The answer to this question has to be “a miracle” since there are a great many variables to say with any sort of certainty that it was any particular stellar event. It appeared in the east: if Persia is meant then it is perhaps a two year journey to find Bethlehem.
It is possible that this simply means, as astrologers, they read the signs and determined that the birth of the messiah was near. “We read his horoscope” sounds far less Christmas-y, but that may be in fact what Matthew meant.
Other things besides stars could be considered as omens and portents. Comets and meteors were always considered signs, it is possible that one of these appears at the right time and made the Magi think that Messiah had been born. In addition, the star guides the Magi to the house, this is unlikely to be a comet, meteor, conjunction, etc.
Why would a star be the sign that the Messiah was born? Balaam’s prophecy in Numbers 24:17 describes a king who will rise from Israel who will rule over the nations:
Numbers 24:17 (ESV) I see him, but not now; I behold him, but not near: a star shall come out of Jacob, and a scepter shall rise out of Israel; it shall crush the forehead of Moab and break down all the sons of Sheth.
While it is difficult to state for certain that this “star” in Numbers was the star in Matthew 2, the connection of a celestial sign with the birth of a great king is a well-known feature of Ancient culture. If Jesus was the Messiah, his birth would have been accompanied with signs and great men (like the magi) would observe and understand the importance of the birth.
One of the most secure facts about Jesus from New Testament is that he was “from Nazareth in Galilee.” If he was the Messiah, son of David, why was he not “from Bethlehem?” As the readers of Matthew and Luke, we know he was born in Bethlehem and some of the reasons why he did not stay there. But as with everything in the story of Jesus’ birth, there is more to the story.
Political and economic issues in first century Palestine are the main reasons that Joseph moves from Bethlehem to Nazareth. Just like laborers today, You go where there is work! Sepphoris and Tiberias, two large cities near Nazareth, had need for stone cutters and other craftsmen. Joseph went to Nazareth there because there was work in the area. Bethlehem was a minor town which probably supplied sheep for the Temple. Perhaps after the census there was simply no way for Joseph to support his growing family so he planned to return to Nazareth where there was family and work.
Matthew has a more theological explanation. He quotes the prophet Hosea: out of Egypt I called my son, he is a Nazarene. Only in Matthew we are told that Herod intended to kill baby boys under the age of two in Bethlehem in an attempt to stop the Messiah from taking his throne. This “slaughter of the innocent” is analogous to killing newborns in Egypt in the book of Exodus. This leads to the “flight to Egypt,” although we are not told how long they remain in Egypt before returning to Galilee.
This fulfills the word of the Lord through Hosea, according to Matthew 2:14-15. While this does not seem like an appropriate use of the verse, the idea in Hosea is that Israel is God’s child who has taken refuge in Egypt, and after a period of time in Egypt he would be recalled back into the land of promise. Hosea is looking back at the story of the Exodus, where Israel was in Egypt for their protection and are called out of Egypt in order to enter the land.
Jesus is, in a very real sense, the Son of God. In another sense, Jesus is re-enacting the experience of Israel by fleeing from the land to Egypt and returning again at the direction of God. There are a number of parallels to the experience of Israel in the gospels, for example, he too will be tempted in the wilderness; on the cross Jesus takes the curse of the law on himself and pays for the nations rebellion himself.
That the family should settle in Nazareth fulfills another scripture for Matthew (2:21-23). This is a bit more problematic since there is no specific text which says that the messiah should be called a Nazarite, or as the NIV translates, a Nazorean. Nazareth was another extremely small, insignificant village, so it is unlikely that a Hebrew prophet would have predicted that he would come from this town, especially since the messiah was to come from the town of David. It is possible that the phrase does not mean that he would come from the town of Nazareth, but rather that he would be a Nazarite, someone who has taken a Nazarite vow. But again, no scripture really says that the messiah would have taken a Nazarite vow.
Another possibility is that the line in Matthew refers to Isaiah 11:1, which says that the messiah will be a “root from the stump of Jesse,” or a branch. The Hebrew word for root / branch is nezer, and Matthew is making a play-on-words with the name of the town (although these are two different words).
Another possibility is that Nazarene was slang for a person from a remote place (Blomberg, Matthew, NAC, 69 suggests this). Perhaps it is like saying that someone is from “Hickville.” Most regions have an “other side of the tracks,” Nazareth was proverbially on the wrong side.
Whatever the reason he was called a Nazarene, the title points to humble origins. As with his birth in Bethlehem, Jesus’ time in Nazareth is an indication that God will do great things through the Messiah who is hidden, who is small and insignificant at first (Matt 13:31-33).