|The new study provides confirmation of both the existence of |
dark energy and its rate of expansion. (NASA/JPL-Caltech)
The paper to be published in the Monthly Notices of the Royal Astronomical Society, has been put together by a team of 26 scientists, including Dr Chris Blake from Melbourne's Swinburne University, and provides the first independent confirmation of both the existence of dark energy and its rate of expansion.
"It shows physicist Albert Einstein was right," says Dr Blake.
"Dark energy is a smooth cosmological constant throughout the universe, rather than a change in the laws of gravity."
A hundred years ago scientists believed the universe was steady and unchanging. Einstein invented the cosmological constant to expand the fabric of space-time after his own equations for general relativity wouldn't allow for the cosmos to remain static as expected in a steady state universe.
Soon afterwards, astronomer Edwin Hubble discovered the universe was actually expanding, consistent with Einstein's original general relativity theory.
Einstein then removed his cosmological constant, describing his failure to predict an expanding universe in theory before it was proven by observation, as his biggest blunder.
In 1998, astronomers studying distant exploding stars called a Type 1A supernovae discovered not only was the universe expanding, but the rate of expansion was accelerating due to some type of unknown force or dark energy. Einstein's cosmological constant was back.
"The acceleration was a shocking discovery, because it showed we have a lot more to learn about physics," Dr Blake says.
To verify the supernovae findings, Dr Blake and colleagues spent four years using a powerful spectrograph at the Australian Astronomical Observatory to collect data on more than 240,000 galaxies going back over seven billion years to when the cosmos was less than half its current age.
"It showed the growth of structure in the universe, the development of galaxy clusters and super clusters has slowed down," Dr Blake says.
"This implies the most distant parts of the universe, which are further back in space-time, have ordinary matter and hence gravity is dominating. But today this antigravity dark energy has taken hold."
The researchers then looked at the distances between pairs of galaxies.
"The average distance between galaxy pairs is about 500,000,000 light years," says Dr Blake.
"Galaxies tend to grow on compression waves called baryon acoustic oscillations, which spread through the universe. They can be detected as ripples in cosmic microwave background radiation."
According to Dr Blake, "the average distance between these galaxy pairs has also been found to have grown because of the expansion of space-time, and that's further confirmation of an antigravity agent."
But, Dr Blake admits that is as much as they currently know.
"Although the exact physics required to explain dark energy still remains a mystery, confirming it exists is a significant step in understanding the origin, evolution and fate of the universe."