Space scientists from The University of Western Australia have worked with the European Space Agency to provide continuous imaging of a space probe passing Earth while on a journey to Mercury.
The scientists from UWA’s Centre of Excellence for Gravitational Wave Discovery (OzGrav) used the powerful robotic Zadko Telescope in Gingin to capture imagery of the space probe, named BepiColumbo. The probe was launched in 2018 and has since completed one and a half orbits around the Sun, travelling a distance of roughly 1.4 billion kilometres. OzGrav scientist Dr Bruce Gendre said BepiColombo would study Mercury’s magnetic field and its interaction with the solar wind, offering insight into how the Earth and solar system formed. “In order to keep the space probe on track to reach Mercury in 2025, BepiColumbo performed a ‘fly-by’ past Earth on 10 April 2020, utilising a gravity assist manoeuvre, which reduces the amount of propellant and thrust needed to complete the mission,” Dr Gendre said. "Space navigation is a complex task and requires large quantities of fuel. To reduce fuel consumption and the resulting cost of the mission, space agencies often use gravitational assistance from planets.” Due to the regional travel restrictions imposed by the WA Government following the COVID-19 outbreak, Dr Gendre was unable to control the Zadko telescope on-site in Gingin and instead operated the telescope remotely from his home in Claremont. “This important contribution to space research helps inspire the engineers and scientists of tomorrow, continuing the legacy of UWA philanthropist James Zadko, who passed away in early 2020,” Dr Gendre said. Associate Professor David Coward, Chief Investigator at OzGrav and Zadko Telescope Director, said tracking the space probe represented a small part of a greater project. “Providing ongoing assistance is part of a broader partnership with the European Space Agency to monitor the space around Earth for potential hazards, including near-earth asteroids,” Associate Professor Coward said. Detlef Koschny, a European Space Agency scientist said the Zadko Telescope was an important part of ensuring the success of the mission. “ESA's Planetary Defence Office is using this flyby as a test for its capabilities to coordinate the observation of possibly dangerous asteroids,” Dr Koschny said. “In the southern hemisphere, there are not many telescopes available for this purpose.” The Zadko Telescope is partially supported by the UWA Faculty of Engineering and Mathematical Sciences and the Australian Research Council Centre of Excellence for Gravitational Wave Discovery (OzGrav). As featured on UWA News
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Coronavirus prompts scientists to make phone app to track symptoms and predict COVID-19 outbreaks16/4/2020 Some of Australia's leading astrophysicists have teamed up with public health experts to detect possible outbreaks of COVID-19, even before testing takes place.
About 12,000 people globally are already using a trial version of an app, which they log into daily to answer questions about symptoms and risk factors not currently recorded by health authorities. The astrophysicists use supercomputers, usually reserved to process data from the world's largest telescopes, to identify geographical clusters of symptoms and detect where COVID-19 could be spreading. Buoyed by promising early results, the team will this week launch the 'BeatCOVID19Now' app to crowdsource anonymous data from users around the world. Swinburne University astrophysics professor Matthew Bailes, who leads Australia's research into gravitational waves, has put that research on hold to devote his time — and supercomputers — to the project. "We're used to catching literally hundreds of gigabytes a second of data from the Square Kilometre Array[radio telescope project]," Professor Bailes said. "And the amount of data we're talking about for this is a small fraction of that." Supercomputers crunch data to predict outbreaks Professor Bailes has teamed up with Swinburne public health professor Richard Osborne, who previously worked with the World Health Organisation and the Australian Bureau of Statistics on disease-tracking surveys. "We need to know where the next epidemic is going to break out … so we can actually beat COVID-19 by getting in there early and supporting people to be safe," Professor Osborne said. The project is independent of a recently announced Australian Government plan to develop an app that would monitor users' movements and contacts. That app would require 40 per cent of Australians to sign up to be effective, the Government believes. For this project, the Swinburne scientists believe they need data from just a few hundred people in a location — as small as a suburb or as large as a city — to produce useful results. "We'd like to be able to turn back the clock on our survey data and say, 'You know what? Three days before that outbreak, we saw lots of people with sore throats or runny noses or they lost their sense of taste'," Professor Bailes said. "Those sorts of statistics could be correlated with actual outbreaks and then we could start predicting outbreaks in the area before they happen. "And that would really help the Government with its planning." How it works:
Initial results point to promise Based on the early data from a small number of users, the researchers said the program indicated there were outbreaks in certain Melbourne suburbs, which matched official Government data. Researchers say that although the analysis was conducted retrospectively, it demonstrates that the program should be effective in predicting outbreaks. The program also saw an influx of people logging in from Los Angeles, days before an outbreak was seen there. The researchers say lots of people using the app could have been an early sign that people there were getting sick. "I think that's what a local pandemic can do to your motivation to want to track your symptoms," Professor Bailes said. To date, most users have discovered the website through social media, but marketing and IT experts have volunteered their time to help promote the phone app. "The reason I got in this project is because I wanted to do something to help," Professor Bailes said. "And I think everybody sitting out there can help by just doing this survey. They can be part of the solution." Professor Osborne said the team was now working on ways to share the data with health authorities — including Australia's Department of Health — and other coronavirus researchers. Nancy Baxter, head of the Melbourne School of Population and Global Health, said the app would be a useful tool if the Swinburne researchers could get enough people to use it. "Having some way of looking and seeing in the population who … likely has COVID-19 can be really helpful in terms of knowing where to target testing," Professor Baxter said. She said it could also help prevent the disease spreading by finding and isolating patients before they fell very ill — but other measures would still be vital, such as widespread testing, surveillance, contact tracing and quarantine. "It can add to what we're doing, but it's not the fundamental part of what's what we need to do," she said. As featured on ABC News Today, team COMPAS (Compact Object Mergers: Population Astrophysics and Statistics) has announced the first public beta release of their rapid binary population synthesis code (available for download here). Initially, the code—co-developed by researchers from the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav)—was created to explore gravitational-wave observations. Gravitational waves are ripples in space-time that radiate out from the collision of two accelerating masses, such as neutron stars or black holes. COMPAS uses models of binary stellar evolution to make predictions for the rates and properties of these collisions. OzGrav Postdoctoral Researcher Simon Stevenson from Swinburne University of Technology says: “COMPAS allows us to understand how the binary neutron stars and black holes being observed in gravitational waves are formed.” COMPAS has since expanded to include other observational signatures of binary evolution, including Galactic Double Neutrons Stars, X-ray Binaries and Luminous Red Novae. Different observations provide new insights into gravitational-wave research and help to complete the picture of binary astrophysics. Most massive stars are known to be born in binary systems. Interactions between companion stars alter the evolution of the stars and binary system. The physical processes involved in binary formation and evolution are currently uncertain; however, scientists are starting gain a better understanding through observations of astrophysical phenomena in different stages of binary evolution. The COMPAS code combines tools for statistical analysis and model selection with rapid population synthesis, allowing scientists to dig deeper into stellar and binary evolution. OzGrav Chief Investigator Ilya Mandel from Monash University explains: “I am very excited that we’ve reached this milestone in the development of the COMPAS binary population synthesis modelling and astrostatistics code, thanks to the hard work of a dedicated group of students and collaborators. I hope that the public release will allow other colleagues interested in this topic to become involved and accelerate the pace at which we can address key questions in the evolution of binary stars.” OzGrav PhD student Jeff Riley from Monash adds: “A lot of people have worked hard to develop COMPAS over a number of years. I’m very happy to have contributed, and very excited about the public release – now we call all get some sleep!” The COMPAS team encourages users to contribute and improve the code, ranging from better evolutionary models to more sophisticated emulation techniques. Please contact compas-user@googlegroups.com with any queries. Humans have been studying the light from stars since the beginning of our history; however, we’ve only just discovered in the last few decades that stars don’t like to be alone. Binary systems—containing two stars orbiting around each other—are one of the most common type of gravitationally-bound collections of stars, yet their evolution is complex. Astronomers are trying to piece together the puzzle of different stellar observations to reveal the bigger picture. Using their understanding of binary evolution, scientists can simulate populations of stellar binaries with the stellar population synthesis code COMPAS—mostly developed by researchers from the ARC Centre of Gravitational Wave Discovery (OzGrav). OzGrav researchers, in collaboration with the Max Planck Institute of Hannover, Monash University and University of Birmingham, recently conducted a study to understand the origin of the properties of ‘Be X-ray’ binaries observed in the Small Magellanic Cloud. Be X-ray binaries are star systems typically composed of a neutron star orbiting around a rapidly rotating massive star. This rotation causes the massive star to produce a disk of outflowing material—some of this is accumulated by the neutron star. The neutron star then shoots off X-ray radiation that scientists can observe and measure. The study, led by OzGrav Affiliate Serena Vinciguerra, used the COMPAS code to simulate an environment like the Small Magellanic Cloud. By comparing the orbital properties of the simulated Be X-ray binaries with the observed ones, researchers revealed the probable evolution of these star systems: Initially, two stars are born in a tight binary system. The most massive star evolves quicker and expands. Because of the proximity between the two stars, the inflated massive star feeds its material to the smaller star. Over time, the massive star may feed and lose most of its mass; however, the smaller star may get too ‘full’ and not accept all the ‘food’ (material).
