Alpha falloff on spheres?

Hello. I created a group of spheres to act as moving “stars” in front of an image background in my scene. They just look like white circles; I was wondering if there was a way to map a material so that they are 100% solid white at the center and then go to 100% alpha towards their edges (to make them more subtle).
they look like so now:

Maybe better to use Points with texture instead of spheres?
For example, like here: three.js examples

I tried points, but I couldn’t get the falloff

Create a custom texture of a radial gradient and use it as map with transparent: true: Edit fiddle - JSFiddle - Code Playground