Made it with glow paint, which was applied in each half of the sphere, with a brush and let to dry. I was kinda aiming to get night sky / space / galaxy motive. The paint is made from phosphors and usually glows a green to greenish - blue color. These glowing materials instantly absorb and store the energy of diverse UV (the Sun) and visible light spectrums (light bulb), and emit that energy in the form of bright light. Because of that, they can glow in dark environments for hours. They just need to be "charged".
Cheers,
VoodooLizard