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Cambridge vs climate change | Vice-Chancellor's blog

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Weather board at Cambridge University Botanic Garden showing data for 25 July 2019

In July this year, staff at the Cambridge University Botanic Garden registered the United Kingdom’s highest ever temperature: 38.7° C. Temperatures in the glasshouses rose to an unbearable 45° C. It is clear that far from being a unique occurrence, this is part of an evolving pattern. It is widely agreed that in the future we will have to contend with increasingly frequent extreme weather events. Climate change is real, and it is happening here and now.

Today sees the beginning of a global week of action on climate change. Around the world, schoolchildren, parents, teachers, environmental campaigners and concerned citizens will be gathering to raise awareness of the dangers posed by climate change. Here in Cambridge, and with the University’s full support, students and members of staff will be among the demonstrators urging policy-makers to heed the advice of the scientific community.

Part of our responsibility as a globally influential academic institution is to take a leading role in helping our society move towards a sustainable future. As young people take to the streets, it is worth reflecting on what the University of Cambridge is doing to mitigate the environmental threat.

Cambridge chemists and physicists are developing next-generation batteries and solar cells – both of which are vital in the transition to a low-carbon economy. Our engineers are supporting the delivery of electric forms of transport that will be essential for the UK to meet its decarbonisation targets. The Cambridge Creative Circular Plastics Centre is developing methods to eliminate plastic waste.

Flood defences

From working with local communities to improve flood defences along the eastern coast, or alerting us to the increased pace of melting glaciers, to identifying populations who are most likely to shoulder the burden of climate change, our researchers are already deeply invested in helping us better understand the multifaceted nature of the challenge.

Our researchers are not only developing greener fuels, better technologies and more sustainable materials, but addressing all aspects of a zero-carbon future: the impact it will have on what we eat, how we work, how we travel, the way we communicate, how we measure economic progress and the way our societies are organised. Crucially, they are producing the knowledge to ensure that policy decisions are based on the best available evidence.

These academic efforts – arguably the greatest contribution we can make to tackling climate change – are backed up by action within the University itself, as we continue to implement the recommendations made by the Divestment Working Group in 2018.

We are leading by example, and demonstrating what is achievable. Our Sustainable Food Policy, launched in 2016, has already reduced food-related carbon emissions from our catering service by a third, and has been widely held up as an example for large institutions.

 

More recently, Cambridge became the first university in the world to announce that it has adopted a science-based target for decarbonisation, committing itself to a 75% decrease of its 2015 energy-related carbon emissions by 2030, and to reducing them to absolute zero by 2048. We are working with local authorities to plan a future that offers staff practical and affordable ways of travelling sustainably to and from work. Through our Green Impact programmewe will be seeking ideas from students and staff on how we can accelerate our decarbonisation.

New initiative

Later this term, we will be formally launching a major new initiative, led by Dr Emily Shuckburgh, harnessing the full breadth of the University’s research and teaching capabilities to respond to climate change and support the transition to a sustainable future, both in the UK and globally.  

The new initiative will develop a bold programme of education, research, demonstration projects and knowledge exchange focused on supporting a zero carbon world. Its ambition is to generate and disseminate the ideas and innovations that will shape our future – and to equip a future generation of leaders with the skills to navigate the global challenges of the coming decades.

It is being launched only a few months after the UK became the first major world economy to legislate for net zero emissions. Eliminating greenhouse gas emissions by 2050 will mean a fundamental change over the coming decades in all aspects of our economy, including how we generate energy, and how we build decarbonisation into policy and investment.

Through the initiative we will engage in active collaboration with other universities and research institutes in the UK and beyond, including the newly established Global Universities Alliance on Climate.

Unite behind the science

As the world’s leaders gather in Chile later this year for the latest round of climate change talks, the University will be decisively setting out its stall to demonstrate how it contributes to tackling this most pressing of global challenges.

I am encouraged by the younger generations’ determination to make their voices heard on the key issue of climate change. I am especially struck by the rallying cry from that remarkable activist, Greta Thunberg, to “unite behind the science”, and to put “the best available science [at] the heart of politics”.

That is exactly what Cambridge is determined to do – not only on this day of climate action, or even this week, but for the long term.

The Vice-Chancellor, Professor Stephen J Toope kicks off a global day of action with a discussion on the University’s efforts to tackle climate change.

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Women in STEM: Angela Harper

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I would like to see the future renewable energy frontiers led by women. I hope I will be one of these women, along with the many other female scientists who are paving the way towards a greener future. It is hard to ignore the global need for better renewable energy sources and storage as soon as possible, and I hope my research will lead to better energy storage alternatives sooner rather than later.

Determination will take you far in life. Any time someone tells you that you aren't good enough to pursue a career in science, or perhaps you should "do something more suited for your skills" take that as a challenge to prove that person wrong. My advice to other women is to be confident that you ARE smart enough, you ARE brilliant, and don't let anyone tell you otherwise.

It never seemed odd to me that a woman would want to pursue physics. I grew up in Clifton Park, New York, and went to a large public high school with almost 1000 students per year. I was fortunate enough to have female science teachers throughout high school, and it was partly their influence that led me to major in physics at university.

