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In the eye of a stellar cyclone - News - The University of Sydney
Wolf-Rayet stars are one in a hundred million in our Galaxy. When paired in a binary system they can make among the most stunning ribbon structures known to astronomy. While on COVID lockdown, University of Sydney student Yinuo Han precisely modelled the Apep…
Professr Peter Tuthill. The fact this relatively simple model can reproduce the spiral geometry to this level of detail is just beautiful, Professor Tuthill said. However, not all of the physics is straightforward. Mr Hans team confirmed that the dust spiral is expanding four times slower than the measured stellar winds, something unheard of in other systems. The leading theory to explain this bizarre behaviour makes Apep a strong contender for producing a gamma-ray burst when it does finally explode, something never before witnessed in the Milky Way. Dr Joe Callingham, a co-author of the study from Leiden University in the Netherlands, said: There has been a flurry of research into Wolf-Rayet star systems: these really are the peacocks of the stellar world. Discoveries about these elegantly beautiful, but potentially dangerous objects, is causing a real buzz in astronomy. He said this paper was one of three to be published this year on the Apep system alone. Recently, the team demonstrated that Apep was not just composed of one Wolf-Rayet star, but in fact two. And colleagues from the Institute of Space and Astronautical Science in Japan will soon publish a paper on another system, Wolf-Rayet 112. Lead author of that paper, Ryan Lau, was a co-author on this paper with Mr Han. Time bombs Wolf-Rayet stars are massive stars that have reached their final stable phase before going supernova and collapsing to form compact remnants such as black holes or neutron stars. They are ticking time bombs, Professor Tuthill said. As well as exhibiting all the usual extreme behaviour of Wolf-Rayets, Apeps main star looks to be rapidly rotating. This means it could have all the ingredients to detonate a long gamma-ray burst when it goes supernova. Gamma-ray bursts are among the most energetic events in the Universe. And they are potentially deadly. If a gamma-ray burst were to impact Earth, it could strip the planet of its precious ozone layer, exposing us all to ultra-violet radiation from the Sun. Fortunately, Apeps axis of rotation means it presents no threat to Earth. 'Mind-blowing' The numbers reveal Apeps extreme nature. The two stars are each about 10 to 15 times more massive than the Sun and more than 100,000 times brighter. Where the surface of our home star is about 5500 degrees, Wolf-Rayet stars are typically 25,000 degrees or more. According to the teams newest findings, the massive stars in the Apep binary orbit each other about every 125 years at a distance comparable to the size of our Solar System. The speeds of the stellar winds produced are just mind-blowing, Mr Han said. They are spinning off the stars about 12 million kilometres an hour; thats 1 percent the speed of light. Yet the dust being produced by this system is expanding much more slowly, at about a quarter of the stellar wind speed. Mr Han said that the best explanation for this points to the fast-rotating nature of the stars. It likely means that stellar winds are launched in different directions at different speeds. The dust expansion we are measuring is driven by slower winds launched near the stars equator, he said. Our model now fits the observed data quite well, but we still havent quite explained the physics of the stellar rotation. Mr Han will continue his astronomical studies at the University of Cambridge when he starts his doctorate later this year. Declaration This work was performed in part under contract with the Jet Propulsion Laboratory funded by NASA through the Sagan Fellowship Program executed by the NASA Exoplanet Science Institute. Other funding from the Nederlandse Organisatie voor Wetenschappelijk.
Heres what armchair COVID experts are getting wrong - News - The University of Sydney
It's easy to be taken in by misinformation about COVID-19 statistics on social media, writes Dr Jacques Raubenheimer from the University of Sydney.
However, social media posts routinely compare COVID-19 figures with those of other causes of death that show: Even when researchers talk of exponential growth, they can still mislead. An Israeli professors widely-shared analysis claimed COVID-19s exponential growth fades after eight weeks. Well, he was clearly wrong. But why? His model assumed COVID-19 cases grow exponentially over a number of days, instead of over a succession of transmissions, each of which may take several days. This led him to plot only the erratic growth of the outbreaks early phase. Better visualisations truncate those erratic first cases, for instance by starting from the 100th case. Or they use estimates of the number of days it takes for the number of cases to double (about six to seven days). 3. Not all infections are cases Then theres the confusion about COVID-19 infections versus cases. In epidemiological terms, a case is a person who is diagnosed with COVID-19, mostly by a positive test result. But there are many more infections than cases. Some infections dont show symptoms, some symptoms are so minor people think its just a cold, testing is not always available to everyone who needs it, and testing does not pick up all infections. Infections cause cases, testing discovers cases. US President Donald Trump was close to the truth when he said the number of cases in the US was high because of the high rate of testing. But he and others still got it totally wrong. More testing does not result in more cases, it allows for a more accurate estimate of the true number of cases. The best strategy, epidemiologically, is not to test less, but to test as widely as possible, minimising the discrepancy between cases and overall infections. 4. We cant compare deaths with cases from the same date Estimates vary, but the time between infection and death could be as much as a month. And the variation in time to recovery is even greater. Some people get really ill and take a long time to recover, some show no symptoms. So deaths recorded on a given date reflect deaths from cases recorded several weeks prior, when the case count may have been less than half the number of current cases. The rapid case-doubling time and protracted recovery time also create a large discrepancy between counts of active and recovered cases. Well only know the true numbers in retrospect. 5. Yes, the data are messy, incomplete and may change Some social media users get angry when the statistics are adjusted, fuellingconspiracy theories. But few realise how mammoth, chaotic and complex the task is of tracking statistics on a disease like this. Countries and even states may count cases and deaths differently. It also takes time to gather the data, meaning retrospective adjustments are made. Well only know the true figures for this pandemic in retrospect. Equally so, early models were not necessarily wrong because the modellers were deceitful, but because they had insufficient data to work from. Welcome to the world of data management, data cleaning and data modelling, which many armchair statisticians dont always appreciate. Until now.
