New gravitational waves show black holes in a spin

Friday, 2 June 2017

Scientists from around the world, including from the University of Adelaide, have made a third detection of gravitational waves ─ generated once again by the merger of two black holes to form a larger one.

Published in the journal Physical Review Letters, this third detection solidifies the case for a new class of black hole pairs (binary black holes). The newest black hole, formed by the merging of two, has a mass about 50 times that of our sun and is located about 3 billion light years away.

Gravitational waves ─ ripples in space and time ─ were first reported to much acclaim and worldwide excitement in February 2016. The discoveries have been made at the Laser Interferometer Gravitational-wave Observatory (LIGO) in the United States and involve the new ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav) in Australia.
Gravitational waves carry information about their origins and about the nature of gravity that cannot otherwise be obtained.

In all three detections to date, each of the twin detectors – in Hanford, Washington and Livingston, Louisiana in the US – detected gravitational waves from the mergers of black hole pairs. The black holes in the first and second detections were 1.3 and 1.4 billion light-years away with solar masses of 62 and 21.

The newest observation also provides clues about the directions in which the black holes are spinning.

“Studying the spin alignment of these black holes gives hints of the formation pathways of such black holes in the early universe. It’s very exciting,” says Associate Professor David Ottaway, one of the University of Adelaide’s chief investigators within the ARC Centre of Excellence.

“This black hole binary was about twice the distance from Earth at the first detected one. At Adelaide we are excited about using our new OzGrav funding to work with our LIGO colleagues to observe even deeper into the universe and thereby increase the rate of detections and learn more about the origins of these amazing objects.”

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.

University of Adelaide researchers are now helping improve the sensitivity of the LIGO detectors and developing new ways to interrogate the data produced.

“We are developing advanced high-power lasers and optical instrumentation for the next generation of gravitational wave detectors,” says fellow chief investigator Professor Peter Veitch, Head of Physics. “With every new detection we are able to build on the picture we are developing of the birth and life of the universe.”

LIGO is funded by the National Science Foundation (NSF), and operated by MIT and Caltech, which conceived and built the project. Financial support for the Advanced LIGO project was led by NSF with Germany (Max Planck Society), the U.K. (Science and Technology Facilities Council) and Australia (Australian Research Council) making significant commitments and contributions to the project. More than 1,000 scientists from around the world participate in the effort through the LIGO Scientific Collaboration, which includes the GEO Collaboration. LIGO partners with the Virgo Collaboration, a consortium including 280 additional scientists throughout Europe supported by the Centre National de la Recherche Scientifique (CNRS), the Istituto Nazionale di Fisica Nucleare (INFN), and Nikhef, as well as Virgo’s host institution, the European Gravitational Observatory. Additional partners are listed at: http://ligo.org/partners.php.

The ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav) is funded by the Australian Government through the Australian Research Council Centres of Excellence funding scheme. OzGrav is a partnership between Swinburne University (host of OzGrav headquarters), the Australian National University, Monash University, University of Adelaide, University of Melbourne, and University of Western Australia, along with other collaborating organisations in Australia and overseas.

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