Phosphorescence
A slow glow that continues after the light source is taken away.
Also: glow in the dark, afterglow
Phosphorescent materials store light energy and release it slowly, sometimes for hours. Glow-in-the-dark stars, watch dials and emergency exit signs use them. The difference from fluorescence is timing: fluorescence stops at once, phosphorescence lingers. Modern glow pigments are far brighter and longer-lasting than the older zinc-based ones. The name comes from the element phosphorus, although the glow of phosphorus is a chemical reaction with air and not the same thing. The light of fireflies and glowing sea plankton is different again, made by living chemistry.