Missing baryonic matter in universe found in inter-galactic space

Researchers at the University of Colorado Boulder have helped to find the last reservoir of ordinary matter hiding in the universe.

Ordinary matter, or "baryons," make up all physical objects in existence, from stars to the cores of black holes. But until now, astrophysicists had only been able to locate about two-thirds of the matter that theorists predict was created by the Big Bang.

In the new research, an international team pinned down the missing third, finding it in the space between galaxies. That lost matter exists as filaments of oxygen gas at temperatures of around 1 million degrees Celsius, said CU Boulder's Michael Shull, a co-author of the study.

The finding is a major step for astrophysics. "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," said Shull of the Department of Astrophysical and Planetary Sciences (APS).

Researchers have a good idea of where to find most of the ordinary matter in the universe—not to be confused with dark matter, which scientists have yet to locate: About 10 percent sits in galaxies, and close to 60 percent is in the diffuse clouds of gas that lie between galaxies.

In 2012, Shull and his colleagues predicted that the missing 30 percent of baryons were likely in a web-like pattern in space called the warm-hot intergalactic medium (WHIM). Charles Danforth, a research associate in APS, contributed to those findings and is a co-author of the new study.

Click to expand...