An international team of researchers,led by the Italian Istituto Nazionale di Astrofisica (INAF) and the Harvard-Smithsonian Center for Astrophysics, has located the last of the universe’s missing ordinary matter, known as baryons.
Scientists have only been able to identify around two-thirds of the baryons that should have been created by the Big Bang - a dilemma referred to as the “missing baryon problem.” It is thought that around 60% of baryons exist in the diffuse clouds of gas that fill the vast space between galaxies, while another 10% can be found inside the galaxies themselves.
The research team analyzed radiation emitted by a distant object called 1ES 1553 which 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. Analyzing how radiation from the quasar passes through space, after a 20-year-long experiment, the scientists found signatures of a form of oxygen gas in web-like patterns, known as the warm-hot intergalactic medium (WHIM), located in regions that lie between 1ES 1553 and our Solar System. When the researchers extrapolated the density of the gas in this region to the entire universe, they found it could account for the hidden 30% of matter. The researchers still need to confirm their findings by analyzing the radiation from different quasars. Finding the missing baryons is important to finally put together the puzzles about how the universe began.