God placed the star in the sky to lead the Magi to Christ, that they might worship Him. Matthew 2:1-2 “Now after Jesus was born in Bethlehem of Judea in the days of Herod the king, behold, Magi from the east arrived in Jerusalem, saying, “Where is He who has been born King of the Jews? For we saw His star in the east and have come to worship Him”.
According to the Detroit Baptist Theological Seminary, Theologically Driven there could be several reasons for the “star” that guided the wise men to Bethlehem to worship Jesus, the newborn king.
First, some think the wise men saw a supernova that left a trail of light in the sky for several days—long enough, at least, to guide the wise men’s journey. Chinese and Korean records indicate that this sort of thing occurred around the time of Jesus’ birth (5/4 B.C.).
Second, some think the wise men followed the blazing tail of a comet. (Of course, whether the tail was as big as a kite is another matter altogether.) Scientists note that Halley’s comet was active at this time, though probably appearing a few years too early to be a real contender (12–11 B.C.).
Third, some suggest the wise men saw a planetary conjunction, which occurs when two or more planets approach each other’s orbits. Johannes Kepler (1571–1630) noted that a rare triple conjunction of Jupiter, Saturn, and Mars occurred in 7–6 B.C. Other records indicate that a conjunction of Jupiter and Venus occurred in 3 B.C., near the luminous star Regulus, and still others that one between Jupiter and Venus took place in 2 B.C. In fact, the latter conjunction is said to have occurred right over Bethlehem on December 25!
Fourth, some suggest the wise men followed something that was simply miraculous in the final analysis. Detroit Baptist Theological Seminary, Theologically Driven,
When I was about nine years old, our schoolteacher took us to the planetarium in Chicago and I remember vividly the presenter showing us the sky the year that Jesus was born in Bethlehem. He explained what the wisemen saw was three planets in alinement shining so brightly that it caught the wisemen’s attention. But whatever the Lord did in the sky during that season, it was a miracle beyond our understanding that God preformed for all to see and remember and later proclaim the miraculous birth of His Son Jesus to a lost and dying world.