All language subtitles for BBC.The.Planets.5of8.Star.DivX5-AC3.www.mvgroup.org.English

(Music: Gustav Holst:
"The Planets")

In 1973,

nine astronauts were
sent to live and work

in the world's first
space station - Skylab.

Their mission was
to observe the sun,

free from the Earth's
distorting atmosphere.

They witnessed what
no one had seen before,

a sun more powerful
than they had ever imagined.

To our ancestors,

the sky was
a patchwork of puzzles.

At night, it was brimming with
pinpoints of light -

stars.

Then there was the sun,

whose arrival banished the stars
and brought warmth and light.

It was hailed as the giver
of life, the first god.

This is the story
of mankind's struggle

to see behind the glare and
glimpse the truth about the sun

and how we came to understand

its power and
its role in the universe.

(Carnival music)

In February 1998,

the Caribbean island
of Guadeloupe

geared itself up
for a rare celestial event.

For a few minutes,
day would become night

during a total
eclipse of the sun.

This was Francisco
Diego's tenth eclipse.

As a boy, he was deeply
affected by his first.

It started a lifelong
fascination with the sun.

'The sun was perceived
as an immaculate'

gold disc, perfect.

It was a religious belief.

Everything was perfect
in the sky.

The sun was
the most perfect circle,

with no blemishes or structure.

A perfect, flat, golden disc.

'It was the sun god
for many religions.'

The sun remained
a symbol of perfection

until a 17th-century
Florentine called Galileo

first pointed
a telescope at the sky,

and instantly recorded
the first scientific milestone.

'Galileo applied the
telescope for the first time,

'and discovered
the sun wasn't perfect.

'It had sunspots.

'That was a major revolution
in philosophy and science.'

Galileo watched the sunspots

move across the sun's surface...

and realised it was spinning.

It was the first of many
secrets sunspots would reveal.

Galileo's insight
heightened speculation

about the true
nature of our sun.

But for two centuries,

astronomers were frustrated
by its blinding disc.

What were sunspots?

What other landscapes
existed on the sun's surface?

What was
the source of its power?

There were moments,
scientists realised,

when the sun offers a rare
and special opportunity.

Roughly six times every decade,

somewhere around the world,

the sun passes
directly behind the Moon.

If the sun's this big,

Earth's a little ball
of 3-4mm in diameter

and the Moon is even smaller.

It's a quarter of the Earth,

400 times smaller than the sun.

The fantastic coincidence

is that the sun is
400 times further away

than the Moon from us,

so we see both more
or less the same size.

(Man ) One minute!

For 4 hours,

Francisco watched the Moon
creep into position.

(Man ) No filters!

He came halfway round the world

for just four minutes
of totality.

But where the sun is concerned,

dedication has never been
any guarantee of success.

(People shout and cheer)

Francisco got just a few moments
to glimpse the hidden sun.

We lost it.

No corona.

Like many astronomers before
him, Francisco was thwarted

as the clouds rolled in
to spoil the party.

Douglas Gough is a
leading solar scientist.

To see his first total eclipse,
he had travelled to Indonesia.

The government had declared it
illegal to watch the eclipse,

at least for the Indonesians.

They had to watch it on TV

or go to the mosque and pray the
dragon would spit the sun out.

They believed
that was happening.

I was standing on a road,

and a little boy came up to me.

I gave him a dark film,
to look at the sun.

An old man of 70, the head of
the village, came too,

and the three of us saw
a fantastic eclipse.

A total eclipse
reveals the sun's corona,

an outer layer
normally lost in the glare.

'An eerie feeling,
and almost total silence.

'The only thing we heard was
the chanting from the mosques.'

This is what early astronomers
travelled the world to see.

Within the corona
were seemingly burning clouds.

The surface looked smothered

in a complex, raging atmosphere.

'You realise,
seeing these things,

'the sun's active,
not a passive ball of gas.

'It's churning away. Interesting
things are happening.'

Discovering new
things is exciting.

That's why explorers explored
places no man had been before.

On Earth, there's little left,
so we go into the universe.

Seeing the sun,
peeling off a layer of mist,

of lack of understanding,
and seeing how something works,

is an amazing experience.

The rarity of a clear eclipse

gave scientists few chances
to study these prominences.

In the 19th century,
Father Angelo Secchi,

the Vatican's chief astronomer,

caused a revolution
in the way we looked at light.

From an observatory
above his church,

he pioneered a new branch
of science - spectroscopy.

His spectroscope split sunlight
into its constituent colours,

then magnified
the light in one region.

It was possible
to see the sun's edge,

without relying on an eclipse.

