̽��ֱ�� of Cambridge - X-ray

Sustainable solar cell material shown to be highly promising for medical imaging

Anonymous — Wed, 10 May 2023 15:05:23 +0000

A team of researchers, jointly led by the Universities of Oxford and Cambridge, have discovered that a solar cell material – bismuth oxyiodide (BiOI) – is capable of detecting X-ray dose rates over 250 times lower than the current best performing detectors used commercially. This has the potential to make medical imaging safer, and open up new opportunities in non-invasive diagnostics, such as X-ray video techniques. Their results are reported in the journal Nature Communications.

“We have developed BiOI single crystals into X-ray detectors that work over 100 times better than the current state-of-the-art for medical imaging,” said Dr Robert Hoye from the ̽��ֱ�� of Oxford, who led the work. “BiOI is nontoxic, stable in air, and can be grown cost-effectively and at scale. We are very excited by the potential BiOI has to make the next generation of non-invasive diagnostics more accessible, safer, and more effective.”

BiOI is a nontoxic semiconductor that absorbs visible light and is stable in air. Owing to these qualities, over the past decade there has been a surge of interest in this material for solar cells (turning sunlight into clean electricity), photoelectrochemical cells (turning sunlight into fuels) and energy harvesting to power smart devices, among many other applications.

BiOI contains two heavy elements – bismuth and iodine – which allows the material to strongly absorb X-rays. However, previous attempts to make BiOI into X-ray detectors were ineffective due to significant energy losses from defects arising from the nanocrystalline nature of the detectors made.

̽��ֱ��researchers developed and patented a method to grow high-quality single crystals of BiOI using a scalable vapour-based approach. ̽��ֱ��low defect density in these crystals led to stable and ultra-low dark currents, which was critical to substantially improve the sensitivity and detection limit of this material to X-rays.

“Showing that these simply-processed, low-temperature grown, stable crystals can give such high sensitivity for X-ray detection is quite remarkable,” said Professor Judith Driscoll from Cambridge’s Department of Materials Science and Metallurgy, who co-led the work. “We began working on this material, BiOI, several years ago, and we find it outshines other rival materials in a range of optoelectronic and sensing applications, when toxicity and performance are considered together.”

̽��ֱ��researchers formed an interdisciplinary team to understand why BiOI works so well as an X-ray detector. They used advanced optical techniques to resolve processes taking place over a trillionth of a second, and coupled these with simulations to link these processes with what is happening at the atomic level.

Through this study, the team revealed the unusual way in which electrons couple to vibrations in the lattice. Unlike other bismuth-halide compounds, the electrons in BiOI remain delocalised, meaning that electrons can easily and rapidly move within the lattice of BiOI. At the same time, the unusual electron coupling with lattice vibrations results in an irreversible energy loss channel that would still be present even if the material were defect-free.

̽��ֱ��researchers found that these losses can be overcome by cooling down the sample to reduce thermal energy, or by applying an electric field to rip away electrons from the lattice. ̽��ֱ��latter case is ideally matched with how X-ray detectors operate. By applying a small electric field, electrons can be transported over a millimetre length-scale, allowing the efficient extraction of electrons generated in the single crystals through the absorption of X-rays.

“We have built a microscopic quantum mechanical model of electrons and ions that can fully explain the remarkable optoelectronic properties of BiOI that make it such a good material for X-ray detection,” said Dr Bartomeu Monserrat from Cambridge’s Department of Materials Science and Metallurgy, who co-led the project. “This gives us a roadmap for designing even more materials with similarly advantageous properties.

This work offers important insights into how delocalised charge-carriers can be achieved in bismuth-halide compounds. ̽��ֱ��researchers are now working on applying these insights to design materials with similarly advantageous properties as BiOI, as well as how to tune the composition of BiOI to improve its transport properties further. They are also working on bringing the unique benefits of BiOI to society by devising routes to increase the size of the BiOI detectors, while preserving the exceptional properties found in single crystals.

̽��ֱ��study also involved researchers from Imperial College London, Queen Mary ̽��ֱ�� London, Technical ̽��ֱ�� Munich and CNRS in Toulouse.

Reference:
R A Jagt, I Bravić, et al. ‘Layered BiOI single crystals capable of detecting low dose rates of X-rays.’ Nature Communications (2023). https://doi.org/10.1038/s41467-023-38008-4

Adapted from a story by the ̽��ֱ�� of Oxford

For more information on energy-related research in Cambridge, please visit Energy IRC, which brings together Cambridge’s research knowledge and expertise, in collaboration with global partners, to create solutions for a sustainable and resilient energy landscape for generations to come.

Using X-rays to see inside the human body has revolutionised non-invasive medical diagnostics. However, the dose of X-rays required for imaging is far higher than background levels, due to the poor performance of the detector materials currently available. This can cause harm to patients, and in some cases even cancer.

