From the X-ray of the Milky Way emerge new clues about dark matter, the still mysterious and invisible matter that occupies about 25% of the universe: there is no trace of a weak X-ray signal observed in nearby galaxies and attributed by some theoretical models to the decay of dark matter particles, whose nature therefore remains unknown. This is what emerges from the study published in the journal Science by the group of the American University of Michigan, coordinated by Christopher Dessert and Benjamin Safdi, together with colleagues from the University of California at Berkeley. The study is based on 20 years of X-ray Milky Way observations with the European Space Agency (ESA) orbiting telescope, Xmm-Newton.
Dark matter, according to current cosmological theories, forms about a quarter of the universe. But so far it has not been possible to observe it directly, because it does not absorb, reflect, or emit light. It makes its presence felt only through the gravitational attraction it exerts on the rest of the matter and which, according to experts, holds the galaxies together.
Even the nature of the particles of which dark matter is formed is still elusive. According to some models, one of these hypothetical particles, the so-called sterile neutrino, could leave a footprint in the form of a weak X-ray signal. But the new observations of the Milky Way with the Xmm Newton telescope have found no trace of this signal. For Safdi, "the study does not rule out that dark matter may be formed from particles such as the sterile neutrino, but shows that there is currently no experimental evidence of their existence".
