Dark Energy Is Real, Galaxy Survey Shows

Sydney, Australia-(ENEWSPF)- A survey of more than 200,000 galaxies made with the Anglo-Australian Telescope in eastern Australia has shown that “dark energy” is real and not a mistake in Einstein’s conception of gravity.

The result is conveyed in two papers written by Dr. Chris Blake (Swinburne University of Technology, Melbourne, Australia) and colleagues, which have been accepted for publication in Monthly Notices of the Royal Astronomical Society.

The galaxy survey, called WiggleZ (“wiggles”), was set up to measure the properties of “dark energy”, a concept invoked in the late 1990s to explain why the Universe seems to be expanding at an accelerating rate.

To account for the acceleration, astronomers had to either rewrite Einstein’s theory of gravity or accept that the Universe is filled with a new kind of energy.

“Our new work shows dark energy is real,” said Dr. Blake. “Einstein remains untoppled.”

Dark energy was originally discovered by studying the brightness of distant supernovae — exploding stars.

The WiggleZ project has used two other kinds of observations that provide an independent check on the supernovae results. One kind involves measuring a pattern in how galaxies are distributed in space (“baryon acoustic oscillations”), and the other, measuring how quickly clusters of galaxies have formed over time. [For details, see Notes for Editors, below.]

Both tests have confirmed the reality of dark energy.

WiggleZ is one of several baryon acoustic oscillations experiments planned or in progress, and is the first one at high redshift to bear significant fruit.

The survey mapped the distribution of galaxies in an unprecedented volume of the Universe, looking eight billion years back in time — more than half the age of the Universe.

“This is the first individual galaxy survey to span such a long stretch of cosmic time,” said Professor Michael Drinkwater (University of Queensland), one of the survey’s leaders. “We’ve broken new ground.”

Professor Matthew Colless is Director of the Australian Astronomical Observatory, which operates the Anglo-Australian Telescope, and a member of the WiggleZ team. “WiggleZ has been a success because we have an instrument attached to the telescope, a spectrograph, that is one of the best in the world for large galaxy surveys of this kind,” he said.

The survey, which began in 2006 and finished this year, was led by Professor Warrick Couch of Swinburne University of Technology in Melbourne and Professor Michael Drinkwater of the University of Queensland. Dr. Chris Blake has led the analysis of the survey results.

The Australian Astronomical Observatory is Australia’s national optical observatory, and is part of the Commonwealth Department of Innovation, Industry, Science and Research. It operates the 3.9-m Anglo-Australian Telescope and the 1.2-m UK Schmidt Telescope at Siding Spring Observatory in New South Wales, Australia.

References

“The WiggleZ Dark Energy Survey: testing the cosmological model with baryon acoustic oscillations at z = 0.6.” Chris Blake, Tamara Davis, Gregory B. Poole et al. [26 authors]. Monthly Notices of the Royal Astronomical Society, in press. Online at http://arxiv.org/abs/1105.2862

“The WiggleZ Dark Energy Survey: the growth rate of cosmic structure since redshift z = 0.9.” Chris Blake, Sarah Brough, Matthew Colless et al. [25 authors]. Monthly Notices of the Royal Astronomical Society, in press. Online at http://arxiv.org/abs/1104.2948