At university, I helped to set up a Women in STEM programme. I attended Wake Forest University, a liberal arts college in North Carolina. With this programme, we created an after-school project with a local middle school called ‘Girls in STEM’ which helped girls age 12-15 start thinking about STEM careers. 

Choosing my Master's project was one of the hardest moments of my research career. I finally had the chance to create my own project, and I found this incredibly challenging but also so rewarding to know that all the work I do on this project is wholly my own. My research sets out to address our global need for storing renewable energy. I currently design lithium-ion battery materials using computational techniques, with the aim of developing a battery with long life and high capacity. This would mean that we are able to use solar, wind, and renewable energy, and store this energy effectively in Li-ion batteries.

I am a theoretical physicist, so each day I come in and work on the computer. My work involves creating models of new materials, calculating energies of different battery material structures, and developing code to better understand these materials. I work in the Theory of Condensed Matter group, located in West Cambridge at the Cavendish site. In chemistry, we learn about different orbitals, energy states, and phases of materials. But actually visualising and creating a material with these chemical properties was something new for me. The first day I was able to actually visualise, on my computer screen, the orbitals in a material I had computationally identified was a fantastic moment. 

In Cambridge, every academic I talk to at all levels is concerned about improving renewable energy sources. For this reason, I have found Cambridge an incredible place to conduct research on energy materials. Furthermore, the international nature of Cambridge has helped me build collaborations in countries I would not have had access to from the United States.  

It is impossible to walk into a pub, coffee shop, or grocery store without hearing incredibly academic conversations, and I have found that academically driven environment to be extremely rewarding.

 

A bold response to the world’s greatest challenge
The University of Cambridge is building on its existing research and launching an ambitious new environment and climate change initiative. Cambridge Zero is not just about developing greener technologies. It will harness the full power of the University’s research and policy expertise, developing solutions that work for our lives, our society and our biosphere.

 

Angela Harper is a PhD candidate at the Cavendish Laboratory, a member of Churchill College, and a Gates Cambridge Scholar. Here, she tells us about her work in renewable energy, setting up a Girls in STEM programme while she was an undergraduate in North Carolina, and the importance of role models when pursuing a career in STEM. 

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Yes

Cambridge researchers awarded European Research Council funding

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One hundred and eighty-five senior scientists from across Europe were awarded grants in today’s announcement, representing a total of €450 million in research funding. The UK has 34 grantees in this year’s funding round, the second-most of any ERC participating country.

ERC grants are awarded through open competition to projects headed by starting and established researchers, irrespective of their origins, who are working or moving to work in Europe. The sole criterion for selection is scientific excellence.

ERC Advanced Grants are designed to support excellent scientists in any field with a recognised track record of research achievements in the last ten years.

Professors Mete Atatüre and Jeremy Baumberg, both based at Cambridge’s Cavendish Laboratory, work on diverse ways to create new and strange interactions of light with matter that is built from tiny nano-sized building blocks.

Baumberg’s PICOFORCE project traps light down to the size of individual atoms which will allow him to invent new ways of tugging them, levitating them, and putting them together. Such work uncovers the mysteries of how molecules and metals interact, crucial for creating energy sustainably, storing it, and developing electronics that can switch with thousands of times less power need than currently.

"This funding recognises the huge need for fundamental science to advance our knowledge of the world – only the most imaginative and game-changing science gets such funding," said Baumberg.

Atatüre’s project, PEDESTAL, investigates diamond as a material platform for quantum networks. What gives gems their colour also turns out to be interesting candidates for quantum computing and communication technologies. By developing large-scale diamond-semiconductor hybrid quantum devices, the project aims to demonstrate high-rate and high-fidelity remote entanglement generation, a building block for a quantum internet.

"The impact of ERC funding on my group’s research had been incredible in the last 12 years, through Starting and Consolidator grants. I am very happy that with this new grant we as UK scientists can continue to play an important part in the vibrant research culture of Europe," said Atatüre.

Professor Judith Driscoll from Cambridge’s Department of Materials Science & Metallurgy was also awarded ERC funding for her work on nanostructured electronic materials. She is also spearheading joint work of her team, as well as those of Baumberg and Atatüre, on low-energy IT devices.

"My approach uses a different way of designing and creating oxide nano-scale film structures with different materials to both create new electronic device functions as well as much more reliable and uniform existing functions," she said. "Cambridge is a fantastic place that enables all our approaches to come together, driven by cohorts of inspirational young researchers in our UK-funded Centre for Doctoral Training in Nanoscience and Nanotechnology – the NanoDTC."

Professor John Robb from Cambridge’s Department of Archaeology was awarded an ERC grant for the ANCESTORS project on the politics of death in prehistoric Europe. The project takes the methods developed in the ‘After the Plague’ project and the taphonomy methods developed in the Scaloria Cave project and apply them to a major theoretical problem in European prehistory - the nature of community and the rise of inequality.

