The Real Star of Bethlehem: A Christmas Special The Sky at Night

Christmas means different things to different people.

To some of us, it's about tradition.

For others, it's family and presents.

And for some, it's about the religious message that underpins it all.

But this is an astronomy show, and there's one piece of the Christmas story

that is particularly relevant to us - the Star of Bethlehem.

So tonight, we're going in search of the Christmas Star.

We'll be looking for the real astronomical phenomena that

could have caused a new star to appear 2,000 years ago.

The candidates are some of the most exciting objects in the night sky.

Welcome to a Sky at Night Christmas special.

Astronomers have been speculating about the cause of

the Star of Bethlehem for centuries.

And there have been all sorts of suggestions as to

what it might have been.

And they've varied from the plausible to the ridiculous.

Could it really have been a UFO?

Well, probably not.

But tonight we've whittled the list down

to the six most plausible candidates.

And over the course of the programme with the help of our experts,

we'll be presenting the case for each of these six possibilities.

In order to choose the most likely explanation, we'll be

reconstructing the skies over Jerusalem 2,000 years ago...

This coming together of these two planets,

I interpret as the Star of Bethlehem.

..and examining the case for all the prime candidates.

And above the stable, poised majestically in the sky, is a beautiful comet.

Dallas Campbell will be sifting through the archaeological

and the historical evidence for events in the skies of the Middle East two millennia ago.

This is real historical evidence

to say at that time, there was an astronomical event that was

important, that people wrote down, that would have looked spectacular.

And finally, Maggie and I will assess the evidence and make

our choice as to what we think the Star of Bethlehem might have been.

But first, Chris introduces perhaps the most dramatic of our six candidates.

The typical Christmas-card image of the Star of Bethlehem

is of a bright new star that suddenly blazes to life in the sky.

That's an event we know can happen in nature -

because in 1604, that exact phenomenon was observed

by Johannes Kepler, one of the greatest astronomers of them all.

His record of the event can still be found in the library

of the Royal Astronomical Society.

And this wonderful book contains Kepler's writings on the subject.

It was printed in 1606.

It's one of only 35 copies left in the world - so I'm going to

be very careful with it and try and turn to the title page.

And we can see that the title is "Stella Nova In Pede Serpentarii".

That's "The New Star in the Foot of the Serpent Bearer" - that's the constellation we call Ophiuchus.

In fact, to confirm that we don't need the title -

we can turn on to Kepler's own star map.

Here it is.

You can see the familiar constellations

and there's Ophiuchus with his serpent wrapped

round him, and the new star is down here in his foot, marked N for new.

And Kepler described this star as like a torch blown by a strong wind.

He said it was the most beautiful and glorious star ever seen.

So he was clearly impressed with his discovery, both from

a sort of scientific point of view, but also, remember, he was

a devout Christian, he believed in astrology, and so a new star must

mark something significant happening on Earth or in the heavens.

If we flick on, we can see him

writing to an adviser to the court of Rudolph II, to whom the book is

dedicated, and he says, "The star that led the Magi" - the wise men -

"to Christ's manger might have had some relation to our star."

In other words, he thinks he's just seen the modern equivalent of the Star of Bethlehem.

What Kepler didn't know was what had caused the new star to appear.

Today, we know it was not caused by a star's birth,

but by its violent death.

A supernova.

This is how the most common type of supernova works.

A star is always in danger of collapsing in on itself, due to its own gravity.

The only thing that stops this is the energy produced by fusion taking place in its core.

This provides an outward pressure which keeps the star stable.

When it runs out of fuel, it can no longer resist its own gravity

and it collapses and rebounds in a massive explosion.

It releases as much energy in that single instant as our sun

will release in its entire lifetime.

It suddenly becomes brighter than tens of billions of ordinary stars.

This picture shows a supernova almost outshining an entire galaxy.

And poetically, the explosive death of these stars are ultimately

responsible for the creation of life, as they spread the elements

essential for life throughout the universe.

Supernovae aren't rare.

In fact, it's thought that throughout the universe, ten occur every second.

But most of these are too distant to notice

and they can only be picked up by the most powerful telescopes.

But sometimes, every few hundred years,

a supernova occurs within our own galaxy.

We know from Kepler's accounts that a nearby supernova is

one of the most impressive sights in the sky.

But we have not seen anything like it since 1604.

All we can find today are the traces that supernovae leave behind.

This is the remnant left by Kepler's Supernova.

And this is the Crab Nebula, a cloud of gas and dust, created by another

supernova explosion that appeared in the skies 500 years earlier.

When the light from this explosion reached Earth 1054,

it was as if a new star suddenly appeared in the night sky.

It blazed as bright as the moon for two years before fading.

But it made a huge impression on the people of the time.

And a new star was recorded by the Chinese, the Japanese

and also in the Middle East.

These rock paintings in the American South West are thought to

show the position where the supernova appeared in the sky.

Just like Kepler's Supernova, the 1054 event had made a huge impact.

That's why I think that a supernova is a great candidate to be

the Star of Bethlehem.

If a supernova had occurred 2,000 years ago, it's easy

to see why people would have taken it as an omen of great events happening here on Earth.

A bright supernova appearing suddenly

does seem to fit all the facts -

that's why it's been such a popular explanation for more than 400 years.

But to really find out what the Star of Bethlehem was

or whether it existed at all,

we need to find an accurate description in the historical record.

