It is possible that the Magi may have heard of a Jewish prophesy about a king whose birth was to be marked by a star (see Numbers 24:17). But how would a normal sign in the sky come to rest over the place where the child was. Jerusalem is only about 5 miles from Bethlehem. They could have walked there in about an hour and 45 minutes. It would be hard to tell the difference from an astronomer’s POV. I like to think that this sign was something that God specifically created to celebrate the birth of his Son! Kind of like the “it’s a boy” signs you sometimes see in a front yard! A special sign for a special birth.