BY:SpaceEyeNews.
The Milky Way gamma-ray glow could hold a clue to dark matter, but its origin remains uncertain. Research suggests that dark matter can form a flattened, uneven distribution near the galaxy’s center. That shape could help explain the mysterious radiation that NASA’s Fermi telescope observes.
The finding changes an important part of the debate. Scientists may have expected the wrong shape from a potential dark matter signal. However, rapidly spinning neutron stars still offer a competing explanation.
Published in Physical Review Letters on October 16, 2025, the study investigates an existing mystery through galaxy simulations.
Why the Milky Way gamma-ray glow puzzles scientists
Fermi observations reveal excess gamma rays near the Galactic Center. Researchers have spent years investigating whether dark matter particles could produce this emission.
In certain theoretical models, particles called WIMPs can undergo self-annihilation when they meet. This process could generate gamma rays, giving scientists an indirect way to investigate dark matter’s particle nature.
Yet the same region contains a dense stellar population. Some of its older stars could contribute to the excess through millisecond pulsars.
Both explanations can account for important features of the signal. Consequently, researchers need more than a general resemblance between a prediction and the observations.
A shape that complicated the search
The emission has a roughly box-like pattern associated with the Milky Way’s central bulge. That connection has supported explanations involving old stars.
By comparison, a simple spherical dark matter model predicts a different spatial pattern. This apparent mismatch has challenged the dark matter interpretation.
The latest modeling addresses that assumption directly: must the inner dark matter distribution actually look spherical?
Reconstructing the galaxy with HESTIA
Lead author Moorits Mihkel Muru and colleagues explored this question using the HESTIA simulations. Their work involved researchers at the Leibniz Institute for Astrophysics Potsdam and collaborating institutions.
These simulations model Milky Way-like galaxies within environments resembling our local cosmic neighborhood. They allow researchers to examine how galaxy formation shapes the matter inside them.
Instead of relying only on an idealized halo, the team investigated distributions that emerge from simulated galactic development. www.aip.de
How the Milky Way’s history matters
The young Milky Way assembled through smaller systems that contributed dark matter and ordinary matter. Those early mergers helped establish the galaxy’s later structure.
As matter accumulated toward the central region, it changed the conditions relevant to a possible particle signal. Higher dark matter concentrations can increase predicted annihilation rates, if dark matter has the required properties.
This history matters because researchers compare telescope observations with theoretical maps. An unrealistic map could make a plausible explanation appear less convincing.
The simulations therefore offer a more detailed framework for interpreting the glow. They do not provide direct observations of dark matter particles.
This distinction separates the measured phenomenon from its proposed explanation. Fermi records gamma rays; the simulations explore how a particular source might produce them. Agreement between the two supports further investigation, while leaving room for another source to explain the same data.
A flattened halo changes the picture
The researchers found that simulated dark matter distributions in the inner galaxy can look flattened and asymmetric.
That result changes the gamma-ray pattern expected from hypothetical annihilation. A dark matter signal need not resemble the simple, rounded glow that earlier comparisons assumed.
The team found similarities between its predicted maps and the gamma-ray observations. This strengthens the argument that the observed shape does not exclude dark matter. www.aip.de
What the visual clue really means
The clue concerns the spatial arrangement of radiation across telescope maps. It is not a visible photograph of dark matter.
Likewise, the simulations do not establish the actual particle source of the emission. They show how dark matter could reproduce relevant features under the model’s assumptions.
The scientific advance is therefore specific: a more realistic distribution weakens one objection to the dark matter explanation.
Why millisecond pulsars remain in contention
Millisecond pulsars provide another way to explain the Milky Way gamma-ray glow. These rapidly rotating neutron stars can emit high-energy radiation.
A large population of faint pulsars could collectively create a glow even when telescopes cannot distinguish every individual source.
Their connection with older stellar populations also makes the central bulge an important place to investigate.
However, this interpretation has its own unresolved issue. The researchers note that explaining the excess requires more pulsars than observations have individually identified in the region.
That gap does not automatically invalidate the idea. Unresolved objects could still contribute light without appearing as separate detections.
For now, neither interpretation gains confirmation simply because it can reproduce the broad signal. Describing both as viable also avoids suggesting a precise, established 50–50 probability.
What could reveal the glow’s origin?
Future observations could compare the competing predictions across different gamma-ray energies. Researchers also need to examine where the emission appears and how its pattern changes.
The study identifies the Cherenkov Telescope Array as a potential contributor to these tests. Its observations could help researchers assess features that existing measurements leave uncertain.
Looking beyond the Galactic Center
The team also plans to investigate predictions for dwarf galaxies surrounding the Milky Way. Comparing expected signals with observations elsewhere could provide another check. hub.jhu.edu
A convincing explanation should withstand several tests, rather than depend entirely on one matching map.
Energy measurements will require careful interpretation, too. Higher-energy photons do not universally identify pulsars, nor do lower-energy photons automatically establish dark matter.
The useful question is which detailed prediction best explains the observations together.
A clearer model, an unresolved mystery
The Milky Way gamma-ray glow remains an intriguing target because its origin could reveal something fundamental about our galaxy.
This study shows how assumptions about dark matter’s shape influence that search. A flattened inner distribution makes the particle explanation harder to dismiss.
Even so, the result leaves the central question open. Scientists must now identify evidence that distinguishes a possible dark matter signal from a hidden population of pulsars.
Main sources:
- Physical Review Letters — Original research, published October 16, 2025
- Leibniz Institute for Astrophysics Potsdam — Research announcement
- Johns Hopkins University — Mysterious glow in Milky Way could be evidence of dark matter