Each star’s individual ‘diet’ depends not only on their constitution and age, but also on the massive star feeding them. In Be X-ray binaries, the stars’ diets are more generous than what astronomers previously assumed. Consequently, the well-fed stars become massive and spin rapidly. Later in their evolution, the original most massive star may explode as a supernova, leaving behind a small but very dense neutron star. If the stars survive the explosion, they form a Be X-ray system, with a neutron star orbiting a massive and rapidly rotating star. Thermal-driven mirror for gravitational wave detectors: The illustration shows the cross-section of a thermal bimorph mirror and its constituents. Controlling the temperature of the mirror changes the curvature of the reflected wavefront. Overlaid on the cross-section is the simulated radial stress, showing a concentration of stress at the boundary of the two layers, where the adhesive holds the structure together. Credit: Huy Tuong Cao, University of Adelaide Researchers have developed a new type of deformable mirror that could increase the sensitivity of ground-based gravitational wave detectors such as the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO). Advanced LIGO measures faint ripples in space time called gravitational waves, which are caused by distant events such as collisions between black holes or neutron stars. “In addition to improving today’s gravitational wave detectors, these new mirrors will also be useful for increasing sensitivity in next generation detectors and allow detection of new sources of gravitational waves,” said research team leader Huy Tuong Cao from the University of Adelaide node of the Australian Research Centre of Excellence for Gravitational Waves Discovery (OzGrav). Deformable mirrors, which are used to shape and control laser light, have a surface made of tiny mirrors that can each be moved, or actuated, to change the overall shape of the mirror. As detailed in The Optical Society’s (OSA) journal Applied Optics, Cao and colleagues have, for the first time, made a deformable mirror based on the bimetallic effect in which a temperature change is used to achieve mechanical displacement. “Our new mirror provides a large actuation range with great precision,” said Cao. “The simplicity of the design means it can turn commercially available optics into a deformable mirror without any complicated or expensive equipment. This makes it useful for any system where precise control of beam shape is crucial.” The new technology was conceived by Cao and Aidan Brooks of LIGO as part of a visitor program between the University of Adelaide and LIGO Laboratory, funded by the Australian Research Council and National Science Foundation. Building a better mirror Ground-based gravitational wave detectors use laser light traveling back and forth down an interferometer’s two arms to monitor the distance between mirrors at each arm’s end. Gravitational waves cause a slight but detectable variation in the distance between the mirrors. Detecting this tiny change requires extremely precise laser beam steering and shaping, which is accomplished with a deformable mirror. “We are reaching a point where the precision needed to improve the sensitivity of gravitational wave detectors is beyond what can be accomplished with the fabrication techniques used to make deformable mirrors,” said Cao. Most deformable mirrors use thin mirrors to induce large amount of actuation, but these thin mirrors can produce undesirable scattering because they are hard to polish. The researchers designed a new type of deformable mirror using the bimetallic effect by attaching a piece of metal to a glass mirror. When the two are heated together the metal expands more than the glass, causing the mirror to bend. The new design not only creates a large amount of precise actuation but is also compact and requires minimum modifications to existing systems. Both the fused silica mirrors and aluminum plates used to create the deformable mirror are commercially available. To attach the two layers, the researchers carefully selected a bonding adhesive that would maximize actuation. “Importantly, the new design has fewer optical surfaces for the laser beam to travel through, said Cao. “This reduces light loss caused by scattering or absorption of coatings.” Precision characterization Creating a highly precise mirror requires precision characterization techniques. The researchers developed and built a highly sensitive Hartmann wave front sensor to measure how the mirror’s deformations changed the shape of laser light. “This sensor was crucial to our experiment and is also used in gravitational detectors to measure minute changes in the core optics of the interferometer,” said Cao. “We used it to characterize the performance of our mirrors and found that the mirrors were highly stable and have a very linear response to changes in temperature.” The tests also showed that the adhesive is the main limiting factor for the mirrors’ actuation range. The researchers are currently working to overcome the limitation caused by the adhesive and will perform more tests to verify compatibility before incorporating the mirrors into Advanced LIGO. Pulsars—a type of rotating neutron star—are well-known for their use as incredibly stable astrophysical clocks. Their regularity, used to measure their radio pulses, has led to some of the most exciting tests of Einstein’s general theory of relativity and allowed scientists to examine the behaviour of the extremely dense matter inside neutron stars. But just like ordinary clocks here on Earth, pulsars are not perfect keepers of time. Much like how a watch loses track of a few seconds each year, the exact rate at which pulsars spin appear to randomly wander by tiny amounts over month- to decade-long timescales. The spins of a small fraction of pulsars have also been seen to rapidly speed up—they start ‘ticking’ slightly faster than usual. These effects, called ‘spin noise’ and ‘glitches’, change from pulsar to pulsar and may tell us how neutron stars evolved over millions of years; however, this requires precision tracking of hundreds of pulsar spins over many years. Thanks to a series of upgrades over the last decade, the Molonglo Telescope—which celebrated its 50th birthday in 2015—can perform spin-tracking observations of hundreds of pulsars every two weeks! This enabled researchers, from the ARC Centre of Gravitational Wave Discovery (OzGrav), to find three new glitch events and measure the strength of the spin noise in 300 pulsars. In a recently published study, led by OzGrav PhD student Marcus Lower, researchers examined 280 pulsars that are most representative of normal pulsar evolution and developed a statistical method similar to the one used for analysing gravitational-wave events detected by LIGO and Virgo. The results, presented at CSIRO’s Australia Telescope National Facility colloquium, showed that spin noise seems to decrease with pulsar age and that there is a scaling relationship between spin noise strength, how quickly a pulsar spins and how fast its spin is slowing down over time. Marcus explains: ‘As spin noise becomes more obvious the longer you stare at a pulsar, we may be able to add additional pulsars to a re-analysis of the Molonglo data set in the future. We can also apply the statistical method to data from telescopes that have been tracking pulsar spins over multiple decades’. The combination of additional pulsars and longer data sets would improve the study’s current measurements and allow researchers to determine the exact cause of spin noise in pulsars. 17th August 2017: a date marked down in the history books—the day the LIGO/Virgo collaboration made the first detection of gravitational waves from the death spiral of two neutron stars. Just 1.7 seconds later, astronomers observed a short burst of high-energy gamma rays known as a gamma-ray burst (GRB). Global efforts by thousands of astronomers later identified the host galaxy and a supernova-like thermal transient called a kilonova. This event gave astronomers insight into several fundamental and important questions, including an unprecedented understanding of where gold and other heavy elements are produced in the Universe, as well as our best measurement of the speed of gravity. Among other things, it confirmed that neutron star mergers originate from short-duration GRBs. Despite the numerous observations, an important question remains unanswered. What was the outcome of this merger?