And so, we've sent Dallas Campbell to see what he could dig up.

The first place to start searching for a record of the star is,

of course, in the Bible.

Even there, it's only mentioned in one place -

in the Gospel of St Matthew.

"When Jesus was born in Bethlehem of Judaea in the days of Herod

"the King, wise men from the East came 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.'

"Then Herod privily called the wise men,

"and learned of them exactly what time the star appeared.

"And they, having heard the King, went their way, and lo,

"the star, which they saw in the East, went before them,

"till it came and stood over where the young child was.

"And when they saw the star, they rejoiced with exceeding great joy."

And that is it. We just have those few paragraphs.

The wise men, they see the star, which brings them to Jerusalem.

We don't know who they are, we don't know how far they've come.

They then see the star again,

which leads them to nearby Bethlehem.

As a piece of writing, it's poetic,

but as a historical document, it doesn't give us a lot to go on.

The Gospel According To St Matthew was written at least 70 years after

the events it describes.

So if I want a more reliable historical document,

I'm going to have to look elsewhere.

The problem is where and when to look, because of course,

we're not entirely sure when all this happened.

One thing we are sure of

is that the Star of Bethlehem didn't appear on 25th December, zero AD.

I've come to see the Reverend Robin Griffiths-Jones to see if he

can tell me where in the historical records I should be looking.

Let me ask you about the birth of Jesus.

Why do we think Jesus was NOT born on 25 December, 2,015 years ago?

This is the kind of date we have - but it's arbitrary, isn't it?

It is slightly arbitrary. We'll do it in two stages.

First of all, we do the time of year.

So why do we think he was born on the 25th December?

The Romans - the pagan Romans celebrated the end of December

with huge festivities - the Saturnalia,

the god Mithras, the winter solstice, everything gathered around this dark, cold time of year

as they looked forward to the future and the next year.

And so, it's easy. You see what happened - the Christians simply took over and Christianized this.

And we're happy with that. Can we be more specific about a year?

Just in terms of what we're looking for here.

-Of course you do - you want the year.

-Can we narrow it down?

Obviously, the calendar itself that we're working with presumably post-dates that anyway.

Of course it does, yes.

-We've plumped for the present dating...

-OK.

..which makes this year 2015,

based upon the calculations of an extraordinary monk called

Dionysius Exiguus. He did an extremely complicated

calculation of the dates of Easter for the 95 years

leading on from his own time in AD 525.

And while he was about this, he realised it was an opportunity

to recalibrate the entire dating system of the world, of the then-Christian world.

It had previously been based on the years of the Emperor Diocletian,

a persecutor of the Christians.

And AD had meant Anno Diocletiani - the year of Diocletian.

Dionysus would have none of it, he was going to start with

the year of Domini - the Lord.

-And so, he had to calculate the year of the birth of Jesus.

-Right.

And he reckons that Jesus was born 753 years after the foundation of the city of Rome.

Bingo! But he didn't get it right. He didn't get it right.

We know actually a couple of mistakes he made,

which meant he ended up about four years out.

This is good news, because we know that Jesus was born

while Herod the Great was still alive.

-Herod the Great died in 4BC, almost certainly.

-OK.

We know when he died, because we're told he died after a lunar eclipse, shortly before Passover.

And we know there was a lunar eclipse in 4BC, one month before Passover.

-Bingo.

-And that's reliable -

-it's interesting we're looking at astronomical events to date.

-We really are. Indeed, we are.

Can I ask you about this star?

You're not bothered it had to be on the day of his birth.

-Oh, good heavens, no!

-OK, well...

It might have been a year before Jesus was born.

Two years before Jesus was born.

So if I'm going to continue my search to look for some

kind of astronomical event,

if Herod died in 4BC, where does that leave us?

Well, I think we're likely to look at the two or three years before.

-So let's make seven to four the main inquiry.

-Seven to four. OK.

Thank you very much indeed.

-You've given me some more clues.

-I hope so.

-Thank you, Robin.

Real pleasure, real pleasure.

Well, hopefully that gives us

a little bit of a clearer idea in terms of an actual date.

Our next task is to find out

what was going in the night sky at that time.

That is, if the star existed at all!

I kind of think there was something

that took place in the Near East around the time that Jesus

was born, that the writer of the Gospel of Matthew was drawing on and building up in terms

of a meaning story - but he wasn't creating it out of nothing.

The idea that the heavens would indicate

something big was going to happen was seen as perfectly normal.

You've got to bear in mind, of course, at that time,

many, many things could not be predicted - life, death, famine,

harvest failure, things of that sort,

and it was very easy, after the event, that you might say,

"Oh, yes, just before the flood came, just before the harvest failed,

"there was a comet, there was a conjunction, there was something like that."

So people were always looking heavenwards to try to understand not

just how the world worked, but why it worked in the way that it did.

History suggests that we should be looking for an event that

happened in the sky between 7 and 4BC.

But what sort of astronomical event would have attracted

the attention of the wise men, or the Magi, as they were known?

Some of the possibilities, like supernovae, would have been very dramatic.

But Chris has been investigating a more subtle possibility.

Not all the candidates to be the Star of Bethlehem are stars.

Some believe that the thing that set the Magi on their journey was

an alignment of planets.

