Original subtitles

We pulled the stars from the skies...

...and brought them down to Earth.

But at what cost?

When we turned on all these lights...

we lost something precious.

The stars.

"Sisters of the Sun"

A long time ago, in a world lit only by fire,

our relationship with the stars

was far more...

personal.

For thousands of generations,

we watched the stars

as if our lives depended on it.

Because they did.

We humans were not the biggest,

the strongest, nor the fastest

of all the animals we competed against.

But we did have one thing going for us...

our intelligence.

One aspect of that was a genius

for pattern recognition.

Night after night, we watched the stars.

And over time, our ancestors noticed

that the motions of the stars across the nights of the year

foretold changes on Earth

that threatened or enhanced our chances for survival.

In a time when our imaginations

were the only stage where stories came to life,

before there were movies or TVs

or electronic devices of any kind,

every human culture connected the dots

to form their own pictures.

These images became the illustrations of a storybook

that, on a deeper level, was also a survival manual.

The names and personalities of the gods, heroes,

farm animals or familiar objects

varied from culture to culture.

But there was one particularly gorgeous group of stars

known to the Ancient Greeks and to us today

as the Pleiades,

a star cluster formed about 100 million years ago.

Each of them is some 40 times brighter than our Sun.

And Alcyone, the most luminous,

outshines our Sun 1,000 times.

For ages, the Pleiades have been used as an eye test

for people all over the world.

If you could see at least six of them,

you were considered normal.

If you saw more than seven,

you were an ideal candidate for a warrior or scout.

Among the Ancient Celts and Druids of the British Isles,

the Pleiades were believed to have a haunting significance.

On the night of the year that they reach

the highest point in the sky at midnight,

the spirits of the dead were thought to wander the Earth.

This is believed to be the origin of the holiday

once known as Samhain,

now called Halloween.

All over the Earth, our ancestors told

wonderful stories to explain

how the Pleiades came to be in the sky.

For the Kiowa people of North America,

it happened something like this.

Long, long ago, some young women

snuck away from their campsite

to dance freely beneath the stars.

Rock, save us!

Rock, take pity on us!

The rock heard their cries and grew taller.

Until it became what is today known as the Devil's Tower.

The maidens were transformed into the stars of the Pleiades,

which may be seen hanging above the tower in midwinter.

The Ancient Greeks also saw those seven jewels

as seven maidens,

the seven daughters of Atlas,

pursued not by bears, but by...

Orion the hunter,

who spied them when he was out walking one day.

Orion became mad with desire.

For seven years, he chased them relentlessly.

- Exhausted... - Zeus, help us.

...they prayed to Zeus for deliverance.

Zeus, the king of the gods, felt sorry for them,

and transformed those seven maidens

into the Pleiades.

But the gods are, if anything, capricious.

When Orion was killed by the sting of a scorpion,

Zeus placed him in the sky where he could resume his pursuit

of the seven gorgeous sisters.

Our ancestors, they wove

brilliantly imaginative stories.

But they can bring us no closer to the stars

than our dreams.

It took yet another few thousand years

until three brilliant scientists unlocked the secrets

of the true lives of the stars.

In 1901,

Harvard was a man's world.

But an astronomer named Edward Charles Pickering

broke that rule.

Oh, Pickering's office is just down the hallway.

And that door over there leads to the room

where he keeps his computers.

We're supposed to call those women "computers," but, uh,

I've heard more than one fellow refer to those gals

as "Pickering's Harem."

Pickering assembled a team of women

to map and classify the types of stars.

One of them provided the key to our understanding

of the substance of the stars.

And another devised a way for us to calculate

the size of the universe.

For some reason, you probably never heard of either of them.

Wonder why.

That's Annie Jump Cannon, the leader of the team.

Before she was through,

she catalogued a quarter of a million stars.

Number 11 is a B7.

That's Alcyone in the Pleiades.

Cannon lost her hearing during a bout of scarlet fever

when she was a young woman.

Number 12 is a B6.

That's Henrietta Swan Leavitt. She's also deaf.

And she's the other great scientist in the room.

Leavitt discovered the law that astronomers still use

more than a century later

to measure the distances to the stars

and the size of the cosmos itself.

Annie Jump Cannon sent out a Christmas card explaining

what she and her sisters were actually doing.

The light from a star is allowed

to fall through a prism placed in the telescope, she wrote.

Thus magnified, the starlight is split up into a band

showing its component colors,

the red rays going to one end and the violet to the other.

