Abundance Patterns in Extremely Metal-Poor Stars

“极端金属贫星的丰度模式”AST-0098617历史上第一次有足够的恒星样本作为探测器来破译银河系演化的初始阶段。20世纪90年代对极度缺乏金属的恒星进行的调查产生了这个样本。在本奖项的这一期间，将使用大型望远镜及其光谱仪来确定准确的化学丰度，从而追踪自古以来重元素合成是如何进行的。还会有额外的好处。钍的丰度可以用来计算最古老恒星的辐射形成年龄，这将给宇宙的年龄设定一个下限。S过程元素(在演化中的恒星内部产生)和r过程元素(由前几代大质量恒星的超新星爆炸贡献)的不同贡献将被评估，并与核合成理论的预期进行比较。人们将寻找那些预计将在不伴随S过程过度的情况下表现出极端碳增强的第三族恒星。还将对外晕中属于银河系球状星团的恒星和附近矮小星系中的恒星进行观测，以寻找低质量星系化学演化的可能丰度特征。

" Abundance Patterns in Extremely Metal-Poor Stars"AST- 0098617For the first time in history there is an adequate sample of stars to use as probes in deciphering the initial phases of galactic evolution. Surveys for extremely metal-poor stars, carried out in the 1990s, produced this sample. During this period of the present award, large telescopes their spectrographs will be used to determine accurate chemical abundances and thus to trace how heavy element synthesis has proceeded since earliest times. There will be additional benefits. Thorium abundances can be used to compute radiogenic ages for the oldest stars, which will put a lower limit on the age of the universe. The different contributions of s-process elements (generated in the interiors of evolving stars) and r-process elements (contributed by supernovae explosions of earlier generations of massive stars) will be assessed and compared with expectations from nucleosynthesis theory. A search will be made for Population III stars that are predicted to show extreme carbon enhancements without accompanying s-process excesses. Observations will also be made of stars belonging to galactic globular clusters in the outer halo and of stars in nearby dwarf galaxies to search for possible abundance signatures characteristic of chemical evolution in low-mass galaxies.