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The Kavli Prize 2020

The Kavli Prize is awarded by a partnership between the Norwegian Academy of Sciences, the Norwegian Ministry of Education and Research and the Kavli Foundation. It recognizes seminal work of scientists in astrophysics, nanoscience and neuroscience, which respectively study the biggest, the smallest and the most complex environments in the universe.

The 2020 Kavli Prize in Astrophysics has been awarded to astronomer and astrophysicist Andrew Fabian for his pioneering research on how black holes influence their surrounding galaxies on both large and small scales.

The 2020 Kavli Prize in Nanoscience has been awarded to Harald Rose, Maximilian Haider, Knut Urban and Ondrej Krivanek, for their research and inventions of aberration-corrected lenses in electron microscopes.

The 2020 Kavli Prize in Neuroscience has been awarded to David Julius and Ardem Patapoutian for their independent discoveries of sensory receptors for temperature and pressure, respectively.

This Collection, put together by editors from Nature Astronomy, Nature Nanotechnology and Scientific Reports, includes papers by the 2020 Kavli Prize Laureates and related work published across the Nature Research journal portfolio.

Astrophysics

X-ray observations of the evolution of a black-hole transient suggest a shrinkage of its corona, rather than a change in the inner edge of the accretion disk.

Letter | | Nature

The lack of sufficiently high energy-resolution spectra has previously prevented the unambiguous identification of emission or absorption lines in the X-ray band of ultraluminous X-ray sources (ULXs), so it has not been possible to test the widely held theory that they are powered by accretion onto a compact object. Here Ciro Pinto et al. report the use of the high energy-resolution reflection grating spectrometer on board ESA's XMM-Newton observatory to identify X-ray emission lines and blueshifted absorption lines in the high-resolution spectra of the ULXs NGC 1313 X-1 and NGC 5408 X-1. The lines indicate that in each case the compact object is surrounded by powerful winds with an outflow velocity of about 0.2 times the speed of light. This agrees with predictions of extreme matter accretion onto compact objects.

Letter | | Nature

Supermassive black holes in the centres of galaxies may moderate the growth of their hosts by a feedback loop involving the brightness of the active galactic nucleus and the amount of gas falling into it from the galaxy. Gas outflows release huge quantities of energy into the interstellar medium, potentially clearing the surrounding gas. Michael Parker et al. report the observation of multiple absorption lines from an ultrafast gas flow in the X-ray spectrum of the active galactic nucleus IRAS 13224 3809, where the absorption is strongly anti-correlated with the emission from the inner regions of the accretion disk. Signatures of the wind are consistent with a single ionized outflow, linking the two phenomena. The detection of the wind responding to the emission from the inner disk demonstrates a connection between accretion processes occurring on very different scales, with the X-rays from within a few gravitational radii of the black hole ionizing the fast outflowing gas as the X-ray flux rises.

Letter | | Nature

Sloshing cold fronts in galaxy clusters—sharp jumps in density and temperature—retain a long-lived history of the motion of the cluster core. Chandra observations show that the cold front in Perseus is extremely sharp and is split into two edges.

Letter | | Nature Astronomy

The emission line arising from a transition of an electron from the iron K shell to the ground state (the K line) is prominent in the reflection spectrum of the hard X-ray continuum irradiating dense accreting matter around a black hole. The corresponding iron L-line emission should be detectable when iron abundance is high. That's the theory, and now broad iron L-line emission has been observed, together with the broad K line in the narrow-line Seyfert galaxy 1H0707. There is a reverberation lag of about 30 s between the direct X-ray continuum and its reflection from matter falling into the hole, a timescale comparable to the light-crossing time of the innermost radii around a supermassive black hole. This discovery opens a window on events close to the black hole event horizon in these objects.

Letter | | Nature

We can't see black holes, they are black on a black background. But we can see where they are, thanks to the bright glow emitted by matter as it falls into the black hole. This disk accretion process is central to much of high-energy astrophysics, but observational clues as to its inner workings are rare. Using remarkable spectra obtained from the stellar-mass black-hole binary GRO J1655–40, Miller et al. have now achieved the long-sought goal of setting observational constraints on the nature of disk accretion onto compact objects. The spectra record an X-ray-absorbing wind that must be powered by a magnetic process that can also drive accretion through the disk. This demonstrates that disk accretion onto black holes is a fundamentally magnetic process.

