Exactly 2,000 years ago, according to a widely accredited source, a celestial body rose in the east and guided three eminent thinkers to the scene of an event that was to change the world. Since then, astronomers and theologians have been baffled as to the precise nature of the star which, as told in the Gospel of St Matthew, led the Magi to where Christ was born.
Was it a miracle, a divine intervention to herald the birth of Christ? Or was there some actual astronomical event that gave rise to the story of the Star of Bethlehem? The question has intrigued scores of writers and artists as diverse as the astronomer Johannes Kepler and the painter Giotto.
Now a British astronomer based in Spain has come up with a theory which, he believes, could lay the mystery to rest.
In his book, The Star of Bethlehem, Mark Kidger of the Instituto de Astrofisica de Canarias in Tenerife examines evidence drawn from modern Biblical scholarship, recent findings in space and ancient Chinese history to suggest that conclusive proof of the star's existence could be at hand.
Mr Kidger begins by arguing that the Nativity well have taken place at some time in March or April rather than in December.
Christ's birth is said to have taken place while shepherds were watching their flocks at night, he says, something that takes place at lambing-time in the spring rather than in the depths of winter. Moreover, if the local inns were full, as Matthew insists, this would be because of the Jewish Passover, which also occurs in the spring.
Mr Kidger thus concludes that Christ was born some time around March in 5 BC, taking account of the generally accepted fact that the inventor of the Christian calendar, the 6th century monk Dionysius Exiguus, was five years out in his calculations.
Mr Kidger dismisses the notion that the "star" could have been an unusual sighting of Venus, or perhaps Halley's Comet or a meteor shower. For his "best guess" he looks to an ancient Chinese chronicle called the Ch'ien-han-shu which states that an object, probably a nova, or new star, was observed in March in 5 BC and remained visible for 70 days. The object would have appeared in the east and remained in the sky long enough to have guided the Magi - Babylonian astrologers, according to some scholars - across the desert to Bethlehem.
"It's hard to believe the Star of Bethlehem could have been anything else," Mr Kidger says of the nova, citing the coincidence in date, the duration of visibility and its position in the sky. And proof of its identity may soon be possible.
In 1925 a nova now known as DO Aquilae was seen very close to the position in the sky given by the Ch'ien-han-shu. It was not visible to the naked eye, but Mr Kidger believes an earlier, greater explosion of the same star could have been the Star of Bethlehem. "But whatever it was, we are probably close to being able to identify the Star of Bethlehem," he says. "If it was a nova, the telltale cloud of hydrogen gas that it ejected is probably still just detectable, and will one day give the star away."