The mysterious gamma radiation emanating from the center of the Galaxy is generated not by decaying dark matter, but by extragalactic cosmic rays, which are decelerated by a giant electromagnetic "trap" of a still unknown nature, NASA reports.
“Ultra-high-energy cosmic rays spend much more time in the center of the Galaxy than we previously thought, and therefore have a stronger effect on the gamma-ray emission of the Galaxy than our colleagues expected,” says Alfredo Urbano of the National Institute of Nuclear Physics in Trieste. (Italy).
Urbano and other scientists from the Fermi collaboration have been investigating for several years one of the most important mysteries of the Galaxy - why its central part produces noticeably more gamma radiation in the high-energy part of the spectrum than predicted by calculations based on the density of distribution of stars and activity in the center of the black hole …
This phenomenon, discovered by the Fermi telescope in 2009, has led many scientists to believe the excess of gamma rays is a consequence of the decay of dark matter particles in the center of the Milky Way. Therefore, astrophysicists and cosmologists constantly monitor the central part of the Galaxy, trying to confirm or deny this idea, and also look for similar traces of gamma radiation in the cores of other galaxies.
From the point of view of astrophysics, to refute it, it is necessary to show that gamma photons from the center of the Milky Way fly towards us from point light sources, which can be pulsars or other compact objects. If they are generated by decaying dark matter particles, the excess radiation will be evenly distributed across the sky.
The unexpected source of these rays, which accounts for almost all the excess gamma radiation in the center of the Galaxy, Urbano and his colleagues discovered using the Fermi space telescope and ground-based HESS, designed to study the highest energy part of the gamma range.
Comparing and combining the data obtained by Fermi and HESS, the scientists noticed that both telescopes, despite significant differences in their ranges of operation, see virtually the same source of gamma photons, producing both relatively soft and ultra-powerful gamma rays …
Trying to understand what could give rise to both weak and powerful gamma photons, the Fermi scientific team drew attention to the fact that light particles generated by ultra-powerful cosmic rays, protons accelerated to 90% of the speed of light, colliding with other particles of matter in the center of the Milky Way.
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Why this is happening, scientists do not yet know - the theory predicts that high-energy cosmic rays should collide with the matter of the center of the Milky Way much less often than it actually happens. So far, we only know that their source is located near Sgr A *, the supermassive black hole of the Galaxy, and has a compact nature.
Scientists plan to test their assumptions by observing other particles that are produced in these collisions - high-energy neutrinos. If IceCube and other telescopes capable of seeing these particles show that most of these particles come from the center of the Galaxy, then the ten-year mystery of "extra" gamma rays will be solved, the authors of the article conclude.