Letter | | Nature

Current black hole spin measurements, in X-rays, radio and gravitational waves, are already constraining models for the growth of black holes, the dynamics of stellar core-collapse and the physics of relativistic jet production.

Review Article | | Nature Astronomy

Do black holes rotate, and if yes, how fast? This question is fundamental and has broad implications, but still remains open. There are significant observational challenges in current spin determinations, but future facilities offer prospects for precision measurements.

Comment | | Nature Astronomy

Every 10 years, X-ray astronomers gather in Bologna, Italy, to review the state of the field. After 30 years of these meetings, is there really still a separate field of X-ray astronomy?

Meeting Report | | Nature Astronomy

Arguably, no mission changed X-ray astronomy in as short a time as did Hitomi. The planned X-ray Astronomy Recovery Mission, XARM, will carry its legacy forward.

Comment | | Nature Astronomy

This paper reports the direct measurement of the spin of a supermassive black hole at a cosmologically significant distance. New observations of the reflection-dominated spectrum of quadruply lensed quasar more than 6 billion light years away at z = 0.658, together with an analysis of archival X-ray data, show that it is rotating rapidly. Much of its radiation comes from a compact region within three or fewer gravitational radii from the black hole. The spin of a black hole provides a record of its co-evolution with its host galaxy through cosmic time, and these new data indicate that this black hole — like those observed previously at z > 2 — grew by coherent accretion rather than in a chaotic manner.

News & Views | | Nature

The properties of the black holes found at the centre of active galaxies can be deduced from their X-ray emission profiles. The problem is that several different models appear to explain the broadening and distortion of these emission lines equally well. Using high-quality broad-band X-ray spectra of the nucleus of the Seyfert galaxy NGC 1365, from the XMM-Newton and NuSTAR space telescopes, Guido Risaliti et al. present an analysis that robustly constrains the spin of the black hole. They use temporal and spectral analyses of the broadened Fe-line emission to disentangle continuum changes arising from time-variable absorption from reflection, which they find arises from a region within 2.5 gravitational radii of a rapidly spinning black hole. Absorption-dominated models that do not include relativistic disk reflection can be ruled out.

News & Views | | Nature

We can't see black holes, they are black on a black background. But we can see where they are, thanks to the bright glow emitted by matter as it falls into the black hole. This disk accretion process is central to much of high-energy astrophysics, but observational clues as to its inner workings are rare. Using remarkable spectra obtained from the stellar-mass black-hole binary GRO J1655–40, Miller et al. have now achieved the long-sought goal of setting observational constraints on the nature of disk accretion onto compact objects. The spectra record an X-ray-absorbing wind that must be powered by a magnetic process that can also drive accretion through the disk. This demonstrates that disk accretion onto black holes is a fundamentally magnetic process.

News & Views | | Nature

The properties of the black holes found at the centre of active galaxies can be deduced from their X-ray emission profiles. The problem is that several different models appear to explain the broadening and distortion of these emission lines equally well. Using high-quality broad-band X-ray spectra of the nucleus of the Seyfert galaxy NGC 1365, from the XMM-Newton and NuSTAR space telescopes, Guido Risaliti et al. present an analysis that robustly constrains the spin of the black hole. They use temporal and spectral analyses of the broadened Fe-line emission to disentangle continuum changes arising from time-variable absorption from reflection, which they find arises from a region within 2.5 gravitational radii of a rapidly spinning black hole. Absorption-dominated models that do not include relativistic disk reflection can be ruled out.

Letter | | Nature

The tidal disruption event Swift J1644+57, first detected on 28 March 2011, is thought to be a consequence of a star being consumed by a once-dormant black hole. Here Erin Kara et al. report observations of relativistic X-ray echoes, or reverberation, arising from gravitationally redshifted iron Kα photons reflected off the inner accretion flow in Swift J1644+57. The authors estimate the mass of the black hole to be a few million solar masses, suggesting an accretion rate of at least 100 times the Eddington limit. These observations do not support the previous interpretation that the X-rays arise from the relativistically moving regions of a jet.

