OzGrav Associate Investigator Dr Adam Deller has helped test Einstein’s theory of general relativity and shown it still can’t be proven wrong, using the complicated orbital dance of three compact stars. Einstein’s strong equivalence principle says all objects should fall the same way in a gravitational field, regardless of their composition or how dense they are.
After five years of intensive observation of a triple stellar system, the international team of nine astronomers was able to conclude that the theory of general relativity is still relevant, as seen in the research paper published in the prestigious international science journal, Nature.
“This particular system consists of one ultra-dense neutron star and two less-dense white dwarf stars, which makes these stars the dream team for testing relativity,” Dr Deller says.
Read the press release here.
A new technique developed to detect the faint background hum of gravitational waves in the Universe is making headlines! Eric Thrane and Rory Smith from OzGrav's Monash Node have made the remarkable prediction that their new technique - combined with the grunt of a supercomputer like Swinburne's OzSTAR - could give them the exquisite level of sensitivity needed to measure the subtle background noise caused by black holes and neutron stars colliding throughout the universe.
Their result is described in The Age and ABC news, and on TV on the 7:30 Report.
On 16 March 2018, OzGrav Deputy Director Prof David McClelland (ANU) received the International Organisation for Quantum Communication, Measurement and Computing Award for Outstanding Achievements in Quantum Experimentation. In bestowing McClelland with this award, the organisation cited his “pioneering experimental work and leadership in the development of squeezed vacuum light sources in the audio-band and its successful application to the gravitational wave detector interferometers GEO and LIGO.” The award was shared in equal parts with OzGrav Partner Investigator Prof Nergis Mavalvala (MIT) and Prof Roman Schnabel (Hamburg).
Advances in this technology are sure to lead to even more discoveries. Says Prof McClelland, "manipulating the quantum world to enhance the sensitivity of world’s biggest laser interferometers will enable the deepest searches yet for new gravitational wave sources".
“It is gratifying to see Professor McClelland's pioneering work in quantum squeezing acknowledged with this prize. His group's work will enable us all to see further into the Universe and accelerate the advancement of the new field of gravitational wave astrophysics", says OzGrav Director Prof Matthew Bailes.
Image: Prof McClelland receiving his award from Prof Joerg Schmiedmayer, Chair of the International Organisation for Quantum Communication, Measurement and Computation.
OzGrav Deputy Director David McClelland was awarded the Walter Boas Medal by the Australian Institute of Physics for his contributions to “one of the greatest achievements in the history of physics”, the direct observation of gravitational waves. "For his role in bringing about the epochal breakthrough, and securing Australia’s place in the international collaboration that made it possible, Professor David McClelland of the Australian National University has been awarded the 2017 Walter Boas Medal by the Australian Institute of Physics."
In addition to his role in OzGrav, he is Professor of Physics, Department of Quantum Science and Director of the ANU Centre for Gravitational Physics. He is also the Chief Investigator for Australia's Partnership in Advanced LIGO. The Walter Boas Medal is awarded yearly by the AIP for excellence in research.
A Swinburne astronomer is part of an international discovery effort bringing scientists one step closer to understanding the physics of binary neutron star mergers and the universe at large.
The discovery, made by an international team of astronomers, suggests that a narrow and super-fast 'jet' of material blasted out during the cataclysmic neutron star merger, slammed into the environment surrounding the merging neutron stars and inflated a bubble-like cocoon.
The findings, published in Nature, contradict a popular theory describing the aftermath of the recently observed neutron star merger — namely, that the beam-like jet thought to be associated with highly energetic phenomena called gamma-ray bursts had been seen directly, immediately after the merger.
“The burst of gamma-rays from this merger didn't come directly from a tightly focused, high-speed jet that just grazed our line of sight; instead, we attribute them to a more slowly moving outflow of material that had absorbed some of the jet’s energy,” says Swinburne astronomer Dr Adam Deller, ARC Future Fellow at the Centre for Astrophysics and Supercomputing and Associate Investigator at the ARC Centre of Excellence for Gravitational Wave Discovery.
“We confirmed this by studying the radio emission produced by this outflowing material weeks and months after the merger.”
Dr Deller believes this finding will impact astronomy in two important ways.
“The 'canonical' model of what happens when neutron stars merge will be revised and improved,” he says. “And when LIGO detects more binary neutron star mergers in the future, we now expect to see an 'afterglow' counterpart more frequently than previously expected, which will help us pin down their locations and is good news for learning more about the extreme physics of these merger events.”
