Vast Filament of Hidden Matter Seen for the First Time

More than one third of the regular matter in the Universe is missing (we’re not talking about dark matter, just regular matter). It’s needed to make the current cosmological models work, so astronomers continue to search for it, and have found many indirect examples of it. Now a team of astronomers has directly observed it as a huge filament of hot gas bridging four galaxy clusters and containing 10 times the mass of the Milky Way.