Spectroscopy revealed
a solar surface

of astonishing complexity.

You were no longer dazzled
by the sunlight.

You could see the things

you can see at the edge
of the sun during an eclipse.

Soon astronomers were
studying the body of the sun.

The sunspots were Earth-sized
tears in the surface.

Like windows
on a mysterious interior.

The surface itself
bubbled before their eyes.

Soon they were cataloguing
the chemicals in the sun.

Dark bands in its
spectrum meant hydrogen,

calcium, iron.

Astronomers discovered an alien
element, unknown on Earth.

They named it after Helios,
the Greek sun god. Helium.

When Secchi turned
his spectroscope to the stars,

he made his most
profound discovery.

He recognised
the pattern immediately.

Their chemistry was
identical to the sun.

One great mystery of
the heavens was resolved.

Our sun was a star.

The sun was a star,
and one realised

it belonged to
the family of stars.

'Scientifically,
that's fantastic,

'as we want to know
what the universe is like.

'By studying the sun,
we study a typical star.'

In the '40s we got
our first inkling

of how deadly
a typical star can be.

As the first rockets rose
to the fringes of space,

they were scorched
with radiation.

Our atmosphere lets
heat and light through,

but shields us
from X-rays, gamma rays

and ultra-violet
light from the sun.

Soon a man was to brave
this deadly radiation,

and come face to
face with a star.

Alexei Leonov.

'Three, two, one, zero.'

In 1973, a solar laboratory

was sent to study
the sun directly from space.

But the sun didn't
give up its secrets lightly.

'When Skylab was launched,
it had a heat shield,

'that was to open up
after it got into orbit.'

Sixty seconds into flight,

that heat shield popped open.

It's still in the air stream,

so the air stream
tore the heat shield off,

and unlocked both solar wings.

Conrad had been on the Moon when
he became crew leader on Skylab.

Their home was no longer
protected by an atmosphere,

and temperatures
started to soar.

They had to find a way
of shielding the station

from the sun's excesses.

'We got this
temporary heat shield rig,

'which we could rig from inside,
through an air lock.'

We could push,
like an umbrella pole,

and mylar sheets popped open
like an umbrella.

'Then we could pull it to where
it was offset a few inches.

'It did make the temperature
go down immediately.'

As the temperatures dropped, the
crew went into the observatory.

They had to get used to life
in a weightless environment.

At first, nausea prevented all
but the most hardy from eating.

That problem quickly passed.
Soon space didn't seem so bad.

Then, with no distorting
atmosphere to blur their sights,

the most extensive period of
solar observation ever began.

'The Skylab flight
is very dear to my heart.'

I know a lot of people
don't understand that...

It means more to me
than going to the Moon.

Part of that was being able
to run the solar telescope

and know we were bringing back a
tremendous amount of information

that nobody had before
in great quantities.

When I switch to the two
positions called h-alpha,

these words stand
for hydrogen-alpha,

called that
because the light here

comes from light from hydrogen
atoms in the sun's atmosphere...

Viewing the sun in the same
wavelengths of light

used by Secchi
100 years earlier,

the astronauts saw incredible
details on the sun's surface.

..wavelength radiated
by the hydrogen atoms.

We can see sunspots,
networks, filaments,

all of these things,
in great detail.

We all took a four-hour turn
at the solar telescope panel.

It's like playing
three 88-keyboard pianos

at the same time.

'It was a very complicated set
of switching and everything.'

It was very intense.

You'd work hard to make sure the
sequences read the right way.

Things would come up in real
time, like solar flares,

so we had to be prepared
to catch that also.

Solar flares are planet-sized
eruptions of boiling gas,

prominences that
break free of the sun.

They'd been seen from Earth, but
not in such detail and quantity.

Somebody was running it and
would call us to take a look.

That happened frequently,

when something unusual came up
that we could witness,

we'd call the other
guys up to take a peek.

In nine months,

successive Skylab crews took
more than 160,000 images,

revealing hitherto
unknown aspects of the sun.

Their most spectacular
discoveries

were the coronal mass ejections,

outbursts of material on a
scale that dwarfed solar flares.

These were the best
views yet of the angry sun.

But what causes
these convulsions?

The answer lies in an
invisible side to our sun,

and once again, sunspots
were the key to its discovery.

Long before the space age,

the summit
of the San Gabriel mountains

was the closest an American
could get to space.

In 1903, George Ellery Hale,

the son of an engineer,
had a dream.

He'd build the world's most
advanced solar observatory,

high above the town of Pasadena.

Sallie Baliunas
is an astrophysicist

at the Mount Wilson observatory.

