In the cold wilderness of space, galaxies huddle together around the campfires of stars and the assuring pull of supermassive black holes. Between these cozy clusters of galaxies, where empty space stretches on for millions of light-years all around, a faint highway of gas bridges the darkness.
This gassy, intergalactic network is known in cosmological models as the cosmic web. Made of long filaments of hydrogen left over from the Big Bang, the web is thought to contain most (more than 60%) of the gas in the universe and to directly feed all of the star-producing regions in space. At the intersections where filaments overlap, galaxies appear. At least, that’s the theory.
The filaments of the galactic web have never been directly observed before, because they are among the faintest structures in the universe and are easily overshadowed by the glow of the galaxies around them. But now, in a study published today (Oct. 3) in the journal Science, researchers have cobbled together the first-ever photograph of cosmic filaments converging on a faraway galaxy cluster, thanks to some of the most sensitive telescopes on Earth.