New results from NASA's Galaxy Evolution Explorer and the Anglo-Australian Telescope atop Siding Spring Mountain in Australia confirm that dark energy is a smooth, uniform force that now dominates over the effects of gravity.
The observations follow from careful measurements of the separations between pairs of galaxies.
Using the Anglo-Australian Telescope, 26 astronomers (from 14 different institutions) contributed to the ‘WiggleZ Dark Energy Survey', which mapped the distribution of galaxies over an unprecedented volume of the Universe.
“This is the first individual galaxy survey to span such a long stretch of cosmic time,” said Michael Drinkwater from the School of Mathematics and Physics (SMP) at The University of Queensland (UQ).
The survey, which covered more than 200,000 galaxies, took four years to complete and aimed to measure the properties of ‘dark energy' -- a concept first cast by Einstein in his Theory of General Relativity.
Dark energy is the name astronomers gave in the late 1990s to an unknown cause of the Universe's accelerating expansion. This mysterious phenomenon, that defies gravity, makes up about 72 percent of the Universe, with the remaining 24 percent constituting dark matter, and 4 percent making up the planets, stars and galaxies that we normally hear about.
“The discovery of acceleration was an enormous shock, because it went against everything we thought we knew about gravity,” co-researcher Dr Tamara Davis from the University of Queensland said. “The problem was, that supernova data couldn't tell us whether dark energy was genuinely there, or whether Einstein's theory of gravity itself was failing."
In a new survey from NASA's Galaxy Evolution Explorer and the Anglo-Australian Telescope atop Siding Spring Mountain in Australia the distances to galaxies were measured using a "standard ruler." This method is based on the preference for pairs of galaxies to be separated by a distance of 490 million light-years today. The separation appears to get smaller as the galaxies move farther away, just like a ruler of fixed length.
WiggleZ used two other kinds of observations to provide an independent check on the supernova results: One measured the pattern of how galaxies are distributed in space and the other measured how quickly clusters of galaxies formed over time.
According to Professor Warrick Couch, Director of the Center for Astrophysics and Supercomputing, confirming the existence of the anti-gravity agent is a significant step forward in understanding the Universe.
“Although the exact physics required to explain dark energy still remains a mystery, knowing that dark energy exists has advanced astronomers' understanding of the origin, evolution and fate of the Universe,” he said.
The WiggleZ observations were possible due to a powerful spectrograph located at the Anglo-Australian Telescope. The spectrograph was able to image 392 galaxies an hour, despite the galaxies being located halfway to the edge of the observable Universe.
The shape-shifting galaxies at top of page have taken on the form of a giant mask. The icy blue eyes are actually the cores of two merging galaxies, called NGC 2207 and IC 2163, and the mask is their spiral arms. The false-color image consists of infrared data from NASA's Spitzer Space Telescope (red) and visible data from NASA's Hubble Space Telescope (blue/green). NGC 2207 and IC 2163 met and began a sort of gravitational tango about 40 million years ago.
The Daily Galaxy via University of Queensland and http://arxiv.org/abs/1105.2862