Far out: The galaxy map produced by the 2dFGRS. Each dot represents a galaxy; our own galaxy lies at the centre of the two wedge-shaped regions. The colour coding indicates how tightly the galaxies are clustered, with red denoting the most highly clustered regions.
Credit: Paul Bourke/University of Western Australia
SYDNEY: A ten-year star survey that found hundreds of thousands of galaxies has seen the project's Australian and British leaders lauded by a U.K. space conference.
Their research led to a number of discoveries, including the first accurate calculation of the ratio of dark matter to 'normal' matter in the universe.
Other key results included confirmation that the universe does not have enough matter for its gravity to rein in its continuing expansion, and that today's galaxies grew from tiny quantum density fluctuations in the early universe.
The team, led by Anglo-Australian Observatory (AAO) ex-director Matthew Colless and John Peacock from the University of Edinburgh, Scotland, were awarded the British Royal Astronomical Society's Group Achievement Award at its national meeting last week in Belfast, Ireland.
The 33-member international team, which included seven Australians, were awarded for the 2-degree Field Galaxy Redshift Survey (2dFGRS), a project that used the Anglo-Australian Telescope to map the distribution of galaxies in the universe.
The survey, which finished in 2002, was almost ten times larger than previous surveys, and mapped more than 220,000 galaxies.
Galactic to subatomic
The project used robotic equipment to accurately place 400 optical fibres on the 3.9-metre telescope's focal plane, so that each fibre received the light from one galaxy. Focussing on two wedge-shaped patches of sky, the researchers measured patterns in the distribution of the galaxies at different scales.
Colless says it was the scale of the 2dFGRS project that made it groundbreaking. "For the first time we were able to map the positions of a huge number of galaxies and see the subtle effects that reveal the different types of matter in the universe."
The results also allowed astronomers to pin down the tightest constraint on the mass of the neutrino, a tiny, chargeless particle created by radioactive decay that beams through space at close to the speed of light. The results of the survey were made publicly available on the web.
Foam on a beer glass
Larger-scale wide field sky surveys are now being undertaken and more are planned, including a survey using Japan's 8.2-metre Subaru telescope in Hawaii. The AAO is also involved in design of the Wide-field Fiber Multi-Object Spectrograph, which will carry 4000 optical fibres.
Astrophysicist John Dickey of the University of Tasmania said the 2dFGRS was a "very big deal" for Australian astronomy - the most ambitious and largest reaching survey of its kind when it began. Wide field sky surveys such as the these greatly increase the speed at which we can map the universe, allowing astronomers to study its large-scale structures, he said.
"We look at the spectra of galaxies to determine how far away they are and their chemical composition. Clustering and velocities of galaxies can shed light onto how much dark matter is in one place versus another."
Stars dwell in galaxies, which in turn are grouped into larger-scale structures called clusters. Clusters group into what astronomers used to call super clusters, but Dickey describes as being a bit like the foam on the side of a beer glass. The clusters are scattered on curvy walls interspersed by voids which are like bubbles in the foam, he said.
"We think these kinds of structures were implanted early in the universe when the stuff that makes galaxies collected in dark matter wells," Dickey added.
