Scale of Universe Measured to 1 Percent Accuracy

Using the most precise ruler yet, researchers have succeeded in measuring astronomical distances within 1 percent accuracy. 

Called the Baryon Oscillation Spectroscopic Survey (BOSS), the program that carried out the study used the Sloan Foundation Telescope in New Mexico starting in 2009 to record spectra of more than 1 million galaxies with redshifts, indicating they are moving away from us.

"One-percent accuracy in the scale of the universe is the most precise such measurement ever made," said David Schlegel, a member of the Physics Division of the US Department of Energy's Lawrence Berkeley National Laboratory.

"Twenty years ago astronomers were arguing about estimates that differed by up to fifty percent," he said. "Five years ago, we'd refined that uncertainty to five percent; a year ago it was two percent. One-percent accuracy will be the standard for a long time to come."

In all, the researchers estimate their observations peered back as far in time as 6 billion years.

"We believe the BOSS database includes more redshifts of galaxies than collected by all the other telescopes in the world," Schlegel, BOSS's principal investigator, said.

The analysis includes more than 8,500 square degrees of the sky visible from the northern hemisphere, making it the largest sample of the universe ever surveyed to this degree of density. Once complete, the program will include spectra from 1.3 million galaxies along with thousands of other space objects, altogether covering 10,000 square degrees.

The results so far, published in the Monthly Notices of the Royal Astronomical Society, "are consistent with an infinite universe," Schlegel said.

Central to the study was a phenomenon known as baryon acoustic oscillations (BAO), or occasional ripples in the distribution of galaxies. 

"It's from fluctuations in the density of galaxies in the volume we're looking at that we extract the BAO standard ruler," Beth Reid, a BOSS collaborator from Berkeley Lab said.

Using this ruler, the researchers say they can now measure the distance between space objects with unprecedented detail. 

"There are not many things in our daily life that we know to 1-percent accuracy," Schlegel said. "I now know the size of the universe better than I know the size of my house."