Typically, one expects the merger of two neutron stars to immediately produce a black hole—an object so dense, that light itself cannot escape; however, observations of other GRBs show evidence for the immediate formation of a massive, rapidly-spinning neutron star. Such merger remnants, if they exist, have important implications for the physical composition of neutron stars. Neutron stars are the only place in the Universe where we can study the behaviour of matter at temperatures up to 100 billion times hotter than on Earth and densities greater than an atomic nucleus—these conditions could never be reproduced on Earth. Nikhil Sarin, Paul Lasky, and Gregory Ashton—three researchers from the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav) at Monash University—recently published a study analysing all short-duration GRBs observed by NASA’s Neil Gehrels Swift Satellite. Out of 72 GRBs analysed, 18 show evidence for the immediate formation of a massive neutron star which later collapses into a black hole. Combining information from all 18 observations, the team were able to accurately describe the physical composition of these neutron stars. The results indicate that these neutron stars are consistent with having a freely-moving ‘quark’ composition and a composition like regular matter, i.e. composed of atomic nuclei—the building blocks of the Universe. Quarks are elementary particles that contain protons, neutrons and atomic nuclei. In regular matter, these quarks are confined inside protons and neutrons, but in the high density and high-temperature regimes seen in neutron stars, they may move around freely. Scientists must first determine the temperature and density of neutron stars to understand the movement and behaviour of quarks and matter. OzGrav PhD student and first author Nikhil Sarin says: ‘Our observations show a slight preference for freely-moving quarks. We look forward to getting more observations to definitively solve this puzzle’. The research also found that, before collapsing into black holes, most neutron stars produce faint gravitational waves which are not likely to be individually detected by LIGO. ‘With the construction of more sensitive gravitational-wave detectors, such as the Einstein Telescope in Europe and the Cosmic Explorer in the US, we’re confident that we’ll eventually detect individual gravitational waves from these systems,’ explains Sarin. A team of astrophysicists led by PhD student Mike Lau, from the ARC Centre of Excellence in Gravitational Wave Discovery (OzGrav), recently predicted that gravitational waves of double neutron stars may be detected by the future space satellite LISA. The results were presented at the 14th annual Australian National Institute for Theoretical Astrophysics (ANITA) science workshop 2020. These measurements may help decipher the life and death of stars. Lau, first author of the paper, compares his team to ‘astro-palaeontologists’: ‘Like learning about a dinosaur from its fossil, we piece together the life of a binary star from their double neutron star fossils.’ A neutron star is the remaining ‘corpse’ of a huge star after the supernova explosion that occurs at the end of its life. A double neutron star, a system of two neutron stars orbiting each other, produces periodic disturbances in the surrounding space-time, much like ripples spreading on a pond surface. These ‘ripples’ are called gravitational waves and made headlines when the LIGO/Virgo Collaboration detected them for the first time in 2015. These gravitational waves formed when a pair of black holes spiralled too close together and merged. However, scientists still haven’t found a way to measure the gravitational waves given off when two neutron stars or black holes are still far apart in their orbit. These weaker waves hold valuable information about the lives of stars and could reveal the existence of entirely new object populations in our Galaxy. The recent study shows that the Laser Interferometer Space Antenna (LISA) could potentially detect these gravitational waves from double neutron stars. LISA is a space-borne gravitational-wave detector that is scheduled for launch in 2034, as part of a mission led by the European Space Agency. It’s made of three satellites linked by laser beams, forming a triangle that will orbit the Sun. Passing gravitational waves will stretch and squeeze the 40 million-kilometre laser arms of this triangle. The highly sensitive detector will pick up the slowly-oscillating waves—these are currently undetectable by LIGO and Virgo. Using computer simulations to model a population of double neutron stars, the team predicts that in four years of operation, LISA will have measured the gravitational waves emitted by dozens of double neutron stars as they orbit each other. Their results were published in the Monthly Notices of the Royal Astronomical Society. A supernova explosion ‘kicks’ the neutron star it forms and makes the initial circular orbit oval-shaped. Usually, gravitational wave emission rounds off the orbit—that is the case for double neutron stars detected by LIGO and Virgo. But LISA will be able to detect double neutron stars when they’re still far apart, so it may be possible to catch a glimpse of the oval orbit. How oval the orbit is, or the eccentricity of the orbit, can tell us a lot about what the two stars looked like before they became double neutron stars. For example, their separation and how strongly they were ‘kicked’ by the supernova. Our understanding of binary stars—stars that are born as a pair—is plagued with many uncertainties. Scientists hope that by the 2030s, LISA’s detection of double neutron stars will shed some light on their secret lives. Astronomers regularly observe gravitational waves (GW)—ripples in space and time—that are caused by pairs of black holes merging into one. Einstein’s theory of gravity predicts that GW, which squeeze and stretch space as they pass, will permanently distort space, leaving a ‘memory’ of the wave behind. However, this memory effect has not yet been detected as it’s extremely small, leaving the faintest traces.
Researchers from the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav) at Monash University have finally developed a method to search and detect GW memory. Led by OzGrav PhD student Moritz Huebner, the recently published paper explains the tricky conquest of searching for memory by analysing data from numerous different observations. Huebner will be presenting these results at the Australian National Institute for Theoretical Astrophysics (ANITA) in Canberra this Thursday 6 February 2020. The scientific models expect memory to leave an extremely faint trace on the detectors which is far smaller than the waves from the black hole collision itself. Therefore, data needs to be combined from many different gravitational wave events. To do this, the team used some of the most precise GW and memory models developed from the study of black hole mergers. ‘Our algorithms carefully comb through the data and measure the exact evidence for the existence of GW memory,’ said Huebner. For each individual observation, this painstaking method can take hundreds of hours on a normal computer chip to explore all the possibilities of how a GW signal came about—this prompted the researchers to focus on fine-tuning the setting to reduce the amount of computing hours without compromising the search. So far, the results of the search applied to the first ten black-hole collisions—detected by LIGO and Virgo between 2015 and 2017—have proven inconclusive. LIGO and Virgo are not yet sensitive enough to make any statements about GW memory. So, will we ever be able to detect memory? ‘Thankfully, we can now use data from the first ten black-hole collisions and have a decent idea of how many observable GW events there will be in the future. We can also calculate how much evidence of memory can be detected in each event,’ said Huebner. Throughout the study, the researchers also discovered that their new search method must take data from approximately 2000 black hole mergers to detect memory. While this might sound implausible, the team expects to hit this number by the mid-2020s. Plus, LIGO and Virgo are continuously being upgraded and have seen more than 40 mergers since April 2019, when the third observation run started. With further technological advances and the Japanese KAGRA observatory soon coming online, the team is confident that they’ll detect multiple binaries every day which will finally lead to revealing GW memory. Link to journal: https://journals.aps.org/prd/abstract/10.1103/PhysRevD.101.023011 Scientists from the ARC Centre of Excellence in Gravitational Wave Discovery (OzGrav) reveal the eccentricity of binary black holes: the shape of the orbit formed when two black holes fall into a dance as they spiral towards each other and eventually collide. While the most common orbit is thought to be circular, about one in 20 are in egg-shaped eccentric orbits, which can indicate completely different binary life histories. Since the first detection of gravitational waves (GW) in September 2015, LIGO and its European counterpart Virgo have published the discovery of ten merging black-hole binaries. The latest run has already uncovered more than 30 new detections, with more forecast by April 2020. OzGrav PhD student (and first author) Isobel Romero-Shaw recently published a study on the origins of GW 190425 – an event which was only announced this month (January 2020) by the LIGO/Virgo collaboration. The GW signals provide a wealth of information about the pre-merger binaries; however, no one has yet deciphered how these black holes pair up in the first place. New research, published in the journal Monthly Notices of the Royal Astronomical Society, reveals an important clue to how these black hole binaries are formed, how long they’ve been ‘together’ and what happens when they finally collide. The study, led by Romero-Shaw, OzGrav Chief Investigator Eric Thrane and Associate Investigator Paul Lasky—all from Monash University—looked at data from the first and second rounds of observation of LIGO and Virgo, in particular, the ten black hole collisions that these two observation runs confirmed. They found that the orbits of all ten of these systems were remarkably circular, which is consistent with the expectation that about one in 20 orbits are not. Artist’s depiction of two black holes falling into a dance as they spiral towards each other and eventually collide. Credit: Isobel Romero-Shaw The current LIGO/Virgo run has already detected more than 30 additional collision signals. According to Romero-Shaw, the large amount of data coming from the third observing run ‘will mean we are much more likely to see eccentric collisions of black holes, which will give us real insight into how these systems form’.
According to Thrane, the more common circular orbits come from black holes who have been together from when they were garden-variety stars before they exploded and became black holes. Thrane explains: ‘These binaries are like siblings if you like. They grew up together and their orbit is circular’. Eccentric orbits occur when black holes fall under each other’s gravitational influence by chance as they are zipping around galaxies. ‘These are more like adults who meet later in life and pair up. Their orbital relationship is more interesting -- much like in life,’ he added. Importantly, when these two objects collide, the shape of their orbit means their gravitational-wave signal looks different. These detected explosions can now be used to retrospectively study the objects that collided. Lasky said that the current LIGO and Virgo observing run is detecting ‘large numbers of these binaries and by April 2020—when the run finishes—we will have a far greater insight into what these events mean’. VIDEO EXPLAINER: https://www.youtube.com/watch?v=LmW4Hd4sJvg Credit: Johan Samsing ASTRONOMERS WITNESS THE DRAGGING OF SPACE-TIME IN STELLAR COSMIC DANCE An international team of astrophysicists led by Australian Professor Matthew Bailes, from the ARC Centre of Excellence of Gravitational Wave Discovery (OzGrav), has found exciting new evidence for ‘frame-dragging’—how the spinning of a celestial body twists space and time—after tracking the orbit of an exotic stellar pair for almost two decades. The data, which is further evidence for Einstein’s theory of General Relativity, is published today (31 January 2020) in the prestigious journal, Science. More than a century ago, Albert Einstein published his iconic theory of General Relativity – that the force of gravity arises from the curvature of space and time and that objects, such as the Sun and the Earth, change this geometry. Advances in instrumentation have led to a flood of recent (Nobel prize-winning) science from phenomena further afield linked to General Relativity. The discovery of gravitational waves was announced in 2016; the first image of a black hole shadow and stars orbiting the supermassive black hole at the centre of our own galaxy was published just last year.
