Collaborative Research: Understanding Stellar Structure Using Lithium and New Steps Toward the Big Bang Lithium Abundance

锂相对于氢的丰度是早期宇宙大爆炸模型的关键预测。 元素的丰度可以用恒星光谱中的吸收线来测量。 但是，当对流将表面物质与更热的恒星内部混合时，恒星中的锂也会被破坏。 恒星大气中锂的丰度较低，在那些预计不会发生锂耗尽过程的恒星中，锂的丰度远远低于预计会发生这种耗尽过程的恒星。 该团队将测量精心挑选的恒星样本大气中锂的丰度，以便更好地了解恒星内部的物理过程。 他们希望确定太阳的质量和年龄是正常的还是异常的星星，在假定相同的恒星中锂的破坏是否存在变化，并更好地理解从微波背景观测推断的大爆炸锂丰度与恒星大气中所见的锂丰度之间的差异。 这是四所大学天文学家的合作努力，其中包括一所主要的本科院校。 该项目将至少完成一篇博士论文，并通过将一个学生团队整合到一个大规模的研究计划中，扩大各个学校本科生的教育机会，使用亚利桑那州，加州和澳大利亚的天文观测站。该研究团队将扩展和扩大其对疏散星团和球状星团中恒星的光谱研究，重点是旧的疏散星团M67和NGC 188，以及最近的球状星团NGC6397 他们的目标是：（a）确定太阳的质量和年龄是正常的还是不正常的星星，（B）确定控制锂破坏的物理机制在假定相同的恒星之间是否存在差异，（c）对恒星金属含量在确定锂耗尽水平方面的作用进行先驱性研究，以及（d）研究恒星演化对晕中缺乏金属的恒星的潜在影响，这一奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

The abundance of Lithium, relative to Hydrogen, is a key prediction of Big Bang models of the early universe. Abundances of the elements can be measured using the absorption lines in stellar spectra. But Lithium can also be destroyed in stars when convection mixes surface material with the hotter stellar interiors. Low abundance of Lithium in stellar atmospheres is seen among stars where processes that deplete Lithium would not be expected to occur, and abundances are far lower than predicted for stars where such depletion processes are expected to be operating. This team will measure the abundance of Lithium in the atmospheres of a carefully selected sample of stars in order to better understand physical processes inside stars. They hope to determine whether the Sun is a normal or abnormal star for its mass and age, whether there is variation in Lithium destruction among supposedly identical stars, and better understand the disagreement between the Big Bang Lithium abundance inferred from the microwave background observations and that seen in stellar atmospheres. This is a collaborative effort among astronomers at four universities, including a predominantly undergraduate institution. This project will lead to at least one PhD thesis and extend the educational opportunities for undergraduates at the individual schools by integrating a team of students in a large-scale research program, using astronomical observatories in Arizona, California, and Australia.The research team will extend and expand its spectroscopic studies of stars in open and globular clusters, emphasizing the old open clusters M67 and NGC188, and the nearest globular cluster, NGC6397. Their goals are (a) determine whether the Sun is a normal or abnormal star for its mass and age, (b) determine if there is variation in the physical mechanisms controlling Li destruction among supposedly identical stars, (c) pioneer studies on the role of stellar metal content in determining the level of Li-depletion, and (d) study the potential impact of stellar evolution on metal deficient stars of the halo, with implications for the true level of disagreement (if any) between the value of the Big Bang Li abundance inferred from the microwave background versus that inferred from halo dwarf surface Li abundances.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.