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

巨大撞击(行星大小的天体之间的碰撞)是行星形成过程中最猛烈的事件。在几个小时内，比地球质量大的天体形成的碰撞释放出比太阳更多的能量。碰撞天体的大部分冰盖和/或岩石地幔被融化和蒸发，施加的巨大扭矩可能会使碰撞后的天体快速旋转。最大天体的质量可能增加，也可能减少，这取决于从系统中喷出的物质的量。撞击可以从根本上改变行星的演化轨迹，因为大气、地壳、地幔和地核的比例都会改变，卫星系统可能会形成。例如，巨大的撞击被认为是天王星的大倾角、水星的高密度以及地球月球的形成的原因。这个项目将探索碰撞如何塑造太阳系和系外系统中的行星。使用最先进的巨型撞击模拟，Lucy将调查富含水的天体之间碰撞的动力学和热力学结果的范围，并开发将结果与撞击参数相关联的“标度定律”。虽然撞击的速度和能量在不同的行星形成模型之间是不同的，但通常情况下，撞击的速度和能量是常见的。通过分析每种情况下撞击的频率和参数，露西将确定在不同情况下，巨大撞击将如何塑造行星系统。此外，通过确定撞击后天体和星系体的观测特征，该项目将旨在提供必要的工具，以确定其他太阳系中的星系体和其他撞击后天体。

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. This project will explore how collisions shape the planets in our solar system and in exosystems. Using state-of-the-art giant impact simulations, the Lucy will 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, Lucy 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 to provide the tools necessary to identify synestias, and other post-impact bodies, in other solar systems.