Yes, i have done this effect,
its kinda simple
first, you need a sprite that is a blurred dot, then you attach that to a physics circle body, the circle needs to be much smaller than the sprite
then you draw all the dots to a render-texture with additive blending,
then you draw that render-texture with alpha-test shader.
You need to tweak the size of the circle shape, the dot sprite, and the alpha-test cutoff point to make everything look right