A strange, never-before-seen light shining through the halo of the Milky Way could be the first source that allowed dark matter to be detected. A new analysis of 15 years of data from the Fermi Gamma-ray Space Telescope has revealed unusually high-energy gamma-ray light that cannot be attributed to any known source.
According to Tomonori Totani, an astronomer at the University of Tokyo in Japan, the phenomenon may be caused by the radiation that is produced when particles of the supposed dark matter collide and cancel each other out. Science Alert notes that this isn’t the first time astronomers have looked for this kind of light — but it’s the first time they’ve found such a glow in the massive bubble of gas and radiation surrounding the Milky Way that peaks at this specific energy level.
The scientific publication presenting the results was published in the Journal of Cosmology and Astroparticle Physics.
Dark matter is one of the great mysteries of the universe. It manifests as “excess” gravity that cannot be attributed to the amount of visible matter. According to scientists’ calculations, normal matter makes up only 16 percent of the universe’s matter distribution, and the remaining 84 percent is made up of dark matter, the composition of which is unknown.
One of the main candidates for dark matter is a hypothetical class of particles called WIMPs. The abbreviation covers the so-called Weakly Interacting Massive Particle. According to certain theories, these would be slow particles that cannot really be detected by electromagnetic methods. However, they can play a major role in the so-called weak interaction and gravity. (Otherwise, they wouldn’t be able to explain the strange motions of certain galaxies.) Current theory is that when WIMPs and their antiparticles collide, they annihilate, resulting in a shower of various particles, including the gamma photons that we can actually see.
Tomonori Totani / University of Tokyo
The researchers believe that if they manage to find gamma rays that are not associated with a source, then it is possible that this glow was generated by the destruction of dark matter. This could be the core of a galaxy, but there is a good chance that there is a source to which gamma radiation can be connected. However, there are far fewer such sources in the envelope surrounding the Milky Way.
The Japanese researchers therefore observed this region, and more precisely compiled the data measured by the space telescope. They found that faint gamma-ray emission was observed around the Milky Way, with one of its peaks at 20 gigaelectron volts. This is the energy level corresponding to WIMP predictions.
Scientists emphasize that this is still not conclusive evidence for the existence of dark matter, but it brings them one step closer to its investigation.
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