December 16, 2008

NASA: Dark energy stifles universe growth

U.S. astronomers say they have, for the first time, clearly observed the effects of dark energy on the most massive collapsed objects in the universe.

National Aeronautics and Space Administration astronomers using the agency's Chandra X-ray Observatory tracked how dark energy has stifled the growth of galaxy clusters. Combining that information with previous studies, scientists say they have obtained the best clues yet about what dark energy is and what the destiny of the universe might be.

NASA said the study strengthens the evidence that dark energy is the cosmological constant. Although it is the leading candidate to explain dark energy, theoretical work suggests it should be about 10 raised to the power of 120 times larger than observed, space agency scientists said. Therefore, alternatives to general relativity, such as theories involving hidden dimensions, are being explored.

This result could be described as 'arrested development of the universe', said Alexey Vikhlinin of the Smithsonian Astrophysical Observatory, who led the research. Whatever is forcing the expansion of the universe to speed up is also forcing its development to slow down.

Added William Forman, a co-author of the study, For years, scientists have wanted to start testing how gravity works on large scales and now, we finally have.

The work will be published in two separate papers in the Feb. 10 issue of The Astrophysical Journal.