News in Science

Astronomers get double pulsar's measure

A new software package developed by an Australian PhD student has helped astronomers calculate the exact distance to a bizarre double pulsar.

As well as providing a major advance in the way scientists measure the positions of distant objects in space, it may also help astronomers put Einstein's general theory of relativity to the ultimate test.

The findings are published in today's issue of the journal Science.

Dr Adam Deller, who recently completed his PhD at Swinburne University in Melbourne, says it is very difficult to measure distances in space using existing telescopes and processing hardware.

Deller's software boosts the sensitivity of a telescope network by correlating signals from multiple telescopes spaced thousands of kilometres apart.

The technique, known as very long baseline interferometry (VLBI), produces an image that has the same resolution as that of a telescope as large as the maximum distance between each telescope in the network.

Deller and colleagues used the software to examine a double pulsar, named J0737-3039A/B.

Unique system

Discovered in 2003, the pulsars are only 800,000 kilometres apart and orbit each other every two and a half hours at a speed of 300 kilometres per second. Despite being only 20 kilometres wide, they each weigh more than the sun.

The team used Dellar's software to collect data from six Australian radio telescopes and analysed it using supercomputers at Swinburne University.

"When you combine signals from each telescope, you get very high resolution images of the object," says Dellar.

Their observations showed that the pulsars are 1150 parsecs, or 35.5 quadrillion kilometres, from earth - more than twice the distance previously estimated.

Testing Einstein

Director of Swinburne's Centre for Astrophysics and Supercomputing, and co-author, Professor Matthew Bailes says that by knowing the exact distance of the pulsars from earth, it will enable the astronomers to gather additional data to test Einstein's theory.

"We can now say with confidence that before 2015, when Einstein's theory will be 100 years old, we'll know how well it stands up to experiment," he says.

"It will now be straight forward to use Parkes [radio telescope] to test Einstein's General Theory of Relativity and in particular the study of gravitational waves."

Bigger applications

Speaking from New Mexico, where he is working with colleagues at the Very Long Baseline Array, Deller says the program will be used in other VLBI experiments around the world.

"It certainly will make life a lot easier for scientists trying to measure the distances between earth and objects, both inside and outside the galaxy," he says.

Curtin University radio astronomer, and co-author, Professor Steven Tingay says the new software could play a role in the proposed Square Kilometre Array (SKA) to be built next decade in either Western Australia or South Africa.

The SKA will consist of hundreds of dishes spread across the country to simulate a dish the size of Australia.

"Adam's achievement is pioneering work," says Tingay. "It is a precursor to the types of things we plan to do with SKA."

"We used six antennas in this experiment; SKA will consist of thousands of antennas."