An anomalous surplus of gamma-ray emissions originating from the core of our Milky Way Galaxy has been identified.
This depiction illustrates the celestial sphere at energies surpassing 1 GeV, compiled from five years of observations by the Large Area Telescope (LAT) aboard NASA’s Fermi Gamma-ray Space Telescope. The most conspicuous element is the luminous band of diffuse luminescence traversing the map’s central axis, signifying the galactic plane of our Milky Way. Credit: NASA / DOE / Fermi LAT Collaboration.
Gamma-rays constitute a potent form of electromagnetic radiation, characterized by their exceptionally short wavelengths and maximal energy levels.
The aberrant gamma-ray signature emanating from the Milky Way’s galactic nucleus was initially observed in 2009 by the Large Area Telescope, the principal payload onboard NASA’s Fermi Gamma-ray Space Telescope.
The genesis of this phenomenon has been a subject of considerable scientific discourse, with leading hypotheses postulating either self-annihilating dark matter or an uncatalogued congregation of millisecond pulsars as the causative agents.
“The observational data gathered by Fermi upon directing its focus towards the Galactic center yielded results that were quite astonishing,” remarked Dr. Noam Libeskind, an astrophysicist affiliated with the Leibniz Institute for Astrophysics Potsdam.
“The instrument detected an unusually high flux of gamma rays, which represent the most energetic form of light detectable within the cosmos.”
“This perplexing observation prompted widespread consternation among astronomers globally, leading to the emergence of numerous competing hypotheses designed to elucidate the so-called gamma-ray excess.”
“Following extensive deliberation, two primary explanations gained prominence: either these gamma rays originated from millisecond pulsars—exceedingly dense neutron stars that rotate thousands of times per second—or they were the byproduct of dark matter particles colliding and annihilating. Both theoretical frameworks, however, present certain limitations.”
“Nevertheless, our findings provide robust corroboration for the hypothesis that the observed gamma-ray surplus is attributable to dark matter annihilation.”
In their comprehensive investigation, Dr. Libeskind and his research associates meticulously modeled the evolutionary trajectory of Milky Way-analogous galaxies under environmental conditions mirroring those of our local cosmic vicinity.
Their analysis revealed that dark matter does not disperse radially outward from the Galactic center; instead, it exhibits a spatial organization analogous to that of stellar distributions, suggesting that this arrangement could indeed account for the observed gamma-ray excess.
“It has long been established that the Milky Way galaxy resides within what is known as a dark matter halo, a vast, roughly spherical envelope surrounding it and permeated by dark matter,” explained Dr. Moorits Mihkel Muru, a fellow astrophysicist at the Leibniz Institute for Astrophysics Potsdam and the University of Tartu.
“However, the degree to which this halo deviates from a perfectly spherical shape, exhibiting an aspherical or ellipsoidal form, has not been adequately appreciated.”
“Our examination of simulations depicting the Milky Way and its associated dark matter halo indicated that the degree of flattening observed within this region is sufficiently pronounced to explain the gamma-ray excess as a direct consequence of dark matter particle self-annihilation.”
“These computational endeavors underscore the imperative to persist in the pursuit of detecting dark matter particles capable of self-annihilation, thereby advancing our comprehension of the enigmatic characteristics of these particles.”
A scholarly article detailing these groundbreaking discoveries was published this month in the esteemed journal Physical Review Letters.
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Moorits Mihkel Muru et al. 2025. Fermi-LAT Galactic Center Excess Morphology of Dark Matter in Simulations of the Milky Way Galaxy. Phys. Rev. Lett 135, 161005; doi: 10.1103/g9qz-h8wd
