Dear Mary:

This subject is under debate. There are several theories that have been posited over the centuries.  Fist let us examine the nine biblical attributes of the Star of Bethlehem found in Matthew chapter 2:

• The star signified birth, it signified kingship, it was related to the Jewish nation, and it rose "in the East"; [verse 2]
• King Herod had not been aware of it; [verse 5]
• It appeared at an exact time; [verse 7]
• It endured over time; [verses 2-10]
• It was in front of the Magi when they traveled south from Jerusalem to Bethlehem, and then it stopped over Bethlehem. [verse 9]

The various theories to explain the Star of Bethlehem include:

• Comet: There were no comets visible around the time of the birth of Jesus (thought to be around 3-2 BC. One person postulates a possible comment appearing in 6 BC. In any event, comets were generally interpreted as bad omens.
• Supernova: A very recent theory is that Star of Bethlehem was a supernova in the Andromeda Galaxy.
• Planetary conjunction: In 3-2 BC there was a triple conjunction of the planet Jupiter (the king planet, called "Sedeq" in Hebrew, meaning "righteousness", a term also used for the Messiah), Venus (symbolizing love and fertility), and the star Regulus (also called the king star). This conjunction could be interpreted by astrologers (the three wise men, the Magi) as the coming of a Hebrew King. It is thought that the wise men in the east, however, could not have seen this conjunction as it occurred at sunset. 

There are other theories. None of these theories quite fit the biblical description of the Star of Bethlehem.

Two other theories may be closer to the truth.

Pious fiction: This theory suggests that Matthew recorded this story as a creation to establish Jesus as the Messiah. It was an apologetic "literary license" to to help tell the story of who Jesus was.

Miraculous Event: St. John Chrysostom favored the view that the Star was a miracle. He said,  "How then, tell me, did the star point out a spot so confined, just the space of a manger and shed, unless it left that height and came down, and stood over the very head of the young child? And at this the evangelist was hinting when he said, "Lo, the star went before them, till it came and stood over where the young Child was."

In my opinion the Star of Bethlehem was a miraculous event. The planetary conjunction of Jupiter, Venus, and the star Regulus is intriguing, and may fit the nine attribute listed above. But, if it is true that the Magi could not have seen this because it was obscured by the sunset, what other explanation is possible? Thus, so far, barring new astrological evidence, the miraculous explanation is the one most likely.

The bottomline is that we really do not know.

I hope this helps.

God Bless,
Bro. Ignatius Mary