Characterizing Exoplanets and Brown Dwarfs from the Ground and from Space

近几十年来，亚恒星天体的发现--包括围绕其他恒星运行的行星和“褐矮星”(质量介于恒星和行星之间的天体)--是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。随着对已知种群的搜索不断扩大，通过相互比较研究和理论模型，已经开始认真地描述亚恒星世界的特征。在凌日中捕捉到的行星特别适合探测它们的大气层。自由漂浮或绕恒星运行轨道较宽的褐矮星也是如此。我提出了一个多方面的研究计划，基于地面和太空中使用各种尖端仪器进行的高精度观测，以促进我们对这两种亚恒星天体的性质、起源和演化的理解。*关于系外行星，我们已经利用包括开普勒太空望远镜在内的前线设施的数据，发表了关于它们的相位变化和热发射的创新性和被高度引用的工作。在我们利用地面上最大的望远镜进行凌日光谱学探索的基础上，包括我们最近在超地球大气中寻找水蒸气，我们将在未来五年内探索各种从地面和太空凌日的系外行星的特征。特别是，我和我的学员将在詹姆斯·韦伯太空望远镜(JWST)上使用加拿大建造的NIRISS仪器进行保证时间的观测，JWST是有史以来建造的最强大、最昂贵的空间天文台，计划于2019年初发射。我们的目标将覆盖所有可用系外行星的温度和质量。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描述NASA凌日系外行星调查卫星发现的明亮恒星周围的行星。*关于棕矮星，我们通过深度成像和光谱调查研究了年轻的亚恒星天体，发现了由于大气中云模式的演变而导致的冷棕矮星的极端亮度变化，并描述了一些与大轨道上的恒星相伴的亚恒星。利用JWST上的保证时间，我们将以前所未有的深度探测附近的年轻星系团，并调查最小质量自由漂浮天体的频率和性质。我们还将利用盖亚太空任务的天体测量数据以及地面光谱观测来确定附近年轻的棕矮星种群的特征。*总体科学目标是探索恒星下世界惊人的多样性，研究它们的物理特征，并为探测太阳系以外的类地行星的大气铺平道路。*****

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. *****