"This project is really exciting and I’ll be working with wonderful colleagues Dr Christiana ‘Freddi’ Scheib at the University of Tartu and Dr Mary Anne Tafuri at Sapienza University of Rome," said Robb. "The results will allow us to evaluate for the first time how inequality affected lives in prehistoric Europe and what role ancestors played in it."

Four researchers at the University of Cambridge have won advanced grants from the European Research Council (ERC), Europe’s premier research funding body.

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Yes

AI techniques used to improve battery health and safety

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The researchers, from Cambridge and Newcastle Universities, have designed a new way to monitor batteries by sending electrical pulses into them and measuring the response. The measurements are then processed by a machine learning algorithm to predict the battery’s health and useful lifespan. Their method is non-invasive and is a simple add-on to any existing battery system. The results are reported in the journal Nature Communications.

Predicting the state of health and the remaining useful lifespan of lithium-ion batteries is one of the big problems limiting widespread adoption of electric vehicles: it’s also a familiar annoyance to mobile phone users. Over time, battery performance degrades via a complex network of subtle chemical processes. Individually, each of these processes doesn’t have much of an effect on battery performance, but collectively they can severely shorten a battery’s performance and lifespan.

Current methods for predicting battery health are based on tracking the current and voltage during battery charging and discharging. This misses important features that indicate battery health. Tracking the many processes that are happening within the battery requires new ways of probing batteries in action, as well as new algorithms that can detect subtle signals as they are charged and discharged.

"Safety and reliability are the most important design criteria as we develop batteries that can pack a lot of energy in a small space," said Dr Alpha Lee from Cambridge’s Cavendish Laboratory, who co-led the research. "By improving the software that monitors charging and discharging, and using data-driven software to control the charging process, I believe we can power a big improvement in battery performance."

The researchers designed a way to monitor batteries by sending electrical pulses into it and measuring its response. A machine learning model is then used to discover specific features in the electrical response that are the tell-tale sign of battery aging. The researchers performed over 20,000 experimental measurements to train the model, the largest dataset of its kind. Importantly, the model learns how to distinguish important signals from irrelevant noise. Their method is non-invasive and is a simple add-on to any existing battery systems.

The researchers also showed that the machine learning model can be interpreted to give hints about the physical mechanism of degradation. The model can inform which electrical signals are most correlated with aging, which in turn allows them to design specific experiments to probe why and how batteries degrade.

"Machine learning complements and augments physical understanding," said co-first author Dr Yunwei Zhang, also from the Cavendish Laboratory. "The interpretable signals identified by our machine learning model are a starting point for future theoretical and experimental studies."

The researchers are now using their machine learning platform to understand degradation in different battery chemistries. They are also developing optimal battery charging protocols, powering by machine learning, to enable fast charging and minimise degradation.

This work was carried out with funding from the Faraday Institution. Dr Lee is also a Research Fellow at St Catharine’s College.

Reference:
Yunwei Zhang et al. ‘Identifying degradation patterns of lithium ion batteries from impedance spectroscopy using machine learning.’ Nature Communications (2020). DOI: 10.1038/s41467-020-15235-7

Researchers have designed a machine learning method that can predict battery health with 10x higher accuracy than current industry standard, which could aid in the development of safer and more reliable batteries for electric vehicles and consumer electronics.

Person holding white Android phone

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Yes

New app collects the sounds of COVID-19

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The COVID-19 Sounds App is now available as a web app for Chrome and Firefox browsers. Versions for Android and iOS will be available soon.

As COVID-19 is a respiratory condition, the sounds made by people with the condition – including voice, breathing and cough sounds – are very specific. A large, crowdsourced data set will be useful in developing machine learning algorithms that could be used for automatic detection of the condition.

"There’s still so much we don’t know about this virus and the illness it causes, and in a pandemic situation like the one we’re currently in, the more reliable information you can get, the better," said Professor Cecilia Mascolo from Cambridge’s Department of Computer Science and Technology, who led the development of the app.

"I am amazed at the speed that we managed to connect across the University to conceive this project, and how Cecilia's team of developers came together to respond to the urgency of the situation," said Professor Pietro Cicuta from Cambridge’s Cavendish Laboratory, a member of the team behind the app’s development. Professor Andres Floto, Professor of Respiratory Biology at the University, and Research Director of the Cambridge Centre for Lung Infection at Papworth Hospital, Cambridge, has also advised on the clinical aspects of the app.

The COVID-19 Sounds App collects basic demographic and medical information from users, as well as spoken voice samples, breathing and coughing samples through the phone’s microphone. The app will also ask users if they have tested positive for the coronavirus.

In addition, the app will collect one coarse grain location sample. The app will not track users, and will only collect location data once when users are actively using it. The data will be stored on University servers and be used solely for research purposes. The app will not provide any medical advice.

Once they have completed their initial analysis of the data collected by the app, the team will release the dataset to other researchers. The dataset could help shed light on disease progression, further relationship of the respiratory complication with medical history, for example.

"Having spoken to doctors, one of the most common things they have noticed about patients with the virus is the way they catch their breath when they’re speaking, as well as a dry cough, and the intervals of their breathing patterns," said Mascolo. "There are very few large datasets of respiratory sounds, so to make better algorithms that could be used for early detection, we need as many samples from as many participants as we can get. Even if we don’t get many positive cases of coronavirus, we could find links with other health conditions."