So I've come here to the Royal Observatory, Greenwich,

with its Peter Harrison planetarium, to simulate the night sky

at the time of Jesus' birth.

Astronomer David Hughes has been studying

the Star of Bethlehem for over 30 years and he thinks he's located it

in an event that occurred in the skies above the Middle East in 7BC.

Well, David, we've got the night sky as seen from Jerusalem a little

more than 2,000 years ago

and it looks pretty familiar to me.

Well, it is familiar.

The constellation shapes have hardly changed.

And we have these two wonderful planets, Jupiter and Saturn,

and they're close together and of course, astrologically,

the fact that they're close together means you've got a conjunction.

They came together in the year 7BC

and this coming together of these two planets,

I interpret as the Star of Bethlehem.

We can watch that using the planetarium.

So this is the 27th March, 7BC,

and if we run time forwards, you can tell us what happens.

What we're seeing is they're coming together.

They don't merge, they come together.

-They get pretty close.

-They get pretty close.

But this is not just one conjunction.

Over the course of several months,

the two planets came together three times -

a so-called triple conjunction.

So these two planets were seen close together first in the dawn sky -

what is known in Matthew as "in the East" - and of course

then, as the months passed,

you got them appearing close together in the evening sky.

And I think, personally, the Magi thought that this indicated the actual birth date

of this new King of the Jews.

OK - so when was that date?

That date was Tuesday 23rd September.

OK, so Christmas was three months ago,

so that's good, we've got that out of the way!

This interpretation of the Star of Bethlehem requires that the Magi

had a detailed understanding of the movement of the planets in the sky.

They must have been skilled astronomers.

But it also requires that they gave very specific astrological meaning

to this interaction between Jupiter and Saturn.

But conjunctions happen reasonably often - triple conjunctions less so.

But why do you think THIS was the Star of Bethlehem?

Firstly, as you say, conjunctions do happen all the time.

Triple conjunctions don't.

You've got to get, in essence, sun, Earth and the two objects lined up

for a triple conjunction, so that's rarer.

And then, the next thing is you've got to introduce actually where in the sky this is happening.

And that is in the constellation of Pisces.

And we can call that up - this is the magic of the Planetarium.

-There you see Pisces and this is rare.

-Yes.

It takes place round about every 800-900 years.

And so the Magi would say,

"Ah! That means this new ruler is in Israel."

Hang on - how do you go from Pisces to Israel?

Well, I don't, but the astrologers 2,000 years ago

actually divided the zodiac up into 12 different constellations,

and each of these constellations was associated with

-one of their neighbouring countries.

-Oh, OK - there's a list somewhere?

-Yes. in Ptolemaic astrology, there is a list.

-OK.

Pisces - Israel. Aries - Syria. And so on.

The Magi, of course, would have been spending their lives looking at the planets.

They knew what was going to happen - a new king,

they know where it was going to happen - Pisces indicating the vicinity of Jerusalem,

and they knew when it was going to happen.

It strikes me that this is the opposite of the primary-school version of the story,

where we have the big, shiny star that hovers in front of the wise men

and settles over the stable.

This is a scientific story you're telling - calculations,

observations that test them and then a conclusion.

There's no big, shiny star.

But if you read Matthew carefully, there's nothing indicating

that the star was out of ordinary.

And it is of course important that you have a star that Herod hadn't noticed.

He hadn't noticed when it had started -

he wanted to know exactly when Jesus was born.

So you want something that is a bit subtle.

And this 7BC triple conjunction does fit in with the general history of the times.

Well, whatever the truth of it is, I really like the idea that there were these people

back then looking up and enjoying the sky just as we do today.

-David, thank you very much.

-Pleasure.

So that's two candidates down.

The bright new star of the supernova

that surely everyone would have noticed.

And the much subtler planetary conjunction, which could explain

why it was only seen by the wise men.

But who were the Magi and where did they come from?

Some scholars think the Magi are Mesopotamian.

Mesopotamia, in particular Babylon, had a great reputation for astronomy

and astrology, so there was a sense in which if men were going to come from the East,

they were likely to be from Mesopotamia.

What would today be Iraq.

A part of the world, of course, in those days with a very rich culture,

Babylon, Nineveh, Sipur and so on.

They would have been men who had been taught how to read the heavens.

So if the Magi were from Mesopotamia, what more can we find out about them?

Their culture is long gone and the ancient cities of Babylon have been

abandoned for thousands of years, but we do have some clues.

There were definitely skilled Babylonian astronomers who

left behind crucial historical records which may shed light

on the triple conjunction theory.

Today they can be found in the British Museum

under the watchful gaze of Christopher Walker.

Christopher - can you just tell us what these wonderful objects are?

What you see now are tablets that actually we have

baked for the sake of their conservation -

but in antiquity, they would have had wet clay, they would have

flattened it out to make an oblong shape like that and then they would

have taken their stylus and written their cuneiform wedges.

I see, I didn't... So the fact that they're baked -

it was us who did this, I didn't realise that. That's amazing.

And let me ask about the people who would have written on these tablets.

Who were they and how accurate would they have been

and why were they making these records?

These were written by professional Babylonian scribes, who were hired

by the temple, basically for life, to sit there making astronomical

observations, watching everything that happened in the sky, day and

night and then do the mathematical calculations month by month,

year by year, to predict various astronomical events in the sky

-and tell you to what kind of things on Earth it might relate...