Australia and the world looking to the skies
The findings were made possible by the cooperative efforts of a team of astronomers and facilities
world-wide, and Dr Deller stresses the importance of having radio telescopes in Australia and the
world monitoring these events.
"As we've kept our radio telescopes trained on the site of this event, we've continued to learn more
and more about the nature of the explosion that accompanied the neutron star merger,” he says.
"Having a suite of radio telescopes world-wide, including in Australia, has underpinned this
monitoring effort. By observing at a range of times and radio frequencies, we've learnt much more
about the explosion than any one facility could have provided alone."
Dr Tara Murphy, an ARC fellow at University of Sydney who led observations with the Australia
Telescope Compact Array, says that detecting and monitoring radio waves is critical to understand
what happens when two neutron stars merge.
“We now know that what we’re observing is not what we expected - we haven’t seen anything quite
like it before.”
“Australian facilities have played a vital role in monitoring radio waves from the merger. We’re able
to detect this high energy event, 130 million light years away, tracking it as the explosion evolves
Looking to the future
The research team say that future observations with international telescopes LIGO, Virgo, and
others will help further clarify the origins and mechanisms of these extreme events.
The observatories should be able to detect additional neutron-star mergers—and perhaps
eventually, mergers of neutron stars and black holes.
The findings were made with the Karl G. Janksy Very Large Array in New Mexico, the CSIRO Australia
Telescope Compact Array, and the Giant Meter-wave Radio Telescope in India. The lead author is Kunal Mooley, formerly of the University of Oxford and now a Jansky Fellow at
To view the complete findings, see: A mildly relativistic wide-angle outflow in the neutron star
Image credit: NRAO/AUI/NSF: D. Berry.
The image shows a radio telescope (upper right) observing GW170817 (lower left). The jet within GW170817 (narrow bright beam emanating from GW170817) has dissipated its energy into the dynamical ejecta (shown in brown/yellow) and thus given rise to a wide-angle outflow (shown in red/pink) - a scenario called the choked-jet cocoon.
Scientists searching for gravitational waves have confirmed yet another detection from their fruitful observing run earlier this year. Dubbed GW170608, the latest discovery was produced by the merger of two relatively light black holes, 7 and 12 times the mass of the sun, at a distance of about a billion light-years from Earth. The merger left behind a final black hole 18 times the mass of the sun, meaning that energy equivalent to about 1 solar mass was emitted as gravitational waves during the collision.
GW170608 is the lightest black hole binary that LIGO and Virgo have observed – and so is one of the first cases where black holes detected through gravitational waves have masses similar to black holes detected indirectly via electromagnetic radiation, such as X-rays.
Prof Matthew Bailes delivers a history of gravitational waves in virtual and augmented reality to a packed theatre at Swinburne University of Technology. We were delighted to have Prof Brian Schmidt as our MC, and a personal message from Prof Barry Barish to launch our Centre of Excellence for Gravitational Wave Discovery (OzGrav).
Read our media announcement here, or watch the OzGrav Director Professor Matthew Bailes explain the discovery:
Australian scientists to discuss new developments in gravitational-wave astronomy
NEWS BRIEFING: Tue 17 Oct 2017 at 09:00 AEDT at Old Parliament House, Canberra and online
Scientists from OzGrav (The ARC Centre of Excellence for Gravitational Wave Discovery), CAASTRO (The ARC Centre of Excellence for All-sky Astrophysics) and the LIGO-Virgo Collaboration will reveal new details and discoveries made in the ongoing search for gravitational waves.
Join us for this media briefing, moderated by Australia's Chief Scientist Dr Alan Finkel, when Australian experts will discuss the research and its implications.
OzGrav congratulates the winners of the Nobel Prize in Physics for their roles in discovering gravitational waves
The Australian Research Council Centre of Excellence for Gravitational Wave Discovery (OzGrav) is delighted to congratulate the winners of this year’s Nobel prize in Physics for the leadership roles they played in the discovery of gravitational waves by the Advanced LIGO detector.
The three winners are Rainer Weiss, from the Massachusetts Institute of Technology, Kip Thorne and Barry Barish, both of whom are from the California Institute of Technology. OzGrav is very fortunate to have Barry Barish serve on our Scientific Advisory Committee.
Australia’s Minister for Education and Training, Simon Birmingham, also congratulated the 2017 Nobel Prize winners. “OzGrav is helping Australia stay at the cutting edge of this new and rapidly advancing field,” said Senator Birmingham. “It will capitalise on the first detections of gravitational waves, to understand the extreme physics of black holes and warped space-time.”