Francesco Milanese uses a dampening field to create a spiral galary using particle systems.
In this tutorial we will see a way to "freeze" an Emitter particle system in a Blender 3D scene when the particles reach a certain configuration, stopping them and avoiding their disappearance in the virtual universe...
… and, speaking of virtual universes, as a practical example will model a galaxy, or at least I'll give you the basics to be able to create a basic one like that shown in figures below, then of course you can experiment with other meshes, other settings for the values, and so on.
