Physicist ponders the Christmas star

Author: Margaret Fosmoe, South Bend Tribune

By Margaret Fosmoe South Bend Tribune | Posted: Sunday, December 8, 2013 6:21 am

SOUTH BEND -- If a very bright star lit up the sky 2,000 years ago when Jesus Christ was born in Bethlehem, what caused it?

A physicist doesn't just wonder about such a question. He studies it.

In the Christian tradition, the Gospel of Matthew and Luke says that when Jesus was born in the days of King Herod, three 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."

A particularly bright star in the sky over Bethlehem 2,000 years ago might have been a comet, a nova, a supernova or an alignment of the planets, Grant Mathews, an astrophysics professor and researcher at the University of Notre Dame, told an audience Saturday afternoon in the digital visualization theater in Jordan Hall of Science.

It was one of three presentations Mathews gave this weekend about the Christmas Star. His lecture on the topic has become an annual tradition on campus.

The wonders of modern science -- including 10 computers and two projectors in the digital visualization theater -- allow people of today to "visit" the past and see what the night sky looked like at any time, including two millennia ago.

"In a sense, it's like a time machine," Mathews said, as images of the constellations shone upon the theater's domed ceiling.

It is likely that the wise men -- the Magi -- were from Babylonia or Mesopotamia, which would have made it about a 500-mile journey to Bethlehem. If they followed a bright star, it might have been a recurring phenomenon or it could have gone behind the sun and emerged later on the other side, according to Mathews

The problem with theories that the Christmas star was a comet, nova or supernova was that all three in ancient times were "considered to be harbingers of disaster," Mathews said. Three kings wouldn't have eagerly traveled hundreds of miles following a star that was seen as a evil omen, he said.

The three kings probably were Zoroastrian priests, scholars of astrology, Mathews said. Based on their knowledge of the constellations of the zodiac, they might have seen a particularly bright star in the east and interpreted it as a sign of a regal birth in Judea, he said. Zoroastrians believed each constellation was related to a time of year and a specific region of the world, he said.

Several planetary alignments mentioned in ancient records have been proposed as the Christmas star, with the two most significant such alignments occurring in about 4 to 8 B.C., the professor said.

One occurred on Feb. 20, 6 B.C., involving an alignment of Mars, Jupiter and Saturn in the constellation Pisces, he said. The other occurred on April 17, 6 B.C., when the sun, Jupiter, the moon and Saturn all were aligned in Aries, while Venus was nearby in Pisces, and Mercury and Mars were nearby in Taurus.

It was quite likely that the Christ child was born in another time of year, perhaps spring, Mathews said. The firm date of Dec. 25 on which Christians have long celebrated was set by the Catholic Church more than 500 years after Christ's birth, he said.

In the end, it is impossible to say for sure what physical phenomenon produced the Christmas star, but the planetary alignment theory seems the most likely, according to Mathews

The event also included a video presentation, "A Season of Lights," describing how winter solstice festivals came to be and how they eventually merged with the annual celebration of Christ's birth.