Using state-of-the-art instruments to cover a quarter of the night sky, researchers at the Lawrence Berkeley National Laboratory are launching the next phase of an ambitious project to map the universe and understand more about its expansion.

The project is part of Sloan III, the third installment of the Sloan Digital Sky Survey, which began in 2000 with the goal of creating a three-dimensional map of the known universe. The first two phases mapped out nearby galaxies, while Sloan III will map galaxies halfway across the universe.

The project uses a telescope, located in New Mexico, that has a 2.5-meter mirror, giving it the widest field of vision of any telescope that size. The telescope will map around 1.5 million galaxies and 160,000 quasars, said Martin White, a Berkeley lab survey scientist for the Baryon Oscillation Spectroscopic Survey, known as BOSS, one of four components of Sloan III.

Sloan III will cost $43 million and will be funded by the Alfred P. Sloan Foundation, the National Science Foundation, the Department of Energy and participating universities, said David Schlegel, the principal investigator of BOSS.

Although the preliminary phase of Sloan III began on July 15, BOSS, which is run by the Berkeley lab, is not yet fully operational pending an upgrade of its instruments.

BOSS's main goal is to determine the universe's rate of expansion, which it will do by measuring the redshifts of galaxies and quasars, said Nikhil Padmanabhan, another BOSS scientist. A redshift is an increase in wavelength that measures how quickly objects are receding into space.

BOSS will last for five years and will begin collecting redshift data in September 2009.

"We're very excited about (the survey)," Schlegel said. "It'll make a map that's very much like the original Sloan map of the universe but it goes out in distance quite a bit further … There is nothing comparable to that being done by anyone else."

BOSS relies on instruments attached to the telescope including a spectrograph, which gathers light from distant galaxies and disperses it into a spectrum. The spectrograph, which will cost $2 million to upgrade, will be 50 percent more efficient at detecting light and will use a new and more precise method of measuring redshifts, Schlegel said.

In 1929, astronomer Edwin Hubble found that the redshift of an object pointed to the speed at which an object moved away into space, a discovery that alerted scientists that the universe was expanding.

"What we expected for fully 70 years after that discovery was that, OK, the universe is expanding, but then everything feels the gravity from everything else, the expansion should slow down," Schlegel said. "But in fact, that's not actually what's happening."

Instead, researchers found that the expansion of the universe was accelerating, a discovery due in part to 1998 research on supernova redshifts at the Berkeley lab. To account for this, they postulated the existence of dark energy, an unknown low-density energy that occupies most of the universe and is responsible for its expansion.

"Either there's a mysterious thing called dark energy that fills up three quarters of the universe, or Einstein's theory of relativity is wrong," White said. "And people don't like to bet against Einstein."

BOSS will peer five billion years into the universe, covering more of the sky than any other survey, he added.

"The thing that's exciting about BOSS is that it is as close to a perfect survey as one could do for the local universe," Padmanabhan said. "It makes the best measurement at the time when dark energy is the most relevant."

Tags: LAWRENCE BERKELEY NATIONAL LABORATORY