Rapidly growing satellite constellations have raised strong concerns among the scientific community. Reflections from satellites can be visible to the unaided eye and extremely bright for professional telescopes. These trails already affect astronomical images across the complete electromagnetic spectrum, with a noticeable cost for operations and mitigation efforts. Contrary to popular perception, satellite trails affect not only ground-based observatories but also space observatories such as the Hubble Space Telescope. However, the current number of satellites is only a fraction (less than 3%) of those to be launched in the next decade. Here we show a forecast of the satellite trail contamination levels for a series of international low-Earth-orbit telescopes on the basis of the proposed telecommunication industry constellations. Our results show that if these constellations are completed, one-third of the images of the Hubble Space Telescope will be contaminated, while the SPHEREx (Spectro-Photometer for the History of the Universe, Epoch of Reionization and Ices Explorer), ARRAKIHS (Analysis of Resolved Remnants of Accreted galaxies as a Key Instrument for Halo Surveys) and Xuntian space telescopes will have more than 96% of their exposures affected, with { 5.6}_{ -0.3}^{ +0.3}, { 69}_{ -22}^{ +21} and { 92}_{ -10}^{ +11} trails per exposure, respectively, with an average surface brightness of μ?=?19?±?2?mag?arcsec?2. Our results demonstrate that light contamination is a growing threat for space telescope operations. We propose a series of actions to minimize the impact of satellite constellations, allowing researchers to predict, model and correct unwanted satellite light pollution from science observations.
物理学Physics
Determination of the spin and parity of all-charm tetraquarks
The traditional quark model accounts for the existence of baryons, such as protons and neutrons, which consist of three quarks, as well as mesons, composed of a quark–antiquark pair. Only recently has substantial evidence started to accumulate for exotic states composed of four or five quarks and antiquarks. The exact nature of their internal structure remains uncertain. Here we report the first measurement of quantum numbers of the recently discovered family of three all-charm tetraquarks, using data collected by the CMS experiment at the Large Hadron Collider from 2016 to 2018. The angular analysis techniques developed for the discovery and characterization of the Higgs boson have been applied to the new exotic states. Here we show that the quantum numbers for parity P and charge conjugation C symmetries are found to be +1. The spin J of these exotic states is determined to be consistent with 2?, while 0? and 1? are excluded at 95% and 99% confidence levels, respectively. The JPC?=?2++ assignment implies particular configurations of constituent spins and orbital angular momenta, which constrain the possible internal structure of these tetraquarks.
Sterile-neutrino search based on 259 days of KATRIN data
Neutrinos are the most abundant fundamental matter particles in the Universe and play a crucial part in particle physics and cosmology. Neutrino oscillation, discovered about 25?years ago, shows that the three known species mix with each other. Anomalous results from reactor and radioactive-source experiments suggest a possible fourth neutrino state, the sterile neutrino, which does not interact through the weak force. The Karlsruhe Tritium Neutrino (KATRIN) experiment, primarily designed to measure the neutrino mass using tritium β-decay, also searches for sterile neutrinos suggested by these anomalies. A sterile-neutrino signal would appear as a distortion in the β-decay energy spectrum, characterized by a discontinuity in curvature (kink) related to the sterile-neutrino mass. This signature, which depends only on the shape of the spectrum rather than its absolute normalization, offers a robust, complementary approach to reactor experiments. Here we report the analysis of the energy spectrum of 36 million tritium β-decay electrons recorded in 259 measurement days within the last 40?eV below the endpoint. The results exclude a substantial part of the parameter space suggested by the gallium anomaly and challenge the Neutrino-4 claim. Together with other neutrino-disappearance experiments, KATRIN probes sterile-to-active mass splittings from a fraction of an eV2to several hundred eV2, excluding light sterile neutrinos with mixing angles above a few per cent.
