Quasars help map the universe

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CLEVELAND, Sept. 18 (UPI) -- U.S. researchers say they've found a possible way to map the spread and structure of the universe, using light from distant quasars as a "mapping" tool.

With the predicted discovery of millions more far-away quasars over the next decade, the technique could yield a view to shortly after the Big Bang, when the universe was a fraction the size it is today, they said.

"It appears we may have a useful tool for mapping out the expansion history of the universe," Case Western Reserve University physics Professor Glenn Starkman said.

Researchers discovered patterns of light variation over time in quasars linked to their redshift, a shift in the light frequency caused by the quasars moving away from Earth in the expansion of the universe.

Knowing the quasar redshift enables an estimate of the relative size of the universe when the light was emitted. The larger the redshift, the farther and older the light source.

"If we could measure the redshifts of millions of quasars, we could use them to map the structures in the universe out to a large redshift," Starkman said in a university release.

Very old and distant quasars have been measured with redshifts suggesting they emitted the light we are seeing today when the universe was as small as one-eighth the size it is today, the researchers said.