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

巨型撞击（行星大小的天体之间的碰撞）是行星形成中最剧烈的事件。在几个小时内，形成比地球质量更大的物体的碰撞释放出比太阳更多的能量。碰撞后的物体的大部分冰和/或岩石地幔被融化和蒸发，施加的巨大扭矩可以使撞击后的物体快速旋转。最大物体的质量可能会增加或减少，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演化的轨迹，因为大气、地壳、地幔和地核的比例都会发生变化，卫星系统也会形成。例如，巨大的撞击被认为是天王星的高密度，水星的高密度和地球月球形成的原因。该项目将探索碰撞如何塑造我们太阳系和系外系统中的行星。使用最先进的巨型撞击模拟，露西将调查富含水的物体之间碰撞的动力学和热力学结果的范围，并制定将结果与撞击参数联系起来的“比例定律”。虽然通常是一种常见的现象，但撞击的速度和能量在不同的行星形成模型之间存在差异。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的撞击将如何塑造行星系统。此外，通过确定撞击后天体和合生天体的观测特征，该项目将致力于提供必要的工具，以查明其他太阳系中的合生天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.