The Bible records that a star led the wise men to Jerusalem at the birth of Christ:
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, 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 worship Him . . . When they heard the king, they departed; and behold the star which they had seen in the East went before them, till it came and stood over where the young child was (Matthew 2:1-2,9).
From this, we see that it was a star in the heavens that led the magi from the East to Jerusalem. From Jerusalem the star then appeared over the place where the child Jesus was. What was this star? Was it sent from God? What was its origin?
Supernova
Some have held the star to be a supernova. A supernova is a star that violently explodes and then proceeds to give off great amounts of light for a short period of time (a few weeks to a few months). But this is only a theory with no evidence to support it. Moreover this theory seems difficult to accept in light of
Matthew 2:9 which says the star stood over the place where Jesus was.
Halleys Comet
Others have speculated that it was a comet that passed overhead at that time. Halleys Comet has been suggested as a possibility. But the time of its occurrence, 12 B.C., is too early for the birth of Christ. Furthermore, a comet would not explain
Matthew 2:9.
Planetary Conjunction
Another theory holds that what the magi saw was a conjunction of planets. In 7 B.C. in the months of May, October and November, there was a conjunction of the planets Jupiter and Saturn in the zodiacal constellation of Pisces. We know that Jews living during the Middle Ages considered this planetary alignment to have Messianic significance. This could explain many details. If the magi saw the conjunction in May, the later alignments in October and November could explain
Matthew 2:9.
The problem with this view is that there is no solid evidence that the ancients referred to such an alignment as a "star." Furthermore, Jupiter and Saturn would have been one degree apart and not fused into the same image. Yet this theory is still a possible explanation of what occurred.
Supernatural Explanation
There are many who believe that the account as given in the Gospel of Matthew demands a purely supernatural interpretation. This would end the need for attempting to find an astronomical explanation of what the magi saw. God may have supernaturally provided the star in the East and then again over the house where the baby Jesus slept. Although the text does not necessarily demand that we take this position, it is entirely possible that we are dealing with a supernatural event that does not find any explanation in the history of astronomy.
Because the evidence is inconclusive we cannot be certain what it was that the magi saw or whether or not it was a supernatural phenomenon. We can, however, be certain that they saw something that was used by God to lead them to Bethlehem and the baby Jesus.