Astronomers are closer to revealing the dark matter enveloping our Milky Way galaxy, thanks to a new map of twelve streams of stars orbiting within our Galactic halo.
Understanding these star streams is very important for astronomers. As well as revealing the dark matter that holds the stars in their orbits, they also tell us about the formation history of the Milky Way, revealing that the Milky Way has steadily grown over billions of years by shredding and consuming smaller stellar systems.
An international team of collaborators, which includes Dr Sergey Koposov, reader in observational astronomy in the School of Physics and Astronomy, initiated a dedicated program - the Southern Stellar Stream Spectroscopic Survey (S5) - to measure the properties of stellar streams: the shredded remains of neighbouring small galaxies and star clusters that are being torn apart by our own Milky Way.
The team, led by Prof Ting Li from the University of Toronto, are the first group of scientists to study such a rich collection of stellar streams, measuring the speeds of stars using the Anglo-Australian Telescope (AAT), a 4-meter optical telescope in Australia. They used the Doppler shift of light, used by the police radar guns to capture speeding drivers, to find out how fast individual stars are moving.
Observations from the European Gaia space mission were also used. These enabled astronomers to efficiently identify individual stars belonging to streams among much more populous stellar populations of the Milky Way.
The properties of stellar streams reveal the presence of the invisible dark matter of the Milky Way. Such observations are essential for determining how our Milky Way arose from the featureless universe after the Big Bang.
The latest results have been accepted for publication in the American Astronomical Society’s Astrophysical Journal.
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Congratulations to Dr Carlo Bruno and Dr Fergus Cullen who have received European Research Council starting grants.
The European Research Council (ERC) has announced recipients of its Starting Grants under the Research and Innovation programme, Horizon Europe. Grants worth on average €1.5 million will help ambitious researchers launch their own projects, form their teams of postdoctoral researchers and PhD students, and pursue their research ideas.
Dr Carlo Bruno
Carlo's research focuses on measuring nuclear reactions of key importance to understand the origin of the elements from the Big Bang to supernovae. This involves collaboration with colleagues at the international accelerator facility FAIR based in Germany and the largest European underground accelerator in Laboratori Nazionali del Gran Sasso in Italy.
Dr Fergus Cullen
Fergus' research is focussed on the chemical evolution of galaxies across cosmic time, tracing the formation and build up of chemical elements from the Big Bang until the present day. These studies will help us to gain insight into how galaxies formed and evolved over the 13.8 billion years of the Universe's history, and enable us to understand how the Universe became enriched with the elements necessary for life to evolve. Fergus' research will be conducted using state-of-the-art ground-based and space-based telescopes, including the recently-launched James Webb Space Telescope which will become operational in mid-2022.
Funding supports collaboration between Edinburgh Complex Fluids Partnership and Corning Incorporated.
The Edinburgh Complex Fluids Partnership (ECFP) has recently received significant funding to continue working with Corning Incorporated: a world-leading innovator in materials science, with expertise in glass and ceramics manufacture.
ECFP are the knowledge exchange centre for the Soft Matter and Biological Physics Group in the School of Physics and Astronomy, and work with industries across multiple sectors to help them improve and innovate in product formulation and processing.
This three-year project, led by Dr Daniel Hodgson and Professor Wilson Poon, will provide Corning with new scientific understanding for the development of technologies and production optimisation in automotive catalyst support and diesel particulate applications. With a global push towards net-zero and a UK government ban on the sale of new petrol and diesel cars beyond 2030, there is still a significant need for improved emissions control over the next decade and beyond. The impact of poor air quality is a substantial global problem, with millions of deaths associated with elevated concentrations of fine particulate matter, including 98 deaths per 100,000 in the UK.
This work builds on several years of collaboration between Corning and ECFP, which has been supported through a mixture of company funding and an EPSRC Impact Acceleration Partnership Award.
Congratulations to Dr Liu who has been awarded the 2021 Institute of Physics Mary Somerville Medal and Prize.
Dark matter and remote controlled robots
Dr XinRan Liu is a particle physicist specialising in the direct detection of dark matter. XinRan developed a project called Remote3 which aims to deliver STEM outreach to school children in some of the most remote areas of Scotland. As part of this project, pupils are helped to build and program miniature Mars rovers that they can then remotely operate in the Science and Technology Facilities Council (STFC) Mars Yard located at the Boulby Underground Laboratory 1.1 km underground, in which XinRan carries out much of his research.
XinRan is currently the chair of the Dark Matter UK public engagement committee, co-chair of the Institute of Physics Astroparticle Physics outreach committee and has been elected as the LUX-ZEPLIN Dark Matter Experiment outreach coordinator in the UK. As such he is instrumental in coordinating the UK public engagement effort for Dark Matter physics.
