Ordinary (baryonic) matter make up all physical objects in existence, from stars to the cores of black holes. But until now, scientists had only been able to locate about two-thirds of the matter that theorists predict was created by the Big Bang. In new research, a multinational group of astronomers and astrophysicists pinned down the missing third, finding it in hot and tenuous filamentary gas between galaxies, known as the warm-hot intergalactic medium (WHIM).
“The lost matter exists as filaments of oxygen gas at temperatures of around one million degrees Celsius,” said co-author Professor Michael Shull, a researcher in the Department of Astrophysical Science at the University of Colorado, Boulder. “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.”
Astrophysicists have a good idea of where to find most of the ordinary matter in the Universe, which is not the same as dark matter: about 10% sits in galaxies, and close to 60% is in the diffuse clouds of gas that lie between galaxies.