Hale is my personal hero.

He was a great scientist and
had instinct about engineering,

so he could successfully build
the world's largest telescopes.

He raised a lot of money
to do these projects.

'As he often said,
he made no small plans.'

The route to the top of
Mount Wilson wasn't easy.

'This road wasn't built
until 1936,

'so all the concrete and steel
had to be brought up

'by backpack or mule train on
a very steep seven-mile trail.'

The packhorses made 60 trips to
transport the telescope alone,

but Hale soon had an observatory
that was the envy of the world.

His first challenge was
to understand the sunspots.

Hale built a spectrograph,

which is here beneath
this table.

75 feet below is a grating,

that disperses
the light of the sun

into its energy components.

The grating
would look like this,

and would break the sunlight
into its different colours.

In this spectrum are the
absorption lines of the gases.

With his unique spectrograph,

Hale started analysing
the sun's surface.

He could take
photographs of sunspots

in more detail
than anyone had before.

During a routine study

of the chemical absorption lines
of the sun's surface,

he made a breakthrough.

'Looking at the
quieter part of the sun,

'he saw ordinary-looking
absorption lines.

'Then as the sunspot
rolled into the slit,

'the lines began
to broaden and split.'

Hale saw the lines split apart
and recognised the phenomenon.

Voil�, magnetic fields.
He could see it. June 1908.

Hale had unravelled one
of the sun's greatest mysteries.

Sunspots were caused
by magnetic distortion.

These distortions
are 4,000 times greater

than the Earth's magnetic field.

They suppress
the upward surge of gases,

cooling the surface
by 2000 degrees,

and causing the dark spots.

'A sunspot on the surface

'is just a twisted
and kinked magnetic field,

'looped out of the surface.'

This magnetogram shows
how the surface is speckled

with positive and negative
lines of magnetic force.

These tortured field lines
channel the sun's storms -

eruptions of plasma,
exploding outwards

for thousands of kilometres,

before being dragged back
into its boiling surface.

'Coronal mass ejections,
prominences,

'all features on the sun's
surface are magnetic in nature.'

In one of the coldest places
on Earth,

15 years before Hale started
his investigation into the sun,

a Norwegian scientist
had drawn his own conclusions

about the sun's magnetism.

In a land where you
can't see the sun for months,

he was convinced you
could feel its presence

in one of the most
beautiful phenomena on Earth.

'It may be strange
to see why we're here,

far to the north, in the
darkness, dealing with the sun.

But here you see
the aurora, the Northern Lights.

I really like to see the aurora.

It's beautiful in many colours

you don't see anywhere else.

It really lights up the dark
days here in wintertime.

'Earlier, it was thought
the Northern Lights

'was the souls
of dead soldiers fighting.'

(Whistling and humming)

Norway is one of the best
places to study auroras.

Truls Hansen monitors
the radioactivity

high in the Earth's atmosphere.

This area of research
goes back over a century.

100 years ago, Norway's
most famous scientist

dedicated his life to the study
of atmospheric disturbances.

His name was
Doctor Christian Birkeland.

Birkeland was
brilliant, but a bit mad.

You might see
that from his book.

It contains not only theories
about particles and the aurora,

but a lot of ideas.

Some right, most wrong.

One of them was Terrela,
which we see clearly here.

A vacuum chamber
with a small globe,

pretending the Earth inside it.

'We can also see Birkeland,
controlling the experiment.'

This experiment artificially
created the Northern Lights.

To protect his brain from
radiation, he always wore a fez.

Birkeland's theories
about the origin of auroras

stemmed from years
of dedicated study.

Auroral activity is
particularly energetic

after a period
of solar activity.

Birkeland wanted to find
a mechanism to link the two.

These are
the old magnetometers,

which have been operating
for more than 100 years.

They're still used
here and there.

Birkeland used
very similar instruments.

Here's a recording
of the magnetic field,

taken with this instrument.

It starts quiet around noon,

and then, here in the evening,

you get a magnetic storm,

which you see clearly here.

During this period you have
a large and very bright aurora.

This is the
Birkeland Terella experiment.

He built several,
but this is the biggest one,

and the last one,
I suppose, being made in 1913.

It's a large vacuum chamber with
a model of the Earth inside.

Birkeland thought the magnetic
storms with the Northern Lights

were caused by
electrically-charged particles

buffeting the Earth's
magnetic field.

He believed these particles
came from the sun,

but his ideas
were never taken up.

In 1917,
Birkeland committed suicide.

In fact, evidence of the
extraordinary reach of the sun

had been visiting
our skies for millennia.

The dusty comet tails always
point away from the sun.