Heart disease stroke research receives 12 4 million federal funding boost - News - The University of Sydney
Improving quality of life for people affected by stroke and heart disease, designing biocompatible heart valves, just some of the projects led by University of Sydney researchers receiving $12.4 million in funding.
The Minister for Health, the Hon Greg Hunt MP announced today $29 million to address one of the leading causes of death in Australia including $12.4 million in funding for University of Sydney-led research initiatives that will reduce the health burden for people affected by stroke and heart disease. Funding will be directed into four key projects at the University: investigating the potential of an anti-inflammatory drug for patients affected by stroke; the design of a more durable biocompatible heart valve; investigating how to help people lead active lives with congenital heart disease the most common of all inborn abnormalities in Australia; and the establishment one of the most extensive datasets profiling congenital heart disease in Australia. This funding is the first round of disbursements from the Governments 10-year, $220 million investment to boost research into heart disease and stroke through the Medical Research Future Funds (MRFF) Cardiovascular Health Mission. Each year, one in five Australians are affected by heart disease and stroke, one Australian dies of cardiovascular disease every 12 minutes, and one Australian experiences a heart attack or stroke every five minutes. Professor Robyn Ward, Pro Vice-Chancellor and Executive Dean of the Faculty of Medicine and Health, said: This is an outstanding outcome for our researchers dedicated to identifying and solving some of the biggest issues in cardiovascular disease. Their work is testament to the innovative and wide-reaching research conducted at the University of Sydney, that draws upon the collaborative expertise and strengths of academics from different disciplines.
Astronomers find regular rhythms among pulsating stars - News - The University of Sydney
Young fast-rotating delta Scuti stars have defied analysis of its oscillations - until now. An Australian-led with Professor Tim Bedding from the University of Sydney has successfully discovered regular patterns in this class of stars oscillations. Their find…
Professor Tim Bedding. The Australian-led team of astronomers has reported the detection of remarkably regular high-frequency pulsation modes in 60 delta Scuti stars, ranging from 60 to 1400 light years away. This definitive identification of pulsation modes opens up a new way by which we can determine the masses, ages and internal structures of these stars, Professor Bedding said. Daniel Hey, a PhD student at the University of Sydney and co-author on the paper, designed the software that allowed the team to process the TESS data. We needed to process all 92,000 light curves, which measure a stars brightness over time. From here we had to cut through the noise, leaving us with the clear patterns of the 60 stars identified in the study, he said. Using the open-source Python library, Lightkurve, we managed to process all of the light curve data on my university desktop computer in a just few days. Asteroseismology The insides of stars were once a mystery to science. But in the past few decades, astronomers have been able to detect the internal oscillations of stars, revealing their structure. They do this by studying stellar pulsations using precise measurements of changes in light output. Over periods of time, variations in the data reveal intricate and often regular patterns, allowing us to stare into the very heart of the massive nuclear furnaces that power the universe. This branch of science, known as asteroseismology, allows us to not only understand the workings of distant stars, but to fathom how our own Sun produces sunspots, flares and deep structural movement. Applied to the Sun, it gives highly accurate information about its temperature, chemical make-up and even production of neutrinos, which could prove important in our hunt for dark matter. Asteroseismology is a powerful tool by which we can understand a broad range of stars, Professor Bedding said. This has been done with great success for many classes of pulsators including low-mass Sun-like stars, red giants, high-mass stars and white dwarfs. The delta Scuti stars had perplexed us until now. Isabel Colman, a co-author and PhD student at the University of Sydney, said: I think its incredible that we can use techniques like this to look at the insides of stars. Some of the stars in our sample host planets, including beta Pictoris, just 60 light years from Earth and which is visible to the naked eye from Australia. The more we know about stars, the more we learn about their potential effects on their planets. Poor 'social distancing' The identification of regular patterns in these intermediate-mass stars will expand the reach of asteroseismology to new frontiers, Professor Bedding said. For example, it will allow us to determine the ages of young moving groups, clusters and stellar streams. Our results show that this class of stars is very young and some tend to hang around in loose associations. They havent got the idea of 'social distancing' rules yet, Professor Bedding said. Dr George Ricker from the MIT Kavli Institute for Astrophysics and Space Research is Principal Investigator for NASAs Transiting Exoplanet Sky Survey, from which the study took its data. He said: We are thrilled that TESS data is being used by astronomers throughout the world to deepen our knowledge of stellar processes. The findings in this exciting new paper led by Tim Bedding have opened up entirely new horizons for better understanding a whole class of stars. Declaration Funding bodies include the Australian Research Council, the US National Science Foundation, NASA, Lithuanian Science Council and the Danish National Research Foundation. For full funding information please see the acknowledgements in the research paper in Nature. The authors wish to recognise and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the Indigenous Hawaiian community; we are most fortunate to have the opportunity to conduct observations from this mountain. We also acknowledge the traditional owners of the land on which the Anglo-Australian Telescope stands, the Gamilaraay people, and pay our respects to elders past, present, and emerging.