The Composition of Stars and Star Clusters in the Galaxy

外行人向天文学家提出的最基本的问题之一是“构成地球和我们身体的原子从何而来？”事实上，在过去的一代中，天文学家已经投入了大量的工作来回答这个问题，他们绘制了恒星爆炸中重元素原子对星际气体的富集图谱，这些原子是在高度进化的恒星内部深处通过复杂的核合成反应由氢形成的。虽然早期的工作集中在确定铁族元素的化学丰度上，但最近的研究表明，铁族元素丰度的增强直到银河系历史上相对较晚的时期才开始。早期（包括大爆炸后的第一个小时），氧、碳和铍元素提供了更好的富集指标。最古老的恒星最好地揭示了这段历史，但它们很微弱，很难观察到。此外，导致铍丰度测定的吸收线位于光谱的紫外线部分，除了在夏威夷的莫纳克亚山这样的高山低纬度天文台之外，地球上的天文学家是无法接近的。首席研究员（PI）多年来一直活跃于研究银河系中老恒星的化学演化，这次她将把研究范围扩大到银河系中微弱的晕星。探测器技术的最新进展也将使PI不仅能够获得更精确的丰度，而且能够对在银河系最初坍缩期间由原星系云形成的恒星的化学演化进行采样。铍的丰度结果也可能允许一个更受约束的大爆炸模型得到发展。

One of the most basic questions astronomers are asked by the layman is "where did the atoms composing the Earth and our bodies" come from?" Indeed during the last generation astronomers have put a great deal of work into answering this question by mapping the enrichment of interstellar gas by heavy element atoms from stellar explosions that occur after these atoms are formed from hydrogen by complex nucleosynthetic reactions in the deep interiors of highly evolved stars. Although earlier work concentrated on determining the chemical abundance of the iron group elements, recent investigations have shown that the iron-group abundance enhancements did not start until comparatively late in the history of the Galaxy. Better indicators of enrichment during the early era (including the first hour after the Big Bang) are provided by the elements oxygen, carbon, and beryllium. The oldest stars betray this history best, but they are faint and difficult to observe. Moreover, the absorption line leading to abundance determinations of beryllium is located in the ultraviolet part of the spectrum that is inaccessible to Earth-based astronomers except in high mountain, low-latitude observatories such as Mauna Kea in Hawaii. The Principal Investigator (PI) has been active in studying chemical evolution studies of old stars in the Galaxy for years and will extend her investigation to the faint halo stars in the Galaxy with this three year award. Recent advances in detector technology should also permit the PI to obtain not only more accurate abundances but also to sample the chemical evolution in stars that were formed during the original collapse of the Galaxy from a proto-galactic cloud. The abundance results for beryllium may also permit a more constrained model of the Big Bang to be developed.