Far-Out Cosmic Walls

New findings suggest that galaxies form massive wall-like structures in the far reaches of the universe. In the 1 November issue of the Astrophysical Journal, Judith Cohen of the California Institute of Technology and colleagues at the University of Hawaii report evidence for what may be walls of galaxies as far as 8 billion light-years away, indicating that matter formed distinct structures earlier in the universe’s history than many scientists expected.

Cohen’s team used the Keck Telescope in Hawaii to calculate the redshifts–an astronomical measure of distance–of 140 objects outside our galaxy in an area of sky called the Hubble Deep Field, where scientists have discerned some of the faintest objects ever seen. They found that the redshifts seem to cluster in six peaks, which were interpreted as six walls. The authors speculate that their line of sight may have punched through distant walls of galaxies like ones observed much closer to our sun. Cohen’s team had reported similar findings this spring for a different patch of sky, but “people thought it was a fluke or a mistake,” she says. This latest measurement, she adds, is evidence that such far-out structures may be widespread.

Not everyone is convinced. Ray Carlberg, an astrophysicist at the University of Toronto, says it’s too soon to say that the clustered redshifts represent walls, filaments, or clusters of galaxies because the scientists only looked at a very narrow piece of sky. Nevertheless, comparing the structures very far out in space–and far back in time–with those closer to our neighborhood will help scientists develop more accurate models of how our universe has evolved, says astrophysicist Marc Davis of the University of California, Berkeley. Cohen’s team is now searching a patch of sky adjacent to the first for a similar pattern.

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