Best evidence yet for existence of dark energy in the Universe

December 17th, 2008 - 12:49 pm ICT by ANI  

Washington, Dec 17 (ANI): A team of astronomers, using NASA’’s Chandra X-ray Observatory, has obtained the best clues yet about the existence of dark energy in the Universe.
Scientists think dark energy is a form of repulsive gravity that now dominates the universe, although they have no clear picture of what it actually is.
By tracking how dark energy has stifled the growth of galaxy clusters and combining this with previous studies, scientists have obtained the best clues yet about what dark energy is and what the destiny of the universe could be.
These new X-ray results provide a crucial independent test of dark energy, long sought by scientists, which depends on how gravity competes with accelerated expansion in the growth of cosmic structures.
“This result could be described as ”arrested development of the universe”,” said Alexey Vikhlinin of the Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, who led the research. “Whatever is forcing the expansion of the universe to speed up is also forcing its development to slow down,” he added.
Vikhlinin and his colleagues used Chandra to observe the hot gas in dozens of galaxy clusters, which are the largest collapsed objects in the universe.
Some of these clusters are relatively close and others are more than halfway across the universe.
The results show the increase in mass of the galaxy clusters over time aligns with a universe dominated by dark energy. It is more difficult for objects like galaxy clusters to grow when space is stretched, as caused by dark energy.
Vikhlinin and his team see this effect clearly in their data.
The results are remarkably consistent with those from the distance measurements, revealing general relativity applies, as expected, on large scales.
“For years, scientists have wanted to start testing how gravity works on large scales and now, we finally have,” said William Forman, a co-author of the study from the Smithsonian Astrophysical Observatory.
When combined with other clues, this new X-ray result gives scientists the best insight to date on the properties of dark energy.
“Putting all of this data together gives us the strongest evidence yet that dark energy is the cosmological constant, or in other words, that ”nothing weighs something”,” said Vikhlinin.
These results have consequences for predicting the ultimate fate of the universe.
If dark energy is explained by the cosmological constant, the expansion of the universe will continue to accelerate, and the Milky Way and its neighbor galaxy, Andromeda, never will merge with the Virgo cluster.
In that case, about a hundred billion years from now, all other galaxies ultimately would disappear from the Milky Way’’s view and, eventually, the local superclusters of galaxies also would disintegrate. (ANI)

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