Almost twenty years ago, a team led by Swinburne University of Technology’s Professor Bailes—director of the ARC Centre of Excellence in Gravitational Wave Discovery (OzGrav)—started observing two stars rotating around each other at astonishing speeds with the CSIRO Parkes 64-metre radio telescope. One is a white dwarf, the size of the Earth but 300,000 times its density; the other is a neutron star which, while only 20 kilometres in diameter, is about 100 billion times the density of the Earth. The system, which was discovered at Parkes, is a relativistic-wonder system that goes by the name ‘PSR J1141-6545’. Before the star blew up (becoming a neutron star), a million or so years ago, it began to swell up discarding its outer core which fell onto the white dwarf nearby. This falling debris made the white dwarf spin faster and faster, until its day was only measured in terms of minutes. In 1918 (three years after Einstein published his Theory), Austrian mathematicians Josef Lense and Hans Thirring realised that if Einstein was right all rotating bodies should ‘drag’ the very fabric of space time around with them. In everyday life, the effect is miniscule and almost undetectable. Earlier this century, the first experimental evidence for this effect was seen in gyroscopes orbiting the Earth, whose orientation was dragged in the direction of the Earth’s spin. A rapidly spinning white dwarf, like the one in PSR J1141-6545, drags space-time 100 million times as strongly! A pulsar in orbit around such a white dwarf presents a unique opportunity to explore Einstein’s theory in a new ultra-relativistic regime. Lead author of the current study, Dr Vivek Venkatraman Krishnan (from Max Planck Institute for Radio Astronomy - MPIfR) was given the unenviable task of untangling all of the competing relativistic effects at play in the system as part of his PhD at Swinburne University of Technology. He noticed that unless he allowed for a gradual change in the orientation of the plane of the orbit, General Relativity made no sense. MPIfR’s Dr Paulo Friere realised that frame-dragging of the entire orbit could explain their tilting orbit and the team presents compelling evidence in support of this in today’s journal article—it shows that General Relativity is alive and well, exhibiting yet another of its many predictions. The result is especially pleasing for team members Bailes, Willem van Straten (Auckland University of Tech) and Ramesh Bhat (ICRAR-Curtin) who have been trekking out to the Parkes 64m telescope since the early 2000s, patiently mapping the orbit with the ultimate aim of studying Einstein’s Universe. ‘This makes all the late nights and early mornings worthwhile’, said Bhat. Expert commentary: Lead author Vivek Venkatraman Krishnan, Max Planck Institute for Radio Astronomy (MPIfR): ‘At first, the stellar pair appeared to exhibit many of the classic effects that Einstein’s theory predicted. We then noticed a gradual change in the orientation of the plane of the orbit.’ ‘Pulsars are cosmic clocks. Their high rotational stability means that any deviations to the expected arrival time of its pulses is probably due to the pulsar’s motion or due to the electrons and magnetic fields that the pulses encounter.’ ‘Pulsar timing is a powerful technique where we use atomic clocks at radio telescopes to estimate the arrival time of the pulses from the pulsar to very high precision. The motion of the pulsar in its orbit modulates the arrival time, thereby enabling its measurement.’ Dr Paulo Freire: ‘We postulated that this might be, at least in-part, due to the so-called “frame-dragging” that all matter is subject to in the presence of a rotating body as predicted by the Austrian mathematicians Lense and Thirring in 1918.’ Professor Thomas Tauris, Aarhus University: ‘In a stellar pair, the first star to collapse is often rapidly rotating due to subsequent mass transfer from its companion. Tauris’s simulations helped quantify the magnitude of the white dwarf’s spin. In this system the entire orbit is being dragged around by the white dwarf’s spin, which is misaligned with the orbit.’ Dr Norbert Wex, Max Planck Institute for Radio Astronomy (MPIfR): ‘One of the first confirmations of frame-dragging used four gyroscopes in a satellite in orbit around the Earth, but in our system the effects are 100 million times stronger.’ Evan Keane (SKA Organisation): ‘Pulsars are super clocks in space. Super clocks in strong gravitational fields are Einstein’s dream laboratories. We have been studying one of the most unusual of these in this binary star system. Treating the periodic pulses of light from the pulsar like the ticks of a clock we can see and disentangle many gravitational effects as they change the orbital configuration, and the arrival time of the clock-tick pulses. In this case we have seen Lens-Thirring precession, a prediction of General Relativity, for the first time in any stellar system.’ From Willem van Straten (AUT): ‘After ruling out a range of potential experimental errors, we started to suspect that the interaction between the white dwarf and neutron star was not as simple as had been assumed to date.’ ANIMATION: Click this link to see an animation depicting a neutron star orbiting a rapidly-spinning white dwarf. The white dwarf's spin drags the very fabric of space-time around with it, causing the orbit to tumble in space. Credit: Mark Myers, OzGrav ARC Centre of Excellence. LINK TO SCIENCE PAPER: https://science.sciencemag.org/cgi/doi/10.1126/science.aax7007 Artificial intelligence is allowing scientists to see the sources of gravitational wave faster and more accurately than ever before. Credit: James Josephide Following the recent overwhelming success of deep learning and artificial intelligence in several fields of research, industry and medicine, researchers from the ARC Centre of Excellence of Gravitational Wave Discovery (OzGrav) and the University of Western Australia (UWA), including PhD student and the paper’s first author Chayan Chatterjee, have built a deep learning model using an Artificial Neural Network to pinpoint where in the sky gravitational wave signals have come from. The model can localise the source of gravitational waves produced by colliding pairs of black holes potentially as much as a thousand times faster than any other technique.
Professor Amitava Datta, a scientist from UWA who contributed to the study, says: ‘This work is a very interesting example of learning patterns from simulated data for predicting the outcome of real events, in this case the location of gravitational wave sources. Perhaps this approach using deep learning will be more and more useful in basic sciences in general.’ Data intensive astronomy expert Kevin Vinsen from the International Centre for Radio Astronomy Research says: ‘This project is an excellent example of how a multi-disciplinary approach can solve the problem’. The basic structure of an Artificial Neural Network. The circles represent the neurons or nodes and the arrows represent connections between one neuron to another. Credit: Chayan Chatterjee Gravitational waves are small ripples in the space-time continuum caused by colossal stellar events such as colliding black holes. In September 2015, following recent advances in detector sensitivity, the LIGO Scientific Collaboration detected gravitational waves for the first time. This was a landmark achievement in human discovery and heralded the birth of the new field of gravitational wave astronomy. The need for speed and accuracy is particularly important in the context of gravitational wave localisation—scientists need to tell a global network of telescopes where to point on the sky as quickly as possible, so they can see any electromagnetic light that may also have come from the gravitational wave event. The current algorithm used to locate gravitational wave sources in real time takes a few seconds to process. More accurate methods usually take several hours to compute. The light generated by gravitational wave events can be very short-lived at certain wavelengths, like short gamma ray bursts, which last a mere 2-3 seconds, so scientists need methods that can rapidly process huge data as fast and accurately as possible. The idea behind deep learning is simple: it’s an algorithm designed to mimic the functioning of neurons in our brain to carry out tasks, like categorising observed stimuli. This is done by making the network learn the correlations between a labelled input dataset and the output it is trying to predict. Just like electric signals or synapses flow through neurons in our brain, the input information provided to an Artificial Neural Network travel through layers of nodes (usually several layers deep), with each layer introducing some non-linearity to the input. This non-linearity helps the network learn complex features of the data. The ‘learning’ happens through a rigorous ‘training’ of the network. During the training, the predictions of the network are compared with the true values, and the parameters of the network are adjusted to minimise any erroneous gaps. In their recently published paper, Chatterjee and the team from UWA successfully trained the Artificial Neural Network to learn the input data for source localisation. The data was pre-processed to extract the important physical Physics parameters from simulated gravitational wave signals, injected into ‘random noise’. The network classified these signals into several classes and accurately identified the source direction of the gravitational waves. The model localised the test samples much faster than other methods and at a low computational cost. The researchers plan to extend this work for pairs of merging neutron stars and neutron star-black hole systems. Chatterjee says: ‘Hopefully the methods we introduce can also be translated to other areas of research and industry and help further untap the seemingly limitless potential of deep learning and artificial intelligence’. OzGrav’s Chief Investigator Professor Linqing Wen who led the study says: ‘The future is wide open for gravitational wave discovery using the machine learning technique’. This paper is an outcome of a multi-disciplinary collaboration of UWA’s Gravitational Wave Astronomy Group led by OzGrav’s Chief Investigator Professor Linqing Wen, data intensive astronomy expert Kevin Vinsen from International Centre for Radio Astronomy Research (ICRAR), and Professor Amitava Datta of UWA’s Computer Science and Software Engineering. Link to publication: https://journals.aps.org/prd/abstract/10.1103/PhysRevD.100.10302 Artist's impression of the binary neutron star merger producing GW190425. Credit: National Science Foundation/LIGO/Sonoma State University/A. Simonnet. A new collaborative study with the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav) reveals a possible collision of two neutron stars earlier in 2019—only the second time this type of cosmic event had ever been detected. The gravitational-wave observatory network, that includes the National Science Foundation's LIGO and the European Virgo detectors, picked up what appeared to be gravitational ripples from a collision of two neutron stars back on 25 April 2019.
