Gravitational Waves Detected
Gravitational waves detected... find out more about the Monash LIGO research team who were involved in the first detection of gravitational waves, and how it felt to be part of such a watershed moment in science.
A team of LIGO* Scientific Collaboration (LSC) researchers at Monash University played an important role in the design and implementation of key hardware and software components associated with the
detection and interpretation of gravitational wave GW150914 in September 2015: the first ever observation of gravitational waves and the first direct detection of black holes.
The Monash team created a system of vetting detections – injecting fake gravitational waves into the detector. By showing that they could recover the fake signal, it enabled the team to verify a genuine gravitational wave.
The team played a key role in data analysis; observing and interpreting data generated by LIGO's detectors in Louisiana and Washington, USA, and were also instrumental in the design of the LIGO mirrors to control their behaviour in extreme conditions and thereby significantly increase LIGOs sensitivity
to faint gravitational waves.
*Laser Interferometer Gravitational-wave Observatory
ARC Centre of Excellence
Monash are now part of the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav).
GRAVITATIONAL WAVES DETECTED 100 YEARS AFTER EINSTEIN'S PREDICTION
LIGO opens new window on the universe with observation of gravitational waves from colliding black holes
Australian scientists play a key role in major discovery
For the first time, scientists have observed ripples in the fabric of spacetime called gravitational waves, arriving at the earth from a cataclysmic event in the distant universe. This confirms a major prediction of Albert Einstein's 1915 general theory of relativity and opens an unprecedented new window onto the cosmos.
Gravitational waves carry information about their dramatic origins and about the nature of gravity that cannot otherwise be obtained. Physicists have concluded that the detected gravitational waves were produced during the final fraction of a second of the merger of two black holes to produce a single, more massive spinning black hole. This collision of two black holes had been predicted but never observed.
The gravitational waves were detected on September 14, 2015 at 5:51 a.m. Eastern Daylight Time (9:51 a.m. UTC) by both of the twin Laser Interferometer Gravitational-wave Observatory (LIGO) detectors, located in Livingston, Louisiana, and Hanford, Washington, USA. The LIGO Observatories are funded by the National Science Foundation (NSF), and were conceived, built, and are operated by Caltech and MIT.
The discovery, accepted for publication 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 GEO600 Collaboration) and the Virgo Collaboration using data from the two LIGO detectors.
Australian scientists from The Australian National University (ANU), the University of Adelaide, The University of Melbourne, the University of Western Australia (UWA), Monash University and Charles Sturt University, contributed to the discovery and helped build some of the super-sensitive instruments used to detect the gravitational waves.
Leader of the Australian Partnership in Advanced LIGO Professor David McClelland from ANU, said the observation would open up new fields of research to help scientists better understand the universe.
"The collision of the two black holes was the most violent event ever recorded," Professor McClelland said.
"To detect it, we have built the largest experiment ever – two detectors 4,000 kilometres apart – with the most sensitive equipment ever made, which has detected the smallest signal ever measured."
Associate Professor Peter Veitch from University of Adelaide said the discovery was the culmination of decades of research and development in Australia and internationally.
"The Advanced LIGO detectors are a technological triumph and the discovery has provided undeniable proof that Einstein's gravitational waves and black holes exist," Professor Veitch said.
"I have spent 35 years working towards this detection and the success is very sweet."
Professor David Blair from UWA said the black hole collision detected by LIGO was invisible to all previous telescopes, despite being the most violent event ever measured.
"Gravitational waves are akin to sound waves that travelled through space at the speed of light," Professor Blair said.
"Up to now humanity has been deaf to the universe. Suddenly we know how to listen. The universe has spoken and we have understood."
With its first discovery, LIGO is already changing how astronomers view the universe, said LIGO researcher Dr Eric Thrane from Monash University.
"The discovery of this gravitational wave suggests that merging black holes are heavier and more numerous than many researchers previously believed," Dr Thrane said.
"This bodes well for detection of large populations of distant black holes – research carried out by our team at Monash University. It will be intriguing to see what other sources of gravitational waves are out there, waiting to be discovered."
The success of LIGO promised a new epoch of discovery, said Professor Andrew Melatos, from The University of Melbourne.
