Scientists find new way to study galaxies

Scientists at institutions including Brookhaven National Laboratory unveiled a new method of peering billions of years back in time to track the movements of galaxies like our Milky Way by observing images created when gas blocks light from distant quasars.

Anze Slosar, a physicist at the Upton facility, presented a paper Sunday that describes how the technique uses intergalactic hydrogen, which blocks light, to see images that quasars emitted about 11 billion years ago. The resulting image is a lot like the negative of a photograph, forming a three-dimensional snapshot of the universe a long time ago.

Most methods of stargazing consist of looking directly at light emitted by objects in space, but the new method works by observing the silhouette-like effect that occurs when the hydrogen gas blocks the super-brilliant light emitted by quasars.

"You can think of it like making a silhouette of a cigarette smoke -- the thicker the smoke, the darker the silhouette," Slosar said. "But our technique allows us to do this separately for smoke that is close to you and smoke that is far away."

The Merriam-Webster Dictionary says quasars, which are among the most distant celestial bodies, resemble stars but whose qualities, such as brightness, "imply extreme distance and huge energy output."

Slosar presented the technique in a paper called "The Backlit Universe: How Distant Quasars Illuminate the Large-Scale Structure," at a meeting of the American Physical Society in Anaheim, Calif.

The method, developed by scientists of the Sloan Digital Sky Survey III, is being billed by Brookhaven Laboratory as producing "the largest ever three-dimensional map of the distant universe." It is part of the Baryon Oscillation Spectroscopic Survey.

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"It's like looking at the moon through clouds -- you can see the shapes of the clouds by the moonlight that they block," Slosar said.

The method uses about 14,000 quasars to light the way into an ancient view of the time when galaxies were clumping together because of gravitational pull. Previous attempts used a similar technique but involved one quasar at a time. French astronomers from the University of Paris analyzed each quasar for this project.

"If we had 14,000 moons all over the sky, we could look at the light blocked by clouds in front of all of them, much like what we can see during the day," he said. "You don't just get many small pictures, you get the big picture."

The Baryon Survey aims to create the most accurate maps of space to track the expansion of the universe throughout history. When the survey's observations end in 2014, astronomers hope to be able to create a map that is 10 times larger than Slosar's map, officials said.

"We opened a new window to the universe," Slosar said. "It's like making a new hole in the wall and now we see that we can peek through it, but it will take time to really see what we see!"