2021 success stories
The Mary Somerville Medal and Prize follows in the footsteps of other recognitions XinRan has received this year. XinRan received an STFC Leadership Fellowship in Public Engagement to expand the scope and reach of his Remote3 project across Scotland; and he received recognition for his public engagement activities by becoming a British Science Association Award Lecture winner.
Institute of Physics
The Institute of Physics (IOP) is the professional body and learned society for physics, and the leading body for practising physicists, in the UK and Ireland. The IOP awards celebrate physicists at every stage of their career; from those just starting out through to physicists at the peak of their careers, and those with a distinguished career behind them. Its annual awards reflect the wide variety of people, places, organisations and achievements that make physics such an exciting discipline.
About Mary Somerville
Mary Somerville was a Scottish science writer and polymath. She studied mathematics and astronomy. She and Caroline Herschel were jointly nominated as the first women members of the Royal Astronomical Society. She is featured on the front of the Royal Bank of Scotland polymer £10 note launched in 2017, alongside a quote from her work 'The Connection of the Physical Sciences', which is one of the biggest-selling science books of the 19th century and was commonly used as a textbook until the early 20th century.
Award recognises contributions to communication, engagement and in advancing public discussion in science.
Alex has a long-standing and sustained track record of outstanding contributions to science’s public engagement, particularly in particle physics, and in dark matter - one of the most common yet most mysterious and hard-to-study substances in the field of physics.
Through his public engagement activities, he has reached diverse audiences in Scotland, the UK, and internationally. Alex has spearheaded innovative public engagement initiatives, including the Remote3 project, which delivers STEM outreach to some of the most remote areas of Scotland by helping pupils build and programme miniature Mars rovers that they can then remotely operate in an underground laboratory.
The Royal Society of Edinburgh (RSE) medals recognise individuals who are exemplary at communicating, facilitating engagement, and advancing public discussion on significant matters.
Alex became elected as a Fellow of the RSE in early 2021. There are around 1,600 RSE Fellows who are leading thinkers and practitioners from Scotland and beyond, whose work has a significant impact on our nation.
Mars explorers searching for signs of ancient life could be fooled by fossil-like specimens created by chemical processes, research suggests.
Rocks on Mars may contain numerous types of non-biological deposits that look similar to the kinds of fossils likely to be found if the planet ever supported life, a study says. Telling these false fossils apart from what could be evidence of ancient life on the surface of Mars – which was temporarily habitable four billion years ago – is key to the success of current and future missions, researchers say.
Astrobiologists from the Universities of Edinburgh and Oxford reviewed evidence of all known processes that could have created lifelike deposits in rocks on Mars. They identified dozens of processes – with many more likely still undiscovered – that can produce structures that mimic those of microscopic, simple lifeforms that may once have existed on Mars.
Among the lifelike specimens these processes can create are deposits that look like bacterial cells and carbon-based molecules that closely resemble the building blocks of all known life. Because signs of life can be so closely mimicked by non-living processes, the origins of any fossil-like specimens found on Mars are likely to be very ambiguous, the team says. They call for greater interdisciplinary research to shed more light on how lifelike deposits could form on Mars, and thereby aid the search for evidence of ancient life there and elsewhere in the solar system.
The research is published in the Journal of the Geological Society.
Dr Sean McMahon, Chancellor’s Fellow in Astrobiology at the University of Edinburgh’s School of Physics and Astronomy, said:
At some stage a Mars rover will almost certainly find something that looks a lot like a fossil, so being able to confidently distinguish these from structures and substances made by chemical reactions is vital. For every type of fossil out there, there is at least one non-biological process that creates very similar things, so there is a real need to improve our understanding of how these form.
Julie Cosmidis, Associate Professor of Geobiology at the University of Oxford, said:
We have been fooled by life-mimicking processes in the past. On many occasions, objects that looked like fossil microbes were described in ancient rocks on Earth and even in meteorites from Mars, but after deeper examination they turned out to have non-biological origins. This article is a cautionary tale in which we call for further research on life-mimicking processes in the context of Mars, so that we avoid falling into the same traps over and over again.
Experiments demonstrate a high reactivity between carbon and hydrogen at conditions comparable with those in the Earth’s upper mantle.
Turning diamond – the finest gem – into methane – one of the worst greenhouse gases, more than 25 times potent than CO2 at trapping heat in the atmosphere – may not sound a brilliant idea. However, an international collaboration between scientists from the University of Edinburgh, the University of Bologna, the Centre National de la Recherche Scientifique (France), HPSTAR (China) and the Institute of Solid State Physics (Chinese Academy of Sciences) discovered that diamond and hydrogen can react yielding to methane, in what may play a key role in cycling carbon in the deep Earth.
