CAREER: Super-Earth or Mini-Neptune? Exploring the Mysterious Origins of the Smallest Transiting Planets

正在进行的对附近恒星的调查揭示了一系列不同的行星系统，其中许多具有与我们太阳系显著不同的特征。也许从这些调查中得到的最大的惊喜之一是发现“超级地球”(质量在地球1-10倍之间的行星)是太阳系外行星中最常见的类型之一。目前我们对这些神秘行星的组成知之甚少，有人提出，这个质量范围可能包括围绕着岩石核心的厚厚氢气包层的“水世界”和“迷你海王星”。PI和她的学生将进行一个精心设计的观测计划，以区分这两种情况，并测量这些系外行星的性质。这些测量将提供对这类令人惊讶的新行星的形成和迁徙历史的关键见解。该计划将支持两名研究生的论文工作，以及一系列本科生暑期研究项目。学生们将有机会在Keck上进行远程观测，并前往望远镜观察Palomar的运行情况。Pi和她的学生将把Keck/Hires径向速度运动与Palomar凌日测光和光谱学相结合，以表征新的低质量凌日行星，并为它们的大气开发改进的云模型。他们将使用径向速度研究来测量行星质量，从而限制整体成分，并将测量精确的轨道星历。对于低密度的超级地球，他们将使用透射谱来表征其大气的平均分子量，以区分那些富含水的大气和那些被H/He包层包围的岩石核心的大气。传输光谱的细节可能会被高层云遮挡，因此他们还将研究“凉爽的海王星”，以便更好地了解云的形成过程。这些观测将利用Palomar的精密光度测量和光谱分析的新能力，并显著提高HST和JWST未来大气特征研究的科学回报。

Ongoing surveys of nearby stars have revealed a diverse array of planetary systems, many of which have characteristics that differ substantially from those of our solar system. Perhaps one of the biggest surprises to come out of these surveys was the discovery that "super-Earths" (planets between 1-10 times the mass of the Earth) are one of the most common types of extrasolar planet. We currently know very little about the compositions of these mysterious planets, and it has been suggested that this mass range may include both "water worlds" and "mini-Neptunes" with thick hydrogen envelopes around a rocky core. THE PI and her students will conduct a carefully-designed observational program to distinguish between these two scenarios and to measure the properties of these exoplanets. These measurements will offer key insights into the formation and migration histories of this surprising new class of planets. This program will support thesis work for two graduate students as well as a series of undergraduate summer research projects. Students will have the opportunity to observe remotely on Keck and to travel to the telescope for observing runs at Palomar.The PI and her students will combine a Keck/HIRES radial velocity campaign with Palomar transit photometry and spectroscopy in order to characterize new low-mass transiting planets and to develop improved cloud models for their atmospheres. They will use radial velocity studies to measure planetary masses, thereby constraining bulk compositions, and they will measure precise orbital ephemerides. For low-density super-Earths, they will use transmission spectroscopy to characterize the mean molecular weight of their atmosphere to distinguish between those that are water-rich and those with rocky cores surrounded by H/He envelopes. Transmission spectroscopy details can be obscured by upper-level clouds, so they will also study "cool Neptunes" in order to develop a better understanding of the cloud formation processes. These observations will utilize new capabilities for precision photometry and spectroscopy at Palomar and significantly enhance the science return from future atmospheric characterization studies with HST and JWST.