"Humanity is at the start of something profound. Gravitational waves let us peer right into the heart of some of the most extreme environments in the Universe, like black holes and neutron stars, to do fundamental physics experiments under conditions that can never be copied in a lab on Earth," Professor Melatos said.
"It is very exciting to think that we now have a new and powerful tool at our disposal to unlock the secrets of all this beautiful physics."
Dr Philip Charlton from Charles Sturt University said the discovery opened a new window on the universe.
"In the same way that radio astronomy led to the discovery of the cosmic microwave background, the ability to 'see' in the gravitational wave spectrum will likely to lead to unexpected discoveries," he said
Professor Susan Scott, who studies General Relativity at ANU, said observing this black hole merger was an important test for Einstein's theory.
"It has passed with flying colours its first test in the strong gravity regime which is a major triumph."
"We now have at our disposal a tool to probe much further back into the Universe than is possible with light, to its earliest epoch."
Australian technology used in the discovery has already spun off into a number of commercial applications. For example, development of the test and measurement system MOKU:Labs by Liquid Instruments; vibration isolation for airborne gravimeters for geophysical exploration; high power lasers for remote mapping of wind-fields, and for airborne searches for methane leaks in gas pipelines.
LIGO research is carried out by the LIGO Scientific Collaboration (LSC), a group of more than 1000 scientists from universities around the United States and in 14 other countries. More than 90 universities and research institutes in the LSC develop detector technology and analyse data; approximately 250 students are strong contributing members of the collaboration.
The LSC detector network includes the LIGO interferometers and the GEO600 detector. The GEO team includes scientists at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute (AEI)), Leibniz Universität Hannover, along with partners at the University of Glasgow, Cardiff University, and other universities in the United Kingdom, funded by Science and Technology Facilities Council (STFC). Significant computer resources have been contributed by the AEI Atlas cluster, the LIGO Laboratory, Syracuse University, and the University of Wisconsin Milwaukee.
LIGO was originally proposed as a means of detecting these gravitational waves in the 1980s by Rainer Weiss, professor of physics, emeritus, from MIT; Kip Thorne, Caltech's Richard P. Feynman Professor of Theoretical Physics, emeritus; and Ronald Drever, professor of physics, emeritus, also from Caltech.
Virgo research is carried out by the Virgo Scientific Collaboration, a group of more than 250 physicists and engineers belonging to 18 different European laboratories, 6 of Centre National de la Recherche Scientifique (CNRS) in France, 8 of Istituto Nazionale di Fisica Nucleare (INFN) in Italy, Nikhef in the Netherlands, the Wigner Institute in Hungary, the POLGRAW group in Poland and the European Gravitational Observatory (EGO), the laboratory hosting the Virgo interferometer.
The discovery was made possible by the enhanced capabilities of Advanced LIGO, a major upgrade that increases the sensitivity of the instruments compared to the first-generation LIGO detectors, enabling a large increase in the volume of the universe probed—and the discovery of gravitational waves during its first observation run. The U.S. National Science Foundation leads in financial support for Advanced LIGO. Funding organizations in Germany (Max Planck Society), the U.K. (STFC) and Australia (Australian Research Council) also have made significant commitments to the project. Several of the key technologies that made Advanced LIGO so much more sensitive have been developed and tested by the German UK GEO collaboration.
Australian Research Contributions
ANU designed, constructed, installed and commissioned a system that stabilises the system and locks the laser and mirrors to each other at the start of experiments. The system also pulls the system back into line if it is disturbed, for example by a magnitude 7 earthquake anywhere in the world.
ANU also built, installed and commissioned 30 small optics steering mirrors for routing the signal beam around the interferometer and into the detectors.
ANU searched LIGO data for gravitational waves from young supernova remnants and worked with the University's SkyMapper telescope to look for flashes of light associated with the first observation of gravitational waves.
University of Western Australia was involved in stabilising the detectors to enable continuous operation. We ran an independent analysis of the data to verify the signals, and we searched the sky with our Zadko robotic telescope to see if there was any explosion visible in light.
