Universe’s ‘Missing’ Third Of Ordinary Matter Found In Intergalactic Cosmic Web Filaments

James Marshall
June 22, 2018

"We found the missing baryons", Shull said.

If you looked at how matter (both dark and baryonic) is distributed across the universe, it would look similar to a large web, with stars, galaxies, and black holes concentrated in places where matter is the most dense (and the easiest to observe).

Researchers have discovered what could be the last of missing matter in the universe-offering an explanation to the long-time puzzle termed as the "missing baryon problem" by astrophysicists.

An worldwide 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.

To search for missing atoms in that region between galaxies, 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. It is important to note that baryons are distinct from the theoretical dark matter that is predicted to make up the majority of the universe's mass. Scientists have found that they are in intergalactic space, where there is about 60% of matter in the form of dispersed clouds of gas.

1ES 1553 is a quasar-an extremely bright object found in the center of some distant galaxies that are powered by gas spiraling at high velocity into supermassive black holes. Gas was 30% of the baryonic matter of the volume of the Universe. "This is happening because there are huge reservoirs of material - including oxygen - lying there, and just in the amount we were expecting, so we finally can close the gap in the baryon budget of the Universe", Fabrizio Nicastro, of the Italian Istituto Nazionale di Astrofisica (INAF)-Osservatorio Astronomico di Roma and the Harvard-Smithsonian Center for Astrophysics, who was lead author of the paper about the discovery, said Wednesday in an ESA statement. This lost matter occurs as oxygen gas filaments at temperatures of about 1 million degrees Celsius in the space between galaxies, stated Michael Shull from CU Boulder, one of the co-authors of the study. "This intergalactic medium contains filaments of gas at temperatures from a few thousand degrees to a few million degrees". "It's basically a really bright lighthouse out in space", Shull said.

Scientists can glean a lot of information by recording how the radiation from a quasar passes through space, like a sailor seeing a lighthouse through fog.

By studying the behavior of the quasar beams as they passed through intergalactic space, scientists got a sense of where these missing baryons might be located.

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. Then, they used the European Space Agency's X-ray Multi-Mirror Mission (XMM-Newton) satellite to home in on those baryons. Quasar's light takes more than 4 billion years to reach Earth. "There's some sort of ecology going on between the two regions, and the details of that are poorly understood".

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