We have produced the highest resolution simulations of the giant impact that is thought to have knocked Uranus’ spin axis into the plane of the solar system. The two orders of magnitude increase in resolution was enabled by our use of the SWIFT hydrodynamics and gravity code on the DiRAC facility in Durham. We incorporated equations of state for various different materials into SWIFT, which has primarily been designed for cosmological applications. The high-resolution simulation of this planetary giant impact shows features that are entirely absent from previous smaller calculations. For instance after the initial impact, the subsequent sloshing around of the system can be sufficiently vigorous to unbind some of the icy mantle from the proto-Uranus – an effect that was not seen in earlier million-particle simulations. Determining what material was placed into orbit as a result of this impact is crucial for deciding if the currently observed Uranian satellites could have formed from this debris. Again, the higher resolution simulations now allow us to make reliable predictions for this. These represent the first scientific results with the SWIFT code, and demonstrate how it will open up new ways to constrain models of planetary giant impacts relevant to most bodies in the solar system.
A mid-collision snapshot of a grazing impact with 10$^8$ SPH particles coloured by their material and internal energy, showing some of the detailed evolution and mixing that can now be resolved. In the left panel, light and dark grey show the target’s ice and rock material, respectively, and purple and brown show the same for the impactor. Light blue is the target’s H-He atmosphere.
This calculation used the Dell 940 system with four Intel skylake with 112 cores. This system was provided by Intel and Dell as a proof-of-concept system as part of the Dell/Intel and DiRAC@Durham industrial engagement at list price of approximately £100k.
