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!

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. 

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.

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.  

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