How is matter distributed within the universe? Simple question, but not so simple answer. It seems that it has a filamentous structure and the Universe is mostly “empty space”. However, matter might exist even within the vast spaces between filaments, as demonstrated by a group of Austrian researchers who conducted the largest computer simulation on the processes that led to the distribution of matter in the Universe. Black holes may play an important role; according to simulations, they would “throw” the matter into the empty space between filaments.
The current understanding on the composition of our Universe tells us that it is made up of about 5% normal matter (the matter we know and study in our laboratories), of about 25% dark matter (the matter we are hunting for within particle accelerators, in the space and in underground laboratories) and about 70% dark energy (the great mystery of modern physics).
The “ordinary” matter, based on protons, neutrons and electrons – that forms nuclei and atoms – is also distributed both in galaxies and large groups of galaxies as well as in the form of intergalactic gas.
But how are galaxies and gas distributed within the Universe?
According to astronomical observations, galaxies and large groups of galaxies are completely unevenly distributed in the Universe – they are grouped into filaments, a sort of “cosmic spider web”.
These filaments occupy a very small volume of the universe – so it seems that the Universe is composed mainly of spaces without matter. Or so it was believed until the new discovery of researchers from the Institute of Astro and Particle Physics, University of Innsbruck, Austria, who have conducted the most important computer simulation on the processes that took place in the Universe and its evolution since 300,000 after the Big Bang (during which radiation separated from matter).
The project, called “Illustris”, has generated a cube of space measuring 350 million light years on each edge and has tracked its evolution (considering the expansion of the Universe) till the present time. Is the most powerful simulation carried out so far.
What were the conclusions the researchers reached from this study that will be published in the Royal Astronomical Society?
It looks like galaxies and large groups of galaxies occupy a small fraction of the volume of the Universe; a volume of only 0.2%, an extremely small volume. Galaxies and large groups of galaxies represent about 50% of the known matter in the Universe. Intergalactic gas represents about 44% of the matter and it is distributed around galaxy filaments, occupying about 20% of the Universe.
But Austrian researchers have discovered a relatively curious fact: just 6% is located in the voids (voids are immense spaces between galaxy filaments). How did the matter get there?
Apparently, a major role was played by supermassive black holes found in the centers of galaxies (including our own galaxy). Some of the matter falling towards the holes is converted into energy. This energy is delivered to the surrounding gas (the gas in the galaxy) and leads to large outflows of matter. This matter is practically thrown at enormous distances from their host galaxies, reaching the empty spaces between galaxies.
So black holes distribute the matter in the Universe, especially in the voids. They also play a major role in the structure of the universe.
This discovery helps us better understand how our Universe is made. There are still many unraveled mysteries, including those of matter and dark energy. What they consist of and how are they distributed in the Universe? Dark energy is also evolving?
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