Collaborative Proposal: Measuring the Composition and Structure of Rocky Extrasolar Bodies

白矮星从围绕其主恒星运行的行星系统中收集剩余的岩石物质，直到恒星到达生命的尽头，导致它们的行星分裂。这些“被污染”的白矮星可以用望远镜来研究，望远镜可以测量它们发出的不同波长的光。不同化学元素的特征出现在不同的波长。通过望远镜发现的化学元素提供了关于那些正在解体的行星中岩石物质的总体化学成分的信息。行星上存在的岩石类型可以从其总体化学成分中重建出来。科学家们提出的研究将利用光谱观测来发现更多被污染的白矮星，并评估围绕白矮星运行的行星体的水和岩石含量，在行星体中寻找类似地球的板块构造的迹象，并研究物质从行星体到宿主恒星的途径。这个项目通过促进我们对围绕其他恒星运行的行星组成的理解来支持美国国家科学基金会的使命。调查人员将包括参加加州大学圣地亚哥分校STARS项目的学生，以及其他针对研究工作中代表性不足群体的机构倡议。研究人员将继续对候选白矮星进行光谱观测，以确定那些污染最严重的白矮星。对所有污染白矮星的母体的水含量的估计将与对被大量氢污染的白矮星的水含量的评估结合起来进行。从近100个白矮星的样本中，他们将估计出其他行星系统中富含水的岩石体的发生率。对于被岩石地壳和地幔物质污染的白矮星子集，他们将对板块构造的化学特征进行深入研究。对钡和锶的探测或深度限制将为太阳系外大质量分化岩石体板块构造的可能性提供信息。动力学模拟将检验碰撞过程剥离大质量分化岩石体最外层地壳和地幔层的能力，然后跟踪这种喷射物及其起源，以探索白矮星是如何被岩石体特定区域的物质污染的。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

White dwarf stars collected leftover rocky material from planetary systems that orbited their host stars until the stars reached their end of life and caused their planets to break apart. These "polluted" white dwarf stars can be studied using telescopes that measure their light broken down into different wavelengths. The signatures of different chemical elements appear at different wavelengths. The chemical elements found telescopically give information about the bulk chemical composition of rocky material in those disintegrating planets. The types of rocks present in the planets can be reconstructed from the bulk chemical composition. The scientists propose studies that will use spectral observations to find more polluted white dwarf stars and assess the water and rocky content of the planetary bodies that orbited the white dwarf stars, looking for signs of earth-like plate tectonics in the planetary bodies, and studying pathways for material to travel from the planetary bodies to the host stars. This project supports the mission of the NSF by promoting our understanding of the composition of planets orbiting other stars. The investigators will include students who participate in the UC San Diego STARS program and other institutional initiatives aimed at underrepresented groups in their research efforts.The investigators will continue spectroscopic observations of candidate white dwarf stars to identify those that are most heavily polluted. Estimates of the water content for all parent bodies polluting white dwarfs will be made in combination with an assessment of the water content in white dwarfs being polluted by substantial quantities of hydrogen. From a sample of nearly 100 white dwarfs, they will estimate the occurrence rate for water-rich rocky bodies in other planetary systems. For the subset of white dwarf stars that are being polluted by rocky crust and mantle material, they will conduct a deep search for the chemical signature of plate tectonics. Detections or deep limits on Ba and Sr will inform the possibility of plate tectonics for massive differentiated rocky bodies outside the Solar System. Dynamical simulations will examine the ability of collisional processes to strip massive differentiated rocky bodies of their outermost crust and mantle layers, and then track this ejecta and the body it originated from to explore how white dwarfs get polluted by material from specific regions of a rocky body.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.