Researchers Found The Missing Ordinary Matter

Rodiano Bonacci
Giugno 22, 2018

An global team of researchers has located the last of the universe's missing ordinary matter-a finding that finally answers a long-standing mystery in the field of astrophysics and shines new light on our understanding of the cosmos.

"After combing through the data, we succeeded at finding the signature of oxygen in the hot intergalactic gas between us and the distant quasar, at two different locations along the line of sight", said Harvard-Smithsonian Center for Astrophysics scientist Fabrizio Nicastro, the lead author on the new paper outlining the discovery.

"This is one of the key pillars of testing the Big Bang theory: figuring out the baryon census of hydrogen and helium and everything else in the periodic table", he stated. They were found between the quasar and the Solar system.

The team of researchers now know where to find the ordinary matter in the universe. However, about 30% of the matter is still left unaccounted.

To search for missing atoms in that perverse territory, the global team pointed a series of satellites at a quasar called 1ES 1553-a black hole at the center of a galaxy that is consuming and spitting out huge quantities of gas.

In 2012, Michael Shull and Charles Danforth, from the University of Colorado, Boulder, suggested where the erstwhile missing baryons could be found. Most of this was created at the time of the Big Bang. To be exact, the baryons exist as filaments of oxygen gas at temperatures of around 1 million degrees Celsius, lying in the spaces between galaxies.

Since at least 2011, researchers have suspected that the missing baryons might be hiding out in this material, called the warm-hot intergalactic medium (WHIM), but the WHIM is hard to observe directly.

Aside from dark matter and the dark energy that comprised the universe, there remained to be 5 percent of what was called the "ordinary matter".

Previous researchers concluded that 10 percent of the baryons end up in the galaxies, and about 60 percent end up in diffused clouds of gas, which are found in the spaces between galaxies. "This intergalactic medium contains filaments of gas at temperatures from a few thousand degrees to a few million degrees". Initially, the scientists used the Cosmic Origins Spectrograph on the Hubble Space Telescope to estimate a place to find the missing baryons in that fog.

By observing the quasar for 18 days, split between 2015 and 2017, the team found that the "highly ionized gas" they detected was at a high-enough density to be accounted for as the missing 30 percent of the ordinary matter or the baryons. Next, the researchers pointed the European Space Agency's XMM-Newton satellite in the direction of the elusive baryons. Quasars are some of the brightest objects in the universe and can outshine all of the stars in their host galaxies, making them visible even from distances of billions of light years. Apparently, it lies in the spaces between entire galaxies. "There's some sort of ecology going on between the two regions, and the details of that are poorly understood".

The new study appeared on 20 June in the journal Nature.

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