The study has been approved by the Ethics Committee of the Department of Computer Science and Technology, and is partly funded by the European Research Council through Project EAR.

How you can support Cambridge's COVID-19 research effort

Donate to support COVID-19 research at Cambridge

 

A new app, which will be used to collect data to develop machine learning algorithms that could automatically detect whether a person is suffering from COVID-19 based on the sound of their voice, their breathing and coughing, has been launched by researchers at the University of Cambridge.

Transmission electron microscopic image of an isolate from the first US case of COVID-19

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Shedding light on dark traps

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A multi-institutional collaboration, co-led by scientists at the University of Cambridge and Okinawa Institute of Science and Technology Graduate University (OIST), has identified the source of efficiency-limiting defects in potential materials for next-generation solar cells and LEDs.

In the last decade, perovskites – a diverse range of materials with a specific crystal structure – have emerged as promising alternatives to silicon solar cells, as they are cheaper and greener to manufacture, while achieving a comparable level of efficiency. 

However, perovskites still show significant performance losses and instabilities, particularly in the specific materials that promise the highest ultimate efficiencyMost research to date has focused on ways to remove these losses, but their actual physical causes remain unknown  

Now, in a paper published in Nature, researchers from Dr Sam Stranks’s group at Cambridge’s Department of Chemical Engineering and Biotechnology and Cavendish Laboratoryand Professor Keshav Dani’s Femtosecond Spectroscopy Unit at OIST in Japan, identify the source of the problem. Their discovery could streamline efforts to increase the efficiency of perovskites, bringing them closer to mass-market production.    

Perovskite materials are much more tolerant of defects in their structure than silicon solar cells, and previous research carried out by Stranks’s group found that to a certain extent, some heterogeneity in their composition actually improves their performance as solar cells and light-emitters 

However, the current limitation of perovskite materials is the presence of a 'deep trap' caused by a defect, or minor blemish, in the material. These are areas in the material where energised charge carriers can get stuck and recombine, losing their energy to heat, rather than converting it into useful electricity or light. This recombination process can have a significant impact on the efficiency and stability of solar panels and LEDs.  

Until now, very little was known about the cause of these traps, in part because they appear to behave differently to traps in traditional solar cell materials 

In 2015, Stranks and colleagues published a paper in Science looking at the luminescence of perovskites, which reveals how good they are at absorbing or emitting lightWe found that the material was very heterogeneous; you had quite large regions that were bright and luminescent and other regions that were really dark,” said StranksThese dark regions correspond to power losses in solar cells or LEDs. But what was causing the power loss was always a mysteryespecially because perovskites are otherwise so defect-tolerant. 

Due to limitations of standard imaging techniques, the group couldn’t tell if the darker areas were caused by one, large trap site, or many smaller traps, making it difficult to establish why they were forming only in certain regions 

In 2017, Dani’s group at OIST made movie of how electrons behave in semiconductors after absorbing light. “You can learn a lot from being able to see how charges move in a material or device after shining lightFor example, you can see where they might be getting trapped,” said DaniHowever, these charges are hard to visualise as they move very fast – on the timescale of a millionth of a billionth of a second; and over very short distances – on the length scale of a billionth of a metre.  

On hearing of Dani’s workStranks reached out to see if they could work together to address the problem visualising the dark regions in perovskites 

The team at OIST used a technique called photoemission electron microscopy (PEEM) for the first time on perovskiteswhere they probed the material with ultraviolet light and built up an image based on how the emitted electrons scattered 

When they looked at the material, they found that the dark regions contained traps, around 10-100 nanometers in length, which were clusters of smaller atomic-sized trap sites. These trap clusters were spread unevenly throughout the perovskite material, explaining the heterogeneous luminescence seen in Stranks’s earlier research. 

When the researchers overlaid images of the trap sites onto images that showed the crystal grains of the perovskite material, they found that the trap clusters only formed at specific places, at the boundaries between certain grains. 

To understand why this only occurred at certain grain boundaries, the groups worked together with Professor Paul Midgley’s team from Cambridge’s Department of Materials Science and Metallurgy using a technique called scanning electron diffraction to create detailed images of the perovskite crystal structure. The project team made use of the electron microscopy setup at the ePSIC facility at the Diamond Light Source Synchrotron, which has specialised equipment for imaging beam-sensitive materials, like perovskites.  

“Because these materials are very beam-sensitive, typical techniques that you would use to probe local crystal structure on these length scales will quite quickly change the material as you're looking at it, which can make interpreting the data very difficult,” said Tiarnan Doherty, a PhD student in Strankss group and co-lead author of the study. Instead, we were able to use very low exposure doses and therefore prevent damage.  

From the work at OIST, we knew where the trap clusters were located, and at ePSIC, we scanned around those same areas to see the local structure. We were then able to quickly pinpoint unexpected variations in the crystal structure around the trap clusters. 

The group discovered that the trap clusters only formed at junctions where an area of the material with slightly distorted structure met an area with pristine structure. 

