These trained students (these were astrologers) of the stars observed an unexplained phenomenon in the heavens, and somehow interpreted this sign with a change in the way things were. They saw it as a sign of the Messiah’s birth!
How to Become Wise Matthew 2: 1-2, 10-11
Now after Jesus was born in Bethlehem of Judea in the days of Herod the king, behold, wise men from the East came to Jerusalem, 2 saying, “Where is He who has been born King of the Jews? For we have seen His star in the East and have come to