Using light from 14,000 distant yet powerful cosmic beacons, astronomers have pieced together the largest and most detailed 3-D map of the ancient universe.

Previous versions plotted the locations of galaxies within 7 billion light-years of Earth. The new version, however, charts clouds of hydrogen in a swath between 10 billion and 12 billion light-years away – farther in distance and deeper in time than any 3-D map before it.

The hydrogen clouds could help answer some of astronomers' more profound questions about the universe, including the nature of dark energy.

"We’re looking for a bump in the data that may tell us how fast universe is expanding," said cosmologist Anže Slosar of Brookhaven National Laboratory, one of the researchers who presented the map May 1 at the American Physical Society meeting in Anaheim, California. "We don’t have enough data to see the bump yet, but we expect to get there in a few years."

To create the map, Slosar joined dozens of other astronomers in the third iteration of the Sloan Digital Sky Survey. The multipurpose telescope hosts an instrument called the Baryon Oscillation Spectroscopic Survey, or BOSS, which can analyze light from individual quasars.

"Quasars are extremely bright galaxies that are very far away. At the center of each, a black hole is eating matter. The matter heats up to such superhigh temperatures that it shines like crazy,” Slosar said. “This allows us to see them from very, very far away."

Light from quasars focuses into a beam which, on the way to Earth,gets partially absorbed by hydrogen gas. The light is then re-emitted in a different wavelength, creating a unique spectrum for each quasar. Because the beam traverses space as well as time, astronomers can use its spectrum to estimate hydrogen cloud expansions and contractions through time.

Slosar said the process is similar to an ice core sample removed from Antarctica. Looking straight on, the core looks like a circle or a point. But slice by slice, one can reconstruct events of the past. In the case of the 3-D map, astronomers can chart the development of galaxy clusters between 10 billion and 12 billion years ago.

The SDSS collaboration has laboriously analyzed 14,000 of about 160,000 known quasars. By 2014, the astronomers hope to have 50,000 or 60,000 quasar slices in their grips – perhaps enough data to say something meaningful about the fate of the universe. The researchers also plan to release a proper 3-D representation of the data (instead of the 2-D images shown here) for the public by then.

Images: 1) Illustration of where the new SDSS map data exists in space and time. The new data are of hydrogen gas emissions between 10 billion and 12 billion light-years away. Older galaxy-based data is shown closer to Earth. (A. Slosar and SDSS-III collaboration) 2) Slice of the full map showing the density of hydrogen gas in the ancient universe. Blue represents little gas, while red represents dense clouds. (A. Slosar and SDSS-III collaboration)

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