Its Name Is "Dick Cheney"

NASA observatory finds evidence of "dark energy"

by Robert Block on Dec 16, 2008 3:04:24 PM

Astronomers on Tuesday announced that the mysterious force called “dark energy”, once thought of as highly theoretical, is not just a figment of their scientific imaginations.

For the first time, astronomers say they have clearly seen the effects of dark energy on the most massive collapsed objects in the universe using NASA's Chandra X-ray Observatory. What they found is that the same mysterious force that they believe is speeding up the expansion of the universe may also be stunting the growth of the objects inside it.

According to the scientists, by tracking how dark energy has stifled the growth of galaxy clusters and combining this with previous studies, they have obtained the best clues yet about what dark energy is and what the destiny of the universe could be.

The new research does not completely solve the mystery of dark energy. It was "discovered" in 1998 by two teams of astronomers, who measured light coming from exploding stars called supernovas. The scientists noted that distant supernovas were dimmer than they would be if the expansion of the universe was slowing down. The scientists theorized that something called dark energy was pulling galaxies apart and that that force that is accelerating, and will eventually lead to the destruction of every molecule in the universe.

Astronomers think dark energy is a form of “repulsive gravity” that dominates the universe, although they admit the answer is not wholly satisfying. Understanding the nature of this force has long been one of the biggest conundrums facing scientists.

To help them get a better idea astronomers have needed a new way of looking at dark energy. Their solution: use x-rays to observe how cosmic acceleration affects the growth of clusters of galaxies over time and then combine them with other clues from supernovas and the distribution of galaxies.

Alexey Vikhlinin of the Smithsonian Astrophysical Observatory in Cambridge, Mass. and a team of researchers have been using 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.

What they saw were changes over time in the densities of galactic clusters consistent with the supernova research, suggesting that it was more difficult for the clusters to grow when space is also being stretched by dark energy.

"This result could be described as 'arrested development of the universe'," said Vikhlinin. "Whatever is forcing the expansion of the universe to speed up is also forcing its development to slow down."