Formation and early evolution of gas giants: The accretion shock and its consequences

气态巨行星的形成和早期演化：吸积激波及其后果

• 批准号: 362583282
• 负责人: Professor Dr. Rolf Kuiper
• 金额: --
• 依托单位: Arbeitsgruppe Numerische Astrophysik
• 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/362583282?language=en
• 关键词: Formation; early; evolution; gas; giants

Recent observational efforts have started to reveal a population of young and bright gas giants at large distances from their stars through the technique of direct imaging. Because of their youth, the brightness of these objects still reflects the conditions of their formation and the physical processes that shape them. Even more recently, a few systems have been discovered in which we are witnessing the ongoing formation of gas giants, as revealed by accretion signatures. The issue with these exciting detections, however, is that models are necessary to infer masses from the luminosities but that these models are currently unconstrained at early times.What is thought to be the single most important element setting a planet's luminosity is the radiative accretion shock at the surface of the planet. The extreme outcomes lead to hot and cold starts, respectively, in which the planet begins its post-formation cooling with a high or low luminosity. These differences in luminosity are colossal and, critically, have been hampering a reliable determination of the masses.Therefore, we propose to conduct the first realistic study of the planet accretion shock by performing two-dimensional radiation-hydrodynamical simulations with detailed microphysics. We will focus on the accretion region at the surface of the planet to determine the post-shock conditions as well as the efficiency of the shock, i.e., the fraction of the incoming kinetic energy which is lost as radiation. In view of the magnetospheric-accretion picture, we will also include the effects of a magnetic field. These results will enable us to predict the luminosity of gas giants after their formation and as well as to provide input to simulations of the observational appearance of (embedded) accreting planets and their thermo-chemical feedback on the disk.This research is designed as a series of smaller tasks which extend and combine existing tools. In view of near-future direct detections, this makes the proposed research a low-risk, high-impact project.

最近的观测工作已经开始通过直接成像技术揭示在离恒星很远的地方有一群年轻明亮的气体巨星。由于它们的年轻，这些天体的亮度仍然反映了它们形成的条件和塑造它们的物理过程。甚至在最近，我们发现了一些系统，在这些系统中，我们正在见证气体巨星的形成，正如吸积特征所揭示的那样。然而，这些令人兴奋的探测的问题是，从光度推断质量需要模型，但这些模型目前在早期是不受约束的。人们认为，决定行星亮度的最重要因素是行星表面的辐射吸积激波。极端的结果分别导致热启动和冷启动，即行星在形成后以高或低亮度开始冷却。光度上的这些差异是巨大的，而且严重地妨碍了对质量的可靠测定。因此，我们建议通过详细的微物理进行二维辐射-流体动力学模拟，对行星吸积冲击进行第一次现实的研究。我们将把重点放在行星表面的吸积区域，以确定冲击后的条件以及冲击的效率，即入射动能中作为辐射损失的部分。考虑到磁层吸积图，我们还将包括磁场的影响。这些结果将使我们能够预测气态巨行星形成后的光度，并为模拟（嵌入的）吸积行星的观测外观及其在盘上的热化学反馈提供输入。这项研究被设计成一系列扩展和组合现有工具的小任务。鉴于近期的直接探测，这使得拟议的研究成为一个低风险、高影响的项目。