Nature, 4 May 2023, VOL 617, ISSUE 7959
《自然》2023年5月4日，第617卷，7959期
天文学Astronomy
An infrared transient from a star engulfing a planet
恒星吞噬行星的红外瞬态
▲ 作者：Kishalay De, Morgan MacLeod, Viraj Karambelkar, Jacob E. Jencson, Deepto Chakrabarty, Charlie Conroy, et al.
▲ 链接：
https://www.nature.com/articles/s41586-023-05842-x
▲ 摘要：
轨道周期短（约不足10天）的行星在像太阳这样的恒星周围很常见。恒星在演化过程中不断膨胀，因此人们预计其行星伴星会被吞噬，或为主星的发光物质喷射提供动力。然而，这一阶段从未被直接观察到。
研究组报道了ZTF SLRN-2020的观测结果，这是银河系盘中一次短暂的光学爆发，伴随着明亮和长寿命的红外发射。由此产生的光曲线和光谱与红新星有着惊人的相似之处，红新星是一类现已证实由双星合并引起的爆发。
其异常低的光学光度（约1035 erg s−1）和辐射能量（约6.5 × 1041 erg）表明，一颗质量小于10个木星的行星被其类似太阳的主星吞噬。研究组估计银河系每年出现这种低光度红新星的频率大约在0.1到几颗之间。
未来的银道面调查应定期识别这些红新星，以显示行星被吞噬的统计数据和内太阳系行星的最终命运。
▲ Abstract：
Planets with short orbital periods (roughly under 10 days) are common around stars like the Sun. Stars expand as they evolve and thus we expect their close planetary companions to be engulfed, possibly powering luminous mass ejections from the host star. However, this phase has never been directly observed. Here we report observations of ZTF SLRN-2020, a short-lived optical outburst in the Galactic disk accompanied by bright and long-lived infrared emission. The resulting light curve and spectra share striking similarities with those of red novae—a class of eruptions now confirmed to arise from mergers of binary stars. Its exceptionally low optical luminosity (approximately 1035 erg s−1) and radiated energy (approximately 6.5 × 1041 erg) point to the engulfment of a planet of fewer than roughly ten Jupiter masses by its Sun-like host star. We estimate the Galactic rate of such subluminous red novae to be roughly between 0.1 and several per year. Future Galactic plane surveys should routinely identify these, showing the demographics of planetary engulfment and the ultimate fate of planets in the inner Solar System.
物理学physics
Quantum critical dynamics in a 5,000-qubit programmable spin glass
5000量子位可编程自旋玻璃中的量子临界动力学
▲ 作者：Andrew D. King, Jack Raymond, Trevor Lanting, Richard Harris, Alex Zucca, Fabio Altomare, et al.
▲ 链接：
https://www.nature.com/articles/s41586-023-05867-2
▲ 摘要：
对无序合金的实验表明，与传统的热退火相比，退火量子涨落可使自旋玻璃更快地进入低能态。由于自旋玻璃作为范例计算试验台的重要性，在可编程系统中再现这一现象仍是量子优化的核心挑战。
研究组通过超导量子退火器在数千量子位上实现量子临界自旋玻璃动力学，实现了这一目标。首先，证明了小自旋玻璃中薛定谔方程的量子退火和时间演化之间的定量一致性；然后，在数千个量子位的三维自旋玻璃中测量动力学，而这在经典多体量子动力学模拟中很难实现。
研究组提取了临界指数，明确区分量子退火与类似蒙特卡罗算法的较慢随机动力学，为大规模量子模拟提供了理论和实验支持，并为能量优化提供了缩放优势。
▲ Abstract：
Experiments on disordered alloys suggest that spin glasses can be brought into low-energy states faster by annealing quantum fluctuations than by conventional thermal annealing. Owing to the importance of spin glasses as a paradigmatic computational testbed, reproducing this phenomenon in a programmable system has remained a central challenge in quantum optimization. Here we achieve this goal by realizing quantum-critical spin-glass dynamics on thousands of qubits with a superconducting quantum annealer. We first demonstrate quantitative agreement between quantum annealing and time evolution of the Schrdinger equation in small spin glasses. We then measure dynamics in three-dimensional spin glasses on thousands of qubits, for which classical simulation of many-body quantum dynamics is intractable. We extract critical exponents that clearly distinguish quantum annealing from the slower stochastic dynamics of analogous Monte Carlo algorithms, providing both theoretical and experimental support for large-scale quantum simulation and a scaling advantage in energy optimization.
材料科学Materials Science
Tracking cubic ice at molecular resolution
以分子分辨率追踪立方冰
▲ 作者：Xudan Huang, Lifen Wang, Keyang Liu, Lei Liao, Huacong Sun, Jianlin Wang, et al.
