Baryon Oscillation Spectroscopic Survey measures the universe to one-percent accuracy

This is an artist's concept of the new measurement of the size of the Universe. 

The gray spheres show the pattern of the "baryon acoustic oscillations (BAO)" from the early Universe. 

Galaxies today have a slight tendency to align on the spheres -- the alignment is greatly exaggerated in this illustration. 

By comparing the size of the spheres (white line) to the predicted value, astronomers can determine to one-percent accuracy how far away the galaxies are. 

Credit: Zosia Rostomian, Lawrence Berkeley National Laboratory

Today the Baryon Oscillation Spectroscopic Survey (BOSS) Collaboration announced that BOSS has measured the scale of the universe to an accuracy of one percent.

This and future measures at this precision are the key to determining the nature of dark energy.

David Schlegel

"One-percent accuracy in the scale of the universe is the most precise such measurement ever made," says BOSS's principal investigator, David Schlegel, a member of the Physics Division of the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab).

"Twenty years ago astronomers were arguing about estimates that differed by up to fifty percent. 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."

BOSS is the largest program in the third Sloan Digital Sky Survey (SDSS-III). Since 2009, BOSS has used the Sloan Foundation Telescope at the Apache Point Observatory in New Mexico to record high-precision spectra of well over a million galaxies with redshifts from 0.2 to 0.7, looking back over six billion years into the universe's past.

Schlegel says, "We believe the BOSS database includes more redshifts of galaxies than collected by all the other telescopes in the world."

Martin White

BOSS will continue gathering data until June, 2014. However, says Martin White, a member of Berkeley Lab, a professor of physics and astronomy at the University of California at Berkeley, and chair of the BOSS science survey team, "We've done the analysis now because we have 90 percent of BOSS's final data and we're tremendously excited by the results."

Baryon acoustic oscillations (BAO) are the regular clustering of galaxies, whose scale provides a "standard ruler" to measure the evolution of the universe's structure.

Accurate measurement dramatically sharpens our knowledge of fundamental cosmological properties, including how dark energy accelerates the expansion of the universe.

More Information: The BOSS analysis is based on SDSS-III's Data Releases 10 and 11 (DR 10 and DR 11) and has been submitted for publication in the Monthly Notices of the Royal Astronomical Society; the analysis is available online at arxiv.org/abs/1312.4877.