Astronomy: Dark matter could explain mysterious gamma-ray excess
More gamma radiation than predicted is coming from the center of the Milky Way. According to simulations, dark matter has become somewhat more likely as a cause.
The Milky Way above the Very Large Telescope (VLT)
(Image: ESO/Y. Beletsky)
Diffusely glowing gamma radiation from the center of the Milky Way could provide the long-sought experimental evidence for dark matter, but this requires a new observatory that is only planned so far. At least, an international research group explains, which was led by the Leibniz Institute for Astrophysics Potsdam (AIP). Their simulations suggest that there are only two possible explanations for an excess of gamma rays from the Milky Way. One does not fit previous observations; the other states that mutually annihilating particles of dark matter are responsible. The latter has thus been further substantiated but not yet confirmed.
Two possible explanations
According to the research group, it has long been suspected that the mutual annihilation of dark matter could be a source of mysterious gamma radiation from the heart of the Milky Way. However, its spatial distribution did not fit the theories until now. New simulations of galaxies existing in an environment similar to the Milky Way have now revealed exactly these patterns. Dark matter would therefore not be evenly distributed but rather arranged like stars and responsible for the excess radiation. The second theory attributes the “gamma-ray excess” to millisecond pulsars. However, there would have to be more of these ultra-dense neutron stars than have been discovered so far. The work was published in Physical Review Letters.
However, it is not possible to clarify which of the two theories explains the excess gamma radiation with current telescopes, adds Johns Hopkins University, where study participants conduct research. An answer could come from the Cherenkov Telescope Array, which is currently being prepared. It is intended to provide insights into cosmic gamma radiation by observing Cherenkov flashes in the Earth's atmosphere. The technology for this is to be built at two locations in Chile and on La Palma. The high-resolution data collected could make a decisive contribution to clarifying whether dark matter particles are indeed responsible for the radiation. Should they show that the radiation has low energies, this would speak for it; high energies would point to millisecond pulsars as the source.
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The question about the nature of dark matter is currently one of the most important in fundamental physics. Its existence was postulated based on astronomical observations in which stellar movements were measured that cannot be sufficiently explained by known matter and its gravity. Overall, there should be five times more dark matter in the cosmos than classical matter. Even more is accounted for by the no less mysterious dark energy. Currently, particles that could constitute it are being searched for in very different ways. For example, the “Light through the Wall” experiment ALPS II at the German Electron Synchrotron (DESY) in Hamburg is pursuing exactly this goal. However, experimental proof is still pending, and therefore there is still room for more radical theories.
(mho)
