Eclipse Mapping Exoplanet Atmospheres with the James Webb Space Telescope

与我们对太阳系行星的了解相比，我们对系外行星的了解明显不足，因为观测它们的难度更大。通过对系外行星大气层的研究，可以发现系外行星的许多性质，这些大气层掌握着关于它们当前状态和形成历史的关键信息。最成功的系外行星探测和表征方法是凌日方法，它可以让我们获得太阳系外行星在凌日过程中的黑侧半球和被其主星遮盖的日侧半球的大气信息。我的研究涉及使用日食映射技术来绘制凌日系外行星的大气图。如果我们在这颗系外行星的经度逐渐进入日食时进行快照观测，那么我们就可以将系统流量的减少归因于该行星的这一区域，并构建其大气层日侧半球的一维发射图。如果行星的轨道从我们的角度来看是倾斜的，那么高纬度的日食速度将比低纬度更快，这使得我们能够进一步将通量减少归因于不同的纬度，从而将我们的地图扩展到2D。用多波长观测日食甚至可以进一步测量从大气层的多个深度发射的辐射，将地图扩展到3D。热木星(高度辐射和潮汐锁定的巨大系外行星，具有一天的轨道周期)为描述系外行星的大气层提供了最典型的条件，因为它们通常高度膨胀，促进强烈信号。我的研究重点是利用JWST上的MIRI/LRS和NIRSpec/G395H仪器获得的空间望远镜GTO计划1353(PI：N.K.Lewis)数据绘制炎热木星WASP-17b的日侧半球图。WASP-17b是这些类型观测的主要候选者，因为它的大气层从白天到黑夜的温度范围跨越1000-2500 K，这使得它可能拥有广泛的光谱活性化学物种。它也是一个有趣的目标，因为它的逆行轨道挑战了当前的行星形成理论-我的研究目的是在我们对行星形成的理解上弥合这样的差距。这项工作是作为JWST-TST合作的一部分进行的，目的是将这个数据集和其他数据集(三次凌日和三次日食，分别由MIRI/LRS、NIRSpec/G395H和JWST上的NIRISS/SOSS仪器获取，覆盖0.6-14微米波长范围)结合在一起，以生成第一张系外行星大气的完整3D地图，这将使我们能够有力地约束它的热、成分和动力学性质、动力学性质对我们理解系外行星科学的方方面面都有重大贡献。然后，这种技术将扩展到其他类型的系外行星，以扩大我们对它们多样性的理解。

Our understanding of exoplanets is significantly lacking in comparison to our understanding of the Solar System planets due to the greater difficulties of observing them. Many properties of exoplanets can be uncovered through the study of their atmospheres, which hold key information on their current state and formation history. The most successful exoplanet detection and characterisation method is the transit method, which allows us access to atmospheric information on the nightside hemisphere of an exoplanet whilst they are in transit and on the dayside hemisphere as they are eclipsed by their host star.My research involves using the technique of eclipse mapping to spatially map the atmospheres of transiting exoplanets. If we take snapshot observations as progressive longitudes of the exoplanet enter eclipse, then we can attribute the reductions in system flux to that region of the planet and construct a 1D emission map of the dayside hemisphere of its atmosphere. If the orbit of the planet is inclined from our viewpoint, then higher latitudes will be eclipsed faster than lower latitudes, allowing us to further sub-attribute the flux reductions to different latitudes, extending our map to 2D. Observing the eclipse at multiple wavelengths then even further allows us to measure the emission from multiple depths of the atmosphere, extending the map to 3D.Hot Jupiters (highly irradiated and tidally locked giant exoplanets with day-scale orbital periods) provide the most exemplary conditions for characterising the atmospheres of exoplanets, owing to their often highly inflated atmospheres which promote strong signals. My research focuses on eclipse mapping the dayside hemisphere of the hot Jupiter WASP-17b using Space Telescope GTO programme 1353 (PI: N.K. Lewis) data obtained by the MIRI/LRS and NIRSpec/G395H instruments onboard JWST. WASP-17b is a prime candidate for these types of observations as the day- to night-side temperature range of its atmosphere spans 1000 - 2500 K, making it likely to host a broad range of spectroscopically active chemical species. It is also an interesting target due to its retrograde orbit, which challenges current planet formation theories - my research aims to contribute to bridging gaps such as this in our understanding of planet formation.This work is undertaken as part of the JWST-TST collaboration, with the aim of combining this dataset and others (three transits and three eclipses, one each respectively obtained by the MIRI/LRS, NIRSpec/G395H, and NIRISS/SOSS instrument onboard JWST, covering the 0.6 - 14 micron wavelength range) to produce the first full 3D map of an exoplanet atmosphere, which will allow us to robustly constrain its thermal, compositional, and dynamical properties, contributing momentously to our understanding of all aspects of exoplanet science. Such techniques will then be extended to other types of exoplanets in order to broaden our understanding of their diversity.