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A Map Made in the Heavens

February 18, 2014 - 4:30pm

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An artist's conception of the measurement scale of the universe. Baryon acoustic oscillations are the tendency of galaxies and other matter to cluster in spheres, which originated as density waves traveling through the plasma of the early universe. The clustering is greatly exaggerated in this illustration. The radius of the spheres (white line) is the scale of a "standard ruler" allowing astronomers to determine, within one percent accuracy, the large-scale structure of the universe and how it has evolved. | Image courtesy of Zosia Rostomian, Lawrence Berkeley National Laboratory.

An artist's conception of the measurement scale of the universe. Baryon acoustic oscillations are the tendency of galaxies and other matter to cluster in spheres, which originated as density waves traveling through the plasma of the early universe. The clustering is greatly exaggerated in this illustration. The radius of the spheres (white line) is the scale of a "standard ruler" allowing astronomers to determine, within one percent accuracy, the large-scale structure of the universe and how it has evolved. | Image courtesy of Zosia Rostomian, Lawrence Berkeley National Laboratory.

A team of researchers at the Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) recently mapped galaxies in clear -- or telescopic -- sight to better understand the universe and the wonders within.

David Schlegel, a physicist at Berkeley Lab, led that team of scientists -- the members of a sky-gazing collaboration known as the Baryon Oscillation Spectroscopic Survey (BOSS). Earlier this month, BOSS scientists announced that they had mapped the locations of 1.2 million galaxies and thereby measured the scale of the universe to an unprecedented accuracy of 1 percent.

That's impressive precision, since some of those galaxies were more than 6 billion light years away, and light travels 186,282 miles each second in vacuum. To get a sense of the survey's accuracy, try putting your hands apart to estimate the distance of one foot. You'd have to be off by just one-tenth of an inch (0.12 inches to be precise) to even approach BOSS's precision. To achieve that incredible -- and unprecedented -- result, researchers used high-precision observations made by the Sloan Foundation Telescope at the Apache Point Observatory coupled with the incredible number-crunching power of the supercomputing resources at Berkeley Lab's National Energy Research Scientific Computing Center.

That still begs the question of why BOSS scientists would want such a precise map, especially since they're not likely to travel to any of the galaxies they plotted anytime soon. BOSS scientists mapped -- and are still mapping -- the universe to understand it better. For instance, their findings show that the universe is almost completely flat, rather than being curved in some way. That has implications for what it may look like one day.

More important -- and this goes to one of the primary purposes of the BOSS survey -- the new map also offers more light on dark energy. Dark energy has effects akin to those experienced by many who have broken their new year's resolutions: They expected (or at least hoped) to find themselves shrinking, but instead have found themselves expanding.

For a long time, scientists expected that the expansion of space that started at the beginning of the universe (the Big Bang) would eventually be slowed down by the pull of gravity. Instead, two teams of scientists, one led by Berkeley Lab's Saul Perlmutter, discovered that the expansion of the universe was actually accelerating … and at an ever-increasing rate.

That's led to more than a bit of head-scratching. Scientists still don't understand what dark energy is -- it remains one of the great questions of physics -- but the BOSS survey gives them a better sense of what it is doing and not doing. That, in turn, allows researchers to improve their models, to cross out some ideas and perhaps pencil in a few others.

Such is the process of science, and of map-making. There's always one more destination to point to, one more wonder to explore. 

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