Gravitational waves and light were first witnessed in the same event in 2017. This second event in 2019, called GW190425, did not result in any light being detected; however, researchers have learned that the collision resulted in a merged object with an unusually high mass. OzGrav postdoctoral researcher Simon Stevenson says: ‘This event is a perfect example of how gravitational-wave astronomy is a completely new and unique way of looking at the Universe. Binaries with similar masses to this event may not exist in the Milky Way or may be completely invisible to conventional radio telescopes’. Neutron stars are the remnants of dead stars that exploded. When two neutron stars spiral together, they undergo a violent merger that sends gravitational waves shuddering through the fabric of space and time. The gravitational waves first detected in 2015 were generated by the fierce collision of two black holes. Since then, scientists have registered dozens of new candidate black hole mergers. The first detection of a neutron star merger took place two years later, in 2017. OzGrav Postdoctoral Researcher Vaishali Adya says: ‘This detection manifests the importance of continued improvement of the already amazingly sensitive gravitational wave detectors, as this event would not have been observable prior to the latest upgrades. OzGrav played a vital role in these upgrades, one of which involved reducing the quantum noise in the detectors’. OzGrav Postdoctoral Researcher Xingjiang Zhu says: ‘The combined mass of the merging objects is surprisingly high, much greater than any previously known double neutron star binaries including the one detected in 2017. This provokes us to think about the nature of this event and how the source might have been formed’. The combined mass of the merged bodies in this event is about 3.4 times that of the mass of the Sun. Typically, neutron star collisions are only known to happen between pairs of neutrons stars with a total mass up to 2.9 times that of the Sun. One possibility for the unusually high mass is that the collision took place not between two neutron stars, but a neutron star and a black hole, since black holes are heavier than neutron stars. But if this were the case, the black hole would have to be exceptionally small for its class. Instead, the scientists believe it is more likely that the event was a shattering of two neutron stars and that their merger resulted in a newly formed black hole. Neutron star pairs are thought to form either early in life—when companion massive stars successively die one by one—or when they come together later in life within dense, busy environments. The data from the 2019 event do not indicate which of these scenarios is more likely—more data and new models are needed to explain the unexpectedly high mass. The discovery suggests that we may have detected an entirely new population of binary neutron star systems. OzGrav Associate Investigator Greg Ashton says: ‘This event was really interesting. The chirp-like signal was seen by two of the three detectors for about 128 seconds before the final merger. Unfortunately, one of the detectors was not observing at the time, which meant that the sky localization was poor. Perhaps because of this, and because it was so far away, no electromagnetic light was observed from this event. Nevertheless, we saw it very clearly in the gravitational wave data and could use that to calculate the masses, spins, and orientations of the objects’. ‘Additional exciting and unexpected discoveries can be expected as the sensitivity of the LIGO detectors improves. OzGrav is working closely with LIGO to improve their sensitivity, developing new instrumentation and analysis techniques’, says Professor Peter Veitch, University of Adelaide OzGrav Node Leader The results were announced today at the American Astronomical Society meeting in Honolulu, Hawaii. The full scientific article will be available here post-embargo: https://dcc.ligo.org/P190425/public
AS FEATURED IN THE AGE Local scientists have begun the groundwork for a campaign to potentially make Australia the site of one of the biggest science instruments ever built. Nicknamed Cosmic Explorer South, the 40-kilometre long, $1.5 billion instrument is designed to detect ripples in space time throughout the entire universe. The global astronomy community is drawing up plans for three such detectors based around the world, which are slated for construction in the 2030s. Australia is the perfect place to build one, local scientists believe. "There is no doubt in my mind that Australia is the best location for this," says Professor Matthew Bailes, who directs the Australian Research Council Centre of Excellence for Gravitational Wave Discovery and is spearheading Australia’s bid, along with Professor David McClelland at the Australian National University. "We don’t have a preferred site yet. But we have been placing little L-shaped things on maps to see where they might fit." Explorer South is a next-generation gravitational wave detector. It would be able to sense gravitational waves from the very first stars born in the universe. It will consist of two, 40-kilometre long vacuum tubes placed at right angles, like a big L. Down the middle scientists would fire a "James Bond-strength" laser, says Professor Bailes. A device of that size would dwarf another piece of big science, the Large Hadron Collider, which is 27 kilometres in diameter and straddles the Franco-Swiss border. A white paper for the gravitational wave project was quietly submitted to the Australian Academy of Science earlier this year, proposing an initial $5 million investment to begin exploratory work. The technique has already been proved by the American-based LIGO, which first detected a gravitational wave in 2015, using two arms, each four kilometres long. How it works When black holes collide, so much energy is released it causes ripples in space time. These ripples spread out through the universe, like ripples on a pond. When they reach Earth, they slightly stretch and then shrink our space-time (yes, you are being very slightly stretched and shrunk too). As a gravitational wave passes through Earth, LIGO's arms stretch a little; a laser beam shone down the middle of the arms allows scientists to detect that tiny change in distance. Scientists now want to go further – using those ripples to get information about the formation of the universe. To do that, they need to go bigger. International astronomers are now planning the next generation of gravitational wave detectors. One wave detector, the Einstein Telescope, is planned in Europe. Another, Cosmic Explorer, is being planned for America. A third detector in the southern hemisphere – Cosmic Explorer South – would allow scientists to triangulate the source of any waves they detected. Senior experts from the National Science Foundation, the American government’s science funding agency, are aware of Australia's interest. Any location needs to be extremely flat and geologically stable, which makes Australia’s vast interior perfect. The arms of the detector need to be perfectly straight. But if you build something 40 kilometres long, you need to take into account the Earth’s curve. "So you want to find a valley, where the shape of the valley is exactly compensated by the curve of the Earth," says Professor Bailes. If you were to place it in Melbourne’s CBD, one 40 kilometre arm would stretch nearly to Healesville and the other well past Sunbury. The extreme size makes Cosmic Explorer South 100 times more powerful than LIGO, says Professor Bailes. It could measure distances down to one ten-thousandth of the width of a proton, and be sensitive enough to detect the gravity of a passing cloud. Professor Bailes would not reveal any possible locations, because of the risk of land speculators buying them. But it would need to be near an airport or regional hub, he said. The government needs long lead times on science mega-projects, and there is a lot of due diligence to do before asking for government funding, Professor Bailes says. If Explorer South were built here, Australia would likely have to spend about $300 million on the project, with the rest kicked in by governments around the world. AS FEATURED IN THE AGE. Neutron stars are among the densest objects in the Universe, and they rotate extremely fast and regularly. Until they don’t. Occasionally, these neutron stars start to spin even faster, caused by portions of the inside of the star moving outwards. It’s called a ’glitch’, and it’s a rare glimpse into what lies within these mysterious objects. In a recent paper published in Nature Astronomy, a team from the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav) at Monash University; McGill University, in Canada; and the University of Tasmania, studied the Vela Pulsar: a neutron star in the southern sky, 1,000 light years away from Earth. According to the paper’s first author Dr Greg Ashton, from OzGrav-Monash, only 5% of pulsars are known to glitch and Vela ‘glitches’ about once every three years. This makes Vela a famous prized jewel among ‘glitch hunters’ like Ashton and his colleague, Dr Paul Lasky, also from OzGrav-Monash. By reanalysing data from observations of the Vela glitch in 2016, taken by co-author Jim Palfreyman from the University of Tasmania, Ashton and his team found that during the glitch the star started spinning even faster, before relaxing down to a final state. According to Dr Lasky, this observation (done at the Mount Pleasant Observatory in Tasmania) is particularly important because, for the first time, scientists got invaluable insights into the interior of the star, revealing that the inside of the star actually has three different components. “One of these components, a soup of superfluid neutrons in the core, moves outwards first and hits the rigid crust of the star causing it to spin up. But then, a second soup of superfluid that moves in the crust catches up to the first causing the spin of the star to slow back down. This overshoot has been predicted a couple of times in the literature, but this is the first real time it’s been identified in observations,” he said. One such prediction of the overshoot came from the study’s co-author Vanessa Graber, from McGill University, who visited the Monash team as an OzGrav international visitor earlier this year. Another observation, according to Dr Ashton, defies explanation: “Immediately before the glitch, we noticed that the star seems to slow down its rotation rate before spinning back up. We actually have no idea why this is, and it’s the first time it’s ever been seen! We speculate it’s related to the cause of the glitch, but we’re honestly not sure,” he said. Ashton suspects this paper will spur some new theories on neutron stars and glitches OzGrav Associate Investigator Adam Deller and the Distributed FX Correlator (DiFX) team was recently awarded the Peter McGregor Prize by the Astronomical Society of Australia (ASA). This is a newly created and prestigious award to celebrate major achievements in the development of astronomical instrumentation and technology, both hardware and software.
