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Searching for super-dense neutron stars

Researchers are using Raijin to perform the deepest ever search of our galaxy for neutron stars. The discoveries will help test Einstein’s theory of general relativity.

Artist's impression of a radio pulsar. Credit: Swinburne Astronomy Productions

Artist’s impression of a radio pulsar. Credit: Swinburne Astronomy Productions

“It’s not possible to test Einstein’s general theory of relativity easily in our solar system because our stars are just not heavy enough to sufficiently bend space–time,” explains Swinburne University of Technology’s Australian Laureate Fellow and “Dynamic Universe” theme leader of the ARC Centre of Excellence for All-Sky Astrophysics, Professor Matthew Bailes.

“We are searching for neutron stars, which have a gravitational field about two hundred billion times stronger than Earth’s, and which will enable us to test aspects of general relativity much more easily than we can here in the laboratory.”

Neutron stars are the super-dense collapsed cores of once-massive stars some 10 times bigger than our sun.

“The density of neutron stars is typically one billion tonnes per cubic centimetre,” says Professor Bailes.

“They are also highly magnetised and spin very rapidly. That combination leads to emission of a beam that sweeps through the galaxy and impacts our telescope after travelling up to thousands of years.”

Neutron stars display a very characteristic signal, says Professor Bailes.

“When a neutron star pulse hits out telescope it first appears in the high frequency radio stations and then it sort of sweeps down to the lower frequency radio stations afterwards.

“We use Raijin to search for these characteristic delays between our 1,024 regularly-spaced radio stations to find our neutron stars.”

So far, the project, which is a collaboration with CSIRO, the Max Planck Institute, the University of Cagliari and Manchester University, has led to the discovery of more than 50 neutron stars.

The undertaking is highly compute-intensive, says Professor Bailes.

“Our dataset is around half a petabyte in size,” he says.

“We’re looking at 16 million consecutive time samples, and we need Raijin’s large memory and processing power to search that data for all the potential neutron stars.”

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