Letter | | Nature

Nanoscience

An imaging technique able to resolve and identify all individual atoms in non-periodic solids would be a very useful tool for materials analysis. Annular dark-field (ADF) imaging in an aberration-corrected scanning transmission electron microscope optimized for low voltage operation allows such an analysis, as shown by Ondrej Krivanek and co-workers. The technique was used to examine a monolayer of boron nitride, in which it revealed individual atomic substitutions involving carbon and oxygen impurity atoms. Careful analysis of the data enables the construction of a detailed map of the atomic structure, with all the atoms of the four species resolved and identified.

Letter | | Nature

Spectroscopies sensitive to the vibrational behaviour of materials and chemical compounds — infrared and Raman spectroscopy for instance — are widely used to give insights into chemical and physical properties. These vibrational excitations can in principle also be detected by electron energy loss spectroscopy (EELS); but the effect is relatively weak and the energy resolution needed to extract such signals has not hitherto been available in electron microscopy. Here Ondrej Krivanek and colleagues demonstrate that recent advances in electron microscopy now mean that vibrational spectroscopy can be undertaken at high spatial resolution in the scanning transmission electron microscope. The authors present examples of applications in inorganic and organic materials, including the direct detection of hydrogen, a capability that could be of great use in the analysis of systems as diverse as hydrogen storage materials and biological tissues.

Letter | | Nature

Scanning transmission electron microscopy is a powerful material probe, but constrained to large atomic number samples due to the issues of beam damage and weak scattering. Here, Ophus et al.propose a method that produces linear phase contrast in a focused electron beam to image dose-sensitive objects.

Article | Open Access | | Nature Communications

Use of electron microscopy to determine morphology, or find where functionally significant biomolecules are located with high spatial resolution is of great interest. Here, Rez, Cohen et al. use aloof electron beam vibrational spectroscopy to probe different bonds in biological samples with no significant radiation damage.

Article | Open Access | | Nature Communications

It is easy to imagine that carbon nanotubes deform under strain, but the microscopic mechanism of deformation is difficult to relate to the large-scale one. Through aberration-corrected transmission microscopy the atomic displacement under bending is now mapped out, revealing unexpected details.

Article | | Nature Materials

Despite recent progress in the synthesis and characterization of molybdenum disulphide, little is yet known about its microstructure. Using refined chemical vapour deposition synthesis, high-quality crystals of monolayer molybdenum disulphide have now been grown. Single-crystal islands and polycrystals containing tilt and mirror twin grain boundaries are characterized, and the influence of the grain boundaries on the material properties of molybdenum disulphide is assessed.

Article | | Nature Materials

Single-atom-thick graphene sheets can now be produced at metre scales, bringing large-area applications in electronics and photovoltaics closer. But such large pieces can be expected to be polycrystalline, so it is important to determine the nature and size of the grains involved. Huang et al. use transmission electron microscopy to produce atomic-resolution images at grain boundaries, and map the location, orientation and shape of several hundred grains and boundaries using diffraction-filtered imaging. By correlating grain imaging with scanned probe and transport measurements, they show that the grain boundaries dramatically weaken the mechanical strength of graphene membranes, but do not as dramatically alter their electrical properties.

Letter | | Nature

van der Waals heterostructures are hybrid structures formed by layering two-dimensional materials into a stack that is held together by the van der Waals forces between the layers. High-quality heterostructures with uniform properties require spatially uniform layers with pristine interfaces that contain no bubbles, wrinkles or foreign contaminants. This paper reports the fabrication of centimetre-scale van der Waals heterostructures of transition-metal dichalcogenide films through layer-by-layer stacking under vacuum. This method achieved uniform stacking with high-quality interfaces even where the lattice was mismatched between the two-dimensional layers. The researchers could uniformly tune the electrical properties of the structures by changing the number and composition of the layers. The stacks were easily detached from the substrate by immersion in water. The team made preliminary explorations into potential applications for these large-area structures, including optical windows with colour-tunable transparency and cantilever arrays for micro- and nanoelectromechanical applications.

