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Australian astronomers cast doubt on understanding of galaxy: 11-year study

Xinhua, September 25, 2015 Adjust font size:

Australian astronomers have potentially cast doubt on the world's understanding of galaxy formation and black holes following an 11-year search for gravitational waves proposed in Einstein's theory of relativity 100 years ago.

According to the result of the study, published in the journal Science on Friday, Australian researchers pushed the Parkes radio telescope in New South Wales to its limit to detect a background " rumble" of the waves coming from the merging of galaxies throughout the universe, however they weren't detected.

"It seems to be all quiet on the cosmic front," lead researcher Dr Ryan Shannon from Australia's scientific body CSIRO said.

"By pushing our telescopes to the limits required for this sort of cosmic search we're moving into new frontiers in all areas of physics, forcing ourselves to understand how galaxies and black holes work."

Galaxies grow by merging and every large one is thought to have a supermassive black hole at its heart, drawing black holes together to form an orbiting pair when two galaxies unite.

Einstein's theory of relativity is then expected to take hold, with the pair predicted to succumb to a death spiral, sending ripples known as gravitational waves through space-time, the very fabric of the universe.

Although Einstein's general theory of relativity has withstood every test thrown at it by scientists, directly detecting gravitational waves remain the one missing piece of the puzzle.

The astronomers investigated the highly regular signals of " millisecond pulsars" - that act like clocks in space - over an 11- year period to reveal the gravitational waves which change the time that the pulsar's signals arrive on earth.

It is believed a gravitational wave passing between the Earth and a millisecond pulsar squeezes and stretches space, changing the distance between each signal by about 10 meters, changing the time the pulsar's signals arrive on earth.

The scientists said there could be a number of reasons why they weren't detected, suspecting it's because black holes merge very fast, spending little time spiraling together and generating gravitational waves.

The failure to detect gravitational waves through pulsar timing has no implication on new research looking for higher-frequency gravitational waves generated by other sources, such as the merging of neutron stars. Endi