“In perovskites, we have regular mosaic grains of material and most of the grains are nice and pristine – the structure we would expect,” said StranksBut every now and again, you get a grain that's slightly distorted and the chemistry of that grain is inhomogeneous. What was really interesting and which initially confused us was that it's not the distorted grain that's the trap but where that grain meets a pristine grain; it's at that junction that the traps cluster.  

With this understanding of the nature of the trapsthe team at OIST also used the custom-built PEEM instrumentation to visualise the dynamics of the charge carrier trapping process happening in the perovskite material. This was possible as one of the unique features of our PEEM setup is that it can image ultrafast processes – as short as femtoseconds,” said Andrew Winchester, a PhD student in Dani’s Unit, and co-lead author of this study. “We found that the trapping process was dominated by charge carriers diffusing to the trap clusters. 

These discoveries represent a breakthrough in the quest to bring perovskites to the solar energy market.  

We still don't know exactly why the traps are clustering there, but we noknow that they do form there, and seemingly only there,” said StranksThat's exciting because it means we now know what to target to bring up the performances of perovskites. We need to target those inhomogeneous phases or get rid of these junctions in some way. 

“The fact that charge carriers must first diffuse to the traps could also suggest other strategies to improve these devices,” said Dani. “Maybe we could alter or control the arrangement of the trap clusters, without necessarily changing their average number, such that charge carriers are less likely to reach these defect sites.”  

The teams’ research focused on one particular perovskite structureThe scientists will now be investigating whether the cause of these trapping clusters is universal across other perovskite materials.  

“Most of the progress in device performance has been trial and error and so far, this has been quite an inefficient process,” said Stranks. “To date, it really hasn't been driven by knowing a specific cause and systematically targeting that. This is one of the first breakthroughs that will help us to use the fundamental science to engineer more efficient devices.” 

Reference:
Tiarnan A.S. Doherty et al. 'Performance-limiting nanoscale trap clusters at grain junctions in halide perovskites.' Nature (2020). DOI: 10.1038/s41586-020-2184-1

 

Researchers pinpoint the origin of defects that sap the performance of next-generation solar technology.

We now know what to target to bring up the performances of perovskites.
Samuel Stranks
Perovskites

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Yes

‘Lost’ world’s rediscovery is step towards finding habitable planets

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Night sky at ESO's Paranal Observatory in Chile

The planet, the size and mass of Saturn with an orbit of thirty-five days, is among hundreds of ‘lost’ worlds that astronomers, including from the University of Cambridge, are using new techniques to track down and characterise, in the hope of finding cooler planets like those in our solar system, and even potentially habitable planets.

Reported in Astrophysical Journal Letters, the planet named NGTS-11b orbits a star 620 light-years away and is located five times closer to its sun than Earth is to our own.

The planet was originally found in a search for planets in 2018 by the University of Warwick-led team using data from NASA’s TESS telescope. This uses the transit method to spot planets, scanning for the tell-tale dip in light from the star that indicates that an object has passed between the telescope and the star.

However, TESS only scans most sections of the sky for 27 days. This means many of the longer period planets only transit once in the TESS data: without a second observation the planet is effectively lost. Researchers from Cambridge’s Cavendish Laboratory are part of the Next-Generation Transit Survey (NGTS) team which, after identifying a single transit event in the TESS data of the star NGTS-11, monitored the system in search of additional transits to confirm the planetary nature of the transiting object.

“By chasing that second transit down we’ve found a longer period planet. It’s the first of hopefully many such finds pushing to longer periods,” said lead author Dr Samuel Gill from the University of Warwick. “These discoveries are rare but important, since they allow us to find longer period planets than other astronomers are finding. Longer period planets are cooler, more like the planets in our own solar system.”

NGTS-11b has a temperature of only 160°C – cooler than Mercury or Venus. Although this is still too hot to support life as we know it, it is closer to the Goldilocks zone than many previously discovered planets which typically have temperatures above 1000°C. The Goldilocks zone refers to a range of orbits that would allow a planet or moon to support liquid water: too close to its star and it will be too hot, but too far away and it will be too cold.

“While we have discovered many planets that orbit close to their host star, we know of fewer at longer periods and cooler temperatures, which makes NGTS-11b an interesting find that takes us one step closer to finding planets in the Goldilocks zone,” said co-author Dr Ed Gillen from Cambridge’s Cavendish Laboratory. “Longer period planets like NGTS-11b may help us to better understand the various evolutionary processes that planetary systems undergo both during and after their formation.”

NGTS has twelve state-of-the-art telescopes at its site in Chile, which means that researchers can monitor multiple stars for months on end, searching for lost planets. The dip in light from NGTS-11b is only 1% deep and occurs only once every 35 days, putting it out of reach of other telescopes.

There are hundreds of single transits detected by TESS that researchers will be monitoring using this method. This will allow them to discover cooler exoplanets of all sizes, including planets more like those in our own solar system. Some of these will be small rocky planets in the Goldilocks zone that are cool enough to host liquid water oceans and potentially extra-terrestrial life.

The research was supported by the Science and Technology Facilities Council (STFC), part of UK Research and Innovation (UKRI).

