Material for sphere object that fades to nothing at edge

Can anyone suggest a material setup that would allow me to fill a sphere with a color that fades out at the edges? I am specifically curious how the fading edges always face the camera no matter where I move it (the camera).

I am wanting to put the sphere inside this glass head so that it softly blocks out the wall lights (white lines) that shine through the head rather busily.

I remember this post from last time! I believe you were just trying to blur the lines behind the head without blurring the brain.

After thinking about it again, it has occurred to me that you may be able to do this with the Vertex Color node and having two different settings of refraction set to Lerp with one of the Vertex Color pins as alpha. Then you could have the parts of the head that aren’t near the brain set to higher refraction and the areas of the head near the brain set to lower refraction.

This video shows how to use Vertex Color in the material editor. You may be able to get it to work with refraction too:
Advanced Vertex Painting Techniques - YouTube

Fresnel might be what you’re looking for, if I understand correctly.