It was assumed that
sunlight alone was the cause.

But in 1947, a German physicist,
Ludwig Bierman,

calculated that something
far more substantial

had to be pushing
the comet tails.

He called it
solar corpuscular radiation,

and his idea
was rejected immediately.

Despite the general derision,
physicist Eugene Parker

was unable to dismiss
Bierman's argument.

'I had a chance
to talk to him in Chicago.'

He said if it isn't sunlight,

then it must be
the solar corpuscular radiation,

the emission
of particles from the sun

that blow the tail away
from the sun.

'His revelations made me see
he had a fundamental point.'

The physicist Sidney Chapman was
very eager to attack Bierman.

He said the sun was 330,000
times more massive than Earth,

and that no particle,
however small,

could escape
its enormous gravitational pull.

Regardless of his scorn
for the solar wind,

Chapman was developing
his own idea

for how the sun was
reaching out to the Earth.

He suggested the corona,

though firmly bound to the sun,

stretched much farther
than is seen during an eclipse.

Eugene Parker met Sidney Chapman
in Boulder, Colorado.

I was thinking about what
I had learned from Chapman,

that the corona extends out
through the solar system.

I realised that Chapman and
Bierman were mutually exclusive.

The solar corpuscular radiation
that affects the comet tails

can't penetrate through a static
corona, interactions block this.

But I could not see that
either one of them was wrong.

Parker worked at the apparent
contradiction in the theories,

and found that both were right.

'I integrated
the equations of motion.'

I found only one solution
that fitted the condition

of strong rebound at the sun
and zero pressure in infinity.

That was the solution providing
the supersonic solar wind.

Parker's solar wind was more
complex than Bierman's version.

He calculated the corona
did have enough thermal energy

to escape its gravity and
stream off at 500km a second.

But when he went public,
Parker himself was ridiculed.

'The referees for my
papers were anonymous.

'I was assured
they were experts.

'They declared
the ideas were absurd.'

Others declared it was false,

and published papers
showing alternatives,

and gave lectures
decrying the idea.

My friends said,
"It was a great idea,

"but great ideas often
fall on their face."

My reaction was, "We'll see
what falls on its face."

Parker waited five years
for his theory to be vindicated.

in 1962, the Mariner 2 probe to
Venus carried particle detectors

designed to discover
how empty space was.

The world's first interplanetary
probe signalled back that space

is awash with a solar wind
exceeding Parker's estimates.

'The JPL plasma detector

'showed there was a wind

'of anywhere from 300
to 800km per second.'

The wind was always
there and never ceased.

I refused to argue
with anybody after that.

Modern telescopes
have revealed the complexity

of Parker's solar wind.

From the sun's equator particles
constantly evaporate into space.

Occasionally, gusts break free

of the sun's gravitational
and magnetic forces.

These are the flares and coronal
mass ejections seen by Skylab.

These electrically-charged
hurricanes

are ferocious and relentless.

The planets lie
in their firing line.

Mercury, closest to the sun,

bares the brunt
of the solar wind.

Any atmosphere this world may
have had has been blown away,

leaving its surface
bathed in deadly radiation.

Mars is four times further
from the sun than Mercury,

yet it's thought
the solar wind has stripped

a third of its
original atmosphere,

leaving a veil one hundred
times thinner than ours.

Venus, our nearest neighbour,

has an atmosphere a
hundred times thicker than ours.

Modern probes
discovered a comet-like tail

that stretches back
to the Earth's orbit.

The clouds on Venus are also
being eroded by the solar wind.

And what of our atmosphere?

Earth has a magnetic field that
stretches far out into space.

It deflects the solar wind
and protects our atmosphere.

A force-field fighting
a constant battle with the sun.

The solar wind and the Earth's
magnetic field battle together.

The magnetic field is being
compressed by the solar wind.

'As this pressure increases,

'and sends the particles through
along the magnetic fields

'down to the
Earth's polar areas,

'we see them as aurora
in the upper atmosphere.'

We live in a region
dominated by the solar wind,

which extends
far out into space.

'The next question is how far
out into space it extends,

'as it spreads out
farther from the sun.'

What is the full
extent of the sun?

The first space
probes venturing to Jupiter

recorded massive
radio emissions.

That was the same battle

between Jupiter's magnetic
field and the solar wind.

As the spacecraft Voyager
visited the outer planets,

it found the same
signature of solar wind

buffeting magnetic fields.

When it left Neptune,
the solar wind was still there.

Where would it end?

Three years beyond Pluto,

it detected a mysterious
burst of radio energy.

The signals were picked up

at the tracking station
at Goldstone, California,

where Don Gurnett had been
keeping in touch with Voyager.

