A PhD student has worked out the most accurate measurements ever, of how fast the universe is expanding.

Florian Beutler, a PhD candidate at The International Centre for Radio Astronomy Research (ICRAR) at The University of Western Australia has calculated the speed of the universe's expansion 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," Beutler said in a news release.

The 6df Galaxy Survey data, each dot is a galaxy and Earth is at the centre of the sphere. Created by Chris Fluke, Centre for Astrophysics & Supercomputing, Swinburne University

The universe is restlessly expanding. As the universe grows, it carries galaxies away from our own Milky Way. The Hubble constant links how fast galaxies are moving with how far they are from Earth.

Through analyzing light coming from a distant galaxy, the speed and direction of the galaxy can be easily measured, while it is much more difficult to determine the galaxy's distance from Earth. Up until now, calculation of their distance was conducted through observing the brightness of individual objects within the galaxy and using our knowledge about the object.

While well-established, this method was prone to errors.

Beutler's new approach used an entirely different method to tackle the task.

His work uses data from the biggest survey to date of over 125,000 neighbor galaxies, conducted by the UK Schmidt Telescope in eastern Australia.

Because Galaxies are clustered rather than evenly distributed through space, a measurement targeted at the clustering galaxies allowed Beutler to come up with the Hubble constant with an uncertainty of less than 5 per cent.

"This way of determining the Hubble constant is as direct and precise as other methods, and provides an independent verification of them," said Professor Matthew Colless, Director of the Australian Astronomical Observatory and one of Mr Beutler's co-authors. "The new measurement agrees well with previous ones, and provides a strong check on previous work."

The new measurement of the Hubble constant is 67.0 ± 3.2 km s-1 Mpc-1, according to the study.

Beutler's study was published in the Monthly Notices of the Royal Astronomical Society Journal, 25 July 2011.

Australia