Reference:
Samuel Gill et al. ‘NGTS-11 b (TOI-1847 b): A Transiting Warm Saturn Recovered from a TESS Single-transit Event.’ The Astrophysical Journal Letters (2020). DOI: 10.3847/2041-8213/ab9eb9

Adapted from a University of Warwick press release.

The rediscovery of a lost planet could pave the way for the detection of a world within the habitable ‘Goldilocks zone’ in a distant solar system.

NGTS-11b is an interesting find that takes us one step closer to finding planets in the Goldilocks zone
Ed Gillen
Paranal nights

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‘Quantum negativity’ can power ultra-precise measurements

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Artist's impression of a quantum metrology device

The researchers, from the University of Cambridge, Harvard and MIT, have shown that quantum particles can carry an unlimited amount of information about things they have interacted with. The results, reported in the journal Nature Communications, could enable far more precise measurements and power new technologies, such as super-precise microscopes and quantum computers.

Metrology is the science of estimations and measurements. If you weighed yourself this morning, you’ve done metrology. In the same way as quantum computing is expected to revolutionise the way complicated calculations are done, quantum metrology, using the strange behaviour of subatomic particles, may revolutionise the way we measure things.

We are used to dealing with probabilities that range from 0% (never happens) to 100% (always happens). To explain results from the quantum world however, the concept of probability needs to be expanded to include a so-called quasi-probability, which can be negative. This quasi-probability allows quantum concepts such as Einstein’s ‘spooky action at a distance’ and wave-particle duality to be explained in an intuitive mathematical language. For example, the probability of an atom being at a certain position and travelling with a specific speed might be a negative number, such as –5%.   

An experiment whose explanation requires negative probabilities is said to possess ‘quantum negativity.’ The scientists have now shown that this quantum negativity can help take more precise measurements.

All metrology needs probes, which can be simple scales or thermometers. In state-of-the-art metrology however, the probes are quantum particles, which can be controlled at the sub-atomic level. These quantum particles are made to interact with the thing being measured. Then the particles are analysed by a detection device.

In theory, the greater number of probing particles there are, the more information will be available to the detection device. But in practice, there is a cap on the rate at which detection devices can analyse particles. The same is true in everyday life: putting on sunglasses can filter out excess light and improve vision. But there is a limit to how much filtering can improve our vision — having sunglasses which are too dark is detrimental.

“We’ve adapted tools from standard information theory to quasi-probabilities and shown that filtering quantum particles can condense the information of a million particles into one,” said lead author Dr David Arvidsson-Shukur from Cambridge’s Cavendish Laboratory and Sarah Woodhead Fellow at Girton College. “That means that detection devices can operate at their ideal influx rate while receiving information corresponding to much higher rates. This is forbidden according to normal probability theory, but quantum negativity makes it possible.”

An experimental group at the University of Toronto has already started building technology to use these new theoretical results. Their goal is to create a quantum device that uses single-photon laser light to provide incredibly precise measurements of optical components. Such measurements are crucial for creating advanced new technologies, such as photonic quantum computers.

“Our discovery opens up exciting new ways to use fundamental quantum phenomena in real-world applications,” said Arvidsson-Shukur.

Quantum metrology can improve measurements of things including distances, angles, temperatures and magnetic fields. These more precise measurements can lead to better and faster technologies, but also better resources to probe fundamental physics and improve our understanding of the universe. For example, many technologies rely on the precise alignment of components or the ability to sense small changes in electric or magnetic fields. Higher precision in aligning mirrors can allow for more precise microscopes or telescopes, and better ways of measuring the earth’s magnetic field can lead to better navigation tools.

Quantum metrology is currently used to enhance the precision of gravitational wave detection in the Nobel Prize-winning LIGO Hanford Observatory. But for the majority of applications, quantum metrology has been overly expensive and unachievable with current technology. The newly-published results offer a cheaper way of doing quantum metrology.

“Scientists often say that ‘there is no such thing as a free lunch’, meaning that you cannot gain anything if you are unwilling to pay the computational price,” said co-author Aleksander Lasek, a PhD candidate at the Cavendish Laboratory. “However, in quantum metrology this price can be made arbitrarily low. That’s highly counterintuitive, and truly amazing!”

Dr Nicole Yunger Halpern, co-author and ITAMP Postdoctoral Fellow at Harvard University, said: “Everyday multiplication commutes: Six times seven equals seven times six. Quantum theory involves multiplication that doesn’t commute. The lack of commutation lets us improve metrology using quantum physics.

“Quantum physics enhances metrology, computation, cryptography, and more; but proving rigorously that it does is difficult. We showed that quantum physics enables us to extract more information from experiments than we could with only classical physics. The key to the proof is a quantum version of probabilities — mathematical objects that resemble probabilities but can assume negative and non-real values.”

 

Reference:
David R. M. Arvidsson-Shukur et al. ‘Quantum advantage in postselected metrology.’ Nature Communications (2020). DOI: 10.1038/s41467-020-17559-w

Scientists have found that a physical property called ‘quantum negativity’ can be used to take more precise measurements of everything from molecular distances to gravitational waves.

