Magnetic fields and stellar evolution

所有的恒星都是天然的磁铁，这要归功于组成它们的动态导电气体。由于恒星的磁场可能非常强，它们代表了天体物理学家关于恒星结构和演化的理论中的一个基本元素。近年来，已经清楚地表明，磁场对恒星的生命有着重要的影响，它改变了恒星内部的气体流动，改变了它们内部的旋转轮廓和核合成化学物质的分布，引导和改变了它们流出的风，并通过所谓的“磁制动”减缓了它们的表面自转。最终，这些效应导致恒星演化的重要变化，特别是导致恒星温度、光度、大小和年龄之间关系的改变。它们还影响恒星在其生命周期中注入周围星际介质的质量和光能方面的重要输出。更值得注意的是，它们还可以影响戏剧性的超新星爆炸，这标志着最大质量恒星的死亡。这些效应直接影响到奇异的残存白矮星和中子星的性质，并改变了恒星群体对当地银河系环境的结构和化学成分的贡献。*随着恒星的老化和演化，它们的磁场也会随之变化。因此，我们希望在恒星经历核燃烧的不同阶段并经历温度、光度和大小的巨大变化时，观察到恒星磁场的重要变化。因此，恒星在其生命的一个阶段的磁场可能与其后期的磁场表现出很大的不同。因此，了解处于非常不同演化阶段的恒星中观测到的磁场之间的关系是非常有意义的。例如，来自较早进化阶段的磁场能否在较晚阶段“孕育”出完全不同的磁场？处于非常不同演化阶段的恒星中具有相似特征的磁场是否有任何直接关系？*我和我的研究团队由加拿大和国际学生和科学家组成，我正在努力回答上述问题引发的许多问题。这项提议所述研究的主要目的是继续我的小组利用全球和太空望远镜对所有类型恒星的磁场特征进行的系统探索。我的提议有两个主要目标：定量地了解磁场如何影响恒星结构和演化，以及了解恒星的可观测磁场如何在恒星演化时间尺度上转换。*

All stars are natural magnets, thanks to the dynamic, electrically conductive gases that compose them. And because the magnetic fields of stars can be very strong, they represent a basic element in astrophysicists' theory of stellar structure and evolution. In recently years it has been clearly demonstrated that magnetic fields have essential impacts on stellar lives, modifying their interior flows of gas, changing their internal rotational profiles and distributions of nucleosynthetic chemicals, channeling and modifying their outflowing winds, and slowing their surface rotation through so-called "magnetic braking". Ultimately, these effects result in important changes in the evolution of stars, leading in particular to modifications of the relationships between stellar temperatures, luminosities, sizes and ages. They also influence the important outputs of stars in terms of the mass and luminous energy injected into the surrounding interstellar medium during their lives. More remarkably, they can also influence the dramatic supernova explosions that mark the deaths of the most massive stars. These effects directly impact the properties of exotic remnant white dwarf and neutron stars, and change how populations of stars contribute to the structure and chemistry of their local Galactic environments. *** As stars age and evolve, so too do their magnetic fields. Hence we expect to observe important transformations of stellar magnetic fields as stars pass through various stages of nuclear burning and undergo large changes to their temperatures, luminosities and sizes. As a consequence, the magnetic field of a star at one stage of its life may appear very different from that at a later stage. It is therefore of great interest to understand the relationships between magnetic fields observed in stars at very different evolutionary stages. For example, can the magnetic fields from an earlier evolutionary stage "seed" the production of a very different magnetic field at a later stage? Do magnetic fields with similar characteristics in stars at very different evolutionary stages have any direct relationship? ***With my research team of Canadian and international students and scientists, I am working to answer many of the questions prompted by the issues described above. The principal aim of the research described in this proposal is to continue my group's systematic exploration of the characteristics of magnetic fields of stars of all types, using telescopes around the globe and in space. My proposal has two main goals: to quantitatively understand how magnetic fields influence stellar structure and evolution, and to understand how the observable magnetic fields of stars transform over stellar evolutionary timescales. *** **