Astronomers have for the first time captured a glimpse of the vast, web-like network of diffuse gas that links all of the galaxies in the cosmos.
Leading cosmological theories suggest that galaxies are cocooned within gigantic, wispy filaments of gas. This “cosmic web” of gas-filled nebulas stretches between large, spacious voids that are tens of millions of light years wide. Like spiders, galaxies mostly appear to lie within the intersections of the long-sought webs.
In observations spied through one of the most powerful telescopes in the world, the 33-foot (10-meter) Keck I Telescope in Hawaii, astronomers led by Sebastiano Cantalupo of the University of California, Santa Cruz, now report that they have detected a very large, luminous filament of gas extending about 2 million light-years across intergalactic space, exactly as predicted by theory.
Essentially, the filament reported in the January 19 Nature represents one of the strands of the cosmic web that holds together the galaxy-rich universe. Astronomers hope to understand both the structure of the universe and the development of galaxies such as our own Milky Way by unraveling the secrets of the cosmic web.
The discovery came thanks to intense radiation bellowing out of a quasar (a hyper-active galaxy) dubbed UM287, 10 billion light years from Earth. The quasar illuminated the neighboring gas filament, revealing its presence with a glow that resembled a cosmic florescent sign.
“This is a very exceptional object: it’s huge, at least twice as large as any nebula detected before, and it extends well beyond the galactic environment of the quasar,” said Cantalupo, in a statement.
“The light from the quasar is like a flashlight beam, and in this case we were lucky that the flashlight is pointing toward the nebula and making the gas glow. We think this is part of a filament that may be even more extended than this, but we only see the part of the filament that is illuminated by the beamed emission from the quasar.”