What was the star of Bethlehem?

Could there be an astronomical explanation for the story of the star of Bethlehem?

StarBethlehem header

Three wise men pointing at the star of Bethlehem is an iconic Christmas image. But will astronomers ever be able to determine exactly what the ‘star’ was?
© iStock


The Gospel according to Matthew contains one of the most famous passages in the Bible: “Where is he that is born King of the Jews? For we have seen his star in the East, and we have come to worship him.”

But just who were the magi who are quoted in St Matthew’s Gospel?

And what exactly was this ‘star’ that was so amazing it persuaded these wise men to travel across hundreds of miles of desert?

Sadly, we can immediately rule out the blazing celestial orb that adorns our Christmas cards.

Since 221BC, Chinese astronomers had been recording everything that unexpectedly disturbed the tranquility of the night sky, including ‘broom stars’ (comets) and ‘guest stars’ (novae and supernovae).

But there’s no mention of any such ‘guest stars’ around the time that Jesus was supposedly born.

The Chinese did report a ‘broom star’ that swept across the sky in 12BC – none other than Halley’s Comet.

An unforgettable view of Halley’s Comet in 1301 inspired Giotto di Bondone to paint one of the most famous depictions of the Star of Bethlehem, as a blazing comet hanging over the stable.

But 12BC was too early for Halley’s Comet to have been the Star.

Cambridge scientist Colin Humphreys believes Chinese astronomers spotted another comet in 5BC, but oriental records tell us it was a dim specimen, unlikely to coerce the wise men away from home.

The very phrase ‘wise men’ gives us a clue to what might have triggered their great journey.

This is a modern translation of the word Greek ‘magi’, which also gives us our words ‘magic’ and ‘magician’. The wise men were actually astrologers.

They were not interested in exploding stars or comets, but looked instead at the motion of the planets.

And in 7BC, the planets Jupiter and Saturn performed a very unusual tango.

Three times that year – in May, September and December – they came close together, and then parted again.

This triple conjunction would have intrigued the magi, but would have meant nothing to Herod’s counsellors or to the Chinese skywatchers.

It was the German astronomer Johannes Kepler who first mooted this idea.

He based it on a conjunction of Jupiter, Saturn and Mars that he observed in 1604, when a brilliant star – a supernova – suddenly appeared near them.

An image of Halley’s Comet captured by the European spacecraft Giotto in 1986. Did the famous comet prompt the story of the star of Bethlehem? Credit: Halley Multicolor Camera Team, Giotto Project, ESA
An image of Halley’s Comet captured by the European spacecraft Giotto in 1986. Did the famous comet prompt the story of the star of Bethlehem?
Credit: Halley Multicolor Camera Team, Giotto Project, ESA

Star of wonder…

Sheffield astronomer David Hughes championed a version of this theory in his 1979 book The Star Of Bethlehem Mystery.

Dismissing the idea of the supernatural star, he proposed that the magi were inspired by the triple conjunction of Jupiter (the King of the Planets) and Saturn (Planet of Justice) in Pisces – the zodiacal sign of the Jewish nation.

The magi didn’t even need to see the conjunction, though, as they could have calculated what the planets were up to.

This prompted American historian Michael Molnar to calculate all the planetary conjunctions at that time.

The result? An even more remarkable event invisible to the naked eye.

On 17 April 6BC, Jupiter was rising just before the Sun (an important time known as heliacal rising), when it was occulted by the Moon.

It was a rare and astrologically important event, supposedly foretelling a royal birth.

However, none of the explanations is particularly convincing.

The planetary conjunction doesn’t match Matthew’s description of a single star, nor the fact that the star “went on before them until it came and stood over the place where the child was”.

There’s another problem too, as Matthew’s gospel repeats almost exactly an ancient Jewish account of the birth of Abraham:

“When the astrologers of Nimrod left the house, they lifted up their eyes towards Heaven to look at the stars, and one great star came from the east and ran athwart the Heavens.”

Matthew was writing soon after a genuine expedition of Eastern magi, led by the Armenian king Tiridates, had arrived in Rome.

They had fallen at Nero’s feet, exclaiming: “I have come to you, my god, to worship you” – just as the wise men, according to Matthew, “saw the Child with Mary, and fell to the ground and worshipped him”.

This was in AD66, when Halley’s Comet was blazing in the sky. So perhaps, ironically, Halley’s Comet did have a role in the Nativity story, in inspiring Matthew.

It prompted him to furnish his account with a special star that matched Abraham’s prenatal spectacle and upstaged Tiridates’s adoration of the pagan Nero.

As a devoted biographer, Matthew was compelled to write a brilliant Star of Bethlehem into his script!


Ultimately, however, it’s unlikely we’ll ever know the true mystery of the star of Bethlehem for sure…

This feature originally appeared in the December 2010 issue of BBC Sky at Night Magazine.