This is the spectrum of the star.

It shows the presence of fine, dark lines.

By comparing them with lines given

by glowing substances in the laboratory,

we can determine that the same elements familiar to us

on the Earth also exist in the outermost star.

This is plate number 12358B.

Number one at this plate is a B-type star.

Make that a B2.

It took Cannon decades

to classify the spectral character

of hundreds of thousands of stars

according to the scheme that she devised.

Cannon discovered that the stars fell

into a continuous sequence of seven broad categories

according to their spectral line patterns.

Each was designated by a letter.

But the spectral lines of two stars in the same letter class

could differ in subtle ways,

minute variations that Cannon learned

to recognize from memory.

To distinguish these spectra from one another,

she assigned ten numerical subcategories for each class.

Annie Jump Cannon organized the stars,

but it would fall to another scientist to decipher

the hidden meaning in her work.

In the England of 1923, women were forbidden

from pursuing advanced degrees in science.

But Cecelia Payne had attended a lecture in London

by the astronomer Sir Arthur Eddington,

the first scientist to provide evidence

that Einstein's revolutionary

General Theory of Relativity was correct.

From that moment on,

she knew that nothing would deter her

from pursing her big dreams.

She resolved to emigrate to America,

where women had already gained the freedom

to study the stars.

Her application was accepted at Harvard.

What she would discover there would challenge

one of the central beliefs of astronomy.

The resulting impact

would be the dawn of modern astrophysics.

As the decades passed,

Annie Jump Cannon and her team kept sifting the stars,

checking each one's spectral signature

with a fleeting glance and then dropping them

into one of seven categories.

They became hundreds of thousands of dots

in a larger picture which no one could yet understand.

Into this community of women came one more.

Well, hello there.

You must be Miss Payne.

We've been waiting for you.

Come on in.

Cecilia Payne had never experienced such kindness

in a scientific setting before.

This sisterhood generously shared

the fruits of their labors with her,

and she turned their observations

into a radical new understanding of the stars.

The two women became great friends.

Cannon taught Payne everything she had learned

about stellar spectra.

And Payne began to analyze Cannon's data

to see if she could determine the actual chemical composition

and physical state of the stars.

She brought to this work her expertise

in theoretical and atomic physics.

The most prominent features in the spectra of stars

showed the presence of heavy elements

such as calcium... and iron,

which are among the most abundant elements in the Earth.

So astronomers naturally concluded

that the stars were made

of the same elements as the Earth

and in roughly the same proportions.

In 1924, Henry Norris Russell was the dean

of American astronomers, having made major contributions

to our understanding of the stars.

40 to 45 of the chemical elements

that we have here on Earth

are also present in the spectrum of the Sun.

So we can assume that the composition of the Sun

resembles that of the Earth.

If one were to heat the crust of the Earth to incandescence,

its spectrum would resemble that of the Sun.

Annie, I think I now understand what it all means.

All your years of work.

Tell me.

I've calculated what the spectra

should look like across a wide range

of temperatures, and they match

your system of classification perfectly.

The spectrum of any star tells you exactly how hot it is.

Your "O-B-A-F-G-K-M" is really a temperature scale of the stars

from the hottest to the coldest.

Here's the headline, Annie. Thanks to your work,

I've discovered that the stars are made almost entirely

of hydrogen and helium.

There's a million times more hydrogen and helium

than the metals in the stars.

I know, it sounds daft.

Are you certain?

Has anyone else checked your calculations?

Not yet, but it's all in my thesis,

which is already on its way to Professor Russell.

Poor woman.

Russell felt sorry for Cecilia Payne.

Her thesis appeared to him to be fundamentally flawed.

It is clearly impossible that hydrogen should be

a million times more abundant than the metals.

Her carefully gathered evidence flew in the face

of conventional scientific wisdom.

"How could I be right," she asked,

"if that must mean

that such a distinguished scientist was wrong?"

Despite her confidence in the quality of her research,

she caved and added a sentence to her thesis

that undermined its greatest insight.

It would be four years

before Russell realized that Payne was right.

To his credit, as soon as he did,

he acknowledged that it was her discovery.

Payne's "Stellar Atmospheres" is widely regarded

as the most brilliant PhD thesis

ever written in astronomy.

It became the standard text in its field.

I was to blame for not having pressed my point.

I had given in to authority when I believed I was right.

If you are sure of your facts,

you should defend your position.

The words of the powerful

may prevail in other spheres of human experience,

but in science, the only thing that counts is the evidence

and the logic of the argument itself.

