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 we are come to worship him . . ."Then Herod, when he had privily called the wise men, enquired of them diligently what time the star appeared. . . . When they heard the king they departed; and lo, the star, which they saw 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. - Matthew 2:1-10

In its customary use as a bright focal image on Christmas cards and decorations, the Star of Bethlehem may seem an innocuous thing. But for Biblical scholars, scientists, historians and theologians, it is a source of thorny controversy.

The question is, was there ever actually such a phenomenon as the Star of Bethlehem, and if so, is there a scientific explanation for it?

Despite centuries of head-scratching and poring over documents, no one has yet come up with a satisfactory answer. Computers have recently joined the discussion with their ability to reckon the positions of heavenly objects 2,000 years ago with exquisite precision.

Hypotheses include comets, meteors, ball lightning, supernovae, unusual groupings of bright planets, and - the last, best refuge of the Biblical scholar - simply a miraculous apparition that was visible to the Wise Men and no one else.

A bibliography of serious writing on the subject compiled by Ruth Freitag of the Library of Congress runs to more than 350 entries. About a third of them are full-length books.

But original documentation of the event is scanty. In fact, the only reference, scriptural or otherwise, is the one passage from the Gospel according to St. Matthew, above.

If the star had been a conspicuous phenomenon, the sort of thing that brings folks pouring out of their houses to watch, one would think it would have rated mention in other writings of the time.

So far as is known, it did not. Even St. Matthew's report presents problems. For one thing, it is not exactly an eyewitness account. Scholars reckon that it was written as recorded oral history about A.D. 70. The oldest surviving manuscripts are from several centuries later.

For another, neither St. Matthew nor any other Biblical account provides enough data to be very helpful to scientists in trying to pinpoint the time and location of the event. And for astronomers, time is of the essence.

For instance, was the star in the east, or did the Wise Men see it when they were in the east? Matthew's account can be read either way.

Who were the Wise Men and what country did they come from? The Bible does not say.

Nor does it say how many Wise Men there were. The notion that there were three took shape about 300 years after Jesus' birth and seems to have been inferred from the account, also in Matthew, that they brought three gifts, of gold and myrrh and frankincense.

Greek Orthodox tradition favors 12 Wise Men, and some post-Biblical writings give figures as high as 14. It was not until about the sixth century that they began being called kings and were given the names Gas-par, Balthazar and Melchior.

The most widely accepted conjecture is that the Wise Men came from Persia or Mesopotamia - today's Iran and Iraq - not because the Bible says so, but because star-gazing was big in those countries in those days.

What time of year did the Nativity take place? Nothing in the Bible specifies, and scholars have struggled in vain with the question. The only clue in scripture is the passage in Luke about the shepherds in the fields, watching over their flock by night. It suggests lambing season, which would be early spring.

Most scholars agree that Dec. 25 wasn't designated Jesus' birthday until about three centuries after the event.

What year was Christ born? This is an even tougher one. The scriptural chronology puts it in the lifetime of Herod, the puppet tyrant of Judea, but when that was, exactly, is unclear.

According to Flavius Josephus, the great Jewish historian who lived in the first century, Herod died shortly after an eclipse of the moon. Astronomers have calculated there was a total eclipse the night of Jan. 9, 1 B.C., which indicates Jesus was born sometime before that.

How soon after the birth of Jesus did the Magi arrive? The next day? Twelve days later? A year? Again, there is no indication in the Bible except that it was while Herod was still living.

When Herod sent his hit men to Bethlehem to butcher every baby boy under the age of 2, was it because his soothsayers had warned him that the future king of the Jews had been born sometime in the previous 24 months? Or was Herod just giving himself a comfortable margin of safety? Again, the Bible doesn't say.

Back to the star. Ancient Chinese chronicles described a bright object in the sky in the spring of 5 B.C. that remained visible for 70 days. The Chinese chroniclers called it a comet, but according to their description, it did not creep across the sky as a comet should, but stood in one place.

About 10 years ago, a trio of English astronomers said the event the Chinese described was a nova and that that could have been the Star of Bethlehem.

The more popular notion nowadays is that the star was actually one of three conjunctions of Jupiter and Saturn that occurred in 7 B.C., or perhaps all three of them.

The theory was first put forth by the great German astronomer Johannes Kepler, who recorded a similar event in 1603 and was able, with the application of mind-numbing mathematical gymnastics, to show when it had occurred previously.

The problem with the conjunction hypothesis is that a conjunction is not a very spectacular event. It means only that the objects are lined up, one above the other, in the purely artificial grid system astronomers and astrologers use.

Typical of scholars who consider the jury still out is LeRoy Doggett, an astronomer at the U.S. Naval Observatory in Washington. Among Doggett's Christmastime duties is to field Star of Bethlehem inquiries from members of Congress.

"I don't prefer any theory," says Doggett, a touch of weariness in his voice. "There's not enough evidence in support of any of them for me to vote for it.