The chemical make-up of the Sun: A 2020 vision
The chemical make-up of the Sun: A 2020 vision
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太阳的化学组成：2020 年愿景
DOI：
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发表时间：
2021
影响因子：
6.5
通讯作者：
N. Grevesse
中科院分区：
文献类型：
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作者：
M. Asplund;A. Amarsi;N. Grevesse
上下文太阳的化学成分是天文学中的一个基本尺度，基本上所有的宇宙物体都是以它为参考的。因此，准确了解太阳元素丰度对于非常广泛的主题至关重要。目标。我们重新评估了所有83种长寿元素的太阳丰度，使用高度逼真的太阳建模和最先进的光谱分析技术，再加上最好的原子数据和观测。方法.我们的太阳光谱分析的基础是太阳表面对流和大气的三维（3D）辐射流体动力学模型，它再现了关键观测诊断的全部武器库。新的完整和全面的三维谱线形成计算考虑到偏离局部热力学平衡（非LTE）的Na，Mg，K，Ca和Fe使用全面的模型原子与可靠的辐射和碰撞数据。我们新推导出的C、N和O的丰度是基于对CH、C2、CO、NH、CN和OH共879个分子跃迁的允许和禁止原子线的3D非LTE分析以及3D LTE计算。基于更新的原子数据，严格选择线，改进的混合物考虑以及文献中可用的新的非LTE计算，重新评估了另外50种元素的先前基于3D的计算。对于无法对安静太阳进行光谱测定的元素，将根据补充方法重新审视推荐的太阳丰度，包括日震学（He）、来自创世记样本返回使命的太阳风数据（惰性气体）、太阳黑子观测（四种元素）以及最原始陨石的测量（15种元素）。结果我们新的改进分析证实了我们以前基于3D的研究中获得的相对较低的太阳C，N和O丰度：log C = 8.46 ± 0.04，log N = 7.83 ± 0.07，log O = 8.69 ± 0.04。所有可用的原子和分子指标之间的良好协议实现C和O，但对于N的原子线意味着较低的丰度比未知原因的分子跃迁。其他元素的太阳丰度修正值也与我们之前推荐的值一致，只有Li、F、Ne、Mg、Cl、Kr、Rb、Rh、Ba、W、Ir和Pb的差异超过0.05 dex。这里提出的现今光球金属质量分数仅略高于我们以前的值，主要是由于创世记太阳风测量的修正后的Ne丰度：X表面= 0.7438 ± 0.0054，Y表面= 0.2423 ± 0.0054，Z表面= 0.0139 ± 0.0006，Z表面/X表面= 0.0187 ± 0.0009。总的来说，太阳的丰度与CI陨石的丰度一致，但我们确定了与冷凝温度的相关性，使得中等挥发性元素在CI陨石中增加了0.04 dex，耐火元素可能减少了0.02 dex，这与过去半个世纪的传统智慧相冲突。相反，太阳的化学成分更接近于CM陨石的细粒基质，除了预期的高挥发性元素。结论.更新的现今太阳光球和原太阳的83种元素的丰度，包括所有长寿命同位素。所谓的太阳建模问题-日震学和太阳内部模型之间的持续差异与低太阳金属丰度类似，在这里主张-仍然与我们修订的太阳丰度保持不变，这表明在现有标准太阳模型中计算的不透明度和/或对流区以下混合处理的缺点。太阳和CI的丰度与凝结温度之间的未揭示趋势尚未被理解，但可能是行星形成的印记，特别是因为在太阳和太阳孪生子之间观察到类似的相反符号趋势。
Context. The chemical composition of the Sun is a fundamental yardstick in astronomy, relative to which essentially all cosmic objects are referenced. As such, having accurate knowledge of the solar elemental abundances is crucial for an extremely broad range of topics. Aims. We reassess the solar abundances of all 83 long-lived elements, using highly realistic solar modelling and state-of-the-art spectroscopic analysis techniques coupled with the best available atomic data and observations. Methods. The basis for our solar spectroscopic analysis is a three-dimensional (3D) radiative-hydrodynamical model of the solar surface convection and atmosphere, which reproduces the full arsenal of key observational diagnostics. New complete and comprehensive 3D spectral line formation calculations taking into account of departures from local thermodynamic equilibrium (non-LTE) are presented for Na, Mg, K, Ca, and Fe using comprehensive model atoms with reliable radiative and collisional data. Our newly derived abundances for C, N, and O are based on a 3D non-LTE analysis of permitted and forbidden atomic lines as well as 3D LTE calculations for a total of 879 molecular transitions of CH, C2, CO, NH, CN, and OH. Previous 3D-based calculations for another 50 elements are re-evaluated based on updated atomic data, a stringent selection of lines, improved consideration of blends, and new non-LTE calculations available in the literature. For elements where spectroscopic determinations of the quiet Sun are not possible, the recommended solar abundances are revisited based on complementary methods, including helioseismology (He), solar wind data from the Genesis sample return mission (noble gases), sunspot observations (four elements), and measurements of the most primitive meteorites (15 elements). Results. Our new improved analysis confirms the relatively low solar abundances of C, N, and O obtained in our previous 3D-based studies: log C = 8.46 ± 0.04, log N = 7.83 ± 0.07, and log O = 8.69 ± 0.04. Excellent agreement between all available atomic and molecular indicators is achieved for C and O, but for N the atomic lines imply a lower abundance than for the molecular transitions for unknown reasons. The revised solar abundances for the other elements also typically agree well with our previously recommended values, with only Li, F, Ne, Mg, Cl, Kr, Rb, Rh, Ba, W, Ir, and Pb differing by more than 0.05 dex. The here-advocated present-day photospheric metal mass fraction is only slightly higher than our previous value, mainly due to the revised Ne abundance from Genesis solar wind measurements: Xsurface = 0.7438 ± 0.0054, Ysurface = 0.2423 ± 0.0054, Zsurface = 0.0139 ± 0.0006, and Zsurface/Xsurface = 0.0187 ± 0.0009. Overall, the solar abundances agree well with those of CI chondritic meteorites, but we identify a correlation with condensation temperature such that moderately volatile elements are enhanced by ≈0.04 dex in the CI chondrites and refractory elements possibly depleted by ≈0.02 dex, conflicting with conventional wisdom of the past half-century. Instead, the solar chemical composition more closely resembles that of the fine-grained matrix of CM chondrites with the expected exception of the highly volatile elements. Conclusions. Updated present-day solar photospheric and proto-solar abundances are presented for 83 elements, including for all long-lived isotopes. The so-called solar modelling problem – a persistent discrepancy between helioseismology and solar interior models constructed with a low solar metallicity similar to that advocated here – remains intact with our revised solar abundances, suggesting shortcomings with the computed opacities and/or treatment of mixing below the convection zone in existing standard solar models. The uncovered trend between the solar and CI chondritic abundances with condensation temperature is not yet understood but is likely imprinted by planet formation, especially since a similar trend of opposite sign is observed between the Sun and solar twins.