John Freeman

Bismuth oxyiodide crystals

̽��ֱ��text in this work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. Images, including our videos, are Copyright © ̽��ֱ�� 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.

Yes

Chandra Observatory shows black hole spins slower than its peers

sc604 — Thu, 30 Jun 2022 16:10:01 +0000

Supermassive black holes contain millions or even billions of times more mass than the Sun. Astronomers think that nearly every large galaxy has a supermassive black hole at its center. While the existence of supermassive black holes is not in dispute, scientists are still working to understand how they grow and evolve. One critical piece of information is how fast the black holes are spinning.

“Every black hole can be defined by just two numbers: its spin and its mass,” said Julia Sisk-Reynes of Cambridge's Institute of Astronomy (IoA), who led the study, published in the Monthly Notices of the Royal Astronomical Society. “While that sounds fairly simple, figuring those values out for most black holes has proved to be incredibly difficult.”

For this result, researchers observed X-rays that bounced off a disk of material swirling around the black hole in a quasar known as H1821+643. Quasars contain rapidly growing supermassive black holes that generate large amounts of radiation in a small region around the black hole. Located in a cluster of galaxies about 3.4 billion light-years from Earth, H1821+643’s black hole is between about three and 30 billion solar masses, making it one of the most massive known. By contrast, the supermassive black hole in the center of our galaxy weighs about four million Suns.

̽��ֱ��strong gravitational forces near the black hole alter the intensity of X-rays at different energies. ̽��ֱ��larger the alteration the closer the inner edge of the disk must be to the point of no return of the black hole, known as the event horizon. Because a spinning black hole drags space around with it and allows matter to orbit closer to it than is possible for a non-spinning one, the X-ray data can show how fast the black hole is spinning.

“We found that the black hole in H1821+643 is spinning about half as quickly as most black holes weighing between about a million and ten million suns,” said co-author Professor Christopher Reynolds, also of the IoA. “ ̽��ֱ��million-dollar question is: why?”

̽��ֱ��answer may lie in how these supermassive black holes grow and evolve. This relatively slow spin supports the idea that the most massive black holes like H1821+643 undergo most of their growth by merging with other black holes, or by gas being pulled inwards in random directions when their large disks are disrupted.

Supermassive black holes growing in these ways are likely to often undergo large changes of spin, including being slowed down or wrenched in the opposite direction. ̽��ֱ��prediction is therefore that the most massive black holes should be observed to have a wider range of spin rates than their less massive relatives.

On the other hand, scientists expect less massive black holes to accumulate most of their mass from a disk of gas spinning around them. Because such disks are expected to be stable, the incoming matter always approaches from a direction that will make the black holes spin faster until they reach the maximum speed possible, which is the speed of light.

“ ̽��ֱ��moderate spin for this ultramassive object may be a testament to the violent, chaotic history of the universe’s biggest black holes,” said co-author Dr James Matthews, also of the IoA. “It may also give insights into what will happen to our galaxy’s supermassive black hole billions of years in the future, when the Milky Way collides with Andromeda and other galaxies.

This black hole provides information that complements what astronomers have learned about the supermassive black holes seen in our galaxy and in M87, which were imaged with the Event Horizon Telescope. In those cases, the black hole’s masses are well known, but the spin is not.

NASA's Marshall Space Flight Center manages the Chandra program. ̽��ֱ��Smithsonian Astrophysical Observatory's Chandra X-ray Center controls science operations from Cambridge, Massachusetts, and flight operations from Burlington, Massachusetts.

Reference:
Júlia Sisk-Reynés et al. 'Evidence for a moderate spin from X-ray reflection of the high-mass supermassive black hole in the cluster-hosted quasar H1821+643.' Monthly Notices of the Royal Astronomical Society (2022). DOI: 10.1093/mnras/stac1389

Adapted from a Chandra press release.

Astronomers have made a record-breaking measurement of a black hole’s spin, one of two fundamental properties of black holes. NASA’s Chandra X-ray Observatory shows this black hole is spinning slower than most of its smaller cousins. This is the most massive black hole with an accurate spin measurement and gives hints about how some of the universe’s biggest black holes grow.

̽��ֱ��moderate spin for this ultramassive object may be a testament to the violent, chaotic history of the universe’s biggest black holes

James Matthews

X-ray: NASA/CXC/Univ. of Cambridge/J. Sisk-Reynés et al.; Radio: NSF/NRAO/VLA; Optical: PanSTARRS

H1821+643, a quasar powered by a supermassive black hole

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. Images, including our videos, are Copyright © ̽��ֱ�� 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.

