The role of giant impacts in the formation of the outer solar system and exosystems

巨大撞击在外太阳系和系外系统形成中的作用

• 批准号: 2779906
• 金额: --
• 依托单位: University of Bristol
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2022
• 资助国家: 英国
• 起止时间: 2022 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2779906
• 关键词: role; giant; impacts; formation; outer

Project Background:Giant impacts (collisions between planet-sized bodies) are the most violent events in planet formation. For a few hours, collisions that form greater than Earth-mass bodies release more energy than the Sun. Large fractions of the icy and/or rocky mantles of the colliding bodies are melted and vaporised, and the huge torques exerted can leave the post-impact body rapidly rotating. The mass of the largest body may either increase or decrease, depending on the amount of material ejected from the system. Impacts can fundamentally alter the trajectory of a planet's evolution, as the ratios of atmosphere, crust, mantle and core all change and systems of moons can be formed. For example, giant impacts are thought to be responsible for the high obliquity of Uranus, the high density of Mercury, and the formation of Earth's Moon.The thermal and rotational states of post-impact bodies are so extreme that a significant fraction of impacts produce synestias, a recently theorisedclass of planetary object (Lock & Stewart, 2017). Synestias are bodies that exceed the corotation limit, defined as the angular momentum at which a planet's equatorial velocity equals that of a circular Keplerian orbit. Post-impact synestias are typically many times larger than cooler planets and form donut-shaped structures (Figure1). The different dynamical and thermodynamical states of synestias have significant implications for moon formation, core formation, and the distribution of volatiles within planets.Only a limited record of giant impacts remains in our solar system, but exoplanet observations are revolutionising this field. Recent space telescopes, such as Kepler and TESS, along with multiple ground-based surveys, are dramatically increasing the number of known exoplanets. Exosystems have a range of architectures and host planets with widely varying densities, and so bear witness to the many possible outcomes of giant impacts and planet formation in general. Furthermore, as we find more and more exoplanets and begin to observe planets around younger stars, we may soon detect planetary bodies in the immediate aftermath of giant impacts.Studies of giant impacts, with which these observations are interpreted, have largely focused on the impacts expected during formation of our inner solar system. There has been little work on collisions between more massive planets, even though such impacts could have helped shape the outer solar system. In addition, ours may not be a typical planetary system. It lacks the most common planets found around other stars: super-Earths and mini-Neptunes (planets with radii between Earth and Neptune). Many of these planets have large ice (e.g., water) and/or gas fractions. Few studies have explored impacts between more massive terrestrial and/or volatile-richbodies and, at present, we do not understand the outcome of what are likely the most frequent planetary collisions in the universe.Project Aims and MethodsThis project will explore how collisions shape the planets in our solar system and in exosystems. Using state-of-the-artgiantimpact simulations, the successful candidatewill investigate the range of dynamic and thermodynamic outcomes of collisions between water-rich bodies, and develop 'scaling laws' that relate the outcomes to the impact parameters. Although generally a common occurrence, the rates and energies of impacts vary between different planet formation models. By analysing the frequency and parameters of impacts in each scenario, the student will ascertain how giant impacts would sculpt planetary systems in different cases. Furthermore, by determining the observational signatures of post-impact bodies and synestias, the project will aim toprovide the tools necessary to identify...

项目背景：巨大的影响（行星大小的身体之间的碰撞）是行星形成中最​​暴力的事件。在几个小时内，形成大于地球物体的碰撞释放出比太阳更多的能量。撞击物体的冰冷和/或岩石披风的大部分是融化和蒸发的，施加的巨大扭矩可能会使后影响的身体迅速旋转。根据系统弹出的材料的数量，最大的身体的质量可能会增加或减少。影响可以从根本上改变行星演变的轨迹，因为可以形成大气，地壳，地幔和核心的比率，所有卫星的变化和系统。例如，巨大的影响被认为是天王星的高倾斜度，高密度和地球月亮的形成的原因。后影响后体的热和旋转状态是如此极端，以至于很大一部分影响会产生合成的一小部分，这是一种近期的Planetare对象（Lock＆Stewart，2017年）的近期理论化。合成是超过旋转极限的物体，该体的定义为行星赤道速度等于圆形开普勒轨道的角动量。影响后的合成子通常比较冷的行星大很多倍，并形成甜甜圈形结构（图1）。合成的不同动力学和热力学状态对月球形成，核心形成和行星内挥发物的分布具有重要意义。只有有限的巨大影响记录仍然存在于我们的太阳系中，但是系超球的观察正在彻底改变这一领域。最近的空间望远镜（例如开普勒和苔丝）以及多个基于地面的调查，正在急剧增加已知系外行星的数量。外部系统具有一系列建筑和寄主行星，其密度差异很大，因此证明了巨大影响和行星形成的许多可能结果。此外，随着我​​们发现越来越多的系外行星并开始观察年轻恒星周围的行星，我们可能很快在巨大的影响后立即发现行星体。巨大影响的研究，这些观察结果被解释了，在很大程度上将重点放在我们内部太阳能系统形成期间预期的影响上。尽管这种影响可能有助于塑造外部太阳系，但在更大的行星之间碰撞几乎没有工作。此外，我们的可能不是典型的行星系统。它缺乏其他恒星周围发现的最常见的行星：超伊斯兰和迷你北极线（地球和海王星之间有半径的行星）。这些行星中有许多具有大冰（例如水）和/或气体分数。很少有研究探讨了更大的陆地和/或挥发性富含富含疫苗的影响，目前我们还不了解宇宙中最常见的行星碰撞结果的结果。项目的目标和方法将探索这些项目将如何探索我们的太阳系和Exosystems中的碰撞。使用最新的ArtgiantImpact模拟，成功的候选人将研究水丰富的身体之间碰撞的动态和热力学结果的范围，并制定将结果与影响参数相关的“缩放定律”。尽管通常是常见的发生，但影响的速率和能量在不同的行星形成模型之间有所不同。通过分析每种情况下影响的频率和参数，学生将在不同情况下确定巨大的影响将如何雕刻行星系统。此外，通过确定影响后身体和合成的观察性特征，该项目将瞄准识别所需的工具...