Astronomers locate universe's 'missing' matter in the largest cosmic structures

Summary

Astronomers have discovered a vast tendril of hot gas linking four galaxy clusters and stretching out for 23 million light-years, 230 times the length of our galaxy. With 10 times the mass of the Milky Way, this filamentary structure accounts for much of the universe's "missing matter," the search for which has baffled scientists for decades.This "missing matter" doesn't refer to dark matter, the mysterious stuff that remains effectively invisible because it doesn't interact with light (sadly, that remains an ongoing puzzle). Instead, it is "ordinary matter" made up of atoms, composed of electrons, protons, and neutrons (collectively called baryons) which make up stars, planets, moons, and our bodies.For decades, our best models of the universe have suggested that a third of the baryonic matter that should be out there in the cosmos is missing. This discovery of that missing matter suggests our best models of the universe were right all along. It could also reveal more about the "Cosmic Web," the vast structure along which entire galaxies grew and gathered during the earlier epochs of our 13.8 billion-year-old universe.The aforementioned models of the cosmos, including the standard model of cosmology, have long posited the idea that the missing baryonic matter of the universe is locked up in vast filaments of gas stretching between the densest pockets of space.Though astronomers have seen these filaments before, the fact that they are faint has meant that their light has been washed out by other sources like galaxies and supermassive black hole-powered quasars. That means the characteristics of these filaments have remained elusive.But now, a team of astronomers has for the first time been able to determine the properties of one of these filaments, which links four galactic clusters in the local universe. These four clusters are all part of the Shapley Supercluster, a gathering of over 8,000 galaxies forming one of the most massive structures in the nearby cosmos."F...