The researchers observed that methane was produced by diamond-hydrogen interactions in seconds at conditions of pressure and temperature analogous to those at 70 km deep. Although the possibility for diamond to form from methane in the Earth’s mantle was known, the opposite reaction was not included in the inventory of processes regulating the deep carbon cycle.
Dr Peña-Alvarez from the University of Edinburgh's Centre for Science at Extreme Conditions commented on the experiment:
To experimentally reproduce deep Earth conditions, we used an experimental apparatus called a diamond-anvil cell, where the flat surfaces of two diamonds are pushed against each other. We noticed that when the cell is loaded with pure hydrogen and heated, the diamonds readily react to form methane and longer-chain hydrocarbons.
Professor Vitale Brovarone from the University of Bologna and the Centre National de la Recherche Scientifique, reported:
This discovery provides a new tile of the deep carbon cycle, which accounts for about 90% of the total carbon on Earth. The genesis of methane from diamond and hydrogen also demonstrates that hydrocarbons unrelated to biological activities can form in deep Earth and may act as source of energy for shallower geological reservoirs.
The collaboration includes former School of Physics and Astronomy PhD students Dr Philip Dalladay-Simpson, who is currently based at HPSTAR, China and Dr Mary-Ellen Donnelly who is currently based at Oak Ridge Spallation Source, United States of America.
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Topological feature could prove useful for dissipationless spintronics.
Researchers in the UK, South Korea and US recently discovered that the two-dimensional layered magnet chromium triiodide (CrI3) acts as a topological magnon insulator in the absence of an external magnetic field. This result sparked a flurry of interest in this material and its potential applications for so-called dissipationless spintronics in which electrons are used to transmit and store information in an ultra-fast and ultra-low power fashion. Thanks to detailed neutron scattering measurements and fine analysis, the team has found that this phenomenon comes from the way in which the layers in the material are stacked together. That is, while a single layer of CrI3 is ferromagnetic, two stacked layers are antiferromagnetic which counterintuitively is different from that in ferromagnetic bulk.
Two-dimensional (2D) materials are made up of atomically thin layers stacked on top of each other. These layers are held together by weak van der Waals forces and the electrons in these materials behave very differently to those in bulk materials. For example, the “Dirac” electrons in graphene, which is one of the most famous of all 2D materials, can move at almost relativistic speeds and behave as if they are massless.
Some 2D materials are also topological insulators – materials in which electrons flow freely along the edges of a 2D sheet, but cannot flow along the surface. This effect is related to the spin of the electrons, making these materials promising for spintronic devices, which store and process information using the electrons’ spin states.
Magnons for spintronics
Certain 2D magnetic materials are also predicted to be magnetic and topological insulators. In such materials, which are very rare, quasiparticles known as magnons would travel along the edges of a sheet, much like electrons in a conventional 2D topological insulator. Magnons are collective oscillations of the spin magnetic moments of a material and are expected to be massless too, meaning that they could travel over long distances without dissipating. This property would make them interesting for spintronics applications too.
Three years ago, Lebing Chen from Rice University and coworkers found such Dirac magnons in CrI3, which has a honeycomb lattice structure much like graphene. They came to their conclusion by studying the material using inelastic neutron scattering at the Spallation Neutron Source at Oak Ridge National Laboratory. In this technique, neutrons, which have magnetic moments, create magnons when they scatter from a CrI3 sheet. By measuring the energy lost by the neutrons during the scattering process, Chen and colleagues were able to calculate the properties of these magnons. They found that these magnons exhibit properties consistent with them being topological and having a dissipation-less edge mode.
Spin-orbit coupling
In their new work, they performed further neutron-scattering measurements at a much larger precision as well as resolution and have found that the magnons’s topological properties arise thanks to spin-orbit coupling – a relativistic interaction of an electron’s spin with its motion. This coupling induces asymmetric interactions between spin of electrons in the materials, explains Elton Santos of the School's Higgs Centre for Theoretical Physics, Jae-Ho Chung of Korea University’s Department of Physics and Pengcheng Dai of Rice University who led the new study. These interactions make the spin “feel” the magnetic field differently, affecting their topological excitations.
Elton commented:
Surprisingly the spins have some chirality like in a mirror where left and right can work differently. We observed that without such chiral interactions, or in more complicated terms Dzyaloshinskii-Moriya exchange, we can’t describe the data.
The result has an accompanying magnetic phenomenon: a stacking-dependent magnetic order in which a single layer of CrI3 is ferromagnetic but two stacked layers are antiferromagnetic. “The reason for this behaviour is that the interaction between stacked layers in CrI3 is a combination of ferromagnetic and antiferromagnetic exchanges - despite apparent ferromagnetic stacking,” explains team member Jae-Ho.
