May 19, 2011

Dark Energy Drives The Universe Apart

According to NASA, dark energy is driving our universe apart at an accelerated rate.

Scientists performed a five-year survey of 200,000 galaxies to help add more evidence to the favored theory of how dark energy works.  This theory says dark energy works as a constant force, uniformly affecting the universe and propelling its runaway expansion. 

"The action of dark energy is as if you threw a ball up in the air, and it kept speeding upward into the sky faster and faster," Chris Blake, of the Swinburne University of Technology in Melbourne, Australia, said in a statement.

NASA said dark energy is thought to dominate our universe, making up about 74 percent of it. 

"The results tell us that dark energy is a cosmological constant, as Einstein proposed. If gravity were the culprit, then we wouldn't be seeing these constant effects of dark energy throughout time."

Astronomers began their study by assembling the largest three-dimensional map of galaxies in the distant universe, spotted by the Galaxy Evolution Explorer.

"The Galaxy Evolution Explorer helped identify bright, young galaxies, which are ideal for this type of study," Christopher Martin, principal investigator for the mission at the California Institute of Technology in Pasadena, said in a statement. "It provided the scaffolding for this enormous 3-D map."

The team acquired detailed information about the light for each galaxy by using the Anglo-Australian Telescope, studying the pattern of distance between them.

NASA said sound waves from the very early universe left imprints in the patterns of galaxies, causing pairs of galaxies to be separate by about 500 million light-years.

The team used this "standard ruler" to determine the distance from the galaxy pairs to Earth.  This distance data was combined with information about the speeds the pairs are moving away from us, revealing the fabric of space is stretching apart faster and faster.

The scientists also used the galaxy map to study how clusters of galaxies grow over time like cities.  The clusters attract new galaxies through gravity, but dark energy tugs the clusters apart

"Observations by astronomers over the last 15 years have produced one of the most startling discoveries in physical science; the expansion of the universe, triggered by the big bang, is speeding up," Jon Morse, astrophysics division director at NASA Headquarters in Washington, said in a statement.

"Using entirely independent methods, data from the Galaxy Evolution Explorer have helped increase our confidence in the existence of dark energy."

Two papers describing the results appeared in recent issues of the Monthly Notices of the Royal Astronomical Society.


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