Cecilia Payne's interpretation of Annie Jump Cannon's sequence

of stellar spectra made it possible for us

to read the life stories of the stars

and to trace the story of life itself back to its beginnings

in their fiery deaths.

There are many kinds of stars.

Some are bright like the Sun.

Some are dim.

The greatest stars are ten million times larger

than the smallest ones.

Some stars are old beyond imagining,

more than ten billion years of age.

Others are being born right now.

When atoms fuse in the hearts of stars,

they make starlight.

Stars are born in litters,

formed from the gas and dust of interstellar clouds.

The mass of the individual stars in a litter

can range from the runts-- not much larger

than the largest planets--

to the supergiant stars that dwarf the Sun.

The stars in the nebula below Orion's Belt are newborns,

around five million years old,

and still swaddled in the gas and dust

that gave birth to them.

The stars in the Pleiades are already toddlers,

about 100 million years old.

They've shed their blankets of gas and dust,

but they're still bound together

by their mutual gravity.

Another few hundred million years,

and they'll drift apart and go their separate ways,

never to meet again.

Most of the stars of the Big Dipper are adolescents,

roughly half a billion years old.

They've already drifted apart from their birth cluster,

although we can still trace their common ancestry.

Eventually, they'll spread out around the Milky Way galaxy.

But most of the familiar constellations

are a mix of entirely unrelated stars,

some faint and nearby,

others bright and far away.

Our own Sun?

From the distance of even a few light-years,

it's hard to find amidst the other stars.

It's that one.

Our Sun is middle-aged

and a long way from where it was born.

Its sister stars,

hatched from the same interstellar cloud,

are dispersed throughout the galaxy.

Many of them have their own planets.

Perhaps some of them nurture

the evolution of life and intelligence.

Most of the stars in our night sky

actually orbit around one or more stellar companions.

With the naked eye,

we usually can't see the fainter members

in such double and multiple star systems.

On a world with three suns,

the nights would be rare

and the days might alternate between red and blue.

It is the destiny of stars to collapse.

Of the thousands of stars you see

when you look up at the night sky,

every one of them is living

in an interval between two collapses...

an initial collapse of a dark, interstellar gas cloud

to form the star,

and a final collapse of the luminous star

on its way to its ultimate fate.

Gravity makes stars contract,

unless some other force intervenes.

The Sun is a great, big ball of incandescent gas.

The super hot gas in its core

pushes the Sun to expand outward.

At the same time, the Sun's own gravity

pulls it inward to contract.

And our Sun is poised between these two forces

in a stable equilibrium

between gravity and nuclear fire,

a balance it will maintain

for another four billion years.

But as the Sun consumes hydrogen,

its core very slowly shrinks,

and the Sun's surface gradually expands in response.

It happens very slowly,

imperceptibly,

over the course of millions of years.

But in about a billion years,

the Sun will be ten percent brighter

than it is today.

Ten percent may not sound like much,

but that extra heat will have a big effect on Earth.

When the Sun finally exhausts its nuclear fuel

four or five billion years from now,

its gas will cool and the pressure will fall.

The Sun's interior

can no longer support the weight

of the outer layers,

and the initial collapse will resume.

Nothing lasts forever.

Even the stars die.

Helium, the ash

of ten billion years of hydrogen fusion,

has built up in the core.

With no nuclear fire to sustain its weight,

the core collapses until it becomes hot enough

to start fusing helium into carbon and oxygen.

The core of the Sun

is now much hotter than it was before.

Its atmosphere rapidly expands.

Over the next billion years, it'll become bloated

to more than 100 times its original size--

a red giant star.

It will envelop and devour

the planets Mercury...

...and Venus...

...and possibly the Earth.

I like to think that

tens of millions of years before that far distant future,

if there still be life born of Earth,

it will have found new homes among the stars.

Once the Sun burns through its helium,

it will become highly unstable,

casting off its outer layers into space.

The exposed, super hot core

will flood its surroundings

with high-energy ultraviolet light.

The atoms will perform a wild, fluorescent dance.

The Sun will collapse like a souffl�,

shrinking a hundredfold to the size of the Earth.

And at that point, the Sun will be so dense

that its overcrowded electrons will push back,

stopping any further contraction.

The kernel of light at the center

will be the only part of the Sun that endures,

a white dwarf star that will go on shining dimly

for another 100 billion years.

Will the beings of a distant future,

sailing past this wreck of a star,

have any idea of the life and worlds that it once warmed?

