A research team used NASA's orbiting Chandra X-Ray Observatory to study 26 clusters of galaxies at distances between one billion and 10 billion light years from Earth. It found new support for the existence of "dark energy," a mysterious force that may be pushing the universe apart.
Study leader Steven Allen of the University of Cambridge told a NASA briefing yesterday that the dark energy appears to behave much like what Einstein dubbed the "cosmological constant," a fudge factor he included in his general theory of relativity in 1917 as a sort of antigravity to keep the universe from collapsing under its own weight.
Later, after astronomers found the universe to be expanding, Einstein called the cosmological constant his greatest blunder. But theorists have been taking a new look at it since 1998, when astronomers found evidence of a repulsive counterpart to gravity in studies of distant exploding stars called supernovae. Researchers also have found evidence for dark energy in close scrutiny of the microwave background radiation left over from the very early universe, reports newsday.com
According to sciam.com new x-ray observations seem to have sealed the case of the universe’s elusive dark energy. Yesterday NASA announced results from the Chandra telescope that offer independent confirmation that three-quarters of the universe is made up of dark energy. "Dark energy is perhaps the biggest mystery in physics," says team leader Steve Allen of the University of Cambridge in England. "As such, it is extremely important to make an independent test of its existence and properties."
Dark energy was first proposed six years ago when observations of distant supernova explosions hinted that the expansion of the universe is accelerating, rather than slowing down as expected. Data from the Wilkinson Microwave Anisotropy Probe (WMAP) on the cosmic microwave background radiation also supported the existence of this unseen force. In the new work, an international team of astronomers used the Chandra X-ray Observatory to study 26 galaxy clusters located between one billion and eight billion light-years away.
Other astronomers hailed the X-ray cluster method as a potential complement to other ways of investigating dark energy but said they would withhold judgment about this particular calculation until they could study the details. Most of the previous studies, including those that led to the discovery of dark energy, used exploding stars known as Type 1a supernovas as cosmic distance markers.
Dr. Adam Riess of the Space Telescope Science Institute in Baltimore, an original discoverer of dark energy, hailed the work as another sign of the new age of "precision cosmology."
Dr. Riess said in an e-mail message: "Cosmologists are all from Missouri, the Show-Me State. It appears that X-ray clusters have been added as a new tool in our surveyor's tool kit. All tests point to a strange form of gravity we call dark energy. Some love it, some hate it; it appears we have to deal with it," inform nytimes.com