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，作为测量太阳系外小行星的主体成分的一种方法。这一发现源于最近对白矮星GD362的Keck I光谱的分析，这颗白矮星的光球丰度自然地被理解为一颗组成类似于地月系统的小行星被摧毁的结果，这颗小行星的碳和钠等挥发性物质的贫化程度超过了10倍。这表明，具有红外线过剩的白矮星，如GD 362，有来自偏离恒星潮汐半径的小行星的吸积碎片，这些白矮星的大气因此提供了一个强大的、目前唯一的机会来测量太阳系外小行星的整体组成。朱拉教授将使用Keck I望远镜和租用光谱仪来获取额外的红外线超额白矮星的光谱(可能是潮汐半径内的尘埃盘的结果)，并确定外部污染元素(包括挥发性元素和难熔元素)的丰度。没有红外线过剩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能够更全面地了解太阳系外类地行星的存在和频率。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.