A recent study has unveiled that dark matter within the Milky Way galaxy has a distinct distribution pattern, potentially explaining the previously observed gamma ray excess emanating from the galaxy’s center. Conducted by researchers at the Leibniz Institute for Astrophysics Potsdam in collaboration with the Hebrew University and Johns Hopkins University, this research advances the understanding of dark matter as a significant contributor to cosmic phenomena.
The findings, published in Physical Review Letters on October 19, 2025, indicate that dark matter in the inner regions of the Milky Way is not uniformly spherical but rather flattened and asymmetrical. This shapes the distribution of dark matter in a way that aligns with the hypothesis that the excess gamma rays observed are the result of dark matter annihilation, rather than alternative explanations such as ancient millisecond pulsars.
Researchers employed high-resolution simulations to model the formation of galaxies similar to the Milky Way under conditions akin to those in the universe surrounding Earth. These simulations produced galaxies that closely resemble the Milky Way, revealing that dark matter is organized similarly to stars, rather than radiating outward from the Galactic Center.
“In the early observations by the Fermi Space Telescope, the detection of an unexpected number of gamma rays raised questions in the astronomical community,” stated Noam Libeskind, a researcher at the Leibniz Institute. “Theories began to emerge to explain the so-called ‘gamma ray excess.'”
Two primary ideas gained traction: either the gamma rays were generated by millisecond pulsars, which are extremely dense neutron stars, or they resulted from dark matter particles colliding and annihilating each other. Each theory faced its own challenges, leading to ongoing debates among scientists.
The breakthrough from the AIP-led team offers compelling evidence supporting the dark matter annihilation theory. Lead author Moorits Mihkel Muru emphasized the significance of their findings, stating, “Our analysis of the dark matter halo surrounding the Milky Way shows that its flattening could sufficiently account for the gamma ray excess through self-annihilation of dark matter particles. This strengthens the case for the existence of dark matter particles that can self-annihilate.”
The research suggests that the previously underestimated aspherical shape of the dark matter halo around the Milky Way is critical to understanding the gamma ray excess. The study illustrates the importance of continued exploration in the search for dark matter particles and their elusive properties.
As scientists work to decode the mysteries of dark matter, these findings mark a pivotal step forward in our understanding of the universe. Future research will likely focus on refining models of dark matter distribution and exploring the implications for astrophysics and cosmology.
For further details, refer to the full study by Muru et al. in Physical Review Letters.