“Our new work also confirms the previously observed topological nature of the spin excitation based on the Dzyaloshinkii-Moriya exchange, and rules out the competing interpretation based on the Kitaev exchange,” comments Pengcheng Dai to Physics World. “The latter is known to be an important spin-spin interaction in more complex materials (i.e. spin liquids), but not for CrI3. This comes as a surprise to us.”
Researchers will be involved in observing the collision in the first mission to demonstrate technology to deflect an asteroid.
Mission
NASA’s Double Asteroid Redirection Test, or DART, is the first mission to demonstrate technology to deflect an asteroid.
DART will use an autonomous guidance system to aim itself at Dimorphos, a carefully chosen non-threatening asteroid. Dimoprhos is actually a small moon orbiting a larger asteroid called Didymos, and the force of the collision will slightly change the orbit of Dimorphos around Didymos. Because it’s not on a path to collide with Earth, the Didymos system poses no actual impact threat to our planet, yet its relatively close proximity provides an easy way for planetary defence experts to observe and measure the effect of the impact. It is expected that the collision will change the orbital period (which is about 12 hours) by a few minutes.
The DART spacecraft will launch on a Space-X rocket in late November, and then take slightly less than a year to reach Didymos and Dimorphos, which it will hit in late September or early October 2022.
Why planetary defence?
Astronomers estimate that there are approximately 25,000 near-Earth asteroids close to 140 meters or larger in size – big enough to cause regional devastation if they were to hit Earth. There is therefore a need to track near-Earth asteroids, and better understand what would be required if an asteroid was heading our way and we want to move it away from the Earth.
Observation
Telescopes around the world will be trained on the Didymos system before and after the collision to measure the effects and learn more about the asteroid, its composition, and the effectiveness of the deflection experiment. School of Physics and Astronomy researchers Dr Colin Snodgrass and Dr Cyrielle Opitom are part of the observing team who will study the asteroid from Earth, applying their experience of observing comets and asteroids with some of the world’s best telescopes, including the European Southern Observatory’s ‘Very Large Telescope’.
Post-impact survey
After the impact experiment, a related European Space Agency (ESA) mission, Hera, will launch to the same asteroid to study the effects of the collision in detail. Hera will launch in 2024 and arrive in 2026, and will go into orbit around the asteroid, to perform a forensic ‘crash scene investigation’. Combined with the observations from DART and from telescopes on the ground, Hera will give a very detailed picture of the physics of the collision process, which will allow scientists and engineers to design the most effective asteroid deflection mission, if we ever have to do this ‘for real’ on an asteroid that threatens the Earth.
Professor Sinead Farrington who was honoured as Physical Sciences and Engineering Laureate (first place) in the 2021 Blavatnik Awards for Young Scientists in the United Kingdom awards ceremony on 25th October in London.
The Blavatnik Awards are administered by the New York Academy of Sciences, of which Prof. Farrington is now a life-member. These awards are the largest unrestricted UK science prize, with an award of $100,000 for each laureate, and $30,000 for each of two additional finalists in the three categories: physical sciences and engineering, chemistry and life sciences.
Professor Farrington was presented the Physical Sciences and Engineering Laureate’s medal at a banquet hosted by Sir Leonard Blavatnik and the Blavatnik Family Foundation, attended by prominent scientists and policy-makers at which she gave a talk on her research, at Banqueting Hall in Whitehall, London. An open public symposium was held the following day where Professor Farrington and her fellow laureates and finalists spoke on their subjects. Professor Farrington and the Life Sciences Laureate, also from Edinburgh - Professor Steven Brusatte from Geosciences - took part in a discussion panel with BBC Science correspondent, Victoria Gill.
Professor Farrington is based in the School’s Particle Physics Experiment research group where she holds an European Research Council (ERC) consolidator grant funding her team of postdocs and PhD students searching for Beyond Standard Model particles. She leads the UK collaboration on the ATLAS experiment at the Large Hadron Collider at CERN. She received the Blavatnik Award in recognition of her leadership of an international working group at CERN that has improved our understanding of the properties of the Higgs boson, and the development of key trigger and analysis techniques for the exploitation of Large Hadron Collider data and searches for new physics beyond the Standard Model.
Prof Farrington commented:
High energy physics is a collaborative endeavour involving very talented individuals from around the world, working together to build machines on a grand scale, and to analyse the data they generate to help us understand how the universe works at its deepest levels. I am privileged to have been able to contribute to this endeavour and to help provide some pieces of nature’s great puzzle, and am honoured to have received this Blavatnik Award.