The Chemical Composition of Extrasolar Minor Planets

这个项目是一个观测项目，目的是确定选定的白矮星的丰度，作为测量系外小行星总体组成的一种方法。它的动机是最近对白矮星GD 362的Keck I光谱的分析，它的光球丰度自然被理解为是由一颗与地球/月球系统成分相似的小行星的破坏造成的，该行星的碳和钠等挥发物的消耗超过10倍。这表明，像GD 362这样的红外辐射过剩的白矮星，已经从偏离恒星潮汐半径的小行星上吸积了碎片，因此这些白矮星的大气层为测量太阳系外小行星的总体成分提供了一个强大的、目前唯一的机会。在这里，Jura教授将使用Keck I望远镜和HIRES光谱仪获得额外的红外过量白矮星的光谱（可能是潮汐半径内的尘埃盘的结果），并确定外部污染元素的丰度（包括挥发性元素和难挥发元素）。没有红外过量的白矮星也将被观察到，以评估星际吸积的作用/可能性。由此产生的数据很可能使我们对太阳系外类地行星的存在和频率有更全面的了解。该项目将直接支持加州大学洛杉矶分校的科学教育和研究生的教育/培训，该研究生的论文将基于这些数据。

This project is an observational program to determine the abundances of select white dwarfs as a method of measuring the bulk compositions of extrasolar minor planets. It is motivated by a recent analysis of Keck I spectra of the white dwarf GD 362 whose photospheric abundances are naturally understood as resulting from the destruction of a minor planet similar in composition to the Earth/Moon system which is depleted in volatiles like carbon and sodium by more than a factor of 10. This suggests that white dwarfs with an infrared excess, such as GD 362, have accreted debris from asteroids that strayed within the star's tidal radius and that the atmospheres of these white dwarfs thus provide a powerful and currently unique opportunity to measure the bulk compositions of extrasolar minor planets.Here, Professor Jura will use the Keck I telescope and HIRES spectrograph to obtain spectra of additional white dwarfs with an infrared excess (presumably the result of a dust disk inside the tidal radius) and determine the abundances of externally contaminated elements (including volatile versus refractory elements). White dwarfs without infrared excesses will also be observed to evaluate the role/possibility of interstellar accretion. The resulting data may well enable a more comprehensive understanding of the existence and frequency of extrasolar Earth-like planets. This project will directly support science education at UCLA and the education/training of a graduate student whose thesis will be based on these data.