Having detected the missing matter of the universe, it is among the galaxies

Cosmic explosions made it possible to detect the missing matter of the universe, that is, what should exist in the universe and of which traces had been lost, despite decades of research. It is found in the space between galaxies in the form of very rarefied gas. Published in the journal Nature, the result is due to researchers coordinated by Jean-Pierre Macquart, of the Australian Curtin University.

"We know from the Big Bang measurements how much matter there was at the beginning of the Universe," said Macquart. But when looking at the present universe this matter is missing from the appeal. The missing matter in this case is the 'normal' matter, called baryonic, which is what stars, planets and man are made of, and not the dark matter that occupies 25% of the universe. In addition to stars and galaxies, which are bright and therefore visible, "it is known that in the space between the stars and between the galaxies there is additional baryonic matter, that is hydrogen gas and helium very dispersed and which is very difficult to see" he said at ANSA the astroparticle physicist Marco Pallavicini, of the executive board of the National Institute of Nuclear Physics (INFN).

In part, he added, "this gas had been observed with radio techniques, but a piece was missing and this research refers to this missing part." The researchers managed to reveal this matter by observing fast radio explosions, short flashes of energy very difficult to intercept, thanks to the Askap (Australian Square Kilometer Array Pathfinder) radio telescope. Thanks to a very sophisticated technique, Pallavicini explained, the researchers analyzed how these flashes propagate in the intergalactic space. As if it were a prism, he added, gas between galaxies has dispersion properties that affect the arrival time of flash radio signals. "By studying this - he concluded - the researchers reconstructed the properties of the intergalactic medium and realized that there is some matter and revealed about half of the matter that there should be".