The Distributed FX Correlator (DiFX) is a software package that contains tools necessary to turn an array of radio telescope signals into a functioning radio interferometer. The nominations and letters of support made a very strong case arguing the innovative nature of the DiFX and its impact. The DiFX transformed long-baseline interferometry. It has contributed significantly to reducing the barrier to entry and play a major role in radio astronomy research internationally. The system has enabled a wide range of science, as testified by the very high number of references to the key technical papers. The open-access nature of the software has put a new tool in the hands of astronomers, with demonstrated positive results. Its scalability and adaptability continues to enable researchers to tailor its behaviour and pursue what would otherwise be difficult science goals. DiFX was also used to image the black hole event horizon in 2018, so it’s evidently powerful. The DiFX collaboration includes the following contributors: Adam Deller (leader), Walter Alef, James Anderson, Matthias Bark, Matthew Bailes, Walter Brisken, Roger Cappallo, Geoff Crew, Richard Dodson, Dave Gordon, Zheng Meyer-Zhao, John Morgan, Chris Phillips, Cormac Reynolds, Jon Romney, Helge Rottman, John Spitzak, Matteo Stagni, Steven Tingay, Jan Wagner, Mark Wainright, Randall Wayth." Congratulations to everyone involved! A glimpse into the past, present and future: Hubble constant measured by neutron star fireball9/7/2019 Image by James Josephides. The Hubble constant is one of the most fundamental pieces of information that describes the state of the Universe in the past, present, and future. It tells us how fast the Universe is expanding – a valuable piece of information in science’s search for answers.
The two best ways of estimating the Hubble constant are based on: the background hiss of the Universe left over from the big bang (the ‘Planck’ observations of the cosmic microwave background radiation), and on massive stars blowing themselves to pieces in the distant Universe (‘type 1a supernovae’ observations). According to the measurements of the exploding stars, the Universe is expanding a bit faster than the measurements of the background hiss would indicate, and the difference is now very significant. So, either one of them is incorrect or something is missing in our understanding of physics and cosmology. We’d like to know what is really happening in the Universe, so we need a third, independent check. This is where the merger of two neutron stars can shed some light. Neutron star mergers are phenomenally energetic events – two stars, each more massive than the Earth’s Sun, whip around each other hundreds of times per second before colliding and producing an enormous blast of material, light and gravitational waves. In 2017, gravitational waves and light were first detected from a neutron star merger that had occurred 130 million years ago, in an event scientists refer to as GW170817. Scientists realised that a burst of gravitational waves can be used as a ‘standard siren’: based on the shape of the gravitational wave signal, we can tell how ‘bright’ the event should have been in gravitational waves. We can then measure the actual brightness of the event and work out what the distance must have been. However, this only works well if we know how the merging stars were oriented on the sky (edge on, face on, or somewhere in between). The gravitational wave data itself can’t accurately tell whether a merger was nearby and edge on, or distant and face on. To answer that question, a team including OzGrav Associate Investigator Adam Deller used radio telescopes to take a super-high-resolution movie of a narrow but powerful jet of material left behind after two neutron stars merged in the GW170817 event. The resolution of the radio images was so high, if it was an optical camera, it would see individual hairs on someone’s head 10 km away. By examining the miniscule changes in this radio-emitting bullet of gas (compared against models developed by supercomputers), the angle of the jet and the orientation of the merging neutron stars was found. Using this information, Adam and the team could tell how far away the merging neutron stars were and, by comparing this with how fast their host galaxy is rushing away from the Earth, they could finally work out the prized Hubble constant. Despite this incredible result, which is published in Nature Astronomy today, the current measurement is still not good enough to distinguish between ‘Planck’ vs ‘Type 1a supernovae’. Further observations of merging neutron stars will soon lead to a more accurate Hubble constant. Image by Carl Knox. Inside a small room in the Melbourne suburb of Hawthorn a team of astrophysicists, with a little help from work experience students and a 12-year-old boy, are leading a global hunt for one of the universe’s most mysterious and powerful phenomena. For one week this is the control centre for about 64 telescopes dotted around – and above – the Earth. The team is on the world’s biggest chase for fast radio bursts, mysterious and super-powerful blasts of radio-wave energy visible clear across the universe. But the Deeper Wider Faster team, as it is known, has even bigger ambitions. Over the past few years, astronomers have spotted a number of these bursts. The CSIRO announced on Friday that it had spotted one and traced its location to a galaxy 3.6 billion light years away. But the scientists in the Hawthorn room not only want to spot one; they hope to find out what causes the bursts. Fast radio bursts – astronomers refer to them as FRBs – are extremely short and powerful bursts of radio waves originating from somewhere outside the Milky Way. Some contain more energy within a moment than our sun produces in decades. “It’s a millisecond burst that goes off once, unpredictably. And you have no idea when. Trying to catch that, it’s hard,” says Jeff Cooke, chief investigator at the ARC Centre for Excellence in Gravitational Wave Discovery. He has spent the past half-decade pulling all this together. Last week's telescope global hook-up finished on Saturday. The team hasn't spotted anything thus far, but there were problems with one of the radio telescopes and data analysis will continue to see if anything was missed. No one knows what the bursts are. Most scientists agree they are not linked to aliens. Each astrophysicist in the control room last week at Swinburne University’s Hawthorn campus has their own favourite theory. Professor Cooke hopes they come from magnetars, a kind of neutron star with a super-powerful magnetic field. An incredibly intense "star-quake" on its surface might produce an FRB. Sara Webb hopes the answer is a blitzar, a pulsar that explodes then collapses into a black hole. And Igor Andreoni hopes FRBs come from colliding neutron stars, which generate explosions so powerful they warp the space-time fabric. To find out, the three have spent five years wrangling telescopes around the world to work together. The global coalition ranged from the high-tech – like IceCube, a sensor embedded deep under the Antarctic ice, and the Hard X-ray Modulation Telescope, flying in a low orbit of Earth – to decidedly low-tech: a telescope set up in a Pakenham backyard by an amateur astronomer. The telescopes have been looking at the same patch of sky. But – and here’s the trick – they all look with different eyes. The X-ray Modulation Telescope, for example, sees in X-rays, while IceCube’s one-kilometre-wide sensor is designed to pick up neutrino signatures. Different signals can travel through space at different speeds. Radio waves typically are the slowest. This means by the time a radio telescope detects a fast radio burst, all the other signals – things that could tell us what the FRB actually is – may have already gone racing past the Earth. The hope for last week's hook-up was that by looking with about 64 sets of different eyes, when an FRB fired off the other telescopes would spot something – a burst of light, or X-rays, or anything at all– that gave a clue as to what the FRB really is. The researchers have done six runs at this in the past four years, each time harnessing more and more telescopes. So far, nothing. Data flowed last week from the telescopes around the world to a supercomputer able to pick out anything that could possibly be a signal – like a space explosion – that could generate an FRB. The probabilities told the scientists their radio telescopes would spot one or two FRBs last week. The supercomputer, however, could identify tens of thousands of possible signals every day. The aim was for humans to check any signals within minutes of their happening in order to send a quick command to giant telescopes in Chile and South Africa that stood ready to try to get a good image of the FRB. However, the team will now need to go back over some of the results due to problems with a telescope not providing needed data. Many scientists don’t even believe an FRB will come with another signal. “So that makes it even harder,” Dr Andreoni says. In the control room one day early last week, in charge of assessing the thousands of possible FRBs is that crack team of astrophysicists – and a few work experience students. There are six of the latter, all here for the day from school. They are joined by Blake Iscaro, a 12-year-old with a deep interest in space who matter-of-factly says he is using scavenged parts to build a radio-telescope in his backyard. The supercomputer sprays the data up on the wall. Then it's up to the team to spot something. Fast. “Computers find things you know pretty well. They don’t find things you have not ever seen before,” Professor Cooke says. “If you’re going to trigger these gigantic telescopes, which cost a ridiculous amount of money, you don’t want them to point at something that wasn’t real.” Two stations down from Professor Cooke, year 10 student Max Petschack leans closer to his screen, face screwed up in concentration, staring at what looks like a yellow blob. The light curve shows the blob became dramatically brighter between measurements. “This one’s interesting,” he says. Michelle Ko leans over to look. “Wow,” she says. Max points at the light curve. “That’s a, what, point four difference?” “Yeah, that’s a huge difference,” says Michelle, before calling Dr Andreoni over. He leans over the children’s shoulders, checking their work. Is this the moment? Sadly, he does not think so. There is a lot of turbulence in the atmosphere messing with their brightness measurements. And the dot Max found is too round. “That means it’s probably a star,” Dr Andreoni says. By Liam Mannix - As featured in The Age.