-OK.

..whether it is relating to the king or the crops, or the like.

So written in Babylonian.

Can you show me here

which of these symbols are actually representing the planets

and where they are, where they would be in the sky?

In this line here, it says that Jupiter and Saturn were in Pisces.

Gosh, so this is the idea of conjunctions.

This is exactly the idea of conjunctions - this is

actually the single line that expresses that best

and it will then go on to tell you a little bit about the moon and the sun

and the points at which the moon changes its position,

or they have an eclipse or the like.

What year would this one be from?

These three tablets all date to the year 7-6BC.

-Which is exactly the time we're looking for.

-Exactly.

So that...so right there - that's it.

That is the famed triple conjunction that could be,

-may be our candidate.

-Yes, yes.

So this is real historical evidence to say at that time,

there was an astronomical event that was important,

that people wrote down, that would have perhaps looked spectacular.

It shows us that there were a group of astronomers working at Babylon

who would have been able to predict the event

and understand its significance, whatever that may have been to them.

I mean, what do you think? Do you think that could be a contender?

It's at least a possible contender.

-It's the only one at least for which we have a written record.

-Yeah.

The problem is both is that it's not quite as spectacular

a conjunction as you might hope, and secondly,

we have hardly any idea what they would have made of a conjunction.

-Yeah.

-Absolutely none of our astronomical texts mentions the West in anything

other than the vaguest terms.

The same to some extent would apply to the Magi.

We have no idea that seeing this kind of planetary conjunction would have

sent them running off to see King Herod in Jerusalem.

There seem to be more questions than answers, really.

I'm going to continue on my journey. I'm going to continue

and look at the other options, but this is fascinating.

It's really interesting to actually see something physical as well.

-Something concrete, as it were, written down. Thank you.

-OK.

So we've got good reliable historical evidence that there was this planetary conjunction,

and people were seeing it, observing it and writing it down.

Whether they then attributed any significance to it is another story.

So I'm going to keep on searching to see what else is out there.

But while we may be able to find archaeological evidence of the star,

is there any chance we can find a trace of it in the sky today?

Pete Lawrence has been out stargazing,

looking for examples of our two candidates so far.

But he also has some new possibilities to suggest.

Now, our first candidate are planetary conjunctions.

These aren't that uncommon, so we can see the same

sort of events today that ancient astronomers would have seen.

At the moment, we've got brilliant Jupiter and Venus

shining away spectacularly, just above the clouds there.

Now, at the moment, they look quite well separated,

but just a few weeks ago, they were really close together,

and that was enough of a draw to get people up early in the morning

and take some spectacular photographs of them.

The conjunction was especially striking when Venus

and Jupiter were also joined in the morning sky by Mars.

You can see why something similar would have appealed to

ancient astronomers in 7BC.

But it's not just planetary conjunctions that we can see today.

We can also find evidence of some of the other candidates thought to be the Star of Bethlehem.

Unless we're unbelievably lucky in the next few hours,

we're probably not going to see a naked eye supernova this evening.

But there are plenty of stars which have the possibility of going

supernova relatively soon.

And one such candidate is Betelgeuse

in the famous constellation of Orion, the Hunter.

If you look at the constellation of Orion,

Betelgeuse is at its left-hand shoulder

and it is a distinct red colour.

That's because as it reaches the end of its life,

it has swollen up to become a red giant.

Betelgeuse is now over a billion miles across.

If you put it at the heart of our solar system, it would

engulf the inner planets and extend out almost as far as Saturn.

Sometime soon, and that can mean

anywhere in the next few million years,

it'll go off as a supernova.

And because it's relatively close to us, at 646 light years' distance,

it's going to put on one hell of a show in the night sky.

Betelgeuse is ten times closer than the star

that gave rise to the Crab Nebula,

or around 30 times closer than the supernova that Kepler saw.

So when it does go, it will be much brighter -

brighter even the moon and probably visible in broad daylight.

Perhaps the Star of Bethlehem was something like this.

If you didn't know what caused it, I can see how that would easily

be mistaken for some sort of divine message.

But there are other suggestions of what the star might have

been that we can see today.

Some have suggested it might have been an aurora -

seen much further south than usual.

Rare but not unknown.

Or it could have been the zodiacal light -

a faint glowing pillar that appears above the horizon caused by light

scattering through dust that fills the plane of the solar system.

But there is one other suggestion which I want to tell you about -

one that I think is particularly persuasive.

The actual words of the original Greek of the Gospel of St Matthew

were "en te Anatole".

And that literally translates as "rising in the East".

But it's thought that "en te Anatole" actually had a very special meaning for ancient astronomers.

It refers to the day of the year when a star reappears into view

from behind the sun.

As the sun moves against the constellations, it hides the stars behind it, of course.

But on that day, that star will be briefly visible just

before the sun rises, and that's known as the star's heliacal rising.

It might seem an obscure phenomenon today,

but heliacal risings were crucial events to many societies.

The ancient Egyptians used the heliacal rising of Sirius

to mark the beginning of the flood cycle of the Nile.

And the Maoris of New Zealand still use the heliacal rising

of the Pleiades star cluster to mark the beginning of their year.

It's been suggested that

the Star of Bethlehem that the wise men saw rising in the East

was the heliacal rising of a star called Sa'd al-Malik,

which we know as Alpha Aquarii.