Yes

Professor Andrew Fabian awarded Kavli Prize

sc604 — Wed, 27 May 2020 13:15:00 +0000

Professor Fabian is one of seven scientists from five countries honoured for breakthrough discoveries in astrophysics, nanoscience and neuroscience.

̽��ֱ��Norwegian Academy of Science and Letters today announced the 2020 Kavli Prize Laureates in the fields of astrophysics, nanoscience and neuroscience. This year’s Kavli Prize honours scientists whose research has transformed our understanding of the very big, the very small and the very complex. ̽��ֱ��laureates in each field will share $1million USD.

“ ̽��ֱ��2020 Kavli Prize Laureates represent truly pioneering science, the kind of science which will benefit humanity in a profound way, inspiring both current and future generations,” says Hans Petter Graver, president of ̽��ֱ��Norwegian Academy of Science and Letters.

The Kavli Prize in Astrophysics is awarded to astronomer and astrophysicist Andrew Fabian for his pioneering research and persistence in pursuing the mystery of how black holes influence their surrounding galaxies on both large and small scales. For decades, researchers have pondered the mechanics and physical processes of galaxies, and many have made discoveries that point to aspects of their inner workings; yet none has the unique vantage point of Fabian: to take a multi-scale understanding and systematically know where to look to put the pieces of the puzzle together and create the bigger picture of this vast ecosystem.

In the current cosmological paradigm, the universe is a ‘living’ system, in which the flows of gas into galaxies and black holes at their centres, and the subsequent release of energy back into the galaxies and their surroundings, all play vital roles. As the darkest objects in the universe, black holes are observed as their gravity attracts surrounding gas, dust and stars, which swirl into them at high velocities, creating intense radiation, much of it X-rays. Observational X-ray astronomy opened up access to view these and other extremely hot and energetic components of the universe, providing stunning evidence for these processes at work, unveiling how the major constituents of the universe can profoundly influence its overall evolution.

Professor Fabian employs X-ray astronomy to explore the physics of the universe. His body of work – from understanding large-scale galactic evolution to the physics of black holes at the centres of galaxies – enabled him to make connections between local conditions around supermassive black holes and the larger gas flows within and between galaxies. This research provided evidence that supermassive black holes at the heart of galaxies are the engines that drive the flow of hot gas out of the galaxy, redistributing energy through the universe and providing the building blocks for future galaxy formation.

“Andrew Fabian is one of the most prolific and influential astronomers of our time,” said Viggo Hansteen, chair of the Kavli Prize Committee in Astrophysics. “His research, breadth of knowledge and insights into the universe provided the essential physical understanding of how disparate phenomena in this ecosystem are interconnected.”

This year’s Kavli Prize Laureates also include Professor Ondrej L Krivanek, an alumnus of Trinity College, Cambridge, who is now based in the United States. Professor Krivanek completed his PhD at the Cavendish Laboratory in 1975 under the supervision of Professor Archie Howie. He was awarded the Kavli Prize in Nanoscience, along with Harald Rose (Germany), Maximilian Haider (Austria), Knut Urban (Germany). Their work enabled humanity to see the structure and chemical composition of materials in three dimensions on unprecedentedly short length scales.

̽��ֱ��Kavli Prize is a partnership between ̽��ֱ��Norwegian Academy of Science and Letters, the Norwegian Ministry of Education and Research and ̽��ֱ��Kavli Foundation (US). ̽��ֱ��Kavli Prize honours scientists for breakthroughs in astrophysics, nanoscience and neuroscience that transform our understanding of the very big, the very small and the very complex. Three million-dollar prizes are awarded every other year in each of the three fields. ̽��ֱ��Norwegian Academy of Science and Letters selects the laureates based on recommendations from three prize committees whose members are nominated by ̽��ֱ��Chinese Academy of Sciences, ̽��ֱ��French Academy of Sciences, ̽��ֱ��Max Planck Society of Germany, ̽��ֱ��U.S. National Academy of Sciences and ̽��ֱ��UK’s Royal Society. First awarded in 2008, ̽��ֱ��Kavli Prize has honoured 54 scientists from 13 countries – Austria, Czech Republic, France, Germany, Japan, Lithuania, ̽��ֱ��Netherlands, Norway, Russia, Sweden, Switzerland, the United Kingdom and the United States.

̽��ֱ��Kavli Prize Laureates are typically celebrated in Oslo, Norway, in a ceremony presided over by His Majesty King Harald followed by a banquet at the Oslo City Hall, the venue of the Nobel Peace Prize. Due to the COVID-19 pandemic, this year’s award ceremony is postponed and will be held together with the 2022 award ceremony in September 2022.

Professor Andrew Fabian from Cambridge's Institute of Astronomy has been awarded the 2020 Kavli Prize in Astrophysics, one of the world's most prestigious science prizes.

