Very nice!
One minor improvement would be to use the following LightSource so that the Sun doesn't look like its being illuminated off to one side. Instead of "Natural", use:
Lighting -> {{"Directional", White, ImageScaled[{0, 0, 1}]}}
This also gives the "limb darkening" effect seen when observing the Sun through solar filters. The center of the Sun looks brighter than the edges.