From the Arabic name, it translates as the "Lucky Star of the King",

and that was seen as an omen for the birth of a new king.

Now obviously, that's an occasion that would happen every year,

so it would need to be coupled with other omens

and signs to mark this specific event.

But I think, given the importance of heliacal risings to ancient cultures,

and also the name Sa'd al-Malik,

which means the Lucky Star of the King,

that puts forward a very persuasive case for this being the cause of the Star of Bethlehem.

Another factor to take into account in the Star of Bethlehem story

is the political situation in Judea at the time.

Occupied by the Romans and with an unpopular king, people were

desperate for change, so there was a hunger for an omen that might

suggest a Messiah was on the way.

It was a mixture of politics

and religion that has been memorably depicted in film.

Wah!

I love The Life Of Brian.

It's got a lot of resonances to the kind of chaotic situation

of Judea in the first century,

and also just at the time

when Jesus was born.

What's this, then?

"People called Romanes, they go the house?"

-It says, "Romans, go home!"

-No, it doesn't.

'The time of Jesus was a time of relative civil and social unrest.

'Romans were occupying most of the known world

'but there was a lot of discomfort, dissatisfaction,'

economic hardship, there had been several famines,

so all in all, things were not great for people, so people

used to look to other sorts of groups for some kind of liberation or some kind of hope.

One of the things I like about The Life Of Brian is that you do

get this idea of all these would-be Messiahs.

There's a line where a John Cleese character says...

Hail, Messiah!

I'm not the Messiah!

I say you are, Lord, and I should know, I've followed a few.

-ALL:

-Hail, Messiah!

And this is because the Pythons had really read Josephus

and the historians of the time - they'd done their homework,

so they knew that there was a lot of expectation

and there were would-be Messiahs and prophets all over the place,

because the end of the rule of Herod the Great was this time

of great expectation and excitement and also just absolute desperation

in terms of what the Romans were not doing for Judeans.

Argh!

'Later on, you had this curious

'incident where Brian gets taken off by aliens in a spaceship,

'and there's a bit of'

a tongue-in-cheek reference to the star

at the point, I think, that the star itself might have been an alien spaceship,

rather than anything astronomical,

so I just think that's really fun.

Ooh, you lucky bastard!

That brings us to our next candidate to be the Star of Bethlehem.

It's one that had a reluctant champion,

a familiar face to Sky At Night viewers.

And this brings me on to my own suggestion,

which I admit is not very convincing, but the best I can do.

And I suggest that the Star of Bethlehem just could be due to two meteors.

Just suppose the wise men were crossing the desert

and they saw one of these really brilliant meteors moving ahead of them.

It wouldn't last for long, but they'd certainly recognise

that as being something very unusual.

All right. Then a little later on,

they see another meteor moving in the same direction with about the same brilliancy.

Quite a coincidence, I agree, but not a too amazing one,

in view of the fact that we do have showers of shooting stars.

And that would explain, first of all, why nobody else saw it -

it would have been visible only from that part of the globe -

and also why nobody else could see it again

when they went to look for it. It would only have lasted for a few seconds.

The trouble with this idea is that meteors are common

and even meteor showers are common.

And especially with the dark skies of 2,000 years ago,

I don't think that seeing one or two or even a whole host of meteors

would have been considered that special.

But there is an extension to this idea that might be worth considering.

When you see a meteor, you're seeing a tiny dust grain burn up in our atmosphere.

But larger objects do hit the Earth and when that happens,

they leave quite a different visual impression.

As these fireballs shoot across the sky,

they seem to be heading for a touchdown on a specific point on Earth.

And that could certainly be interpreted as a sign from the heavens.

These events are so rare and so spectacular that they would

certainly have attracted attention 2,000 years ago.

They still do today.

In February 2013,

an object 20m across entered the Earth's atmosphere,

travelling at 40,000mph.

It burnt up, producing this spectacular fireball across the Russian sky.

It exploded 30km above the city of Chelyabinsk.

The explosion was more than 20 times as powerful as the atomic bomb

detonated over Hiroshima.

The shock waves injured 150 people and damaged thousands of buildings.

Events like that at Chelyabinsk aren't actually that rare.

We think that objects of that size hit the Earth

two or three times a century.

But most go unrecorded, as they happen over uninhabited areas.

But you can see, looking at those videos,

that if something had hit over the Middle East during the first century BC,

it would have been interpreted as a miraculous sign

and written into the legends of the time, and so that makes

a meteorite strike our fourth candidate to be the Star of Bethlehem.

Back on the quest for historical evidence for the star,

I've directed my search several thousand miles further east,

because the Babylonians weren't the only ancient civilisation to

make astronomical observations.

The Chinese were also making detailed records of everything

they saw in the sky.

Christopher Cullen is an expert in ancient Chinese astronomy.

So Christopher, tell us what we're looking at here.

We're looking at a chapter of the Han Shu.

The Book of Han - a history of China written in about 100AD.

And this is a record of phenomena seen in the sky.

And how accurate a record is it?

It was written a long time ago before what

we would recognise as science, if you like, was happening.

This was written by professionals.

The Emperor maintains a staff of skywatchers, whose job is

to be up there noting down everything that happens.

And there's a reason for that,

explained on the first page of this chapter - chapter 26.