Sam Fabian

Professor Andrew Fabian

Yes

Dead satellite finds a calm centre at the heart of brightest galaxy cluster in the sky

sc604 — Wed, 06 Jul 2016 17:30:00 +0000

̽��ֱ��result, published in the journal Nature, allows the mass of the Perseus Cluster – a swarm of thousands of galaxies that spans two million light years across and is one of the most massive known objects in the universe – to be calculated more accurately than before. Once this technique can be extended to other clusters, it will allow cosmologists to use them as better probes of our models of the Universe’s evolution from the Big Bang to the present time.

Hitomi (originally known as ASTRO-H) is the sixth in a series of Japanese x-ray observatories. Led by the Japan Aerospace Exploration Agency (JAXA), it is a collaboration of over 60 institutes and 200 scientists and engineers from Japan, the US, Canada, and Europe, including from the ̽��ֱ�� of Cambridge. ̽��ֱ��spacecraft was launched on 17 February 2016 from the Tanegashima Space Center, Japan. However, JAXA announced in April that it was no longer possible to communicate with the satellite.

“Hitomi targeted the Perseus cluster just a week after it arrived in space,” said Matteo Guainazzi, the European Space Agency’s (ESA) Hitomi Resident Astronomer at the Institute of Space and Astronautical Science, Japan. “Perseus is the brightest x-ray galaxy cluster in the sky. It was therefore the best choice to fully demonstrate the power of the Soft X-ray Spectrometer (SXS), an x-ray micro-calorimeter that promised to deliver an unprecedented accuracy in the reconstruction of the energy of the incoming x-ray photons.” Waiting astronomers were not disappointed.

̽��ֱ��Hitomi collaboration found that SXS could measure the turbulence in the cluster to a precision of 10 kilometres/second. But it was the absolute velocity of the gas that took them by surprise. It was just 164 ± 10 kilometres/second. ̽��ֱ��previous best measurement for Perseus was taken with ESA’s XMM-Newton x-ray observatory. Using a different type of spectrometer, it could only constrain the speed to be lower than 500 kilometres/second.

Hitomi’s measurement is therefore much more precise than any similar measurements performed in x-rays so far. “This is due to the outstanding performance and stability of the SXS in space. This demonstrates that the technology of x-ray micro-calorimeters can yield truly transformational results,” said Guainazzi.

̽��ֱ��result indicates that the cluster gas has very little turbulent motions within. Turbulent motions in a fluid are part of our everyday life, as airplane passengers, swimmers, or parents filling a bathtub all experience. ̽��ֱ��study of such chaotic behaviour is also a powerful tool for astronomers to understand the behaviour of celestial objects.

Turbulent energy in Perseus is just four percent of the energy stored in the gas as heat. This is extraordinary considering that the active galaxy NGC 1275 sits at the heart of the cluster. It is pumping jetted energy into its surroundings, creating bubbles of extremely hot gas. It was thought that these bubbles induce turbulence, which keeps the central gas hot.

Hitomi shows that turbulent motion is almost absent from the cluster, and this gives rise to a mystery: what is keeping the cluster’s widespread gas hot?

“This result from Hitomi is telling us that in terms of how cluster cores work, we have to think very carefully about what is going on,” said the paper’s senior author Professor Andy Fabian of Cambridge’s Institute of Astronomy, and part of the Hitomi collaboration.

Fabian is working on the possibility of sound waves as the means of spreading the energy evenly throughout the gas. This is because in a sound wave, energy can be moved while the medium itself remains more or less stationary.

There are wider implications for this work too. Clusters of galaxies are the largest bound structures in the Universe. At the same time, they are also the smallest self-contained ‘boxes’. This means that matter is not flowing in or out of a cluster of galaxies. Instead, they each represent an island in which cosmic evolution has played out and been recorded.

Computer models of the expanding Universe use the distribution of cluster masses as an observational test of whether they are correct. Calculating the mass of a cluster depends upon the ratio of turbulent to quiescent gas. Any way of more accurately measuring turbulence allows better masses to be calculated, and therefore better computer models of the whole Universe to be developed.

Unfortunately, just a few weeks after the Perseus observation, a malfunction in the attitude control system put Hitomi into an uncontrollable spin that resulted in the break up and loss of the satellite.

“It is really disappointing that we have lost Hitomi and can’t go on with the programme that we had to look at many more clusters,” says Fabian.

̽��ֱ��next mission that will be capable of fully following up the Hitomi programme is ESA’s Athena, an X-ray observatory scheduled for launch in the 2020s.

“Scientifically and technically, the Hitomi results are an exciting foretaste of Athena,” said David Lumb, ESA's Athena Study Scientist. “ ̽��ֱ��demonstration of a radically new imaging spectrometer instrument concept gives huge confidence for future developments for Athena.”