The psychedelic death shrouds

of ordinary stars are fleeting,

lasting only tens of thousands of years

before dissipating in the interstellar gas and dust

from which the new stars will be born.

The stars in a binary star system

can have a different fate.

Sirius, the brightest star in the night sky,

has a very faint stellar companion--

a white dwarf.

It was once a Sun-like star.

Someday, when Sirius runs out of fuel

and becomes a red giant,

it will shed its substance onto the white dwarf.

The intense gravity of the companion

will attract that gas,

pulling it into a spiraling disk.

When the gas from the larger star

falls onto the surface of the white dwarf,

it will trigger nuclear explosions.

The greatest burst will release

100,000 times more energy than the Sun.

Each one of those star bursts is called a "nova,"

from the Latin for "new."

A star about 15 times as massive as the Sun,

one like Rigel, the blue supergiant

that forms the right foot of Orion,

has a different fate in store.

Its collapse will not be stopped by the pressure of electrons.

The star will keep falling in on itself,

until its nuclei become so overcrowded

that they push back.

Rigel will shrink down about 100,000 times,

until there's no space left between the nuclei

and it can shrink no more.

At that point, it ignites

a more powerful nuclear reaction, a supernova.

Most stellar evolution

takes millions or billions of years.

But the interior collapse

that triggers a supernova explosion takes only seconds.

What remains will be an atomic nucleus

the size of a small city--

a rapidly rotating neutron star called a pulsar.

But for a star more than

30 times as massive as the Sun--

a star like Alnilam, in Orion's Belt--

there will be no stopping its collapse.

In a few million years,

when Alnilam runs out of fuel,

it, too, will go supernova.

The imploding core of Alnilam

will be so massive that not even nuclear forces

will be strong enough to hold off its collapse.

Nothing can withstand such gravity.

And such a star has an astonishing destiny.

It will continues to collapse,

crossing a boundary in space-time

called the "event horizon,"

beyond which we cannot see.

When it traverses that frontier,

the star will vanish completely from sight.

It will be inside a black hole,

a place where gravity is so strong

that nothing, not even light, can escape.

But there's an even

more dramatic fate

that awaits a rare kind of star.

There's one of them in our galaxy.

It's so unstable that when it goes,

it won't become a mere nova or supernova.

It'll become something far more catastrophic...

a hypernova.

And it could happen in our lifetime.

There are few places on Earth to get a better view

of the night sky than the Australian Outback.

No buildings,

no cars, streetlights, nothing out here;

just lots of starlight...

and the occasional kangaroo.

You can get a particularly good view

of the Milky Way from down here.

The center of our galaxy

rises high in the sky,

and it arches across the heavens

like the backbone of night.

We live in a spiral galaxy.

And when we look at the Milky Way,

we're seeing light from billions of stars in its spiral disk.

And under this beautiful dark sky,

you can see that the Milky Way isn't a uniform band of light.

There are dark patches, breaks in the starlight.

Those dark patches are caused by interstellar dust.

The dust blocks the starlight, and there's lots of it.

Most cultures looked up at the stars

and connected the dots

to form familiar images in the sky.

Constellations.

But the Aboriginal people of Australia

saw a pattern in the darkness

running through the Milky Way.

They saw an emu, a large bird

native to this continent.

Not in the stars, but in the absence of stars.

There are so many ways to look at the night sky.

For a million years or more, we've watched the sky.

And a lot's happened in that time.

Supernova explode in our galaxy about once a century.

If we could compress all those nights of stargazing

into a single minute,

this is what we would see.

Now, if our eyes were telescopes,

if they were light buckets as big as wagon wheels

and our vision was not limited to just one kind of light,

then this is the Milky Way we would see.

A galaxy in near-infrared light

with streaming tendrils of dust

hurled outward by those exploding supernovas,

silhouetted against a backdrop

of countless stars.

About 7,500 light-years away,

in another part of our galaxy,

there is a place of upheaval

on an inconceivable scale.

This is the Carina Nebula.

A star-making machine.

It takes a ray of light 50 years to cross it.

The titanic stars born here

sear the surrounding gas and dust

with their fierce ultraviolet radiation.

When a massive star dies,

it blows itself to smithereens.

Its substance is propelled across the vastness

to be stirred by starlight

and gathered up by gravity.

Stars to dust

and dust to stars.

In the cosmos, nothing is wasted.

But there's an upper limit to how massive a star can be.

