Radiate from center of object

Hi all,

I’m trying to create a procedural material that radiates from the center, that graduates to transparent by the time it gets to the surface. The goal to create something like below using textures:

This tutorial seems to be on the right track. But I’ve tried downloading the blend file, and it makes absolutely no sense to me.

I’ve tried using volumetrics, which kind of works, but not in the way I want it to. Hoping someone can understand what I’m asking and how it can be done - if at possible.