Athena will have 100 times more collecting area and 100 times more pixels than Hitomi. Among the key scientific objectives of Athena are to investigate the evolution of clusters of galaxies including their interplay with energy injection from supermassive black holes.

“ ̽��ֱ��Hitomi data show the potential that will be unleashed with Athena vastly increased imaging capability and sensitivity,” said Lumb.

Reference:
Hitomi Collaboration. ‘ ̽��ֱ��quiet intracluster medium in the core of the Perseus cluster.’ Nature (2016). doi:10.1038/nature18627.

Adapted from an ESA press release.

With its very first – and last – observation, the Hitomi x-ray observatory has discovered that the gas in the Perseus cluster of galaxies is much less turbulent than expected, despite being home to NGC 1275, a highly energetic active galaxy.

This result is telling us that in terms of how cluster cores work, we have to think very carefully about what is going on.

Andy Fabian

Background: NASA/CXO; Spectrum: Hitomi Collaboration/JAXA, NASA, ESA, SRON, CSA

X-ray view of the Perseus cluster

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. For image use please see separate credits above.

Yes

Winds a quarter the speed of light spotted leaving mysterious binary systems

sc604 — Wed, 27 Apr 2016 17:00:00 +0000

Two black holes in nearby galaxies have been observed devouring their companion stars at a rate exceeding classically understood limits, and in the process, kicking out matter into surrounding space at astonishing speeds of around a quarter the speed of light.

̽��ֱ��researchers, from the ̽��ֱ�� of Cambridge, used data from the European Space Agency’s (ESA) XMM-Newton space observatory to reveal for the first time strong winds gusting at very high speeds from two mysterious sources of x-ray radiation. ̽��ֱ��discovery, published in the journal Nature, confirms that these sources conceal a compact object pulling in matter at extraordinarily high rates.

When observing the Universe at x-ray wavelengths, the celestial sky is dominated by two types of astronomical objects: supermassive black holes, sitting at the centres of large galaxies and ferociously devouring the material around them, and binary systems, consisting of a stellar remnant – a white dwarf, neutron star or black hole – feeding on gas from a companion star.

In both cases, the gas forms a swirling disc around the compact and very dense central object. Friction in the disc causes the gas to heat up and emit light at different wavelengths, with a peak in x-rays.

But an intermediate class of objects was discovered in the 1980s and is still not well understood. Ten to a hundred times brighter than ordinary x-ray binaries, these sources are nevertheless too faint to be linked to supermassive black holes, and in any case, are usually found far from the centre of their host galaxy.

“We think these so-called ‘ultra-luminous x-ray sources’ are special binary systems, sucking up gas at a much higher rate than an ordinary x-ray binary,” said Dr Ciro Pinto from Cambridge’s Institute of Astronomy, the paper’s lead author. “Some of these sources host highly magnetised neutron stars, while others might conceal the long-sought-after intermediate-mass black holes, which have masses around one thousand times the mass of the Sun. But in the majority of cases, the reason for their extreme behaviour is still unclear.”

Pinto and his colleagues collected several days’ worth of observations of three ultra-luminous x-ray sources, all located in nearby galaxies located less than 22 million light-years from the Milky Way. ̽��ֱ��data was obtained over several years with the Reflection Grating Spectrometer on XMM-Newton, which allowed the researchers to identify subtle features in the spectrum of the x-rays from the sources.

In all three sources, the scientists were able to identify x-ray emission from gas in the outer portions of the disc surrounding the central compact object, slowly flowing towards it.

But two of the three sources – known as NGC 1313 X-1 and NGC 5408 X-1 – also show clear signs of x-rays being absorbed by gas that is streaming away from the central source at 70,000 kilometres per second – almost a quarter of the speed of light.

“This is the first time we’ve seen winds streaming away from ultra-luminous x-ray sources,” said Pinto. “And the very high speed of these outflows is telling us something about the nature of the compact objects in these sources, which are frantically devouring matter.”

While the hot gas is pulled inwards by the central object's gravity, it also shines brightly, and the pressure exerted by the radiation pushes it outwards. This is a balancing act: the greater the mass, the faster it draws the surrounding gas; but this also causes the gas to heat up faster, emitting more light and increasing the pressure that blows the gas away.

There is a theoretical limit to how much matter can be pulled in by an object of a given mass, known as the Eddington limit. ̽��ֱ��limit was first calculated for stars by astronomer Arthur Eddington, but it can also be applied to compact objects like black holes and neutron stars.

Eddington’s calculation refers to an ideal case in which both the matter being accreted onto the central object and the radiation being emitted by it do so equally in all directions.

But the sources studied by Pinto and his collaborators are potentially being fed through a disc which has been puffed up due to internal pressures arising from the incredible rates of material passing through it. These thick discs can naturally exceed the Eddington limit and can even trap the radiation in a cone, making these sources appear brighter when we look straight at them. As the thick disc moves material further from the black hole's gravitational grasp it also gives rise to very high-speed winds like the ones observed by the Cambridge researchers.

