Gravitational Waves Unveil New Insight into Black Hole Weight Gain

In a new study, scientists used gravitational wave data to access new information regarding the growth of supermassive black holes, the centerpiece of every galaxy.

"This is the first time we've been able to use information about gravitational waves to study another aspect of the universe -- the growth of massive black holes," co-author Ramesh Bhat, a researcher from the Curtin University node of the International Center for Radio Astronomy Research (ICRAR), said in a statement.

Using this data, the researchers say they have already been able to rule out one theory regarding black hole growth, and have begun examining others.

Albert Einstein predicted gravitational waves, ripples in space-time created when massive bodies change speed or direction -- such as when galaxies merge and their black holes meet.

"When the black holes get close to meeting they emit gravitational waves at just the frequency that we should be able to detect," Bhat explained.

Using CSIRO's Parkes radio telescope in Australia and 20 spinning stars known as pulsars, astronomers have searched the skies for these gravitational waves. Because the pulses emitted by these stars are so exact, any changes in timing signal interference. Waves, with their ability to swell or shrink the distances between objects, alter the pulses' arrival.

Sifting through 20 years of timing data, researchers say that, while unable to detect gravitational waves outright, they are closer than ever.

"The [findings] are showing us how low the background rate of gravitational waves is," Bhat said. "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."

Based on their study, the scientists have ruled out black holes merely gaining mass through merging, though other models remain an option.

"Black holes are almost impossible to observe directly," Bhat said, "but armed with this powerful new tool we're in for some exciting times in astronomy."