Matthew’s account of an extraordinary star light during Jesus’ birth has drawn the attention of laymen and astronomers for years. As a key symbol of Christmas, it is not surprising that almost 250 major scholarly papers have been published in the last 100 years, attempting to provide a solid scientific explanation behind the star of Bethlehem.

Among the possibilities given are the occurrence of a nova, a comet, the Aurora Borealis (northern lights) and a zodiacal light. But the triple planetary conjunction theory is more widely accepted both for its astronomical justification and astrological meaning.

In the early 17th century, the German imperial mathematician and astronomer Johannes Kepler calculated a triple conjunction of Jupiter and Saturn occurring in 7-6 B.C. (the birth year of Jesus). A planetary conjunction happens when celestial bodies position on the same degree of longitude while a triple conjunctions refers to two or three planets making such conjunctions three times within a year.

According to Kepler, the first triple conjunction began about the end of February in 7 B.C., when Jupiter moved out of the constellation Aquarius towards Saturn in Pisces. On May 29, visible for almost two hours in the morning sky, the first close conjunction took place in the 21st degree of Pisces. The second appeared on October 3 in the 18th degree of Pisces while the third on December 4 in the 16th degree of Pisces. Mathematical calculations established further the rare three-fold planetary conjunction was particularly visible in the Mediterranean area.

Kepler, who formulated the planetary laws named after him, though not convinced himself that the phenomenon was the actual “Christmas star”, believed that the phenomenon prompted the three Magi about a coming star.

Choosing to live

The Magi, as skygazers of the east, would have attached special significance to each planetary body. Pisces in Jewish tradition is the symbol of Israel. Jupiter is thought as a lucky and royal star while Saturn is the symbol for the protector of Israel. With these astrological signs, the Magi would have interpreted the star to mean that “the king of Israel and a ruler of the Universe was about to be born in Israel.”

The Magi could have observed the first conjunction and calculated the second encounter. So they started out on their journey west to Judea. By the time the second conjunction had taken place, they had visited Herod who directed them to Bethlehem, and traveling through a caravan they would arrive in Jerusalem towards the end of November, just in time for the third conjunction.

Kepler’s fascinating discovery was published but eventually lost prominence until 1925, when the German scholar P. Schnabel deciphered a Neo-Babylon cuneiform from the ancient School of Astrology at Sippar (now Iraq). The cuneiform tells about the positions of Jupiter and Saturn in the constellation of Pisces over a five month period in 7 B.C., which confirms Kepler’s point.

Experts agree that a triple conjunction is more plausible than the sudden appearance of a spectacular star as told by tradition.

Other theories

While Kepler’s theory seems to wrap things up nicely, experts argue that the conjunction was never close enough to be mistaken as a single object, as Matthew definitely describes “a singular bright star.”

It is unlikely that a nova or a comet is the star of Bethlehem, according to Dr. Augusto Morales of the College of Science Department of Mathematics and Physics.


A nova is a dwarf star that literally explodes, which may increase in brightness a thousand to a million times. Apart from the unavailability of Western and Chinese records of a nova during Christ’s birth, there is no known supernova remnant at the birth of Jesus, according to astronomers.

The comet theory began with Origen, the Christian apologetic who mentioned it in 248 AD. Comets have tails and these can be imagined to point a direction. However, comets are known to last only less than an hour.

“Comets are short-lived, while a nova does not move,” Morales said.

The authenticity of every astronomical explanation hinges on the real date of Christ’s birth and unless experts could arrive at a concrete date, the search for the star of Bethlehem will continue. With reports from Werner Keller’s The Bible as History.


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