“By observing x-ray sources that are radiating beyond the Eddington limit, it is possible to study their accretion process in great detail, investigating by how much the limit can be exceeded and what exactly triggers the outflow of such powerful winds,” said Norbert Schartel, ESA XMM-Newton Project Scientist.

̽��ֱ��nature of the compact objects hosted at the core of the two sources observed in this study is, however, still uncertain.

Based on the x-ray brightness, the scientists suspect that these mighty winds are driven from accretion flows onto either neutron stars or black holes, the latter with masses of several to a few dozen times that of the Sun.

To investigate further, the team is still scrutinising the data archive of XMM-Newton, searching for more sources of this type, and are also planning future observations, in x-rays as well as at optical and radio wavelengths.

“With a broader sample of sources and multi-wavelength observations, we hope to finally uncover the physical nature of these powerful, peculiar objects,” said Pinto.

Reference:
C. Pinto et al. ‘Resolved atomic lines reveal outflows in two ultraluminous X-ray sources’ Nature (2016). DOI: 10.1038/nature17417.

Adapted from an ESA press release.

Astronomers have observed two black holes in nearby galaxies devouring their companion stars at an extremely high rate, and spitting out matter at a quarter the speed of light.

This is the first time we’ve seen winds streaming away from ultra-luminous x-ray sources.

Ciro Pinto

ESA - C. Carreau

Artist’s impression depicting a compact object – either a black hole or a neutron star – feeding on gas from a companion star in a binary system.

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. For image use please see separate credits above.

Yes

Uncovering the afterlife of ancient Egypt

sjr81 — Thu, 25 Feb 2016 15:31:24 +0000

Going beyond the images of mummies, animal-headed gods, pharaohs and mystery often associated with ancient Egypt, Death on the Nile explores the beliefs and working practices behind these objects and reveals fascinating new information on how they were made.

Golden yellow, and covered from head to toe in bright hieroglyphs and pictures in reds, greens and blues, the set of coffins belonging to the man named Nespawershefyt (also known as Nes-Amun) was one of the very first gifts to the Fitzwilliam collection, given by two members of the ̽��ֱ�� of Cambridge in 1822, just a few years after the Museum was founded in 1816.

̽��ֱ��following year, Giovanni Belzoni presented the ̽��ֱ�� with the seven-ton granite sarcophagus lid of Ramesses III which he had retrieved from the Valley of the Kings. These and other gifts, as well as material from excavations, for which the Museum was a sponsor, created the remarkable collection of Egyptian coffins at the Fitzwilliam today.

̽��ֱ��coffins of Nes-Amun are not only incredibly beautiful, they also contain valuable clues to the man who commissioned them and to precisely how Egyptian coffins in his time were made. It is one of the finest coffin sets of its type in the world and in an outstanding state of preservation.

To uncover its hidden secrets, the coffins have been extensively studied with X-radiography at the Museum. And in February this year, the inner coffin was sent for CT scanning at the radiology department of Addenbrooke's Hospital, part of Cambridge ̽��ֱ�� Hospitals (CUH).

Julie Dawson, Head of Conservation at the Fitzwilliam Museum and co-curator of the exhibition, said: “ ̽��ֱ��inner coffin box is made up of a multitude of pieces of wood, including sections from at least one older coffin. Evidence of re-use includes cuts across old dowel holes, patching to change the profile of the coffin sides and a number of places where old mortise holes have been filled in and new ones cut beside them. Wood was a precious commodity and the craftsmen were incredibly skilled at making these complex objects from sometimes unpromising starting materials.

“ ̽��ֱ��radiographs and scans also reveal how people tried to restore or preserve the coffins in the past. Some parts of Nespawershefyt’s coffins are held together with 19th century ironmongery. Without these old repairs the coffins might not have survived so well, but they are quite intrusive on the original object and have rusted into the wood in places, causing damage.”

Examining the surface revealed other surprises, including several 3,000 year old fingerprints, suggesting that the craftsmen moved the lid of the inner coffin before the varnish had dried. NesAmun clearly commissioned his coffins during his lifetime, presumably at the point where he could afford a set worthy of his status as a priest of Amun-Re.

However, by the time of his death he had risen in rank and his new titles — as supervisor of craftsmen's workshops in Karnak and the supervisor of temple scribes of Amun-Re — had to be inscribed over the top of the old ones. This shows the importance attached to being properly prepared for death in ancient Egypt, even while one was still alive.

̽��ֱ��Nes-Amun coffin set is one of many stunning objects in Death on the Nile, the majority from the Fitzwilliam’s collections and complemented by loans from the British Museum and the Musée du Louvre. Through scientific analysis, the woods and the pigments and varnishes used by the craftsmen to make the decoration have been identified.

