Some attempts to simulate star collisions in Blender using only the available tools.

The first few sequences are using the smoke simulator with a force field attracting density. However, the simulation has problems with preserving density on larger forces and on collisions in general. Further there are artifacts causing these characteristic fountains along the axis. Another restriction is that you can't disable air drag to replicate a vacuum.

The last test was a SPH particle simulation using self attracting particles to replicate gravitational attraction. The particles were remeshed using metaballs and a volume shader together with particle emissions was used to colorize the mesh depending on velocity.

I also tried Elbeem fluid simulator just to learn that it doesn't support force fields at all. With only one predefined gravity vector available there was no way to simulate self attracting spherical structures like celestial bodies - not very flexible unfortunately.

Music: Evergreen by Lamprey (CC BY)

Made with Blender