The curious phone calls about the Star of Bethlehem -- the Christmas beacon the Bible says led wise men to a cradle where the baby Jesus lay -- are part of the holiday season at planetariums and university astronomy departments around the country.
"It happens every year," said David van Blerkom, chairman of astronomy programs at the University of Massachusetts in Amherst. "They want to know if it was real, what it was, will it happen again."
And astronomers since Johannes Kepler in 1604 have put considerable energy and imagination into explaining the Christmas star, despite a sketchy historical record.
One long-time researcher of the Star of Bethlehem is Karlis Kaufmanis, a retired astronomy professor at the University of Minnesota.
"I truly believe the star was real and not a creation of imagination, as some astronomers think," said Dr. Kaufmanis, 80, a native of Latvia.
The "facts" are presented in a single source, the second chapter of the Gospel of Matthew in the Bible:
"Now, when Jesus was born in Bethlehem of Judea, in the days of Herod the king, behold, there came wise men from the east to Jerusalem, saying, Where is he that is born King of the Jews? For we have seen his star in the east, and are come to worship him.
"And lo, the star, which they had seen in the east, went before them, till it came and stood over where the young child was. When they saw the star, they rejoiced with exceeding great joy."
For centuries, the Star of Bethlehem was accepted by believers as a religious miracle, a "divine phenomenon to announce the arrival of the Son of God," Dr. Kaufmanis said.
But with the advent of scientific inquiry, astronomers began trying to fit the events related in Matthew to known celestial observations.
"There are two basic problems here," said LeRoy Doggett, an astronomer at the U.S. Naval Observatory in Washington. "It's impossible to pin down from the biblical description enough details of the star, and it appears equally impossible to determine when Christ was born."
Theologians long ago gave up the belief that Jesus' birth day was in 0 B.C. (or A.D. 0). Present scholarly thinking places the event between 8 B.C. and 4 B.C.
And that time frame, according to researchers, produced a number of astronomical phenomena that fit the description of relatively bright, temporary objects recorded by Chinese observers and others.
More appealing to astronomical detectives are a number of planetary "conjunctions," or alignments of planets as seen from Earth.
One involved Jupiter and Venus in 2 B.C., and the astrological symbolism is powerful: Jupiter was associated with the birth of kings, Venus with fertility. The conjunction took place in the constellation Leo the lion, connected in the Old Testament with the Jewish people.
But it's another planetary lineup that now seems most popular among astronomers in explaining the Christmas star. Ironically, it's the same conjunction noted by Kepler.
A rare "triple" alignment of Jupiter and Saturn in 7 B.C., it involved a series of three crossings of the planets between April and December. Saturn was considered the protector of the Hebrews; it rose with Jupiter in the constellation Pisces, also with strong Jewish symbolism.
Dr. Kaufmanis calls this scenario "the closest to the events that ,, took place."
Some astronomers support the April date in 7 B.C. as Jesus' birth day because the shepherds mentioned in the Bible, "watching their flocks by night," would have had their sheep out under the stars only in the spring, not in the cold of December, they say.
But there are more basic disagreements than that among Christmas star researchers, leaving little hope for a consensus.
Patrick Moore, a British astronomer, wrote last year that the star "almost certainly" did not exist and was probably a story "invented or picked up" by Matthew.
And two astronomers at Illinois State University -- Sherman Kanagy and Carl Wenning -- raised eyebrows among their colleagues in 1980 when they came out against the scientific explanation and suggested the star was, indeed, a divine manifestation.
Dr. Doggett wearily points out that the issue rightfully belongs in the lap of biblical scholars who "understand the context of that period, not with astronomers. It's a problem that involves religious symbolism, questions of interpretation."
The wise men, the Magi, were apparently the only mortals to recognize the Christmas star, and researchers have concluded they were learned astrologers, alert for a sign of the Messiah's birth.
"How can you prove it or disprove it?" asked Dr. van Blerkom. "Astronomers want what they do to be at least partially verifiable by observation, and you can't do that with this.
"Let people have their mysteries," he said. "I prefer to leave it as a miracle."