly different from our simulations predict, or if the dark matter in dwarf galaxies behaves differently, the two results could still be compatible.

But it takes more than an explanation to convince scientists. No doubt, more observations will follow. Detecting the same emissions from dwarf galaxies, for example, would support Totani’s claim.

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“This may be achieved once more data is accumulated, and if so, it would provide even stronger evidence that the gamma rays originate from dark matter,” said Totani.

The jury is still out, but we may have just taken a massive step toward solving the biggest mystery in the universe.

Journal Reference: Tomonori Totani, “20 GeV halo-like excess of the Galactic diffuse emission and implications for dark matter annihilation,” Journal of Cosmology and Astroparticle Physics (IOPscience): November 26, 2025