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Supermassive black holes: every large galaxy’s got one but how did they grow so big?

Black holes that collide generate gravitational waves. New data about the effect of these waves on surrounding spinning stars called pulsars has challenged existing ideas about the growth of supermassive black holes.

A paper published in Science today led by University of Melbourne and CSIRO scientists shows a new limit to the strength of gravitational waves.  

Mr Vikram Ravi, a PhD candidate at the School of Physics, University of Melbourne and Dr Ryan Shannon, a Postdoctoral Fellow with CSIRO jointly led the study at the CSIRO Parkes radio telescope in eastern Australia.

“For the first time, we’ve used information about gravitational waves as a tool in astrophysics,” said Dr Shannon. “It’s a powerful new tool. These black holes are very hard to observe directly, so this is a new chapter in astronomy.”

 “One existing model for black-hole growth has failed our test and we’re painting the others into a corner. They may not break, but they’ll have to bend,” said Mr Ravi.
Gravitational waves are ripples in spacetime, which produce tiny changes in the distances between objects in space so with current instruments they are difficult to observe.

“But we can measure the effect they have on pulsars because they are like accurate ticking clocks in space in that they generate regular pulses of radiation,” said Mr Ravi.

“We are very excited about these findings, it give us a better understanding of the universe”, said Mr Ravi   

Scientists can measure the regular pulses on Earth to within a tenth of a microsecond and are able to determine upper limits to the effects of gravitational waves.

The Parkes Pulsar Timing Array project includes an esteemed group of national and international astronomers. The international consortium is planning to combine the Parkes pulsar-timing data with data from other telescopes in Europe and the USA move towards directly detecting gravitational waves.

Multi media link to studying pulsars and black hole evolution