An article published in the journal “Monthly Notices of the Royal Astronomical Society” describes a research on the distribution of matter in the universe. According to the results 20% of ordinary matter is contained in the so-called cosmic voids and galaxies are only 1/500th of the volume of the universe. A team led by Dr Markus Haider of the Institute of Astro and Particle Physics at the University of Innsbruck in Austria, has used simulations of the Illustris project to reach these conclusions.
The Illustris simulations are created trying to reproduce faithfully the structure of the universe. Therefore, it includes not only ordinary – or baryonic – matter but also dark matter and in particular its gravitational effects. On this basis, it was possible to reproduce with good fidelity the formation and evolution of galaxies and also the filament structures which extend along the ends of cosmic voids.
According to these simulations, about half of the mass existing in the universe is contained in galaxies but in a volume that makes up only 0.2% of today’s universe. Another 44% of matter is contained in the filaments and the remaining 6% is contained in cosmic voids, which make up 80% of the volume of the universe.
Cosmic voids are structures between filaments in which matter density is very low. Actually, sometimes you can find galaxies or gas clouds in these large areas but they’re isolated. Some of these voids are so large that they’re called supervoids. According to this research they’re not so empty.
A surprising result emerged from the Illustris simulations is that 20% of ordinary matter was moved to cosmic voids. The culprits could be the supermassive black holes that exist in the center of galaxies. A portion of the materials that fall into black holes is converted into energy. The gas around the black holes receives this energy and is pushed away to distances even of hundreds of thousands of light years away, far beyond the borders of their host galaxies.
This phenomenon may also explain the so-called missing baryon problem. Astronomers have found a smaller amount of ordinary matter than that predicted by their models but if the missing one ended up outside galaxies, into cosmic voids, the problem could be solved.
The researchers keep on carrying out simulations and the results should be avaible in the coming months. The biggest problem will be to try to detect matter in cosmic voids with direct observation to verify the accuracy of the simulations because it’s probably too cold and tenuous to emit electromagnetic radiation such as X-rays.