ST. PAUL, Minn. (CNS) — If it weren’t for the Gospel of Matthew’s brief reference to a star guiding Magi from the East to the newborn Messiah, “we wouldn’t know anything about the star of Bethlehem,” according to a Minnesota astronomer.

The Gospel account is the only historical reference from that time correlating a celestial event with Jesus’ birth, said Terrence Flower, a professor of physics at St. Catherine University in St. Paul who has delivered an annual public lecture about the star in the lead up to Christmas for more than 30 years.

“I think one thing you have to recognize is that the event (from an astronomical point of view) maybe wasn’t one that was earth-shaking and likely may not have even been one that was recorded with significant detail by others,” he said.

Still, even though the star of Bethlehem is only mentioned in a few verses of the Bible, it has become an integral part of our Christmas traditions — from the customary decoration we place atop our Christmas trees to its mention in popular carols such as “We Three Kings” and “The First Noel.”

What exactly did the Magi see that prompted them to make the long trek across the Middle Eastern desert to bring special gifts to the Christ Child?

It shouldn’t be surprising that a star was associated with the birth of the Messiah; a footnote in the New American Bible explains it was a common ancient belief that a new star appeared at the time of a ruler’s birth.

People of faith, of course, can’t rule out the possibility that God temporarily placed a special star in the sky to signal Jesus’ birth, Flower said. But science would have a difficult time proving such an extraordinary event.

Could the guiding light have been a phenomenon more familiar to sky watchers both then and now?

One idea is that the star of Bethlehem was a meteor — commonly known as a “shooting star.” But because of a shooting star’s ephemeral nature — even a spectacular one lasts for only a second or two — it wouldn’t have garnered much notice, Flower told The Catholic Spirit, newspaper of the Archdiocese of St. Paul and Minneapolis.

Another possibility is that the star of Bethlehem was a nova — a sudden brightening of a star that already exists — or a supernova, an extremely bright, exploding star.

A supernova is a fairly rare occurrence and probably would have been easily visible to the naked eye. Records indicate that a supernova was seen in about 126 B.C. and then not again until about A.D. 134, Flower said. If one occurred near the time of Jesus’ birth, it likely would have been recorded elsewhere in addition to the Gospel of Matthew.

A comet is another possibility, Flower said. Halley’s Comet, perhaps the best-known short-period comet, which is visible from Earth every 75 to 76 years, made an appearance in 12 B.C. That was too early, however, to coincide with Jesus’ birth, which, based on the known date of King Herod’s death in 4 B.C. and accounting for a mistake made when the Roman calendar was re-dated in the sixth century, likely occurred sometime between 7 B.C. and 4 B.C.

A better candidate, Flower said, is a conjunction of the planets Jupiter and Saturn that occurred three times in 7 B.C.

“Conjunction” is a term describing when two planets are closest together in the sky, as seen from Earth. At the time of Jesus’ birth, Jupiter and Saturn were among the five planets known to astrologers and sky watchers. The world “planet” means “wandering star”; planets are so named because they appear to move in relation to the set background of stars.

The triple conjunction of Jupiter and Saturn occurred in May, October and December of 7 B.C., Flower said.

The Magi — believed to be wise men or astrologers from the East — would have viewed this as a significant event for several reasons, he noted. In ancient times, Jupiter was considered the star of kings, Saturn was the protector of Israel, and the constellation Pisces — where all three conjunctions occurred — was associated with the land of the Jews.

So when the Magi saw this “star at its rising” — meaning they saw it rise in the morning sky — they may have considered a trip toward Jerusalem, where they may have thought that a significant event was about to take place. Bethlehem is only six miles from there.

Reflecting on what the star of Bethlehem might have been offers insights into part of the Christmas story, Flower said. But it shouldn’t overshadow the real meaning of the feast.

“A star is not what Christmas is about. The star, on one hand, is a guide to the Wise Men and, on the other hand, is an announcement of something important,” he said. Ultimately, though, it only serves to shed more light on what the main focus of Christmas is: the birth of Christ.