Letter | | Nature

The vibrational excitations of nanostructures have a fundamental effect on their suitability for various electronic, optical and thermal applications. Maureen Lagos and colleagues probe these excitations, using state-of-the-art electron microscopy to map the vibrational modes both at the surface and within the body of individual nanoparticles. Such information not only contributes to our knowledge of these fundamental vibrational modes, but will also be valuable for the design and optimization of nanostructures for practical use.

Letter | | Nature

Combining an electron microscope pixel-array detector that collects the entire distribution of scattered electrons with full-field ptychography greatly improves image resolution and contrast compared to traditional techniques, even at low beam energies.

Article | | Nature

Neuroscience

Mechanosensitive cation channels convert external mechanical stimuli into various biological actions, including touch, hearing, balance and cardiovascular regulation. The eukaryotic Piezo proteins are mechanotransduction channels, although their structure and gating mechanisms are not well elucidated. In related papers in this issue of Nature, two groups report cryo-electron microscopy structures of the full-length mouse Piezo1 and reveal three flexible propeller blades. Each blade is made up of at least 26 helices, forming a series of helical bundles, which adopt a curved transmembrane region. A kinked beam and anchor domain link these Piezo repeats to the pore, giving clues as to how the channel responds to membrane tension and mechanical force.

Article | | Nature

Proprioception, the sense of body and limb position, begins in nerve cells called proprioceptors that are activated by muscle or joint stretch. The molecular mechanism of mechanotransduction in mammalian proprioceptors is unknown. The authors show that the mechanically activated cation channel Piezo2 is the principal mechanotransducer in murine proprioceptors.

Article | | Nature Neuroscience

Piezo ion channels function as mechanotransducers involved in vascular development and touch sensing, but their structural features remain unknown. Here the authors find that the C-terminal region of Piezo protein encompasses the pore and identify a glutamate residue within this region involved in ion conduction properties.

Article | Open Access | | Nature Communications

Recent decades have seen the mechanisms of sensing photons (vision), chemicals (olfaction, taste) and temperature (thermosensation) elucidated in some detail. The sense of touch, implying the transduction of mechanical forces into electrical signals, is less well understood. Here Ardem Patapoutian and colleagues show that mice lacking the mechanically activated ion channel Piezo2 in both sensory neurons and in Merkel cells, a type of modified skin cell, are almost totally incapable of light-touch sensation. As the mice are intact in other somatosensory functions such as mechanical nociception, the work implies that other mechanically activated ion channels must now be identified to account for painful touch sensation.

Letter | | Nature

Transient receptor potential (TRP) channels are sensors for a wide range of physical and chemical stimuli. In the first of a pair of related papers, Maofu Liao et al. solve the high-resolution electron cryo-microscopy structure of rat TRPV1, the receptor for capsaicin (a pungent agent from chili peppers), in a 'closed' state. The overall structure is fairly similar to that of a voltage-gated ion channel, but there are several structural features unique to TRP channels. In the second paper, Erhu Cao et al. present the structures of rat TRPV1 in the presence of a peptide neurotoxin (resiniferatoxin) and in the presence of capsaicin, yielding structures of activated states of the channel. Comparison of the closed and open structures suggests that TRPV1 has a unique two-gate mechanism of channel activation.

Article | | Nature

Many tissues are able to detect and respond to mechanical forces, and this mechanical sensitivity has been implicated in many biological processes and diseases, including touch, pain, deafness and hypertension. The conversion of mechanical force into biological signals, or 'mechanotransduction', is thought to involve specialized cation channels. In a pair of papers, Ardem Patapoutian and colleagues establish that the large transmembrane proteins of the 'Piezo' family — conserved from animals to plants and protozoa — are among the long-sought-after mechanically activated ion channels. Coste et al. show that the Drosophila melanogaster Piezo protein induces mechanically activated cationic currents in human embryonic kidney cells, establishing functional conservation. Comparison of the mechanically activated currents induced by mouse and fly Piezos reveals ion-channel activities with unique pore properties, suggesting that Piezos are bona fide ion channels. Kim et al. show that D. melanogaster Piezo is essential for sensing mechanical pain in fruitflies, giving the first demonstration that Piezos are physiologically relevant mechanosensors in vivo.