The Laser Interferometer Gravitational-Wave Observatories (LIGO) are the world's largest gravitational wave observatories and a marvel of precision engineering. First predicted by Albert Einstein a century ago, gravitational waves are ripples in space-time. LIGO was responsible for the first direct detection of gravitational waves in 2015 and this led to the 2017 Nobel Prize in Physics being award to the three of the co-founders of the LIGO experiment.
The LIGO detectors consist of two interferometers spaced 3,000 kilometres apart in the US. Each L-shaped facility has two four-km arms positioned at right angles to the central building. Lasers traverse along each arm and bounce back from mirrors and, by exploiting the wave nature of light, these ripples in space-time can be detected. The sensitivity of these devices is such that scientists can measure a change in length as small as 1/10,000 the width of a proton, representing the incredibly small scale of the effects imparted by passing gravitational waves. Essentially, LIGO can be thought of as "ears" listening for gravitational waves, or even as a skin trying to "feel" the slightest of movements. Students from the ARC Centre of Excellence for Gravitational Waver Discovery (OzGrav) in Adelaide, have developed a “mini LIGO” dubbed AMIGO (Adelaide’s Mini Interferometer for Gravitational-wave Outreach) through the generous support in part by OzGrav and the University of Adelaide. They use AMIGO to demonstrate the properties of light and principals of precision measurement to students of all ages. Craig Ingram, a post-graduate student at the University of Adelaide said of the students “Many would normally run a mile if you tell them that you were going to talk to them about physics. Instead [with AMIGO] we end up with the students wide-eyed and engaged.” In the 12 months since the outreach program started in Adelaide, the researchers have delivered the program to thousands of students across the country. This includes a highly successful exhibition at the World Science Festival in Brisbane. During this two-day event, Ms Deeksha Beniwal and Ms Georgia Bolingbroke, two integral members of the AMIGO outreach team, interacted with over a thousand members of the general public. In January this year, Mr Ingram was invited to Google X headquarters in California, home to the developers of technologies such as Google Glass and WAYMO driverless cars, to use AMIGO as a tool to explain the fundamental properties of light. According to Mr. Ingram, it is only after understanding the fundamental nature of light that we can build on this to develop new technologies that Google X are investigating, such as quantum computing. The AMIGO interferometer consists of an eye-safe laser which is split and bounced through the use of strategically placed mirrors and laser beams. The desktop AMIGO is used to illustrate, along with the use of less technical props like ropes, to illustrate the wave nature of light and “in turn what gravitational waves are and how they are detected,” Ms Beniwal said. “It’s a really cool way to show how the fundamentals of physics can be used to teach us about how the universe works.” As featured on The Advertiser. Australian scientists on the hunt for gravitational waves rely on AARNet for transferring data from LIGO detectors in the USA to OzGrav nodes in Australia for analysis.
Dozens of researchers from the Australian Research Council Centre of Excellence for Gravitational Wave Discovery (OzGrav) are part of an international team of scientists making significant discoveries in the emerging field of gravitational-wave astronomy. Gravitational waves carry unique information about their dramatic origins and the nature of gravity. In 2015, scientists detected gravitational waves for the first time and concluded they were produced during the final moments of the merger of two black holes to produce a single, more massive spinning black hole. This collision of two black holes confirmed the predictions of Albert Einstein’s 1915 general theory of relativity. In 2018, the scientists detected the most massive binary black hole merger yet witnessed in the universe. The black hole that resulted from this cataclysmic event is more than 80 times as massive as our Sun. The discovery – along with evidence of nine other black hole mergers – came just over one year since scientists announced they had witnessed, for the first time, the violent death spiral of two dense neutron stars via gravitational waves. Scientists use the extremely sensitive detectors LIGO (two interferometers in the states of Louisiana and Washington, USA) and VIRGO (an interferometer in Cascina, Italy) to survey space for gravitational waves arriving at the earth from a cataclysmic event in the distant universe. Both these detectors have recently been upgraded and have almost doubled their sensitivity which means that they can survey an even larger volume of space for powerful, wave-making events, such as the collisions of black holes. One of the key upgrades to the LIGO detectors employs a technique called “squeezing” to reduce levels of quantum noise that can mask faint gravitational-wave signals. The technique was developed at the Australian National University, and has been routinely used since 2010 at the GEO600 detector. In April 2019, not long after the LIGO and VIRGO detectors were upgraded, there was much excitement around the world when astronomers revealed the first ever images of a black hole, created in the United States by Massachusetts Institute of Technology’s Dr Katie Bouman using enormous volumes of telescope data. Detection data streams are analysed using high performance computing at the LIGO and VIRGO nodes. Some of this data is transferred to international collaborators over research and education networks for further analysis and discovery, including over AARNet to the OzGrav nodes at partner institutions in Australia. OzGrav is hosted at Swinburne University in partnership with the Australian National University, Monash University, University of Adelaide, University of Melbourne, University of Western Australia, CSIRO and the Australian Astronomical Observatory and collaborators in Europe and the USA. Colm Talbot, an OzGrav scientist from Monash University says gravitational wave astronomy requires a global approach. “By studying black hole collisions and other wave-making events we act as cosmos archaeologists to understand how the universe works. From detecting events through to analysis and discovery, working together nationally and globally improves the quality of individual tasks and leads to better research outcomes.” he said. AARNet provides the reliable, scalable and secure high-speed network required for moving data between OzGrav scientists and their international collaborators to support gravitational wave research. Author: Jane Gifford from AARNet as featured on The Field. Ripples of excitement spread through the world of science this week as astronomers revealed the first ever images of a black hole, created using reams of telescope data by MIT's Dr Katie Bouman.
Black holes must rate as one of our Universe's most mysterious phenomena - colossal, monstrous objects that devour any matter and light that dares get too close. The images show "light swirling around the event horizon of a black hole right before falling into it, never to be seen again", UWA's Teresa Slaven-Blair told the AusSMC. "It’s this evidence of light being removed from the Universe that is so amazing." Monash University's Professor Ilya Mandel says that this particular black hole is in Messier 87, a galaxy in the nearby Virgo cluster, and that it weighs "a whopping 6 billion times the mass of the Sun". It lives "more than 50 million light years away", he added. So, how do you snap something in a galaxy far, far away? Swinburne University's Dr Adam Deller says the team behind the image used radio telescopes thousands of kilometres apart and lined up their signals with extraordinary precision, "to around a millionth of a millionth of a second". That allowed them "to make phenomenally sharp images – if your digital camera was this good, you could take a photo of a person hundreds of kilometres away and make out individual strands of hair on their head," he said. "They used this capability to capture the shadow that a supermassive black hole casts – it’s the first time astronomers have ever really 'seen' a black hole." Curtin University's Professor Steven Tingay explained the significance of the images - confirmation of Einstein's theory of General Relativity: "For decades, we have been studying black holes but could only indirectly see the effects of their extreme masses and gravitational fields," he said. "The images show, for the first time, the point close to the black hole from which nothing can escape, even light - the so-called event horizon...confirming the predictions of General Relativity." "Einstein’s theory passes yet another test," confirmed OzGrav's Dr Daniel Reardon. "It's a monster, but a very law-abiding one, precisely following the rules laid out by General Relativity," said Professor Mandel. Read Professor Alister Graham's article in The Conversation: Observing the invisible: the long journey to the first image of a black hole. Congratulations to Prof Linqing Wen, Dr Qi Chu and the group at UWA, as their SPIIR pipeline officially joins the LIGO-Virgo automatic public alert processing! The SPIIR pipeline also reached another major milestone this week, as it detected the first binary black hole candidate from the LIGO-Virgo 3rd observating run.
