Characterizing Exoplanets and Brown Dwarfs from the Ground and from Space

亚恒星天体的发现——既包括围绕其他恒星运行的行星，也包括“褐矮星”（质量介于恒星和行星之间的天体）——是近几十年来天体物理学中最令人兴奋的进展之一。在已经确定的数千个世界中，世界的多样性确实令人震惊。随着对已知种群的研究不断扩大，通过相互比较和与理论模型的比较研究，对次恒星世界的描述已经正式开始。被捕获的凌日行星特别适合探测它们的大气层。自由漂浮或绕恒星大轨道运行的褐矮星也是如此。我提出了一个多方面的研究计划，基于地面和太空中各种尖端仪器的高精度观测，以推进我们对这两种类型的次恒星物体的性质、起源和演变的理解。******关于系外行星，我们已经发表了关于它们的相位变化和热辐射的创新和高引用的工作，使用了包括开普勒太空望远镜在内的一线设施的数据。在我们利用地面上最大的望远镜对凌日光谱进行探索的基础上，包括我们最近对超级地球大气层中水蒸气的研究，我们将在未来五年内从地面和太空中探测各种凌日系外行星的特征。特别是，我和我的学员将参与詹姆斯·韦伯太空望远镜（JWST）上加拿大建造的NIRISS仪器的保证时间观测。詹姆斯·韦伯太空望远镜是有史以来建造的最强大、最昂贵的太空天文台，计划于2019年初发射。就温度和质量而言，我们的目标将跨越所有可用的系外行星。我们还将在地面望远镜上使用两台新的高分辨率红外光谱仪来表征美国宇航局凌日系外行星测量卫星发现的明亮恒星周围的行星。******关于褐矮星，我们通过深度成像和光谱调查研究了年轻的亚恒星物体，发现了由于大气中云模式的演变而导致的冷褐矮星的极端亮度变化，并描述了一些宽轨道恒星的亚恒星伴星。利用JWST上的保证时间，我们将对附近的一个年轻星团进行前所未有的深度探测，并研究质量最低的自由漂浮物体的频率和性质。我们还将利用盖亚太空任务的天文测量数据以及地面光谱观测来描述附近年轻的褐矮星群。******总体的科学目标是探索亚恒星世界的显著多样性，研究它们的物理特性，并为探测太阳系以外的类地行星的大气层铺平道路。* * * * *

The discovery of sub-stellar objects --both planets around other stars and "brown dwarfs" (objects with masses between stars and planets)-- rank among the most exciting advances in astrophysics in recent decades. The diversity of worlds, among the thousands already identified, is truly astounding. As searches continue to expand upon the known populations, characterization of sub-stellar worlds, through comparative studies with each other and with theoretical models, has begun in earnest. Planets caught in transit are particularly well suited for probing their atmospheres. So are brown dwarfs that are free-floating or in wide orbits around stars. I propose a multi-faceted research program, based on high-precision observations with a variety of cutting-edge instruments on the ground and in space, to advance our understanding of the nature, origins and evolution of both types of sub-stellar objects. ******With regard to exoplanets, we have already published innovative and highly-cited work on their phase variations and thermal emission, using data from frontline facilities including the Kepler space telescope. Building on our forays into transit spectroscopy with the largest telescopes on the ground, including our recent search for water vapor in a super-Earth atmosphere, we will probe the characteristics of a wide variety of transiting exoplanets from the ground and from space over the next five years. In particular, my trainees and I will be involved in guaranteed-time observations with the Canadian-built NIRISS instrument on the James Webb Space Telescope (JWST), the most powerful and the most expensive space observatory ever constructed, slated for launch in early 2019. Our targets will span the full available range of exoplanets in terms of their temperatures and masses. We will also use two new high-resolution infrared spectrographs on ground-based telescopes to characterize planets around bright stars discovered by NASA's Transiting Exoplanet Survey Satellite.******With regard to brown dwarfs, we have investigated young sub-stellar objects through deep imaging and spectroscopic surveys, found extreme brightness changes in cool brown dwarfs resulting from evolving cloud patterns in their atmospheres, and characterized a number of sub-stellar companions to stars in wide orbits. Using guaranteed time on JWST, we will probe a nearby young cluster to unprecedented depth, and investigate the frequency and properties of the lowest-mass free-floating objects. We will also utilize astrometric data from the Gaia space mission as well as ground-based spectroscopic observations to characterize nearby young brown dwarf populations. ******The overall scientific goals are to explore the remarkable diversity of sub-stellar worlds, investigate their physical characteristics and pave the way for probing atmospheres of terrestrial planets beyond our solar system. *****