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Black hole boffins close in on gravity waves

Peering at pulsars produces promising pulling premise

CSIRO Parkes radio telescope

While the world looks for ways to directly observe gravity waves, boffins at Australia's Commonwealth Scientific and Industrial Research Organisation (CSIRO) say they've used information about the Einsteinian prediction to examine huge black holes in space.

In what they call a “new chapter in astronomy”, post-doctoral CSIRO fellow Dr Ryan Shannon and PhD student Vikram Ravi believe they've worked out the likely – and low – rate of background gravitational waves in the universe.

They've done this by examining data from the Parkes radio-telescope's PPTA (Parkes Pulsar Timing Array) project which, along with a previous CSIRO-Swinburne University collaboration provides 20 years' worth of pulsar timing data.

The timing of pulsar signals is extremely precise, the researchers say, but as a gravitational wave passes the pulsar's region, it would swell or shrink distances in that region, changing the timing of the pulse from Earth's point of view.

“The strength of the gravitational wave background depends on how often supermassive black holes spiral together and merge, how massive they are, and how far away they are. So if the background is low, that puts a limit on one or more of those factors,” CSIRO says in its media release.

As a result, the group believes one model used to explain supermassive black holes, galactic merger, should be discarded because it doesn't explain enough of the mass of black holes. The timing data will next be used to test other models of supermassive black hole growth.

Project leader, CSIRO's Dr George Hobbs, believes the timing data will one day allow direct detection of gravitational waves. “We haven't yet detected gravitational waves outright, but we're now into the right ballpark to do so,” he says.

He explained that combining pulsar-timing data from Parkes with that from other telescopes in Europe and the USA — a total of about 50 pulsars — should provide enough accuracy to detect gravitational waves “within ten years”.

The CSIRO video below illustrates spinning black holes generating gravitational waves. ®

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