We’ve shown that filtering quantum particles can condense the information of a million particles into one
David Arvidsson-Shukur
Artist's impression of a quantum metrology device

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AI shows how hydrogen becomes a metal inside giant planets

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Dense metallic hydrogen – a phase of hydrogen which behaves like an electrical conductor – makes up the interior of giant planets, but it is difficult to study and poorly understood. By combining artificial intelligence and quantum mechanics, researchers have found how hydrogen becomes a metal under the extreme pressure conditions of these planets.

The researchers, from the University of Cambridge, IBM Research and EPFL, used machine learning to mimic the interactions between hydrogen atoms in order to overcome the size and timescale limitations of even the most powerful supercomputers. They found that instead of happening as a sudden, or first-order, transition, the hydrogen changes in a smooth and gradual way. The results are reported in the journal Nature.

Hydrogen, consisting of one proton and one electron, is both the simplest and the most abundant element in the Universe. It is the dominant component of the interior of the giant planets in our solar system – Jupiter, Saturn, Uranus, and Neptune – as well as exoplanets orbiting other stars.

At the surfaces of giant planets, hydrogen remains a molecular gas. Moving deeper into the interiors of giant planets however, the pressure exceeds millions of standard atmospheres. Under this extreme compression, hydrogen undergoes a phase transition: the covalent bonds inside hydrogen molecules break, and the gas becomes a metal that conducts electricity.

“The existence of metallic hydrogen was theorised a century ago, but what we haven’t known is how this process occurs, due to the difficulties in recreating the extreme pressure conditions of the interior of a giant planet in a laboratory setting, and the enormous complexities of predicting the behaviour of large hydrogen systems,” said lead author Dr Bingqing Cheng from Cambridge’s Cavendish Laboratory.

Experimentalists have attempted to investigate dense hydrogen using a diamond anvil cell, in which two diamonds apply high pressure to a confined sample. Although diamond is the hardest substance on Earth, the device will fail under extreme pressure and high temperatures, especially when in contact with hydrogen, contrary to the claim that a diamond is forever. This makes the experiments both difficult and expensive.

Theoretical studies are also challenging: although the motion of hydrogen atoms can be solved using equations based on quantum mechanics, the computational power needed to calculate the behaviour of systems with more than a few thousand atoms for longer than a few nanoseconds exceeds the capability of the world’s largest and fastest supercomputers.

It is commonly assumed that the transition of dense hydrogen is first-order, which is accompanied by abrupt changes in all physical properties. A common example of a first-order phase transition is boiling liquid water: once the liquid becomes a vapour, its appearance and behaviour completely change despite the fact that the temperature and the pressure remain the same.

In the current theoretical study, Cheng and her colleagues used machine learning to mimic the interactions between hydrogen atoms, in order to overcome limitations of direct quantum mechanical calculations.

“We reached a surprising conclusion and found evidence for a continuous molecular to atomic transition in the dense hydrogen fluid, instead of a first-order one,” said Cheng, who is also a Junior Research Fellow at Trinity College.

The transition is smooth because the associated ‘critical point’ is hidden. Critical points are ubiquitous in all phase transitions between fluids: all substances that can exist in two phases have critical points. A system with an exposed critical point, such as the one for vapour and liquid water, has clearly distinct phases. However, the dense hydrogen fluid, with the hidden critical point, can transform gradually and continuously between the molecular and the atomic phases. Furthermore, this hidden critical point also induces other unusual phenomena, including density and heat capacity maxima.

The finding about the continuous transition provides a new way of interpreting the contradicting body of experiments on dense hydrogen. It also implies a smooth transition between insulating and metallic layers in giant gas planets. The study would not be possible without combining machine learning, quantum mechanics, and statistical mechanics. Without any doubt, this approach will uncover more physical insights about hydrogen systems in the future. As the next step, the researchers aim to answer the many open questions concerning the solid phase diagram of dense hydrogen.

 

Reference:
Bingqing Cheng et al. ‘Evidence for supercritical behaviour of high-pressure liquid hydrogen.’ Nature (2020). DOI: 10.1038/s41586-020-2677-y.

Researchers have used a combination of AI and quantum mechanics to reveal how hydrogen gradually turns into a metal in giant planets.

The existence of metallic hydrogen was theorised a century ago, but what we haven’t known is how this process occurs
Bingqing Cheng

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Hints of life discovered on Venus

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Synthesized false colour image of Venus

Astronomers have speculated for decades that high clouds on Venus could offer a home for microbes – floating free of the scorching surface, but tolerating very high acidity. The detection of phosphine molecules, which consist of hydrogen and phosphorus, is an important step in the search for life beyond Earth, a key question in science. The results are reported in the journal Nature Astronomy.

The discovery was made by Professor Jane Greaves while she was a visitor at the University of Cambridge’s Institute of Astronomy. Greaves and her collaborators used the James Clerk Maxwell Telescope (JCMT) in Hawaii to detect the phosphine, and followed up their discovery on the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile. Both facilities observe Venus at a wavelength of about 1 millimetre, much longer than the human eye can see.

