Astronomers Get First Glimpse of Cosmic Web

Computer simulations suggest that matter in the universe is distributed in a “cosmic web” of filaments, as seen in the image above from a large-scale dark-matter simulation. The inset is a zoomed-in, high-resolution image of a smaller part of the cosmic web, 10 million light-years across, from a simulation that includes gas as well as dark matter. The intense radiation from a quasar can, like a flashlight, illuminate part of the surrounding cosmic web (highlighted in the image) and make a filament of gas glow, as was observed in the case of quasar UM287. Credit: Anatoly Klypin and Joel Primack, S. Cantalupo

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.

This deep image shows the Nebula (cyan) with a size of 2 million light-years discovered around the quasar UM287 (at the centre of the image). The energetic radiation of the quasar makes the surrounding intergalactic gas glow revealing the morphology and physical properties of a "Cosmic Web" filament. Credit: S. Cantalupo
This deep image shows the Nebula (cyan) with a size of 2 million light-years discovered around the quasar UM287 (at center) . The energetic radiation of the quasar makes the surrounding intergalactic gas glow revealing the morphology and physical properties of a “Cosmic Web” filament. Credit: S. Cantalupo

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.”


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Changing Planet

Meet the Author
Andrew Fazekas, aka The Night Sky Guy, is a science writer, broadcaster, and lecturer who loves to share his passion for the wonders of the universe through all media. He is a regular contributor to National Geographic News and is the national cosmic correspondent for Canada’s Weather Network TV channel, space columnist for CBC Radio network, and a consultant for the Canadian Space Agency. As a member of the Royal Astronomical Society of Canada, Andrew has been observing the heavens from Montreal for over a quarter century and has never met a clear night sky he didn’t like.