Back in the 17th century, when Edmond Halley

crossed the equator to map the southern constellations,

Eta Carinae seemed like just another faint star.

But in 1843, Eta Carinae

suddenly became the second brightest star in the sky,

outshined only by Sirius.

And it's been flipping out ever since.

That dumbbell-shaped cloud

is the expanding remnant of that event.

At its center is one crazy star.

Talk about unstable--

Eta Carinae is at least 100 times

more massive than the Sun,

and pouring out five million times more light.

It's pushing the upper limit of what a star can be.

What's more, there's evidence that Eta Carinae

is being gravitationally tormented by an evil twin--

another massive star in orbit around it

as close as Saturn is to the Sun.

The core of a supermassive star pours out so much light

that the outward pressure can overwhelm the star's gravity.

If a star is too massive,

its radiation pressure overpowers its gravity

and blows the star apart.

The fate of Eta Carinae was sealed

when it was born millions of years ago.

When it finally does blow up--

and who knows, maybe it already has;

after all, we're looking at it by light that left the star

7,500 years ago--

it will be a cataclysm unlike anything we've seen before.

A hypernova.

An explosion so powerful, it'll make a supernova

seem like a firecracker by comparison.

If there are nearby solar systems

with planets harboring life, their days are numbered.

A hypernova spews so much radiation into space--

not just light, but X-rays and gamma rays--

that planets that are dozens

or perhaps hundreds of light-years away

could be stripped of their atmospheres

and bathed in deadly radiation.

It would wreak havoc

in thousands of nearby star systems.

Right about now, you're probably asking yourself,

"Are we safe?"

If Eta Carinae blows up,

what happens to Earth?

Rest assured, Earth will be just fine.

Remember, we're 7,500 light-years

away from Eta Carinae.

The intensity of radiation from a star,

even an exploding star,

falls off rapidly with distance.

But still, Eta Carinae in its death throes

will put on quite a show.

It will light up the night of the southern hemisphere

with the brightness of a second moon.

The most dramatic swan song a star can sing.

Our ancestors worshipped the Sun.

And they were far from foolish.

It makes good sense to revere the Sun and stars,

because we are their children.

The silicon in the rocks, the oxygen in the air,

the carbon in our DNA, the iron in our skyscrapers,

the silver in our jewelry

were all made in stars billions of years ago.

Our planet, our society and we ourselves

are stardust.

Well, what is it that makes the atoms dance?

How is the energy of a star transformed

into everything that happens in the world?

What is energy?

We're awash in it.

When hydrogen atoms fuse inside the Sun,

they make helium atoms.

And this fusion emits a burst of energy

that can wander inside the Sun for ten million years

before making its way to the surface.

And once there, it's free to fly

straight from the Sun to the Earth

as visible light.

If it should strike the surface of a leaf,

it will be stored in the plant as chemical energy.

Sunshine...

into moonshine.

I can feel my brain turning the chemical energy of the wine

into the electrical energy of my thoughts

and directing my vocal chords

to produce the acoustic energy of my voice.

Such transformations of energy

are happening everywhere all the time.

Energy from our star

drives the wind and the waves

and the life around us.

How lucky we are to have this vast source of clean energy

falling like manna from heaven on all of us.

To Annie Jump Cannon,

Henrietta Swan Leavitt

and Cecilia Payne

for blazing the trail to modern astrophysics.

And to all the sisters of the Sun.

There's no refuge from change in the cosmos.

Some ten or 20 million years from now,

it'll seem for a cosmic moment

as if Orion is finally about to catch the seven sisters.

But before he has them in his clutches,

the biggest stars of Orion will go supernova.

Orion's pursuit of the Pleiades will finally end,

and the seven sisters

will glide serenely into the waiting arms

of the Milky Way.

We on Earth marvel-- and rightly so--

at the return of our solitary Sun.

But from a planet orbiting a star

in a distant globular cluster,

a still more glorious dawn awaits.

Not a sunrise...

but a galaxy rise.

A morning filled with 200 billion suns.

The rising of the Milky Way.

An enormous spiral form with collapsing gas clouds,

condensing planetary systems, luminous supergiants,

stable middle-aged suns, red giants, white dwarfs,

planetary nebulas, supernovas,

neutron stars, pulsars, black holes

and, there is every reason to think,

other exotic objects that we have yet to discover.

From such a world, high above the Milky Way,

it would be clear, as it is beginning

to be clear on our world,

that we are made by the atoms and the stars,

that our matter and our form

are forged by the great and ancient cosmos,

of which we are a part.