The stars and planets, all the lights up there, are a great control panel

of indicator lights and if one of them starts blinking, or

if a light appears where it's unexpected, that means something big is happening,

because everything in the sky mirrors what's happening on the Earth.

So it was the same idea, that this idea of portents

-and omens of what was going on in the sky reflected human concerns.

-Yeah, yeah.

OK - so here's the question.

-We're looking round about 7BC-4BC, round that sort of time.

-Yeah.

Is there anything of note in this book that we should

look at in terms of bright objects?

The nice thing about Chinese books is that they've got dates in them.

So we turn through the chapter, looking at...everything's got a date there.

And we come to near the end of the chapter.

And we see in the second year - that's 5BC...

5BC, OK, well that's ballpark.

Second month - that's lunar month, this is early March to early April.

-Which again...

-Yeah? All right? Nice.

-..sounds good.

A broom star appeared in the constellation of the Ox for more than 70 days.

-Will that do you?

-Well, that's pretty good.

By broom star, presumably we're talking about a comet?

Most of the time, I think.

When you see records of movement and statements about how long it was,

like a tail, it's usually called a broom star.

I'd go probably for a comet, but it doesn't have to be.

I'm just trying work out, could it be something else - could it be a supernova, for example?

I would not say it was impossible it could be a supernova.

Of course, to prove it was a supernova,

what we'd like to do is to find the actual remnant,

the nebula left today, as we can with the Crab Nebula.

But there's no remnant been proposed for this.

-And 70 days - that gives us quite a wide area of time.

-Mmm.

-OK.

And they say later, they say the fact that it was up there for

so long means that it really shows something big.

So much so that the Emperor was actually persuaded for a short

while to start recounting the years of his reign from this year.

So not the second year, now it's now the first year

because something so important has happened.

-Wow - that is really interesting. So, big political news.

-Yeah.

This is 5BC.

-This broom star, this comet, would have been seen in the Middle East as well.

-Absolutely.

How accurate do you think these records are?

Because we're going back a long way.

Are you confident in the dates, for example?

Yes, I am. Basically, Chinese dates in history are reliable to the year,

from about the middle of the 9th century BC, this is fairly well established.

Sometimes, you will find someone's miscopied a month.

But to check that, look at the next entry - the next entry tells us

basically that a little later, Jupiter was seen moving

through a certain constellation

and they say it did this retrograde loop.

It's where you do a calculation to check, you find that yeah,

that date is when Jupiter would have done a retrograde loop.

There are other things like the moon going in front of particular star.

You can check - and it did.

Christopher, that's absolutely fascinating.

This is a whole new area, line of inquiry

that I didn't even knew existed, so thank you very much indeed.

-It's been a great pleasure.

-It's been an absolute treat to look at this. Thank you.

-Thanks.

So far, we've learned that the Star of Bethlehem may have been

a number of things -

a bright supernova,

a rare alignment of planets,

a meteor or the rising of a star.

There are only two to go and the Chinese records immediately raise

another prime candidate - a comet.

We asked planetary scientist Alan Fitzsimmons to explain why

he thinks the Star of Bethlehem could have been a comet.

I think comets are fascinating objects.

I always have done and that's why I've worked on them all my life.

Now historically, the appearance of a comet has been seen as an omen

of events here on Earth

and that's why I think it could have been a comet

that took on religious significance as the Star of Bethlehem.

So, the idea that a comet was the Star of Bethlehem

has been around for hundreds, if not thousands of years.

In fact, it was first written down, to our knowledge,

by the Christian writer Origen in the year 248 AD.

But this is the picture that really puts comets in the frame.

It's by Giotto, the finest painter of his time, back in 1305.

It shows a typical Nativity scene, based around the infant Jesus,

and above the stable,

poised majestically in the sky, is a beautiful comet.

Comets come from the very outer edges of the solar system.

They are the frozen leftovers from the formation of the planets.

We might not know they existed at all if they weren't occasionally

sent catapulting into the inner solar system.

As they approach the sun,

they reveal themselves by putting on the most extraordinary show,

and the closer they get to the sun, the brighter they get.

So, when I first read these accounts by ancient Chinese

astronomers of a comet that could be seen for 70 days

in the early morning skies,

I knew it must be incredibly bright for part of that time.

Also, if it's in the morning sky, it's near the sun

and those two things together make me think of sungrazing comets.

Here we've got a set of images and wonderful movies of Comet ISON,

a sungrazing comet that appeared just two years ago.

You can see it does get incredibly bright.

The reason that sungrazers get so bright

is that they get red hot as they pass close to the sun.

In a normal comet far away from the sun, the sun's heat is enough

to vaporise the ice, that streams away as gas, also releasing

small dust particles, and they go into forming the tails of the comet.

In a sungrazing comet, as it approaches the sun,

everything starts getting red hot and everything vaporises.

The ice, the comet dust, even any rock that could be in there.

Everything goes and in doing so,

that's what makes the sungrazing comet so bright.

Many of the chunks that we see in the satellite images are small,

just 10 to 15 metres across, and we can't really see them

from Earth, but now and then, a much bigger chunk comes along.

This is a picture of Comet McNaught, the Christmas comet of 2006

and one of the brightest comets to be seen from Earth

over the past 1,000 years.

So bright because it passed close to our sun.

You can see the tail here, pointing downwards towards the horizon,

as if indicating that something is happening over there.