Article | | Nature

Many tissues are able to detect and respond to mechanical forces, and this mechanical sensitivity has been implicated in many biological processes and diseases, including touch, pain, deafness and hypertension. The conversion of mechanical force into biological signals, or 'mechanotransduction', is thought to involve specialized cation channels. In a pair of papers, Ardem Patapoutian and colleagues establish that the large transmembrane proteins of the 'Piezo' family — conserved from animals to plants and protozoa — are among the long-sought-after mechanically activated ion channels. Coste et al. show that the Drosophila melanogaster Piezo protein induces mechanically activated cationic currents in human embryonic kidney cells, establishing functional conservation. Comparison of the mechanically activated currents induced by mouse and fly Piezos reveals ion-channel activities with unique pore properties, suggesting that Piezos are bona fide ion channels. Kim et al. show that D. melanogaster Piezo is essential for sensing mechanical pain in fruitflies, giving the first demonstration that Piezos are physiologically relevant mechanosensors in vivo.

Letter | | Nature

Blood-feeding vampire bats have evolved the ability to detect infrared (IR) radiation as a means of locating hot spots on warm-blooded prey. Only three other vertebrate lineages have this 'sixth' sense: three distantly related groups of snakes (pit vipers, pythons and boas). In all cases, the IR sensor is a highly specialized facial structure called the pit organ. In the snakes, a non-heat-sensitive ion channel (vertebrate TRPA1) has become an infrared detector. As reported in this issue, vampire bats use a slightly different molecular mechanism whereby RNA splicing generates a variant of the ubiquitous TRPV1 heat-sensitive channel that is tuned to lower temperatures. Comparison of this channel's gene sequence with the equivalent in other mammals lends support to the hypothesis based on molecular data that these bats are evolutionarily grouped with horses, dogs, cows, moles and dolphins (in the Laurasiatheria superorder), rather than with humans, monkeys and rodents (in the Euarchontoglires) as originally proposed on anatomical criteria.

Letter | | Nature

Transient receptor potential (TRP) channels are the most prominent family of nociceptive ion-channel transducer proteins. This Review highlights evidence supporting particular TRP channels as targets for analgesics, indicates the likely efficacy profiles of TRP-channel-acting compounds and looks at recent clinical trials with TRP-channel-acting drugs.

Review Article | | Nature Reviews Drug Discovery

The TRPA1 ion channel, found in neurons associated with sensing pain, responds to noxious and pungent compounds and also to cold. Gene knockout experiments in mice confirm that TRPA1 is a physiologicallyrequired pain sensor. How such diverse stimuli activate TRPA1 was not known but Macpherson et al. show that that TRPA1 is activated by covalent modification of its cysteine residues. It is not unusual for proteins to be modified by cysteine reactive agents, but this is the first ion channel known to be activated by this method. The role of TRPA1 activation in response to electrophile toxicity and oxidative stress may be to warn the organism of potential tissue damage.

Letter | | Nature

A variety of different ion channels have been suggested to underlie the detection of cold stimuli, and the role of each of these in detecting innocuous cool versus noxious cold has been much debated. The menthol receptor TRPM8 is a strong candidate as a cold transducer, but its physiological importance has been questioned. A study of cold sensitivity in TRPM8 knockout mice has clarified matters. Mice lacking the receptor are deficient in the ability to sense cold at the cellular level, in intact nerve fibres and in whole animal (behavioural) tests. TRPM8 is clearly the primary contributor to peripheral cold sensation, with animals lacking this channel unable to discriminate between warm and cold surfaces until the temperature drops to below 10 °C.

Letter | | Nature

Three peptides isolated from the venom of the West Indian tarantula Psalmopoeus cambridgei have been found to promote pain and inflammation by activating the same neuronal receptor as capsaicin, the hot component of chilli peppers. This suggests that tarantulas and chillis use similar tactics to deter predators. The newly discovered peptides are also unusual because they trigger an excitatory response. Peptides with similar structures that bind to other ion channels are already known, but are inhibitory.

Letter | | Nature