Ordinary matter, which makes up everything that we know — stars, planets, people — corresponds to five percent of the Universe. Only about half of this small percentage has actually been discovered; the other half has, until now, eluded scientists.
Numerical simulations have made it possible to predict that the rest of this ordinary matter should be located in large-scale structures that form the “cosmic web” at temperatures between 100,000 and 10 million degrees.
Scientists are the University of Geneva (UNIGE) in Switzerland have observed this phenomenon directly. Their research, recently published in Nature, shows that the majority of the missing ordinary matter is found in the form of a very hot gas associated with intergalactic filaments.
Galaxies are formed when ordinary matter collapses and then proceeds to cool down. In order to understand the origin of this formation, it is required to understand the form, as well as the location of the ordinary matter that we do not perceive (missing baryons) is located.
Astrophysicists from UNIGE and the Ecole polytechnique fédérale de Lausanne (EPFL) focused on Abell 2744, a massive cluster of galaxies with a complex distribution of dark and luminous matter at its core. The researchers observed this cluster with the XMM space telescope whose sensitivity to X-rays allows it to detect signatures of very hot gas.
Previous large-scale galaxy research has shown that the distribution of ordinary matter in the Universe is not homogenous, instead, it is concentrated into filamentary structures. These structures form a network of knots and links, referred to as the “cosmic web,” which connect to one another through filaments. Researchers were able to measure the temperature and density of these objects by focusing on the areas where they suspected to find these filaments.
“Now we must verify that the discovery of Abell 2744’s missing baryons is applicable to the entire universe. This will consist in studying these filamentary regions in detail, and measuring their temperature distribution and the various atoms that compose them, in order to understand how many heavy elements there are in the universe,” says lead scientist Dominique Eckert in the press release.
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