Scientists detect more gravitational waves

Thursday, 16 June 2016

An international team of researchers, including from the University of Adelaide, have detected gravitational waves for the second time─just four months since the report of the first detection brought enormous excitement around the world.

These gravitational waves─ripples in space and time─were caused by a second pair of colliding black holes about 1.4 billion years ago. They were detected on 26 December 2015, and are being reported today at a meeting of the American Astronomical Society (AAS) in San Diego, California.

The discovery, published in the journal Physical Review Letters, was made by the LIGO Scientific Collaboration (which includes the Australian Consortium for Interferometric Gravitational Astronomy (ACIGA)) and the Virgo Collaboration. LIGO involves more than 1000 scientists from more than 90 universities around the world.

Gravitational waves carry information about their origins and about the nature of gravity that cannot otherwise be obtained. Physicists concluded that these gravitational waves were produced during the final moments of the merger of two black holes—14 and 8 times the mass of the sun—to produce a single, more massive spinning black hole that is 21 times the mass of the sun.

“Detecting a second burst of gravitational waves means we are well on the way to being able to map the populations of black holes in our universe,” says Associate Professor Peter Veitch, Head of Physics at the University of Adelaide. “Perhaps even more excitingly, who knows what else will be revealed as we continue to improve the sensitivity of the detectors?”

The University of Adelaide developed and installed ultra-high precision optical sensors used to correct the distortion of the laser beams within the LIGO detectors, enabling the high sensitivity needed to detect these minute signals. The current Adelaide team includes Associate Professor Veitch, Professor Emeritus Jesper Munch, Associate Professor David Ottaway, Dr Won Kim and Dr Miftar Ganija, and postgraduate students Elli King, Huy Cao and Deeksha Beniwal.

“The first detection was an amazing signal but it is very reassuring to see another strong signal from two smaller mass black holes that was more challenging to detect,” says Associate Professor David Ottaway, also from the University’s School of Physical Sciences.

The first detection of gravitational waves, announced on February 11, 2016, was a milestone in physics and astronomy; it confirmed a major prediction of Albert Einstein’s 1915 general theory of relativity, and marked the beginning of the new field of gravitational-wave astronomy.

“The dawn of the new field of gravitational-wave astronomy is a wonderful culmination of decades of work by hundreds of scientists and engineers worldwide. The University of Adelaide team joined this effort in 1993, contributing expertise and research in lasers and optics, and gratefully acknowledges the continuing support by the University and the ARC. We are looking forward to additional detectors joining the search to pinpoint the location of the source,” says Emeritus Professor Jesper Munch.

Australian scientists from ACIGA, comprising the University of Adelaide, Australian National University (ANU), the University of Melbourne, the University of Western Australia, Monash University and Charles Sturt University, contributed to the discovery and helped build the super-sensitive instruments used to detect the gravitational waves.

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