Comparative Exoplanetology: Ground-Based Observations of the Atmospheres of Transiting Exoplanets

随着探测到的系外行星数量的不断增加，一个特定的子集为详细研究系外行星本身的特性提供了独特的机会。凌日系外行星的透射光谱是通过凌日观测与凌日外观测的比较得到的，可以用来直接测量系外行星及其大气或外逸层的有效半径。这种在强光学跃迁（例如Na I， K I）中的测量可以用来测量大气的金属丰度，冷凝物的雨出，恒星通量的分布，以及大气成分的光电离。在这里，雷德菲尔德博士和他的团队将在成功的基础上，通过透射光谱探测到一颗凌日系外行星的第一个大气层。德克萨斯大学奥斯汀分校麦克唐纳天文台的9.2米霍比·埃伯利望远镜最近获得了一大块调查时间，将用于将他们的计划扩展到其他几个明亮的过境系外行星。这一大规模的观测项目是一项重大任务，需要对数据简化和分析作出重大承诺。必须解决的重要问题包括大地光谱的去除，连续体和恒星线核心之间的差异恒星边缘变暗贡献的模型，以及对系统误差贡献的评估。该项目的主要目标是测量几颗凌日系外行星的全光透射光谱，并首次对透射光谱得出的系外行星大气特性进行比较研究。由此产生的观测数据库将非常丰富，并将导致除透射光谱学之外的几个辅助研究项目，包括恒星变异性监测、反射光搜索和恒星金属丰度测量。为了帮助传播研究结果，麦克唐纳天文台教育和公众推广办公室将与雷德菲尔德博士合作，举办一系列年度研讨会。这些讲习班将为从全国范围内的申请者中选出的15名中学教师设计，并将向他们介绍与太阳系外行星、它们的大气以及用于研究它们的高光谱分辨率观测有关的科学问题。还将进行广泛的讲习班后评价，以评估将讲习班开展的活动转化为课堂的有效性。

As the number of detected extrasolar planets continues to rise, a particular subset provides unique opportunities for detailed investigations into the properties of the extrasolar planets themselves. The transmission spectrum of a transiting exoplanet, obtained by the comparison of observations taken in-transit with those taken out-of-transit, can be used to directly measure the effective radius of the exoplanet and its atmosphere or exosphere. Such measurements in strong optical transitions (e.g., Na I, K I) can be used to measure the atmospheric metallicity, rainout of condensates, distribution of stellar flux, and photoionization of atmospheric constituents. Here, Dr. Redfield and his team will build upon their success in detecting the first atmosphere of a transiting exoplanet via transmission spectra. A recently granted large block of survey time on the 9.2-m Hobby Eberly telescope at the McDonald Observatory of the University of Texas at Austin will be used to expand their program to several other bright transiting exoplanets. This large-scale observational program is a major undertaking, and will require a nontrivial commitment to data reduction and analysis. Important issues that must be addressed include the removal of the telluric spectrum, a model of the contribution of differential stellar limb-darkening between the continuum and the cores of stellar lines, and an assessment of the contribution of systematic errors.The main objective of this project is to measure the full optical transmission spectrum for several transiting exoplanets, and enable the first comparative study of exoplanetary atmospheric properties derived from transmission spectra. The resulting observational database will be very rich and will lead to several auxiliary research programs other than transmission spectroscopy, including stellar variability monitoring, reflected light searches, and stellar metallicity measurements.To aid in the dissemination of the results, the McDonald Observatory Education and Public Outreach Office will work with Dr. Redfield to create a series of annual workshops. These workshops will be designed for fifteen secondary school teachers selected from a nationwide applicant pool, and will introduce them to the scientific issues related to extrasolar planets, their atmospheres, and the high spectral resolution observations used to study them. An extensive post-workshop evaluation will also take place in order to assess the effectiveness of the translation of activities developed in the workshop to the classroom.