Revealing atmospheric structures, clouds and chemistry of brown dwarfs and free-floating planetary mass objects

光谱反演技术，又称大气反演技术，最初是为遥感地球大气条件而开发的，现在已经应用于太阳系行星、系外行星和褐矮星。在这个项目中，你将使用Ben Burningham的大气检索框架（“Brewster”：http://adsabs.harvard.edu/abs/2017MNRAS.470.1177B）来估计棕矮星、孤立的行星质量物体和恒星的行星质量伴星的大气结构、化学和云特性。这一结果将用于测试完全自洽的辐射对流平衡模型的预测，并确定我们对巨大系外行星和褐矮星的大气物理理解中的不足之处。学生有机会确定新的研究方向；然而，有希望的例子包括：测试偏离化学平衡和评估作为重力函数的不平衡效应；揭示云的性质，如凝结物种类、云结构、颗粒大小；在一定温度范围内测试热结构的预测。这些项目最初将利用档案数据，但新数据将扩展到可用的新数据集。使用布鲁斯特的大气检索也将在分析2021年春季发射的詹姆斯韦伯太空望远镜（JWST）的数据方面发挥关键作用。

Spectral inversion techniques, also known as atmospheric retrievals, were first developed for remote sensing the Earth's atmospheric conditions, and have now been applied to Solar system planets, exoplanets and brown dwarfs. In this project you will use Ben Burningham's atmospheric retrieval framework ("Brewster": http://adsabs.harvard.edu/abs/2017MNRAS.470.1177B) to estimate atmospheric structure, chemistry and cloud properties of brown dwarfs, isolated planetary mass objects and planetary mass companions to stars. The results of this will then be used to test predictions from fully self-consistent radiative-convective equilibrium models and identify shortcomings in our understanding of the atmospheric physics of giant exoplanets and brown dwarfs. There is scope for the student to identify new lines of enquiry; however, promising examples include: testing for departures from chemical equilibrium and evaluating disequilibrium effects as a function of gravity; revealing cloud properties such as condensate species, cloud structure, particle sizes; testing predictions for thermal structure across a range of temperatures. These projects will initially exploit archival data, but new data will extend to new data sets as they become available. Atmospheric retrievals using Brewster will also play a key role in analysing data from the James Webb Space Telescope (JWST) following its launch in spring 2021.