Student measures expansion of universe

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PERTH, Australia, July 26 (UPI) -- A university student in Australia has produced one of the most accurate measurements ever of how fast the universe is expanding, astronomers say.

Florian Beutler, a doctoral candidate at the University of West Australia's International Center for Radio Astronomy Research in Perth, has calculated how fast the universe is growing by measuring the so-called Hubble constant, an ICRAR release said Tuesday.

"The Hubble constant is a key number in astronomy because it's used to calculate the size and age of the universe," Beutler said.

As the universe expands, it carries other galaxies away from ours, and the Hubble constant links how fast galaxies are moving with how far they are from us.

By analyzing light coming from a distant galaxy, the speed and direction of that galaxy can be easily measured, and by observing the brightness of individual objects within the galaxy astronomers can calculate how far away the galaxy must be.

However, this method of determining a galaxy's distance from Earth is prone to systematic errors, astronomers said.

Beutler analyzed more than 125,000 galaxies in the biggest survey to date of relatively nearby galaxies, covering almost half the sky.

Galaxies are not spread evenly through space, but are clustered, and by measuring the clustering of the galaxies surveyed, plus other information derived from observations of the early universe, Beutler has measured the Hubble constant with an uncertainly of less than 5 percent.

"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 Beutler's co-authors. "The new measurement agrees well with previous ones, and provides a strong check on previous work."