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

白矮星从行星系统中收集剩余的岩石物质，这些物质围绕着它们的宿主恒星运行，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测量它们分解成不同波长的光来研究。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有关这些正在解体的行星中岩石物质的大部分化学成分的信息。行星上存在的岩石类型可以从主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受污染的白矮星，评估围绕白矮星运行的行星体的水和岩石含量，寻找行星体中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路径。该项目通过促进我们对围绕其他恒星运行的行星组成的了解来支持NSF的任务。调查人员将包括参加加州大学圣地亚哥分校恒星计划和其他机构倡议的学生，这些计划旨在研究工作中代表不足的群体。调查人员将继续对候选白矮星进行光谱观测，以确定污染最严重的恒星。对所有污染白矮星的母体的水分含量的估计将与对被大量氢污染的白矮星的水分含量的评估结合起来。从近100颗白矮星的样本中，他们将估计富含水的岩质天体在其他行星系中的出现频率。对于受到岩石地壳和地幔物质污染的白矮星子集，他们将深入寻找板块构造的化学特征。对Ba和Sr的探测或深层限制将为太阳系外的块状分异岩体提供板块构造的可能性。动力学模拟将检验碰撞过程剥离巨大差异岩石天体最外层地壳和地幔的能力，然后追踪这个抛射物和它的起源，以探索白矮星是如何被来自岩石天体特定区域的物质污染的。这一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智力优势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.