After Jesus was born in Bethlehem in Judea, during the time of King Herod, Magi from the east came to Jerusalem and asked, “Where is the one who has been born king of the Jews? We saw his star when it rose and have come to worship him.” … After they had heard the king, they went on their way, and the star they had seen when it rose went ahead of the until it stopped over the place where the child was. When they saw the star, they were overjoyed. On coming to the house, they saw the child with his mother Mary, and they bowed down and worshiped him. – Matthew 2:1-2, 9-11

Magi are hereditary priests in ancient Medes and Persia. Their first appearance in history is in 7th century B.C., where they are described as favoring priestly, mysterious, and occult powers. Magi held to the primacy of the elements of earth, air, water, and fire, and burnt offerings were a significant part of their worship. Dream interpretation was a very important way of discerning God’s will to them.
Magi were not, as is often thought, magicians or sorcerers, as that translation came about during the Hellenistic period, much later than their first appearance in history. Nonetheless, the Magi were not children of Israel. They were religious people of the neighboring countries who relied upon dreams and the sky to discern God’s will.
So, God used dreams and the sky to communicate with them when it was time to announce his own incarnation.

Although divination is prohibited in Deuteronomy and Isaiah derides Babylon for relying on astrology for predictions, God used astrology to communicate to the Magi from the east who lived at the time that Jesus was born.
God is bigger than our religious categories. God is bigger than our fear of customs different than our own. God speaks our own languages. If God wants to reach somebody, he can do so in a way that they will recognize. God communicates to us in ways that we don’t expect.
God announced his unexpected arrival as a helpless baby through the stars.