Observing and modeling young transiting planets

目前还不清楚大质量气态巨行星是如何形成的，是通过直接的引力坍缩（即收缩），还是首先通过尘埃凝聚和固体核心的缓慢增长（增长），然后吸积大气层；或者两条路是否都有可能。一种方法是测量年轻形成行星的半径和组成。这是可能的，目前只有通过行星凌日技术，半径和质量（连同径向速度观测）可以确定。在目前已知的许多凌日行星中，没有一颗（只有两颗）的年龄小于100兆日。我们的目标是找到年轻的形成行星，并确定它们的半径和质量，从而揭示它们形成过程的特征。作为该项目的第二部分，我们将对这些太阳系外（年轻）巨行星的内部组成进行理论建模。我们还考虑了行星的大气层，它与恒星辐射和更深的内部的耦合。通过在广泛的压力和温度范围内对行星材料氢、氦、水、氨和MgO进行广泛的有限温度密度泛函数理论分子动力学（DFT-MD）模拟，得到了新的状态方程数据。基于这种从头开始的状态方程数据，我们对气态巨行星的内部进行了建模，该内部包括三大部分：固体核心、流体层和气体大气。利用探测到的观测值（例如总质量和半径）作为模型的约束条件，我们可以预测，例如，固体核心的质量，行星中金属的总质量和金属层中的金属分数。另一个结果是大气的质量和范围。预期的结果将使我们能够区分不同的形成情景，从而更好地理解行星的形成过程及其内部结构。

It is still not clear how massive gas giant planets form, whether by direct gravitational collapse (i.e. contracting) or first by dust coagulation and slow growth of a solid core (growing), then accreting an atmosphere; or whether both paths are possible. One way to find out is to measure radii and compositions of young forming planets. This is possible currently only with the planet transit technique, where the radii and masses (together with radial velocity observations) can be determined. Among the many transiting planets know so far, none (but 2) is younger than some 100 Myr. We aim to find young forming planets and determine their radii and masses, so that characteristics of their formation process can be revealed.As second part of the project we will perform theoretical modeling of the inner composition of those extra-solar (young) giant planets. We consider the atmosphere of the planet as well, its coupling to the stellar radiation and to the deeper interior. New equation of state data have been derived at the U Rostock by performing extensive finite-temperature density functional theory molecular dynamics (DFT-MD) simulations for the planetary materials hydrogen, helium, water, ammonia, and MgO for a wide range of pressures and temperatures. Based on this ab initio equation of state data we model the interior of gas giant planets accounting for three major parts: solid core, fluid layer(s) and a gas atmosphere.Using the detected observables (e.g. total mass and radius) as constraints for the models we can predict, e.g., the mass of a solid core, the total mass of metals in the planet and the metal fraction in the layer(s). Another result is the mass and extent of the atmosphere. The expected results would enable us to discriminate between different formation scenarios and, thus, lead to a better understanding of planetary formation processes and their interior structure in general.