A new project to create a 3D map of space so large that scientists can find a 500 million-light-year-size remnant from the early universe inside it began operation last month.

The Baryon Oscillation Spectroscopic Survey opened its eyes to the universe, taking in data from hundreds of galaxies and quasars in the constellation Aquarius, from its perch on the Apache Point Observatory in New Mexico. Eventually, it will image two million galaxies and quasars.

“The data from BOSS will be some of the best ever obtained on the large-scale structure of the universe," said David Schlegel, an astronomer heading the team from Lawrence Berkeley National Laboratory, in a press release.

BOSS was built atop the Sloan Digital Sky Survey infrastructure, which created a smaller map of the universe in our neighborhood. The scientists put in new CCDs to better capture the infrared light that arrives redshifted from its trip across billions of light-years. They also remade the fiber optics system so they could capture more objects.

"We've rebuilt this telescope to make a much bigger map of the sky. We put in more optical fibers. We jammed in as many as we could fit," Schlegel said. "It's a mix of high-tech and low-tech. Every object we observe, we machine these plug plates and plug in these optical fibers." (See the image at the top of the page.)

Over vast areas millions of light-years across, the astronomers will map the enormous imprint of compression waves that blew through the early, hot universe and became etched into the distribution of matter. It's like measuring a sound wave pushing air molecules around, Schlegel said, but what the wave has moved is galaxies instead of molecules.

"These sound waves have been imprinted on the structure of everything in the universe. Most famously, they are seen in the microwave background," Schlegel told Wired.com. "But you can also see it imprinted on all the structures of the galaxies today."

That imprint, called the baryon acoustic oscillation, will yield important insights about the nature of dark energy, about which we know next to nothing. Scientists will be able to use the BAO as an enormous ruler for measuring how the universe has expanded.

"It's a big-ass ruler," said Schlegel. "It happens to be about 500 million light-years. Even for us, that's big."

BOSS will be observing the sky for the next five years. What the scientists hope the ruler will allow them to do is understand the period of accelerating expansion that began about six billion years ago.

"What we think happened is that we've entered this period of acceleration of the universe just in the last six billion years," Schlegel said. "When the universe was half as old as it is now, it was decelerating and then all of a sudden it started accelerating, which we don't understand."

The problem is that we don't have good data from that time period. Thanks to intensive study of the cosmic background radiation, we have expansion information from when the universe was only 400,000 years old. Then we have very recent observations from supernovae.

"But we don't have much in between," Schlegel said.

If BOSS can fill in that gap, we could not only learn about this mysterious something we call dark energy, but also grasp what happened during the universe's adolescent growth spurt.

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