NPCs should have different text when an event is happening. Signy could be like the guide in terraria and tell you what's going on. For example, for the Azure lights event, Signy could say "Your going to have a bad time" "Azure lights in the sky makes skeletons really angry. Like, so angry that they catch on fire." And the old man could say something like, "I'd go outside to watch the stars, but i'd rather stay here. Also my feet are stuck to the floor."
There should also be an event (maybe azure lights, maybe the asteroid event) that causes the sky to become filled with stars, like it is falling from juice school and in the main menu.