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 University of Melbourne is continuing to analyse LIGO data on massive supercomputers in the hunt for persistent signals from neutron stars, some of the most extreme objects in the universe.
Monash University played a leading role in data analysis and in the design and implementation of key hardware and software components associated with the detection and interpretation of GW150914: the first ever observation of gravitational waves.
Charles Sturt University has contributed to detector characterisation, validation of the calibration of the instruments and development of the detection pipeline for the stochastic background of gravitational waves.
CSIRO was contracted by LIGO to provide coatings for some mirrors, precisely controlled layers of optical materials and a top layer of gold, designed for thermal shielding. They are among the most uniform and highly precise ever made.
The Monash LIGO research team
Monash lecturer and member of the LIGO Scientific Collaboration
Dr Eric Thrane joined the School of Physics and Astronomy at Monash from Caltech in early 2015. His research focus is astrophysics, cosmology, and gravitational-wave astronomy.
Since 2011 he has co-chaired one of LIGO's four data analysis groups, studying data from the LIGO detectors. His Monash group also works on aspects of the detectors themselves, for example, by characterising problematic noise sources, which threaten to limit LIGO's sensitivity. He and his team demonstrated that LIGO can detect simulated gravitational wave signals introduced by shaking the mirrors. This vetting process helped ensure that the collaboration could be confident in the first discovery of gravitational waves.
Dr Thrane described the discovery of gravitational wave GW150914 as monumental. "This is a watershed moment in the history of astronomy. LIGO 's detection represents a whole new way of doing astronomy that can unlock the secrets of the universe. It has been a privilege to work with the international LIGO collaboration toward this discovery," Dr Thrane said.
However, he described this first discovery as just the tip of the iceberg. "The discovery of this gravitational wave suggests that merging black holes are heavier and more numerous than many researchers previously believed. This bodes well for detection of large populations of distant black holes – research carried out by our team at Monash University. It will be intriguing to see what other sources of gravitational waves are out there, waiting to be discovered," Dr Thrane said.
Watch a video of Eric making gravitational wave sounds.
Monash lecturer and member of the LIGO Scientific Collaboration
Dr Paul Lasky is a postdoctoral research fellow in gravitational-wave astrophysics. An active member of the LIGO Scientific Collaboration since 2012, Dr Lasky's primary responsibilities within LIGO include predicting and searching for gravitational waves from super-dense stellar corpses known as neutron stars, as well as understanding the complex physics that governs these exotic objects.
His recent technical review highlights the many possible ways neutron stars can create gravitational waves that could be detected in the very near future with LIGO. He is currently focussed on developing a method for testing Einstein's theory of General Relativity near the surfaces of black holes using observations of gravitational waves from black hole collisions such as this first event.
Dr Lasky is also an active member of both Australia's Parkes Pulsar Timing Array and the International Pulsar Timing array, which both aim to use the most rapidly spinning neutron stars (spinning faster than a kitchen blender!) to detect gravitational waves that come from the mergers of supermassive black holes weighing more than a billion times the mass of our Sun (compared to the black holes LIGO measures that weigh about 10 times our Sun). As well as developing and implementing data analysis algorithms, he is pioneering new techniques for combining gravitational-wave observations with both LIGO and pulsar timing arrays that could aid in our understanding of the earliest phases of the Universe.
Dr Lasky describes the discovery of gravitational waves as 'simply mind-blowing'. "About 1.4 billion years ago, two black holes collided in a single impact that, in less than a second, released more energy than 5,000 suns emit in their full lifetime. This energy was released as ripples of gravity that have been travelling towards Earth until, on 14 September 2015, they caused the two LIGO instruments to wobble a minuscule amount. I feel truly honoured to be a part of the amazing team that has made it possible to detect such a tiny wobble from such a cataclysmic, astronomical event," Dr Lasky said.
Monash lecturer and member of the LIGO Scientific Collaboration
Professor Yuri Levin's key research interests are astrophysical gravitational waves, neutron stars and supermassive black holes (especially the one at the centre of our Galaxy, called SgrA*).
