The term implies a lasting glow, which continues without an external light source. The phosphorescent stars on the ceiling shimmered all night.
Pro Tip 2/3
Safety Use
Phosphorescent materials are used for safety signs because they can be seen in the dark. Exit signs use phosphorescent paint to glow during a power outage.
Pro Tip 3/3
No Heat Involved
Understand that phosphorescent objects do not get warm, unlike objects that give off light due to heat. Despite its bright glow, the phosphorescent material stayed cool to the touch.