Light Element Studies

AST-0505899安·博伊斯加德夏威夷大学光元素实验室恒星的化学成分为我们宇宙中许多最基本的问题提供了答案。特别是，锂、铍和硼等轻元素的研究在现代天体物理学的许多领域都很重要，如大爆炸核合成、元素起源、银河系化学演化、恒星内部和演化。第一个是测定金属含量低于太阳千分之一的最古老恒星中铍的丰度。如果在这些恒星中发现铍丰度的"高原"，这将意味着早期宇宙的不均匀性，具有高密度的富含质子的气泡。第二个项目是通过铍含量随时间的增长研究银河系的化学演变。银河系中各种化学元素的富集揭示了大质量恒星形成和超新星早期产生的历史。跟踪铍随时间的增加可以提供有关前几代恒星的敏感信息。探测最早期（通过对低金属含量恒星的观测）和中间年龄将有助于更好地了解银河系的演化。最后，大多数低金属量的恒星都有类似的锂含量，这是由于大爆炸期间锂的产生。然而，其中一些非常古老的恒星缺乏锂。在第三个项目中，通过测定缺乏锂的老恒星中的铍含量，将检验两种关于锂耗尽起源的相互竞争的理论（混合，这应该破坏锂而不是铍，以及质量转移，这应该耗尽两种元素）。这项研究将利用世界上最大的两个望远镜：Manna Kea天文台的ESPRIK-I 10米望远镜和Subaru 8.2米望远镜。研究生将得到支持和培训，以使用这些望远镜并进行恒星组成研究。

AST-0505899Ann BoesgaardUniversity of HawaiiLight Element StudiesThe chemical composition of stars holds the answers for many of the most fundamental questions about our universe. In particular, the study of the light elements, lithium, beryllium, and boron, is important in many areas of modern astrophysics, such as Big Bang nucleosynthesis, the origin of the elements, Galactic chemical evolution, stellar interiors and evolution.Here, three projects will be carried out. The first is the determination of beryllium abundances in the oldest stars with metal contents lower than one one-thousandth that of the sun. If a "plateau" in beryllium abundances is found among such stars, it will imply an inhomogeneity in the early universe with high-density proton-rich bubbles. The second project is a study of the chemical evolution of the Galaxy through the growth in the beryllium content over time. The enrichment of various chemical elements in the Galaxy reveals the history of formation of massive stars and the early production of supernovae. Tracking the increase of beryllium over time gives sensitive information about previous generations of stars. Probing both the earliest times (via observations of stars with low metal contents) and the intermediate ages will result in a greater understanding of the evolution of the Galaxy. Finally, most stars of low metallicity have a similar lithium content due to the production of lithium during the Big Bang. However, some of these very old stars are deficient in lithium. In the third project, by determining the beryllium content in the lithium-deficient old stars, two competing theories of the origin of the lithium depletions will be tested (mixing, which should destroy lithium but not beryllium, and mass transfer, which should deplete both elements). Understanding this will illuminate stellar mixing processes and the primordial lithium value.This research will take advantage of two of the world's largest telescopes: the Keck-I 10-m telescope and the Subaru 8.2-m telescope at the Manna Kea Observatory. Graduate students will be supported and trained to use these telescopes and conduct research in the compositions of stars.