▲ 链接：
https://www.nature.com/articles/s41586-023-05864-5
▲ 摘要：
冰在地球上无处不在，在云物理、气候变化和低温保存等几个领域都发挥着重要作用。冰的作用由其形成行为和相关结构决定。然而，这些尚未被人们完全理解。
尤其是，关于水是否可以冻结形成立方冰（目前在普通六方冰的相空间中尚未描述的相）存在长期争论。从实验室数据收集中推断出的主流观点将这种分歧归因于无法区分立方冰和无序堆叠冰（立方相和六方相的混合物）。
利用低温透射电子显微镜结合低剂量成像技术，研究组发现立方冰在低温界面上优先成核，在102K时水蒸气沉积形成立方冰和六方冰两种不同的结晶类型。此外，他们还发现了一系列立方冰缺陷，包括两种类型的堆叠无序，揭示了分子动力学模拟支持的结构演化动力学。
在分子水平上实现冰的形成及其动力学行为的直接、实时成像，为利用透射电子显微镜在分子水平上研究冰提供了机遇，且有望扩展到其他氢键晶体。
▲ Abstract：
Ice is present everywhere on Earth and has an essential role in several areas, such as cloud physics, climate change and cryopreservation. The role of ice is determined by its formation behaviour and associated structure. However, these are not fully understood. In particular, there is a long-standing debate about whether water can freeze to form cubic ice—a currently undescribed phase in the phase space of ordinary hexagonal ice. The mainstream view inferred from a collection of laboratory data attributes this divergence to the inability to discern cubic ice from stacking-disordered ice—a mixture of cubic and hexagonal sequences. Using cryogenic transmission electron microscopy combined with low-dose imaging, we show here the preferential nucleation of cubic ice at low-temperature interfaces, resulting in two types of separate crystallization of cubic ice and hexagonal ice from water vapour deposition at 102 K. Moreover, we identify a series of cubic-ice defects, including two types of stacking disorder, revealing the structure evolution dynamics supported by molecular dynamics simulations. The realization of direct, real-space imaging of ice formation and its dynamic behaviour at the molecular level provides an opportunity for ice research at the molecular level using transmission electron microscopy, which may be extended to other hydrogen-bonding crystals.
Electrically driven amplified spontaneous emission from colloidal quantum dots
胶体量子点的电驱动放大自发辐射
▲ 作者：Namyoung Ahn, Clément Livache, Valerio Pinchetti, Heeyoung Jung, Ho Jin, Donghyo Hahm, et al.
▲ 链接：
https://www.nature.com/articles/s41586-023-05855-6
▲ 摘要：
胶体量子点（QDs）是实现溶液可加工激光二极管的颇具吸引力的材料，可受益于尺寸控制的发射波长、低光学增益阈值以及易于与光子和电子电路集成。
然而，这种器件的实现受制于增益激活多载流子态的快速俄歇复合、高电流密度下QD薄膜稳定性差，以及在薄电致发光QD层与光学损耗电荷传导层结合的复杂器件堆层中难以获得净光学增益。
研究组解决了这些挑战，并实现了电泵浦胶体QD的放大自发辐射（ASE）。所开发的器件使用紧凑、连续梯度的量子点，将抑制俄歇复合结合至低损耗光子波导补充的脉冲、高电流密度电荷注入结构中。这些胶体QD ASE二极管具有强大的宽带光学增益，并表现出瞬时功率高达170μW的亮边辐射。
▲ Abstract：
Colloidal quantum dots (QDs) are attractive materials for realizing solution-processable laser diodes that could benefit from size-controlled emission wavelengths, low optical-gain thresholds and ease of integration with photonic and electronic circuits. However, the implementation of such devices has been hampered by fast Auger recombination of gain-active multicarrier states, poor stability of QD films at high current densities and the difficulty to obtain net optical gain in a complex device stack wherein a thin electroluminescent QD layer is combined with optically lossy charge-conducting layers. Here we resolve these challenges and achieve amplified spontaneous emission (ASE) from electrically pumped colloidal QDs. The developed devices use compact, continuously graded QDs with suppressed Auger recombination incorporated into a pulsed, high-current-density charge-injection structure supplemented by a low-loss photonic waveguide. These colloidal QD ASE diodes exhibit strong, broadband optical gain and demonstrate bright edge emission with instantaneous power of up to 170 μW.
地球科学Earth Science
Bipolar impact and phasing of Heinrich-type climate variability
海因里希型气候变异性的两极影响和阶段化
▲ 作者：Kaden C. Martin, Christo Buizert, Jon S. Edwards, Michael L. Kalk, Ben Riddell-Young, Edward J. Brook, et al.
