Nice!
To avoid over-exposition because the glow layer is performed over the whole sphere, you can use the same trick than @PatrickRyan to have only the blue color being emissive:
https://playground.babylonjs.com/#C6LD7D#5
Starting frame:
Left: material without glow layer - Middle: updated material with glow layer - Right: your material with glow layer
As you can see, 1 and 2 are the same but 3 is over exposed.
One frame during animation:
Note that setting the clear color alpha value of the glow layer to 0 (gl.neutralColor.a) allows to get rid of the artefact around the sphere, so no need to add an animation that fades out the glow intensity.