Evidence of working practices, from the variety of tool marks found on the wood to the drawing and painting techniques used to make the images, have been revealed through close study and a range of imaging techniques.

All this information helps bring us closer to the people who made the coffins as do the very human touches and stumbles – secret repairs hidden underneath a perfect finish, mistakes in drawings that had to be changed in the final painting and even the odd practice doodle on the underside of a coffin box.

A series of reconstructions will show how some of the coffins were made and, in a live conservation area, visitors will be able to examine in more detail the scientific techniques and the materials and construction methods uncovered during the project.

Helen Strudwick, Egyptologist and exhibition co-curator said: “This is a chance for us to encourage visitors to look more closely at these extraordinary objects. A coffin artisan in ancient Egypt had to deal creatively with many practical problems and sometimes restrictions on materials available because of the economic or political climate. Objects always had to be tailored to cost, but the finish had to meet the high aspirations of the customer. ̽��ֱ��coffins show the skill and care with which the Egyptians prepared for the afterlife.

“To us, for whom death is a taboo subject, this seems like a morbid preoccupation. In fact, it was an obsession with life and an urgent wish to ensure its perfected continuation.

“This is also a very appropriate exhibition for our bicentenary year. Not only did the Museum’s collection of Egyptian artefacts start with the gift of a beautiful set of coffins, that gift was also given in the year that Egyptology as a subject was born: 1822 was the year that Jean-François Champollion first announced his theories on the hieroglyphic script. And, as part of the ̽��ֱ�� of Cambridge, it is an excellent opportunity for us to bring the research we are carrying out on the Museum’s Egyptian coffin collection to the attention of a wider audience.”

Death on the Nile: Uncovering the afterlife of ancient Egypt is at the Fitzwilliam Museum, Cambridge 23 February – 22 May 2016. Admission is free.

̽��ֱ��Fitzwilliam Museum is marking its bicentenary anniversary celebrations with an exhibition on its remarkable collection of Egyptian coffins.

To us, for whom death is a taboo subject, this seems like a morbid preoccupation. In fact, it was an obsession with life.

Helen Strudwick

Death on the Nile - Teaser Trailer

Full length view of coffin from the coffin set of Nespawershefyt, About 1000 BC

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Meteorite impact turns silica into stishovite in a billionth of a second

Anonymous — Tue, 13 Oct 2015 12:49:29 +0000

̽��ֱ��Barringer meteor crater is an iconic Arizona landmark, more than 1km wide and 170 metres deep, left behind by a massive 300,000 tonne meteorite that hit Earth 50,000 years ago with a force equivalent to a ten megaton nuclear bomb. ̽��ֱ��forces unleashed by such an impact are hard to comprehend, but a team of Stanford scientists has recreated the conditions experienced during the first billionths of a second as the meteor struck in order to reveal the effects it had on the rock underneath.

̽��ֱ��sandstone rocks of Arizona were, on that day of impact 50,000 years ago, pushed beyond their limits and momentarily – for the first few trillionths and billionths of a second – transformed into a new state. ̽��ֱ��Stanford scientists, in a study published in the journal Nature Materials, recreated the conditions as the impact shockwave passed through the ground through computer models of half a million atoms of silica. Blasted by fragments of an asteroid that fell to Earth at tens of kilometres a second, the silica quartz crystals in the sandstone rocks would have experienced pressures of hundreds of thousands of atmospheres, and temperatures of thousands of degrees Celsius.

What the model reveals is that atoms form an immensely dense structure almost instantaneously as the shock wave hits at more than 7km/s. Within ten trillionths of a second the silica has reached temperatures of around 3,000℃ and pressures of more than half a million atmospheres. Then, within the next billionth of a second, the dense silica crystallises into a very rare mineral called stishovite.

̽��ֱ��results are particularly exciting because stishovite is exactly the mineral found in shocked rocks at the Barringer Crater and similar sites across the globe. Indeed, stishovite (named after a Russian high-pressure physics researcher) was first found at the Barringer Crater in 1962. ̽��ֱ��latest simulations give an insight into the birth of mineral grains in the first moments of meteorite impact.

Simulations show how crystals form in billionths of a second

̽��ֱ��size of the crystals that form in the impact event appears to be indicative of the size and nature of the impact. ̽��ֱ��simulations arrive at crystals of stishovite very similar to the range of sizes actually observed in geological samples of asteroid impacts.

Studying transformations of minerals such as quartz, the commonest mineral of Earth’s continental crust, under such extreme conditions of temperature and pressure is challenging. To measure what happens on such short timescales adds another degree of complexity to the problem.