Professor Levin completed his PhD at Caltech on the physics and astrophysics of LIGO under the mentorship of Professor Kip Thorne, one of the three founders of the LIGO project. Levin's key contribution was to develop a theoretical framework for evaluating the noise due to thermal fluctuations of the LIGO mirrors, and to point out the importance of using high-quality reflective coatings. Levin's work has been widely used within the collaboration and has guided the LIGO team in its choices of the mirror materials, optimised to increase the advanced LIGO sensitivity. Furthermore, together with his colleagues, Levin showed that a certain type of optical filter can help reduce the quantum fluctuations that interfere with gravitational-wave measurements. These filtering techniques will be implemented in future experiments with Advanced LIGO.
The Advanced LIGO discovery of gravitational waves from a black-hole merger has focused Professor Levin's attention on the physics and astrophysics that can be learned from a multitude of such mergers. "After the initial excitement, it is important to think about the next steps," Professor Levin said. "First, the detector noise has to be reduced by another order of magnitude, so that it reaches the target sensitivity for Advanced LIGO. Then a flood of new data will bring a multitude of signals such as the one we are celebrating today. We have to think intelligently about what to do with all this data."
A film about Professor Levin and his research can be found here and is free for media usage.
Monash lecturer and member of the LIGO Scientific Collaboration
Dr Duncan Galloway established his research career with X-ray studies of accreting neutron stars during postdoctoral positions at the Massachusetts Institute of Technology (MIT).
His research interests include searches for gravitational waves from rapidly-rotating neutron stars, and searches for optical flashes which may accompany gravitational-wave bursts detectable by LIGO.
Preparations are already underway to fully exploit this new way of gathering information about the universe. A team of Monash researchers, in collaboration with Warwick University and other UK partners is developing a robotic optical telescope, the Gravitational-wave Optical Transient Explorer (GOTO) on the Canary Island of La Palma, to detect the optical flashes that may be associated with gravitational wave signals.
Dr Galloway explains the significance of discovering gravitational waves and what this will mean for future research. "The first detection of gravitational waves by LIGO opens up whole new opportunities in astrophysics. The identification of optical flashes associated with gravitational wave signals will enable the position of the source to be determined to much greater accuracy, and will significantly increase the amount of information that can be obtained from these extreme sources," Dr Galloway said.
"But the really exciting aspect is the sources that we haven't predicted, the truly unexpected discoveries that, history shows, often accompany the opening of a fundamentally new window on the universe".
Postdoctoral Researcher at Monash and member of the LIGO Scientific Collaboration
Dr Letizia Sammut is heavily involved in LIGO research and has been a member of the LIGO collaboration since 2009. She joined Monash in 2015, and is now in charge of a search for gravitational waves from the sum of many astrophysical sources, most notably mergers of black holes. This search uses techniques developed by Dr Eric Thrane (see above) and other LIGO collaborators.
Dr Sammut was inspired by an undergraduate project to pursue a PhD in gravitational wave astrophysics. During her PhD, she developed and performed searches for gravitational waves from ultra-dense neutron stars in binary orbits.
"It was incredibly exciting to be involved in the first direct detection of gravitational waves whilst in the final stages of my PhD dissertation, and in anticipation of starting my new role with the gravitational wave group in the School of Physics and Astronomy at Monash University. It is a fascinating and rewarding field within which I am delighted to be involved," Dr Sammut said.
"Almost 100 years after Einstein first predicted their existence, the first direct detection of gravitational waves, and the direct observation of two merging black holes, marks a significant achievement in physics and astronomy, which stands on decades of instrumental and technical development," Dr Sammut said.
Monash Science Honours Student and member of the LIGO Scientific Collaboration
During his undergraduate studies, Chris Whittle completed a research project under Dr Eric Thrane's supervision on the prospects of utilising machine learning techniques for the detection of subthreshold gravitational wave signals amidst a sea of complicated noise patterns. Chris will be continuing his work on investigating data analysis techniques for gravitational wave detection as an Honours student in the Faculty of Science this year.
"The fortuitous timing of my involvement with the LIGO Scientific Collaboration has afforded me a privileged insight into this momentous discovery. I am thrilled to be working with the LIGO community during such a pivotal period, and to have my own research so readily informed by the latest developments."