The Age, Formation and Evolution of the Elements

cowan, John j . P.I.正在继续他对重元素的年龄、形成和演化的研究，特别是在我们银河系中最古老的恒星内部的s（低）和r（快）中子捕获核过程中形成的重元素。P.I.和他的合作者在这些银河晕恒星中发现了几颗长寿命的放射性元素钍，在一颗中发现了铀，这为直接确定最古老恒星的年龄提供了一个令人兴奋的，也许是独一无二的机会。利用广泛的、新的、准确得多的数据，P.I.将首先扩展和扩展他对恒星放射性年龄的研究，通过确定一些金属贫乏的恒星的丰度（即古老的、铁等元素含量低的恒星）。这些新的钍和铀探测对于减少观测的不确定性和确认早期的恒星和银河系年龄估计是必要的。利用新确定的贫金属恒星的丰度分布，P.I.将计算放射性元素Th和U的初始丰度值（也称为核计时器或时钟），并根据观察到的（即衰变的）钍丰度对其他低金属丰度恒星进行新的年龄测定。这些研究结果比以前更准确地估计了最古老恒星的年龄，并将有助于回答银河系和宇宙年龄的基本问题。更广泛的影响。研究生和本科生都参与了私家侦探的研究活动，包括接受私家侦探培训和指导的女性和代表性不足的少数民族学生。私家侦探还自愿在当地一所小学（六年级）任教，并定期向公众发表天文学讲座。此外，P.I.维护了一个网站，其中包括可供社区使用的研究论文。网站上还包括技术创新的例子，比如他们如何利用互联网的能力来传输大量的天文数据。为说明nsf支持的活动（如P.I.）的结果而制作的教育图片（美国宇航局的超新星和黑洞观测），学生和公众都可以在网站上找到。最后，P.I.在他的网站上包括并维护着可供天文团体访问的数据库。

AST 0307279Cowan, John J.The P.I. is continuing his research on the age, formation and evolution of the heavy elements, specifically, those formed in the s(low) and r(apid) neutron-capture nuclear processes, in the interiors of the oldest stars in our Galaxy. The detection by the P.I. and his collaborators of the long-lived radioactive element thorium in several, and uranium in one, of these Galactic halo stars has provided an exciting, and perhaps unique, opportunity to directly determine the ages of the oldest stars. Employing extensive, new and far more accurate data, the P.I. will first extend and expand his studies of stellar radioactive ages by determining the abundances for a number of metal-poor stars (i.e., old, with low levels of elements such as iron). These new thorium and uranium detections will be necessary to reduce any observational uncertainties and confirm earlier stellar and Galactic age estimates. Utilizing the newly determined abundance distributions in the metal-poor stars, the P.I. will calculate the initial abundance values of the radioactive elements Th and U (also known as nuclear chronometers or clocks) and make new age determinations of other low-metallicity stars, based upon their observed (i.e., decayed) thorium abundances. These studies result in more accurate age estimates for the oldest stars than previously possible and will help to answer the fundamental questions of just how old are the Galaxy and the Universe. Broader impacts. Both graduate and undergraduate students are involved in the research activities of the P.I., including female and underrepresented minority students who are being trained and mentored by the P.I. The P.I. also teaches voluntarily in one of the local elementary schools (sixth grade), and regularly gives public lectures on astronomy to the general community.In addition, the P.I. maintains a web site that includes research papers available to the community. Also included on the web site are examples of technology innovation, such as how they are utilizing the capabilities of the Internet 2 to transfer large amounts of astronomical data. Educational images, produced to illustrate the results of NSF-supported activities (such as the P.I.'s observations of supernovae and black holes), are available on the site for students and the general public. Finally, the P.I. includes and maintains databases on his web site that can be accessed by the astronomical community.