Surely if a comet like this had appeared in the Middle Eastern skies

some 2,000 years ago, the Magi would have been drawn towards that

direction and maybe ended up in a stable in the town of Bethlehem.

There are other details of the Nativity story

that suggest that a comet could have been the star.

Matthew's Gospel implies that the star was seen twice.

Once to bring the Magi to Jerusalem,

a journey that must have taken weeks, if not months.

Then a second time to lead them to Bethlehem.

That behaviour is typical of many comets.

So, this is a first edition of Newton's Principia from 1687

and right at the front of the book we have this beautiful diagram

showing the path of a great comet that Isaac Newton himself saw.

You can see how it appeared firstly in November 1680

on its way into the sun.

It disappeared for a couple of weeks when it was closest to the sun,

then reappeared in our skies in early 1681.

This showed that comets followed regular paths under the influence

of the laws of gravity that Isaac Newton had discovered.

It's this behaviour of the comet that could explain how

the Star of Bethlehem appeared twice to the Magi.

So putting it all together, there is a bright comet

seen at the right time by Chinese astronomers.

If the Star of Bethlehem appeared twice, then comets can do that too.

Comets have been seen as omens of important events

for hundreds or thousands of years

and a comet tail pointing down towards the eastern horizon

could imply something important was happening there.

Altogether, if there was a Star of Bethlehem,

I think it could have been a comet.

A comet just suddenly popping up always created a sense of instability

in what was going on.

Unexpected and often quite frightening.

It's not a good omen.

Shortly before the death of Nero, comets were seen in the sky.

Julius Caesar, at the time of his murder.

This is not just the Babylonians,

this is the Romans, the Greeks, it's everybody.

In other contexts, comets are not necessarily bad news.

So, there is a text in the Book of Isaiah in the Jewish Scriptures that

talks about a star falling from the heavenly realm into the underworld.

This is a bad god, a bad divine being who is being sent

out of the heavenly realm and into the underworld,

so it's bad news for him,

but good news for the rest of humankind.

In the same way, for those that think

the Star of Bethlehem is a comet, it's bad news for King Herod,

but good news for the followers of Jesus.

With the addition of a comet, that leaves one final candidate.

Maggie has been to meet Mark Kidger,

who believes the Chinese record in 5BC is not a comet,

but something much more intriguing.

He believes it was an event called a nova.

If he's right, the Star of Bethlehem is still lurking in the sky,

exactly where the Chinese saw it.

And you're saying that the Star of Bethlehem is still in the star field?

Yes, if my ideas of the Star of Bethlehem are right,

it's still there, round about where it is marked with the arrow.

I can't see anything bright enough in there

that could possibly be the Star of Bethlehem.

Exactly, because now the Star of Bethlehem is very, very faint.

You may not even be able to see it

with the biggest telescope in the world, but what we do know

from the Chinese records is that it was pretty bright.

The Chinese say that they saw it for 70 days.

They just give this position in the sky

close to Alpha and Beta Capricorni.

It's a star that appeared,

stayed visible to the naked eye for 2.5 months.

The Chinese monsoon came, the Chinese lost it

and it faded away in that time.

When they were able to look at the sky again, it had disappeared.

So, for me, there is one simple, obvious candidate for that,

which is a nova.

A nova? Describe to me what a nova is.

Right, a nova is something very much smaller than a supernova.

It's a pair of stars, a binary star,

a big old red giant we see there, arriving at the end of its life,

and a little white dwarf star

that's already been a red giant and it's died.

What is happening is, this white dwarf star is a cannibal

and material from the red giant is spiralling down

onto the white dwarf.

It falls on, gets hotter and hotter, accumulates and accumulates

and then suddenly, boom!

You get to a critical point, there is a critical mass

and the whole thing explodes and a cloud of gas

and dust goes out into space and it is very bright for a time,

months, sometimes only for a few days and then fades away

and disappears and then slowly accretes material on top again.

Then 10 years, 100 years, 1,000 years,

maybe even 10,000 years later,

boom again as the material builds up.

I suppose it's got to get that critical mass before it goes boom!

It varies from nova to nova?

It varies from nova to nova, it depends how much is falling

onto the small star, how quickly it's happening,

how big the small star is.

It gets hotter and hotter and hotter and suddenly, crisis and boom!

On that basis, if it goes boom every so often,

-it means we could again see the Star of Bethlehem in the future?

-Exactly.

That is one of the beauties of this theory, because as you said,

you cannot see the star there, but one day, if you are patient and

keep observing the sky, that star,

if it really was a nova, will reappear.

It might not be in time for this Christmas special

and it might not be for next year's Christmas special,

but 1,000 years - it may happen.

It's a neat idea

and it's possible that the Chinese records are of a star going nova.

But we still need to explain why this particular effect was so special.

Nova aren't particularly rare.

Why would this one draw the three wise men to follow a star?

OK, so, the first thing, it was bright. It wasn't just any nova.

It's the sort of nova you only see once every few hundred years.

That's one thing.

The second thing is, it followed a series

of other interesting events.

We had that triple conjunction that was observed in 6BC when Jupiter

and Saturn came close together and separated and came close again,

three times over a period of months.

Jupiter, the King of the Gods, symbol of kings.

Saturn, the changer of ages.

If you are a Persian astrologer,

that sort of thing would have been tremendously significant.

