"1After Jesus was born in Bethlehem in Judea, during the time of King Herod, Magi from the east came to Jerusalem 2and asked, "Where is the one who has been born king of the Jews? We saw his star in the east and have come to worship him." Matthew 2:1-2
These Magi from Persia, specifically Babylon, were astrologers. They saw a star and equated it to the birth of a king in Israel. Why?
At this point in history, Jewish people had been living in Babylon for 500 years. As well as astrology, the magi were versed in literature and tradition. They knew the Jews were awaiting a Messiah. The Roman historian Suetonius wrote: "there had spread over the Orient an old and established belief, that it was fated at that time for men coming from Judea to rule the world."
So what are the possibilities of the star?
1. It could have been a divinely caused miracle.
2. It could have been a super nova--a star exploding, visible over a period of months.
3. Hally's Comet blew past in 11 BC
4. In 7 BC there were three separate conjunctions of Saturn & Jupiter: that would have been pretty bright.
5. For four years--5 to 2 BC--the Dog Star, Sirius rose brightly on the first day of the month the Persians called Mesori, meaning; "Birth of a Prince." It appears that Sirius was equated with Israel.
But wait, all these events happened before 0 BC/AD. DING-DING-DING! You are correct! It turns out that whoever developed the Julian calendar used in the West did a good job, but not a great one. He was off by a few years. It appears that Jesus was born several years--we can't fix it definitely--before the BC/AD crossover. However, Hally's 11 BC pass is most likely too early.
As astrologers, the magi looked for fixed signs in the heavens to foretell events. Had the star been simply a single, miraculous event, the Magi would have been impressed, but would not have made the assumption that it referred to Messiah. So I have to put my money with #5: Sirius rising on the first day of the month "Birth of a Prince" in the land of Israel. Viola, "Where is the one who has been born king of the Jews? We saw his star in the east and have come to worship him."