“This was an experiment made out of pure curiosity, really – taking advantage of JCMT’s powerful technology, and thinking about future instruments,” said Greaves, who is based at Cardiff University. “I thought we’d just be able to rule out extreme scenarios, like the clouds being stuffed full of organisms. When we got the first hints of phosphine in Venus’ spectrum, it was a shock!”

Luckily, conditions were good at ALMA for follow-up observations while Venus was at a suitable angle to Earth. Processing the data was challenging, however, as ALMA isn’t usually looking for subtle effects in bright objects like Venus.

“In the end, we found that both observatories had seen the same thing – faint absorption at the right wavelength to be phosphine gas, where the molecules are backlit by the warmer clouds below,” said Greaves.

Using existing models of the Venusian atmosphere to interpret the data, the researchers found that phosphine is present but scarce – only about twenty molecules in every billion. The astronomers then ran calculations to see if the phosphine could come from natural processes on Venus. They caution that some information is lacking – in fact, the only other study of phosphorus on Venus came from one lander experiment, carried by the Soviet Vega 2 mission in 1985.

On Earth, phosphine is only made industrially or by microbes that thrive in oxygen-free environments. Co-author Dr William Bains from MIT led the work on assessing natural ways to make phosphine on Venus. Ideas included sunlight, minerals blown upwards from the surface, volcanoes, or lightning, but none of these could make anywhere near enough. Natural sources were found to make at most one ten-thousandth of the amount of phosphine that the telescopes saw.

To create the observed quantity of phosphine on Venus, terrestrial organisms would only need to work at about 10% of their maximum productivity, according to calculations by co-author Dr Paul Rimmer of Cambridge’s Department of Earth Sciences. Any microbes on Venus will likely be very different from their Earth cousins though, to survive in hyper-acidic conditions.

“This discovery brings us right to the shores of the unknown,” said Rimmer, who is also affiliated with Cambridge's Cavendish Laboratory. “Phosphine is very hard to make in the oxygen-rich, hydrogen-poor clouds of Venus and fairly easy to destroy. The presence of life is the only known explanation for the amount of phosphine inferred by observations.

“Both of these facts lie at the edge of our knowledge: the observations could be caused by an unknown molecule, or could be caused by chemistry we’re not aware of. Ultimately, the only way to find out what's really happening is to send a mission into the clouds of Venus to take a sample of the droplets and look at them to see what's inside.”

Earth bacteria can absorb phosphate minerals, add hydrogen, and ultimately expel phosphine gas. It costs them energy to do this, so why they do it is not clear. The phosphine could be just a waste product, but other scientists have suggested purposes like warding off rival bacteria.

Co-author Dr Clara Sousa Silva from MIT was also thinking about searching for phosphine as a ‘biosignature’ gas of non-oxygen-using life on planets around other stars because normal chemistry makes so little of it. “Finding phosphine on Venus was an unexpected bonus,” she said. “The discovery raises many questions, such as how any organisms could survive. On Earth, some microbes can cope with up to about 5% acid in their environment – but the clouds of Venus are almost entirely made of acid.”

Other possible biosignatures in the Solar System may exist, like methane on Mars and water venting from the icy moons Europa and Enceladus. On Venus, it has been suggested that dark streaks where ultraviolet light is absorbed could come from colonies of microbes. The Akatsuki spacecraft, launched by the Japanese space agency JAXA, is currently mapping these dark streaks to understand more about this unknown ultraviolet absorber.

The team believes their discovery is significant because they can rule out many alternative ways to make phosphine, but they acknowledge that confirming the presence of ‘life’ needs a lot more work. Although the high clouds of Venus have temperatures up to a pleasant 30 degrees Celsius, they are incredibly acidic – around 90% sulphuric acid – posing major issues for microbes to survive there. The researchers are investigating the possibility that the microbes could shield themselves inside droplets.

The team is now awaiting more telescope time to establish whether the phosphine is in a relatively temperate part of the clouds and to look for other gases associated with life. New space missions could also travel to our neighbouring planet, and sample the clouds to search for signs of life.

Professor Emma Bunce, President of the Royal Astronomical Society, said: “A key question in science is whether life exists beyond Earth, and the discovery by Professor Jane Greaves and her team is a key step forward in that quest. I’m particularly delighted to see UK scientists leading such an important breakthrough – something that makes a strong case for a return space mission to Venus.”

Reference:
Jane S. Greaves et al. ‘Phosphine Gas in the Cloud Decks of Venus.’ Nature Astronomy (2020). DOI: 10.1038/s41550-020-1174-4

Adapted from an RAS press release.

A UK-led team of astronomers has discovered a rare molecule – phosphine – in the clouds of Venus, pointing to the possibility of extra-terrestrial ‘aerial’ life.

The presence of life is the only known explanation for the amount of phosphine inferred by observations
Paul Rimmer
Synthesized false colour image of Venus

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The text in this work is licensed under a Creative Commons Attribution 4.0 International License. Images, including our videos, are Copyright ©University of Cambridge and licensors/contributors as identified.  All rights reserved. We make our image and video content available in a number of ways – as here, on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

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