Solar fusion III: New data and theory for hydrogen-burning stars

In stars that lie on the main sequence in the Hertzsprung-Russell diagram, like our Sun, hydrogen is fused to helium in a number of nuclear reaction chains and series, such as the proton-proton chain and the carbon-nitrogen-oxygen cycles. Precisely determined thermonuclear rates of these reactions lie at the foundation of the standard solar model. This review, the third decadal evaluation of the nuclear physics of hydrogen-burning stars, is motivated by the great advances made in recent years by solar neutrino observatories, putting experimental knowledge of the proton-proton (pp)-chain neutrino fluxes in the few-percent precision range. The basis of the review is a one-week community meeting held in July 2022 in Berkeley, California, and many subsequent digital meetings and exchanges. The relevant reactions of solar and stellar hydrogen burning are reviewed here from both theoretical and experimental perspectives. Recommendations for the state of the art of the astrophysical S factor and its uncertainty are formulated for each of them. Several other topics of paramount importance for the solar model are reviewed as well: recent and future neutrino experiments, electron screening, radiative opacities, and current and upcoming experimental facilities. In addition to reaction-specific recommendations, general recommendations are also formed.

在赫茨普龙-罗素图（Hertzsprung-Russell diagram）的主序星中，诸如太阳这类恒星会通过多条核反应链与反应系列将氢聚变为氦，例如质子-质子链（proton-proton chain）与碳氮氧循环（carbon-nitrogen-oxygen cycles）。上述反应的精准热核速率是构建标准太阳模型（standard solar model）的核心基础。本综述为氢燃烧恒星核物理领域的第三次十年期评估，其撰写动因源于近年太阳中微子观测站（solar neutrino observatories）取得的突破性进展，使得质子-质子（pp）链中微子通量（neutrino fluxes）的实验测量精度迈入百分之几的区间。本综述的筹备基础为2022年7月于美国加利福尼亚州伯克利召开的为期一周的天体物理社区研讨会，以及后续多场线上交流与研讨活动。本文从理论与实验双重视角，全面综述了太阳及恒星氢燃烧过程中的相关核反应，并针对每一类反应制定了天体物理S因子（astrophysical S factor）的当前技术水平及其不确定度的推荐规范。此外，本文还综述了对太阳模型而言至关重要的其他多项议题：近期及未来的中微子实验、电子屏蔽（electron screening）、辐射不透明度（radiative opacities），以及当前运行与即将建成的实验设施。除针对具体反应的专项推荐方案外，本综述同时形成了通用指导性推荐意见。