This is the trope when outer space is associated, not with epic Space Battles or dangerous Negative Space Wedgies, but rather sleep or dreams.

After all, the moon and stars are visible at night, and night is when people (or at least, most people) sleep. Common in lullabies and children's stories with a "Getting Ready for Bed" Plot are mentions that the humans are asleep but the moon and stars are "awake", and there might be mentions of celestial bodies "watching over" the sleeping humans protectively. A character might also be seen dreaming about being in space.