人工智能Artificial Intelligence
Glasses-free 3D display with ultrawide viewing range using deep learning
Glasses-free three-dimensional (3D) displays provide users with an immersive visual experience without the need of any wearable devices. To achieve high-quality 3D imaging, a display should have both large linear dimensions and a wide viewing angle. However, the trade-off between spatial extent and bandwidth of optical systems, the space–bandwidth product, conventionally constrains the simultaneous maximization of the two. The two most common approaches to 3D displays are holographic and automultiscopic, which, respectively, sacrifice either scale or viewing angle. Recently, some implementations enhanced by artificial intelligence have shown directions to mitigate these constraints, but they still operate within a set space–bandwidth product. As a result, it remains challenging to fabricate large-scale wide-angle 3D displays. Here we report the realization of a large-scale full-parallax 3D display with seamless viewing beyond 100°, maintained at over 50?Hz and 1,920?×?1,080 resolution on a low-cost light-field delivery setup. This device, called EyeReal, is realized by accurately modelling binocular view and combining it with a deep-learning real-time optimization, enabling the generation of optimal light-field outputs for each of the eyes. Our device could potentially enable applications in educational tools, 3D design and virtual reality.
材料科学Materials Science
Tin-based perovskite solar cells with a homogeneous buried interface
Tin-based perovskite solar cells (TPSCs) have emerged as a promising non-toxic and environmentally friendly alternative to lead-based devices, with certified power conversion efficiencies (PCEs) of inverted architectures now exceeding 16%. Despite an ideal bandgap supporting a theoretical PCE of more than 33%, TPSCs still lag in performance and stability, partly because of suboptimal hole transport layers and a poor buried interface that hinder hole extraction. Here we report (E)-(2-(4′,5′-bis(4-(bis(4-methoxyphenyl)amino)phenyl)-[2,2′-bithiophen]?5-yl)?1-cyanovinyl)phosphonic acid at the buried interface, using a molecular film to optimize hole transport layers in inverted TPSCs. This molecular film forms a homogeneous interfacial layer with well-matched energy-level alignment, markedly enhancing hole extraction. Moreover, this approach creates a superwetting underlayer that guides the growth of uniform, high-quality Sn-based perovskite films with reduced defect density and minimized non-radiative recombination losses. The resulting inverted small-area TPSCs demonstrate a record PCE of 17.89% (certified 17.71% under reverse scanning mode). Furthermore, the encapsulated device maintains more than 95% of the initial PCE after 1,344?h of ambient shelf storage and more than 94% after 1,550?h of continuous operation under 1-sun illumination. Notably, we achieve a record PCE of 14.40% for 1?cm2 TPSCs, highlighting the scalability of our strategy.
A matrix-confined molecular layer for perovskite photovoltaic modules
钙钛矿光伏组件的基质约束分子层
▲ 作者：Yugang Liang, Guodong Chen, Yao Wang, Yu Zou, Menglei Feng, Yanming Wang, et al.
Metal halide perovskites with remarkable optoelectronic properties have become a competitive candidate for supporting the efficiency progression of photovoltaics. As the latest reported power conversion efficiency of research cells is comparable to that of commercialized silicon cells, the industrialization of perovskite solar cells is on the horizon. However, most high-efficiency inverted perovskite solar cells based on self-assembled molecules (SAMs) face challenges owing to the aggregation and hydrophobicity of the SAMs. Here we report a ‘SAM-in-matrix’ strategy to distribute partial SAMs into a stable matrix of tris(pentafluorophenyl)borane, which breaks the original molecular-stacking-induced aggregation. Two-dimensional lattice Monte Carlo simulations and experimental results reveal that this strategy forms efficient charge transport channels. SAM-in-matrix hole-transport-layer-based devices show universally higher efficiencies for various SAMs, with compact surface coverage, good conductivity and substantially fewer buried nanovoids. Moreover, this strategy shows prominent application potential for scalable production. A SAM-in-matrix hole transport layer on fluorine-doped tin oxide/NiOxsubstrate facilitates the formation of large-area perovskite films with good crystalline quality and enhanced conductivity of NiOx. A 1?m?×?2?m large-area perovskite solar module is thus achieved with a certified efficiency of 20.05%.
