Exploring the Diversity of Exoplanets in the Mass-Density Diagram

在质量密度图中探索系外行星的多样性

• 批准号: 362398782
• 负责人: Professor Dr. Artie P. Hatzes
• 金额: --
• 依托单位: Thüringer Landessternwarte Tautenburg (TLS) - Karl-Schwarzschild-Observatorium
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2017
• 资助国家: 德国
• 起止时间: 2016-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/362398782?language=en
• 关键词: Exploring; Diversity; Exoplanets; Mass; Density

The mass-density diagram is an important diagnostic for understanding the large diversity in bulk densities that exoplanets exhibit. In this diagram low-mass planets with masses below ~0.3 MJup show a large scatter in density. For example, super-Earths with masses ~10 MEarth can have a bulk density consistent with a rocky planet (density = 5-8 gm/cm3) or a Neptune-like structure (density ~ 2 gm/cm3). Understanding this diversity may yield clues as to the planet formation. On the other hand, giant planets and brown dwarfs in the mass range 0.3 - 62 MJup show a tight linear relationship in the mass-density diagram with no distinguishing features between the two classes of objects. The mass-density diagram can thus provide clues as to the nature of giant planets and brown dwarfs orbiting stars. Are these really different objects?The light curves of transiting planets obtained from space-based missions like CoRoT and Kepler provide us with the best possible measurements of the planetary radius. However, CoRoT and Kepler targeted relatively faint stars. The determination of the planetary mass via Doppler measurements from the ground was thus difficult. The re-vamped Kepler mission, K2, is observing stars that are 3 magnitudes brighter than Kepler and CoRoT targets. By the end of our proposed project K2 will have obtained precise light curves for almost 300,000 stars. Light curves from TESS shall be included in this project after its successful launch in 2017. The discoveries from K2 and eventually TESS will greatly increase the number of extrasolar planets for which we have accurate measurements of the mass, radius, and bulk density.For this project we have assembled a team from three institutes to exploit the light curves from the K2 and eventually TESS missions. Our team builds on its vast experience as members of the CoRoT Exoplanet Science Team. We have experts in the processing of raw light curves from space instruments, the detections in the light curves, and the modeling of the transit light curves needed to obtain the planetary radius. We also have experts on stellar spectroscopy which will determine the properties of the host stars. We expect this project to yield manyl dozen transiting extrasolar planets with accurate bulk densities throughout the mass-density diagram. This will help us understand the diversity in bulk densities for low-mass planets and the nature of giant planets/brown dwarfs.

质量密度图对于理解系外行星在体积密度上的巨大差异是一个重要的诊断。在这张图中，质量低于~0.3 MJup的低质量行星在密度上显示出很大的分散。例如，质量约为地球10倍的超级地球，其体积密度与岩石行星一致（密度= 5-8克/立方厘米），或具有类似海王星的结构（密度约为2克/立方厘米）。了解这种多样性可能会为行星的形成提供线索。另一方面，质量在0.3 - 62 MJup范围内的巨行星和褐矮星在质量密度图中表现出紧密的线性关系，两类天体之间没有明显的区别。因此，质量密度图可以提供关于巨型行星和围绕恒星运行的褐矮星性质的线索。它们真的是不同的物体吗？从像CoRoT和开普勒这样的太空任务中获得的凌日行星的光曲线为我们提供了行星半径的最佳测量。然而，CoRoT和开普勒瞄准的是相对较暗的恒星。因此，在地面上通过多普勒测量来确定行星质量是困难的。改造后的开普勒任务K2正在观测比开普勒和CoRoT目标亮3等的恒星。在我们提出的项目结束时，K2将获得近30万颗恒星的精确光曲线。TESS的光曲线将在2017年成功发射后纳入本项目。K2和TESS的发现将大大增加太阳系外行星的数量，我们可以精确测量它们的质量、半径和体积密度。在这个项目中，我们组建了一个来自三个研究所的团队，利用K2和TESS任务的光曲线。我们的团队以其作为CoRoT系外行星科学团队成员的丰富经验为基础。我们在处理来自空间仪器的原始光曲线，光曲线的检测以及获得行星半径所需的过境光曲线建模方面拥有专家。我们也有恒星光谱学方面的专家，这将决定主星的性质。我们期望这个项目能在质量密度图中发现许多具有精确体积密度的凌日系外行星。这将有助于我们了解低质量行星的体积密度多样性以及巨行星/褐矮星的性质。