These computer models point the way forward, and will guide experimentalists in the studies of shock events in the future. In the next few years we can expect to see these computer simulations backed up with further laboratory studies of impact events using the next generation of X-ray instruments, called X-ray free electron lasers, which have the potential to “see” materials transform under the same conditions and on the same sorts of timescales.

Simon Redfern, Professor in Earth Sciences, ̽��ֱ�� of Cambridge

This article was originally published on ̽��ֱ��Conversation. Read the original article.

Inset image: Barringer meteor Crater, Arizona (NASA Earth Observatory).

̽��ֱ��opinions expressed in this article are those of the individual author(s) and do not represent the views of the ̽��ֱ�� of Cambridge.

Simon Redfern from the Department of Earth Sciences discusses a study that has recreated the conditions experienced during the meteor strike that formed the Barringer Crater in Arizona.

United States Geological Survey/D. Roddy

Barringer Crater aerial photo

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Fossil skull sheds new light on transition from water to land

fpjl2 — Mon, 16 Mar 2015 11:18:28 +0000

A new 3D reconstruction of skull of one of the earliest four-footed vertebrate – which differs from earlier 2D reconstructions – suggests such creatures, which lived their lives primarily in shallow water environments, were more like modern crocodiles than previously thought.

̽��ֱ��researchers applied high-resolution X-ray computed tomography (CT) scanning to several specimens of Acanthostega gunnari, one of the ‘four-footed’ vertebrates known as tetrapods which invaded the land during one of the great evolutionary transitions in Earth’s history, 380-360 million years ago. Tetrapods evolved from lobe-finned fishes and display a number of adaptations to help them survive on land.

An iconic fossil species, Acanthostega gunnari is crucial for understanding the anatomy and ecology of the earliest tetrapods. However, after hundreds of millions of years in the ground fossils are often damaged and deformed. No single specimen of Acanthostega preserves a skull that is complete and three-dimensional which has limited scientists’ understanding of how this key animal fed and breathed – until now.

Researchers from Cambridge and Bristol ̽��ֱ�� used specialist software to ‘digitally prepared’ a number of Acanthostega specimens from East Greenland, stripping away layers of rock to reveal the underlying bones.

They uncovered a number of bones deep within the skull, including some that had never before been seen or described, resulting in a detailed anatomical description of the Acanthostega skull.

Once all of the bones and teeth were digitally separated from each other, cracks were repaired and missing elements duplicated. Bones could then be manipulated individually in 3D space. Using information from other specimens, the bones were fitted together like puzzle pieces to produce the first 3D reconstruction of the skull of Acanthostega, with surprising results.

Co-author Dr Laura Porro, formerly of Cambridge’s Department of Zoology and Bristol’s School of Earth Sciences (now at the Royal Veterinary College) said: “Because early tetrapods skulls are often ‘pancaked’ during the fossilization process, these animals are usually reconstructed having very flat heads. Our new reconstruction suggests the skull of Acanthostega was taller and somewhat narrower than previously interpreted, more similar to the skull of a modern crocodile.”

̽��ֱ��researchers also found clues to how Acanthostega fed. ̽��ֱ��size and distribution of its teeth and the shape of contacts between individual bones of the skull (called sutures) suggest Acanthostega may have initially seized prey at the front of its jaws using its large front teeth and hook-shaped lower jaw.

̽��ֱ��team say that these new analyses provide fresh clues about the evolution of the jaws and feeding system as the earliest animals with limbs and digits began to conquer the land.

̽��ֱ��researchers plan to apply these methods to other flattened fossils of the earliest tetrapods to better understand how these early animals modified their bones and teeth to meet the challenges of living on land.

“This work is the first stage of a study towards understanding how the earliest tetrapods fed, and that might lead us to what they fed on, and give further clues as to when and how they started to feed on land,” said co-author Professor Jennifer Clack from Cambridge’s Zoology Department.

Digital models of the original fossils and the 3D reconstruction are also useful in scientific research and education. They can be accessed by researchers around the world, without risking damage to fragile original fossils and without scientists having to travel thousands of miles to see original specimens. Furthermore, digital models and 3D printouts can be easily and safely handled by students taking courses and by the public during outreach events. ̽��ֱ��study is published recently in the journal PLOS ONE.

Adapted from a Bristol ̽��ֱ�� press release.

Inset image: 3D model showing the complete skull on top with ‘exploded’ views of the upper and lower jaws below.

̽��ֱ��first 3D reconstruction of the skull of a 360 million-year-old near-ancestor of land vertebrates has been created by scientists.

This work is the first stage of a study towards understanding how the earliest tetrapods fed, and that might lead us to what they fed on

Jennifer Clack

Porro/Clack

Left: 3D model with the jaws open; the individual bones are colour-coded to show the boundaries between them. Right: Original fossil skull of Acanthostega gunnari

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