SPIIR is an online low-latency real-time search pipeline to detect binary mergers from ground-based detectors. Wen's group harnesses the computational efficiencies of parallel processing using Graphics Processing Units (GPUs) in order to make the detections as fast as possible. This is especially important for mergers that produce electromagnetic radiation that can be observed by telescopes. Researchers from the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav), as part of an international team of scientists, are set to resume their hunt for gravitational waves - ripples in space and time - on April 1. They will be taking full advantage of a series of major upgrades to the LIGO detectors. LIGO - which consists of twin detectors located in Washington and Louisiana, USA - is now about 40% more sensitive, which means that it can survey an even larger volume of space for powerful, wave-making events, such as the collisions of black holes. Joining the search will be Virgo, the gravitational-wave detector located at the European Gravitational Observatory (EGO) in Italy, which has almost doubled its sensitivity since its last run and is also starting up April 1. One of the key upgrades to the LIGO detectors employs a technique called "squeezing” to reduce levels of quantum noise that can mask faint gravitational-wave signals. The technique was developed at the Australian National University, and has been routinely used since 2010 at the GEO600 detector. Says OzGrav’s Professor David McClelland who leads this effort at ANU, "manipulating the quantum world to enhance the sensitivity of the world’s biggest laser interferometers will enable the deepest searches yet for new gravitational wave sources". OzGrav researchers have also spent time in the US installing the instrumentation, including PhD student Nutsinee Kijbunchoo who says “with every improvement in our squeezing technology, we can push further out into Universe. Seeing the range jump to more than 100 megaparsecs for the first time after injecting squeezing was one of the most exciting moments of my PhD!” Image: LIGO team members (left-to-right: Fabrice Matichard, Sheila Dwyer, Hugh Radkins) install in-vacuum equipment as part of the squeezed-light upgrade. Credit: Nutsinee Kijbunchoo/ANU Over at University of Adelaide, OzGrav postdoctoral researcher Dan Brown has also been working on developing new systems to improve LIGO’s performance. Says Dr Brown, “The group at Adelaide have been developing a variety of new sensors and adaptive optics to compensate for thermal effects from the detector’s increased laser power. Myself and students have spent much of the last year onsite at LIGO helping to prepare these systems for the next observation run, and now I’m eager to see what new discoveries they’ll enable”.
One of the challenges in gravitational wave discovery is being able to rapidly point telescopes at the source of the waves, in order to observe any emitted light before it fades. Most of the previous discoveries were found in the data with a delay of a few minutes. According to University of Western Australia’s Dr Qi Chu, “We expect the coming run to surprise us with faster detections, and we have developed a fast search pipeline to look for gravitational waves from double merger sources. Our pipeline will be processing data directly from LIGO and Virgo during this run, and will send alerts to other astronomers within seconds.” Understanding the physical and astronomical implications of detected events is done with sophisticated software that utilises state-of-the-art data-analysis techniques. New software developed at Monash University will begin operating on LIGO and Virgo data in this observing run. “It’s truly exciting to know that all new gravitational-wave events will be studied using software written and conceived in Australia” said Monash University Senior Lecturer Dr Paul Lasky. “We’re obviously excited to see what new black hole and neutron star collisions the new observing run will bring, but even more excited to see what other surprises the Universe will throw at us in the coming twelve months.” An exciting potential source for the next observing run is the explosion of a massive star called a core-collapse supernova. At Swinburne University of Technology and Monash University, researchers carry out massive simulations of exploding stars on Swinburne's new supercomputer OzSTAR to predict what their gravitational wave signal would look like. Says Dr Jade Powell (Swinburne), “Exploding stars also emit a huge number of neutrinos, which means they could produce the first ever joint detection between neutrinos, gravitational waves, and electromagnetic light.” So far LIGO and Virgo have seen ten binary black holes and one binary neutron star. “Binaries containing both a neutron star and a black hole should be out there too, so it would be great to pick up a signal from one of those as well!”, says OzGrav’s Dr Hannah Middleton (University of Melbourne). “It would also be fantastic to observe something completely different. So far the signals we have seen are all short duration, lasting several seconds at most. There should also be very long duration signals in the data, these are called continuous gravitational waves”. Those kinds of gravitational waves are expected to come from rotating neutron stars. OzGrav researchers at University of Melbourne are working on applying signal processing techniques in order to pull these incredibly faint signals out of the data. An international group of scientists, including dozens of Australians, this weekend announced the detection of the most massive binary black hole merger yet witnessed in the universe. The black hole that resulted from this cataclysmic event is more than 80 times as massive as our Sun.
The discovery of GW170729 – along with evidence of nine other black hole mergers – comes just over one year since scientists announced they had witnessed, for the first time, the violent death spiral of two dense neutron stars via gravitational waves, another set of major astrophysical discoveries have been announced in the US. The series of papers including the work of the Australians, all from the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav), present the full catalogue of observations of binary black hole and binary neutron star mergers from the first two observing runs (2015, 2016-17) of the Advanced LIGO (US) and Advanced Virgo (Italy) gravitational-wave detectors. According to Dr Meg Millhouse, from OzGrav and the University of Melbourne, the papers outline a catalogue of all gravitational wave signals "heard" by the Advanced LIGO detectors in the last three years. “These signals are generated by some of the most violent events in the universe, when pairs of neutron stars and black holes – each with many times more mass than our sun – come crashing together,” she said. Dr Simon Stevenson, from OzGrav and Swinburne University, said that the additional information of the other nine binary black holes, “means we are learning things about the population, such as how frequently binary black holes merge in the universe (once every few hundred seconds somewhere in the universe) and whether small (low mass) or large (high mass) black holes are more common -- there are many more light black holes (around 5-10 times the mass of the sun) in the universe than heavy black holes (around 30-40 times the mass of the sun), but the heavy ones are ‘louder’ in gravitational-waves, and easier to ‘hear’ colliding,” he said. “With each new detection we learn something more about how these extraordinary objects came to be. The detections also help to answer questions about the theory of gravity, the formation of galaxies, and how heavy elements (including gold and platinum) are produced”, said co-author Dr Xu (Sundae) Chen from OzGrav and the University of Western Australia. Another author, student Colm Talbot from OzGrav and Monash University, in a separate paper describes how the detection of these new black holes will assist in understanding the Universe’s entire population of black holes. “Each of these black holes formed from huge stars which died in violent explosions called supernovae. By studying these black holes, we act as black hole archaeologists to learn how these cosmic giants die,” he said. Last year Dr Paul Altin from OzGrav and the Australian National University was part of LIGO's "rapid response team", whose job it is to be ready to receive a detection alert at any time, day or night, in order to quickly analyse the data and decide whether the event is significant enough for an alert to be sent to our partner astronomers for follow-up observations. According to Dr Altin, in 2019 Advanced LIGO comes back online with even higher sensitivity, in part due to the use of quantum squeezing. “Squeezing allows us to get around noise that comes from quantum mechanics, the fundamental theory that governs microscopic particles,” he said. The Advanced LIGO squeezer was designed at ANU and is currently being installed in the US. Several OzGrav members are currently in the US at LIGO Hanford installing upgrades to the detector. According to Dr Dan Brown, from OzGrav and the University of Adelaide, the next observation run aims to use squeezed light to reach the target sensitivity to look for extreme events. “With OzGrav's expertise in squeezed light and adaptive optics for compensating thermal effects from the increased laser power we're making significant contributions towards improving LIGO for the next run,” he said. 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 of Technology (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. LIGO is funded by the NSF, and operated by Caltech and MIT, which conceived of LIGO and led the Initial and Advanced LIGO projects. Financial support for the Advanced LIGO project was led by the 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 1,200 scientists and some 100 institutions from around the world participate in the effort through the LIGO Scientific Collaboration, which includes the GEO Collaboration and the Australian collaboration OzGrav. Additional partners are listed at http://ligo.org/partners.php. The Virgo collaboration consists of more than 280 physicists and engineers belonging to 20 different European research groups: six from Centre National de la Recherche Scientifique (CNRS) in France; eight from the Istituto Nazionale di Fisica Nucleare (INFN) in Italy; two in the Netherlands with Nikhef; the MTA Wigner RCP in Hungary; the POLGRAW group in Poland; Spain with the University of Valencia; and the European Gravitational Observatory, EGO, the laboratory hosting the Virgo detector near Pisa in Italy, funded by CNRS, INFN, and Nikhef Dr Aidan Brooks (LIGO Laboratory Caltech) visited Australia in Aug-27 through Sep-21 2018 to visit the University of Adelaide (UoA) with additional short trips to UWA, ANU and Monash. The focus of the trip was divided into three main research areas with different time horizons:
Advanced LIGO support Extensive discussions were held with Dan and Peter on how Adelaide can continue to support the Hartmann sensor (HWS) code for LIGO. I also discussed the cavity eigenmode modulation (CEM) technique for cavity mode-matching and alignment that Alexei has developed. A+ preparation A+ is a medium-scale upgrade to Advanced LIGO (aLIGO) that will introduce frequency dependent squeezing and new coatings to the aLIGO test masses. Much of the trip was focused on development of adaptive optics, designed at Adelaide, for use in A+. Successful deployment of these optics will significantly reduce the complexity of the A+ adaptive optics system and could potentially reduce the budget for this system by $200k or more. LIGO-Voyager The third generation of LIGO will be called LIGO-Voyager and will require, amongst other large-scale upgrades, a 2-micron laser source so Seb showed me the one that UoA are developing. Work at other OzGrav Nodes At UWA, I had long discussions with Zhao and gave some input on their plans to develop technologies for Voyager. The Gingin facility is potentially the only site in the next few years to have a suspended Fabry-Perot cavity with silicon optics and two micron lasers and thus could be valuable for testing. I spent two days at ANU (overlapping with Rana Adhikari during that time). We provided input on the OzGrav proposal to build a high-frequency GW detector in Australia, and Bram and I discussed the requirements for two-stage tip-tilt. |
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