My primary interest now
is following the solar wind

as it expands out from the sun.

It has to be stopped some
place by the interstellar gas.

This boundary
we call the heliopause.

The radio burst picked up by
Voyager was totally unexpected.

There were no giant planets
within three billion kilometres.

We didn't know
the signal's origin.

We thought it was coming
from Jupiter or Saturn.

Or maybe it was coming from
much further away from the sun.

Their search led them back to
the heart of the solar system.

We noticed a series of very
powerful coronal mass ejections,

'some 400 days
before the radio burst.'

Checking
through Voyager's log,

Don found it had been overtaken
by the outburst

after 100 days.

300 days later, the solar gust
reached a magnetic boundary.

Was this the heliopause, the
outer limit of the solar wind?

Our model is that
this coronal mass ejection

produced a plasma pulse
coming out from the sun

that propagated for 400 days.

We detected it
going by Voyager One and Two.

That pulse of plasma eventually
reached the heliopause,

and caused the radio emission.

The radio burst
places the heliopause

at four times
the distance of Pluto.

This is the extent of the sun.

Even the most distant planets,

where the sun's
just a bright star,

bathe in its
evaporating atmosphere.

The planets are bound
by our sun's gravity.

They were formed as
a by-product of its creation.

There's a more fundamental bond

between the planets
and the stars.

The very stuff of life
is built inside them.

A star's core is
the ultimate fusion reactor.

Douglas Gough wants
to see it in action.

'My goal is to learn about
the structure of the core,

'because the nuclear physics
is so interesting.'

The nuclear reactions
that change material,

that produce new
particles that leave the sun,

help us understand the physics
of elementary matter.

1995 saw the launch of a
new era of solar exploration.

A journey that may take us to
the heart of a star.

The solar observatory SOHO
can view the sun in X-rays,

ultra-violet and visible light.

But SOHO doesn't
just look. It listens.

In 1975,

when Gough learned the sun's
surface rippled like a pond,

he instantly saw
a way to see to its core.

'I realised this is a way
of seeing inside the sun.'

You can't see inside the
sun with light, it's opaque.

But this was sound.
You can hear inside it.

By doing so, you could learn
the structure of the sun inside.

I found that an amazing concept,

that you could
get inside a star.

The surface of
the sun is heaving.

Every six minutes the entire
star breathes in and out.

Its gaseous ocean
swells and dips,

and a complex pattern of ripples
shimmer across its surface.

Clues to the structure within.

'The sun's like
a chorus of instruments,

'playing, but not in tune.'

It's cacophonous, which gives

much information
about the detailed interior.

The sound waves
move back and forth,

and give tones,
like a musical instrument.

SOHO has revealed
new surface phenomena.

After a solar flare,
seismic quakes spread out

for thousands of kilometres.
But there's much more.

'We've learned
about the sun's outside'

from studying the
sound waves from SOHO.

We've learned about the dynamics
and the chemical composition.

We want to do something
similar in the core.

SOHO has started to strip
away the sun's outer layers.

Under its surface, it
discovered rivers of plasma,

super-heated gases
that circle its pole.

Looking like the
jet stream on Earth,

it seems the sun
has weather too.

But deep in the core is that
remarkable chemical factory.

'The stars make all
the matter that we are made of,

'from hydrogen and helium.
That's what we're made of.

'They're the factories
that make material.

'To understand the universe,
we need to study the stars.'

Every star has a core.

Almost all stars are
generating nuclear energy,

transmuting elements
from one to another,

building up the heavy
elements of the universe.

We believe the stars' physics
are the same as on Earth.

This physics we must
understand more carefully,

so we can work out
what that implies

about the structure of the
universe and how it evolves.

In the beginning, the universe
contained hydrogen and helium.

For 12 billion years, stars
have been transforming them

into more complex elements.

Our sun is born
from that process.

4.5 billion years ago,

a star on the fringes
of our galaxy

ended its existence
as a supernova.

Its death throes sent the
contents of its core into space.

These heated grains of silicon,
iron and many other elements

careered into a cloud of gas,
causing it to collapse.

As the gas and dust mixture
went to the cloud's centre,

they ignited a nuclear reaction
and our sun burst into life.

The remaining debris from the
supernova formed the planets.

We are made of star dust,
forged in the heart of a star.

In the last 400 years,

science has peeled back
our sun's layers,

to reveal a star, one of the
countless engines of creation,

which made the planets,
which made us.

Our ancestors saw a
perfect disc of light. A god.

Science has revealed
an entity more powerful

than they could
ever have imagined.