For nearly a century, dark matter has remained an unanswered question at the heart of astrophysics. This invisible material, first proposed in the 1930s to explain why galaxies spin faster than their apparent mass allows, appears only through gravitational pull, not light. Now, new observations from NASA's Fermi Gamma-ray Space Telescope have revealed a halo-shaped burst of gamma rays at the Milky Way's core – a signal that matches the long-predicted behavior of dark matter particles.
In a new study published in the journal Journal of Cosmology and Astroparticle PhysicsUniversity of Tokyo astronomer Tomonori Totani said this signature of gamma rays matches what theorists have predicted for nearly a century. If confirmed, the discovery could provide the first direct view of dark matter – a breakthrough that will change both cosmology and particle physics.
“If this is correct, then to my knowledge, this will mark the first time that 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 marks an important achievement in astronomy and physics,” Tomonori Totani said in his report. press release.
Difficulty in detecting dark matter
Despite its dominant influence on the cosmos, dark matter remains invisible to all the instruments astronomers point at the sky. The particles that make it up are not thought to emit or reflect light, and they do not interact with electromagnetic forces the way normal matter does. Instead, scientists detect it by the extra gravitational glue that keeps galaxies intact.
One long-standing theory suggests that dark matter may be made of weakly interacting massive particles, or WIMPs. These hypothetical particles rarely interact with ordinary matter, but when two of them collide, they annihilate each other and emit gamma-ray photons with very specific energies. For years, astronomers have focused their attention on the regions with the highest density of dark matter, especially center of the Milky Way.
Read more: Space tornadoes swirl around the core of the Milky Way
Why does this gamma-ray glow look like dark matter?
When Totani analyzed the latest data from NASA's Fermi Telescope, one feature immediately stood out near the center of the Milky Way.
Gamma ray intensity map covering approximately 100 degrees towards the galactic center.
(Image credit: Tomonori Totani, University of Tokyo)
“We detected gamma rays with photon energies of 20 gigaelectronvolts (or 20 billion electronvolts, an extremely high amount of energy) propagating in a halo-like structure towards the center of the Milky Way galaxy. The gamma ray component closely matches the shape expected from a dark matter halo,” Totani said in a press release.
The gamma ray intensity pattern – the energy spectrum – also matches predictions of what happens when two hypothetical WIMPs annihilate each other, a process that would be expected to release gamma rays at these energies. The estimated mass of the particles, about 500 times heavier than a proton, is within standard theoretical expectations, and the estimated annihilation rate is consistent with long-standing models.
The nature of the emission is also difficult to explain using more familiar astrophysical sources. According to Totani, the usual phenomena that produce gamma radiation do not match the shape or intensity of the signal, making it a strong candidate for the long-predicted signature dark matter.
Confirmation of results
Totani's results are promising, but they need independent verification. The researchers also hope to see the same 20 GeV gamma-ray signature in other dark matter-rich regions, such as the dwarf galaxies of the Milky Way. Finding the same signal there would provide much stronger evidence that Fermi had captured the long-predicted glow from dark matter.
Read more: How many suns are there in the Milky Way? It's Complicated
Article sources
Our authors in discovermagazine.com use peer-reviewed research and high-quality sources for our articles, and our editors review scientific accuracy and editorial standards. Review the sources used below for this article:
- This article refers to information from a new study published in the journal Journal of Cosmology and Astroparticle Physics: Halo-like excess of 20 GeV Galaxy diffuse radiation and implications for dark matter annihilation
