This animation shows the process of binary planetesimal formation via the process of gravitational collapse and appears as a supplementary animation in the paper "Investigating Gravitational Collapse of a Pebble Cloud to form Transneptunian Binaries" by Robinson et al. 2020 (submitted to A&A).
We show the cloud collapse process for an example simulation in our main dataset. The left-hand panel shows the xy projection of particle position in the simulation box. Marker size scales linearly with particle radius and colour scales logarithmically with particle mass. The panel is initially zoomed in on the cloud and then zooms out until it shows the extent of the whole simulation box. The centre of mass of the cloud is marked with a black ‘×’ and the position of the most massive particle is shown with a red ‘+’. The right-hand panel shows an expanded view centred on the most massive particle at that timestep. Here the marker size scales with the radius squared to emphasise the larger particles. The blue ellipse indicates the binary orbit that is detected between the most massive particle and its largest companion.