It marks something happening, something coming up?

Something was coming up and then just over a year later, bang!

You get the brightest nova you have seen in the sky in centuries.

Now is the moment. Get those camels, wagons roll!

OK, yes!

So, in terms of its position,

would it have drawn the Magi in the right direction?

That's the beauty of this theory.

It does everything that you need, just the stars in their courses,

behaving naturally.

Matthew's Gospel says that the Magi saw the star at its rising.

It would've been in the East at dawn.

They took six weeks, if they were in a real hurry,

maybe two months to reach Jerusalem. They spoke to King Herod.

Two months later, where would the star be?

It rises a little bit earlier each night,

then it would have been due south at dawn.

Right over the town of Bethlehem,

and they really would have followed it towards Bethlehem.

It really would've guided them on that last leg of their journey.

So, to you, all the evidence adds up

and to you, the Star of Bethlehem was a nova?

This is just the simplest theory.

That's the beauty of it. It's very, very simple.

The stars in their courses do everything that you need.

And it's a natural event, but it's a quite rare natural event,

and that's the beauty of it. It's what I like about the nova theory.

Well, it's a nice theory,

so thank you very much for describing it to me.

-And thank you very much indeed to you.

-Thank you.

We now have six plausible candidates

that could have given rise to the Star of Bethlehem.

A nova or supernova,

a comet or meteor,

the rising of a star,

or an alignment of the planets.

And now Chris, and I have to assess the evidence

and choose what we think was the most likely cause.

What do you reckon, Maggie?

I think, rather than homing in on what I think it is,

-I'd rather home in on what I think it isn't.

-All right.

Meteors fall all the time. I don't think that would be enough to cause

-people to leave their home and travel afar.

-Right.

And even if we had a really spectacular one like Chelyabinsk

we would have seen more records.

Someone might even have found the meteorite...

-Yeah, that would be fun!

-..if it touched down.

-It seems unlikely to me.

-Yeah. Good. Down to five.

What about the supernova?

This is the Christmas card Star of Bethlehem.

It's a bright new star that hangs in the sky.

There's poetry there as well - the death of a star marks

the birth of a king. And it would have been quite spectacular.

The problem is we don't see a remnant from this supernova.

When there has been one in the last few thousand years, we see

the nebula that's left over,

like the Crab, which is beautiful, from 1,000 years ago.

-I think there's a gap there.

-I'm happy to dismiss.

Fine. Let's also talk about this one. This is the rising of the star.

It happens every year.

Why would this mark a significant event?

Right. We're either missing a few thousand Messiahs, or I agree,

-I think this is the sort of thing you use to mark the New Year.

-Yes.

Right? Or to mark a significant annual event - it's not a one-off.

-Yes.

-And so, I think that can go.

'We are now down to our three final possibilities -

'the nova,

'the comet

'and the planetary conjunction.

'It's possible to make a compelling case for each of them.

'At this point it's down to the piece

'of evidence we choose to put the most weight on.

'We know that the triple conjunction happened

'and was recorded by astronomers in the Middle East.

'But I wonder if this subtle event

'would really have been significant enough.'

I don't think it would've been that spectacular in the sky.

Yes, it's almost the opposite.

Planets get close to each other all the time - we had Venus

and Jupiter close to each other last month in the morning sky.

So the argument that it is this conjunction rests on this idea

that there is something significant about the fact that

it's Jupiter and Saturn, the old king and the new king,

that it rests on the fact it's in Pisces,

which according to one text

is associated with this particular patch of land.

But the thing is, we don't know what the right astrology was.

Astrologers don't agree with each today, let alone 2,000 years ago.

And you can pretty much support any story you like.

Well, on that basis, I think this one goes as well.

Yep. So that leaves us with what? A nova and a comet.

The thing that both of these have going for them, I think,

is that they are described, in that Chinese observations.

I quite like the idea of a nova

because I love the idea of a nova, it might appear again.

The whole process can reignite and it could reappear in our night sky.

There is no evidence against it,

but there's not much evidence, for me, for it.

My fear with the comet is that

in the past, many people have associated comets with doom.

-That's true.

-And so, why would you associate a comet with the birth

of a Messiah, a new king?

-We should be careful about taking what we think about comets...

-Yes.

..or what Westerners thought about comets and imposing it...

That's right and we don't know how far that belief goes.

What the comet has over the nova to me, is that it looks like it is pointing.

-The comet has a direction.

-Yes.

It's an arrow. They're also beautiful and noteworthy,

so I can imagine following that.

And I think it can do the magical thing of disappearing as it

-goes round the back of the sun and coming back again.

-Yes.

So there's a very straightforward explanation of why it would be

-seen twice.

-I like the independent verification,

the fact that other sources - nothing to do with the story,

saw it. It was significant. It was commented on across the world.

Who knows, that could've got into legend and ended up in the story.

If it's real, for me, it's a comet.

-I'd be happy to go with a comet.

-All right.

That's it, then. The Sky At Night verdict is that

the Star of Bethlehem was most probably a comet.

That's it for this month.

We're off air next month to make way for Stargazing Live.

We'll be back in February.

But in the meantime, you can still check out the website to find

Pete's guide to the highlights of January's night sky and to find out

how to find a message in the stars

with the Whispering Stars messaging service.

-In the meanwhile, get outside and get looking up.

-Goodnight.