▲ 链接：
https://www.nature.com/articles/s41586-023-05875-2
▲ 摘要：
在最后一个冰期，劳伦泰德冰原出现了北大西洋沉积物中记录的极端冰山排放事件。这些海因里希事件具有深远的气候影响，包括对水文和生物地球化学循环的广泛破坏。它们发生在海因里希冰退阶段，即大西洋翻转环流强烈减弱的寒冷时期。
海因里希型变异性在格陵兰水同位素比率（一种年代久远的现场温度指标）中并不明显，这使评估其区域气候影响和分阶段应对南极气候变化的工作变得复杂。
研究组表明未检测到海因里希事件对格陵兰岛的温度影响，冷却发生在几个海因里希冰退阶段的初期，两种类型的海因里希变异性对南极气候都有明显影响。南极冰芯显示，尽管没有格陵兰气候信号，但在海因里希事件期间，加速变暖与甲烷增加同步，这表明存在大气遥相关。
格陵兰冰芯氮稳定同位素比率是一个敏感的温度指标，表明在海因里希冰退阶段1（距今17800年前，于1950年定义）开始时，温度突然下降了约3摄氏度。南极变暖比这种变冷滞后了133±93年，与海洋遥相关一致。矛盾的是，近端站点受海因里希事件的影响小于远端站点，表明了空间复杂的事件动态。
▲ Abstract：
During the last ice age, the Laurentide Ice Sheet exhibited extreme iceberg discharge events that are recorded in North Atlantic sediments. These Heinrich events have far-reaching climate impacts, including widespread disruptions to hydrological and biogeochemical cycles. They occurred during Heinrich stadials—cold periods with strongly weakened Atlantic overturning circulation. Heinrich-type variability is not distinctive in Greenland water isotope ratios, a well-dated site temperature proxy, complicating efforts to assess their regional climate impact and phasing against Antarctic climate change. Here we show that Heinrich events have no detectable temperature impact on Greenland and cooling occurs at the onset of several Heinrich stadials, and that both types of Heinrich variability have a distinct imprint on Antarctic climate. Antarctic ice cores show accelerated warming that is synchronous with increases in methane during Heinrich events, suggesting an atmospheric teleconnection, despite the absence of a Greenland climate signal. Greenland ice-core nitrogen stable isotope ratios, a sensitive temperature proxy, indicate an abrupt cooling of about three degrees Celsius at the onset of Heinrich Stadial 1 (17.8 thousand years before present, where present is defined as 1950). Antarctic warming lags this cooling by 133 ± 93 years, consistent with an oceanic teleconnection. Paradoxically, proximal sites are less affected by Heinrich events than remote sites, suggesting spatially complex event dynamics.
Rapid, buoyancy-driven ice-sheet retreat of hundreds of metres per day
浮力驱动的冰盖每天快速后退数百米
▲ 作者：Christine L. Batchelor, Frazer D. W. Christie, Dag Ottesen, Aleksandr Montelli, Jeffrey Evans, Evelyn K. Dowdeswell, et al.
▲ 链接：
https://www.nature.com/articles/s41586-023-05876-1
▲ 摘要：
冰盖接地线后退速率可通过海底冰消区波纹脊的间距来量化，这为大约50年的冰盖变化卫星记录提供了长期背景。然而，这些地形的少数现存例子仅限于海底的小区域，限制了人们对未来接地线后退速率以及海平面上升的理解。
研究组使用测深数据绘制了横跨挪威中部大陆架30000平方千米的7600多个波纹脊。脊的间距表明，在末次冰消期，在低梯度（±1°）冰盖床上出现了接地线快速后退脉冲，其速度为每日后退55~610米。这些数值远远超过了此前报道的所有卫星和海洋地质记录中的接地线后退速率。
在前一个海床最平坦区域测量到的后退速率最高，这表明在接地线接近全浮力的地方，可能发生几乎瞬间的冰盖不接地和后退。流体静力学原理表明，即使在当今的气候强迫下，在低梯度的南极冰盖床上也可能发生类似的接地线快速后退脉冲。
最后，该研究结果强调了冰盖平层区域一个经常被忽视的脆弱性，即其很容易受到极快速、浮力驱动后退脉冲的影响。
▲ Abstract：
Rates of ice-sheet grounding-line retreat can be quantified from the spacing of corrugation ridges on deglaciated regions of the seafloor, providing a long-term context for the approximately 50-year satellite record of ice-sheet change. However, the few existing examples of these landforms are restricted to small areas of the seafloor, limiting our understanding of future rates of grounding-line retreat and, hence, sea-level rise. Here we use bathymetric data to map more than 7,600 corrugation ridges across 30,000 km2 of the mid-Norwegian shelf. The spacing of the ridges shows that pulses of rapid grounding-line retreat, at rates ranging from 55 to 610 m day−1, occurred across low-gradient (±1°) ice-sheet beds during the last deglaciation. These values far exceed all previously reported rates of grounding-line retreat across the satellite and marine-geological records. The highest retreat rates were measured across the flattest areas of the former bed, suggesting that near-instantaneous ice-sheet ungrounding and retreat can occur where the grounding line approaches full buoyancy. Hydrostatic principles show that pulses of similarly rapid grounding-line retreat could occur across low-gradient Antarctic ice-sheet beds even under present-day climatic forcing. Ultimately, our results highlight the often-overlooked vulnerability of flat-bedded areas of ice sheets to pulses of extremely rapid, buoyancy-driven retreat.
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