Cloudbusting with JWST: characterising aerosols, aurorae and chemistry in substellar atmospheresto the water cloud regime

JWST将通过对波长的敏感性来彻底改变对外星世界的研究，在这些波长上，它们的大部分热量会逃逸到太空--地面上不容易观察到的光的波长。JWST将瞄准的最重要的行星群之一是围绕其他恒星运行的巨型行星，类似于木星。这些世界对于理解行星系统的形成和演化很重要，因为它们代表了行星系统中的大部分质量，就像木星统治我们自己的太阳系一样。而且，和木星一样，巨大的系外行星被认为在向其系统中的岩石行星输送水方面发挥了重要作用，这些行星可能是宜居的。巨行星也是太阳系外最容易观察到的行星，因此它们也为提高我们研究各种系外行星的能力提供了试验场，甚至是潜在的宜居行星。研究系外行星最具挑战性的问题之一是如何处理云层。云层遮挡了我们的视线，还以复杂和难以测量的方式改变了外星大气的组成和其他性质。正因为如此，云层经常被视为系外行星科学的障碍。然而，多亏了JWST和我们开发的分析工具，云将很快能够提供对外星世界的组成、化学和动力学的新见解。除了云层，在被称为棕矮星的自由漂浮的类似木星的星球上也发现了强大的极光，我们预计未来还会在巨大的系外行星上发现类似的极光。有趣的是，所有显示极光的棕矮星在自转时亮度也会发生变化。这种变化在许多其他棕矮星甚至一些巨大的系外行星上都可以看到，通常认为是因为天气不同，云层覆盖不同，产生了亮和暗的斑块。也有可能一些变化是由极光驱动的，甚至天气和相关的大尺度大气流动可能以尚未被发现的方式与极光相互作用。有了这笔资金，我们将学习如何解码遥远星球的JWST光谱，以揭示它们的云层属性、组成和热结构，并了解它们的极光与大气是如何相互作用的。我们还将使用JWST来研究一些已知的最冷的棕矮星，称为Y矮星。Y矮星的温度足够低，大气层中可以形成水冰云。这将是对太阳系以外的水云的首次研究。多亏了对其中一些棕矮星组成的先验知识，我们将能够校准我们对云的理解，然后利用这些知识来研究巨型行星。我们还将能够测试不同的云形成和化学理论，以及研究这些外星世界的天气。这项工作将开发我们研究各种多云系外行星所需的技术。它还将为强有力地估计巨大系外行星的组成铺平道路--这是揭示它们及其所在行星系统形成历史的重要证据。

JWST will revolutionise the study of alien worlds via its sensitivity to the wavelengths where most of their heat escapes into space - wavelengths of light that cannot be observed easily from the ground. One of the most important groups of planets that JWST will target are giant planets, similar to Jupiter, that orbit other stars. These worlds are important for understanding how planetary systems form and evolve because they represent most of the mass in their planetary systems, in the same way that Jupiter dominates our own Solar system. And, like Jupiter, giant exoplanets are thought to play an important role in delivering water to rocky, possibly habitable, planets in their systems. Giant planets are also the easiest planets to observe outside the Solar System, so they also provide a testing ground for enhancing our ability to study all kinds of exoplanets, even potentially habitable ones. One of the most challenging problems in studying exoplanets is how to deal with clouds. Clouds block our view, and also change the composition and other properties of alien atmospheres in complicated and difficult to measure ways. Because of this, clouds are often seen as an obstacle to exoplanet science. However, thanks to JWST and the analysis tools that we have developed, clouds will soon be able provide new insights into the composition, chemistry and dynamics of alien worlds. Alongside clouds, powerful aurorae have been discovered on free floating Jupiter-like worlds known as brown dwarfs, and we expect to find similar aurorae on giant exoplanets in the future. Interestingly, all the brown dwarfs that show aurorae also show variations in their brightness as they rotate. Such variability has been seen in many other brown dwarfs and even some giant exoplanets, and it is generally thought to be due to weather creating bright and dark patches due to differing cloud cover. It is also possible that some of the variability is driven by aurorae, or even that weather, and associated large scale atmospheric flows, may interact with the aurorae in ways yet to be discovered. With this funding, we will learn how to decode JWST spectra of distant worlds to reveal their cloud properties, composition, and thermal structure, and understand how their aurorae interact with their atmospheres. We will also use JWST to study some of the coolest brown dwarfs known, called Y dwarfs. Y dwarfs are cool enough to have water ice clouds in their atmospheres. These will be the first studies of water clouds beyond the Solar system. Thanks to prior knowledge of the compositions of some of these brown dwarfs, we will be able to calibrate our understanding of clouds, and then use this knowledge to study giant planets. We will also be able to test different theories of cloud formation and chemistry, as well as study the weather on these alien worlds. This work will develop techniques that we will need in order study all kinds of cloudy exoplanets. It will also pave the way for robust estimates of the composition of giant exoplanets - an essential piece of evidence for revealing their formation histories and that of their home planetary systems.