Matter as we know it – or that which composes everything known – is a mere 5 percent of the great and mighty universe, and about half of that is still undetected.

Researchers from the University of Geneva and the Ecole polytechnique fédérale de Lausanne (EPFL) found that a major part of the ordinary matter unaccounted for is in a really hot gas form linked to intergalactic filaments.

Writing in the journal Nature and using numerical simulations, they observed that it is possible to forecast that the rest of this ordinary matter should be found in the massive structures forming the “cosmic web” at 100,000 to 10 million degree temperatures.

As galaxies form after ordinary matter breaks down and cools down, the team sought to understand the start of this formation through knowing where and in what specific form “missing baryons” – ordinary matter remaining unperceived – are found.  

They looked at the massive galaxy cluster Abell 2744 through the XMM space telescope, which can detect very hot gases due to its X-ray sensitivity.

The findings showed that the universe’s ordinary matter is not homogenously distributed – instead, it is determined by gravity, and that it assumes a kind of filamentary network dubbed as “cosmic web.”

Researchers aimed the space telescope at the predicted locations of these filaments, measuring the temperature and density of objects found in the region. What they found was aligned with their numerical simulations’ predictions: 10-million-degree hot gas structures come with these filaments.

The team deemed this a very significant confirmation of models of galaxy formation in the universe.

"Now we must verify that the discovery of Abell 2744's missing baryons is applicable to the entire universe,” said lead scientist Dominique Eckert, who added that this includes studying the filament regions more closely, measuring the distribution of temperatures and atoms, and analyzing the number of heavy elements present.

For instance, if the astrophysicists successfully measure atoms present in such filaments, they can estimate the number of star-formed heavy nuclei that are there since the beginning of the universe.

The European Space Agency is now working on a new space telescope called Athena, to be operational by middle of 2020s.

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