New measurement of Universe taken

By AAP and AG staff 28 July 2011
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An Australian scientist has made the most accurate measurement yet of how fast the Universe is expanding.

ONE OF THE MOST accurate measurements ever made of how fast the universe is expanding comes from a student at the University of Western Australia.

Florian Beutler, a doctoral candidate with The International Centre for Radio Astronomy Research (ICRAR) at the Perth-based university, made the calculation by measuring the Hubble constant.

“The Hubble constant is a key number in astronomy because it’s used to calculate the size and age of the universe,” Florian says. As the universe swells, it carries other galaxies away from ours, and the Hubble constant links how fast galaxies are moving with how far they are away from us.

By analysing light coming from a distant galaxy, scientists can easily measure the speed and direction of that galaxy, he says. But determining the galaxy’s distance from Earth is much more difficult. This is usually done by observing the brightness of individual objects within a galaxy, then calculating how far away the galaxy must be – but that system is prone to errors.

Completly new method

To make the breakthrough, the University of WA researcher tackled the problem using a completely different method. Published on Wednesday in the Monthly Notices of the Royal Astronomical Society, Florian’s work draws on data from a survey of more than 125,000 galaxies carried out with the UK Schmidt Telescope in eastern Australia. Called the 6dF Galaxy Survey, it is the biggest survey to date of relatively nearby galaxies, covering almost half the sky.

Using a measurement of the clustering of the galaxies surveyed, plus other information derived from observations of the early universe, Florian has measured the Hubble constant with an certainty of more than 95 per cent.

“This way of determining the Hubble constant is as direct and precise as other methods, and provides an independent verification of them,” says Professor Matthew Colless, director of the Australian Astronomical Observatory in NSW and one of Florian’s co-authors. “The new measurement agrees well with previous ones, and provides a strong check on previous work,” he adds.

Professor Lister Staveley-Smith, ICRAR’s deputy director of science, says that large surveys like the one used for Florian’s work, generate numerous scientific outcomes for astronomers around the world.