All language subtitles for How the Universe Works s01e04 Stars.eng

Stars...
they're big, they're hot,

and they are everywhere.

Stars rule the universe.

Our destiny is linked
to the destiny of stars.

Born in violence,
dying in epic explosions.

They fill the universe
with stardust,

the building blocks of life.

Every atom in your body

was produced
inside the fiery core of a star.

Stars are what
make our universe work.

All life begins here.

The night sky is packed
with stars.

On a clear night in the country,
if you're lucky,

you can see maybe 3,000 stars.

But that's just the tip
of a vast cosmic iceberg.

In our galaxy alone, there are
over 100 billion stars.

And, in fact, there are
over 100 billion galaxies

in the observable universe.

There are more stars than there
are specks of sand on Earth.

Every star is powerful,

creating the basic matter

for everything
in the universe...

...including us.

Most are so far away,
we know little about them.

But there is one star
that's really close,

and virtually everything
we know about stars,

we've learned
from that neighbor.

The sunlight from our sun
that bathes us

and warms us every day
is nothing but starlight

because our sun is nothing
but a star like all the rest.

Seen from Earth,

our sun is a blinding ball
of light.

But take away the glare,

and one of the most
powerful objects in the universe

appears in our own backyard.

It's a ball of superheated gas
that's been lighting

our solar system
for 4.6 billion years

and dominates all life on Earth.

The Sun
is 93 million miles away.

And that means,
in actuality, it's immense.

You could fit a million Earths
inside the Sun.

It's nearly
a million miles in diameter,

yet our sun is tiny

compared to the really
big stars out there.

Eta Carinae... over five million
times larger than our sun.

Betelgeuse... 300 times larger
than Eta Carinae.

If it was our sun, it would
reach as far out as Jupiter.

And then there's this monster...
V.Y. Canis Majoris,

the largest star
ever discovered.

A billion times bigger
than our sun.

Stars burn in different colors,
from red to yellow to blue.

Some live alone.

Others in pairs,
orbiting each other...

...and coming together
in huge galaxies...

entire cities
made up of billions of stars.

Each star is a one of a kind.

But they all start life
in the same way...

As clouds of dust and gas
called nebulas.

Many billions of miles across,

they drift through space,
forming spectacular shapes.

The Flame nebula.

The Horsehead nebula.

The Orion nebula.

Each nebula is a star nursery

where millions of new stars
are being born.

But this birth
is hidden from view.

Some of the more
dramatic parts of a nebula

are not
the beautiful glowing gas

that you see but the dark parts.

The dark parts have areas
of dense gas and dust,

and that's where
the real action is happening

in terms of star formation.

The dust clouds are so thick,

regular telescopes
can't see inside.

There's nothing
more important to us than stars,

but for a long time,

the way they formed
was a complete mystery.

We couldn't observe them.
Imagine that.

We could not see the first
moments of a star at all.

Until 2004 when NASA
launched the Spitzer space telescope.

And liftoff.

Seeking hidden secrets

and the evolution
of our universe.

Spitzer is
an infrared telescope.

It only sees heat.

Heat passes through
the thick dust of the nebulas,

allowing Spitzer to see
new stars coming to life inside.

These remarkable pictures

capture the earliest moments
in a star's life

as pockets of hydrogen gas
begin to heat up.

Any little bit
of gas and dust is glowing.

Areas that were entirely dark
now became bright.

We can actually see
the very earliest parts

of star formation.

All you need to make a star
is hydrogen, gravity, and time.

Gravity pulls the dust and
gas into a giant swirling vortex.

Gravity brings matter together.

And when you bring
matter together

and you squeeze things
into smaller spaces,

they necessarily heat up.

It's a simple law of chemistry.

You compress something,
you drive the temperature up.

Over hundreds
of thousands of years,

the cloud gets thicker
and forms a giant spinning disk

bigger than
our entire solar system.

At its center,
gravity crushes the gas

into a superdense,
super-hot ball.

Pressure builds
until huge jets of gas

burst out from the center.

That really shows you

how violent a process
star formation is.

These jets
are many light-years across.

Something is literally
accelerating material very fast

across unimaginable distances.

Gravity keeps the pressure on,

sucking in gas
and dust particles

that smash into each other,
generating more and more heat.

Over the next
half a million years,

the young star gets smaller,
brighter, and hotter.

Temperatures at its core
reach 15 million degrees.

Only at that
mind-boggling temperature

can atoms of gas
begin to fuse together,

releasing massive amounts
of energy.

And just like that,
a star is born.

It will shine for millions,

even billions,

or perhaps even trillions
of years.

Stars produce massive
amounts of heat and light

over billions of years.

But that takes fuel
and lots of it.

Until the early 20th century,

no one had any idea
what this fuel was.

The greatest problem
facing physics

at the turn
of the last century was,

what drives the energy of stars?

All you had to do
was look outside

and realize
there was a huge gaping hole

in our understanding.

To solve the secret
of the stars,

we needed a new engine.

We needed
a fabulous source of energy

that could drive a star
for billions of years at a time.

And it took a genius
to discover it...

Albert Einstein.

His theories proved

that stars could tap
into the energy inside atoms.

The secret of the stars
is Einstein's equation e=mc2.

In some sense, matter,
which makes up our body,

is concentrated energy,
condensed energy...

energy that has condensed
into the atoms

that make up our universe.

Einstein showed
that it's possible

to release this energy
by smashing atoms together.

It's called fusion, the same
force that powers stars.

It's astonishing to realize
that the physics

of the very small
subatomic particle physics

determines the structure
and nature of stars.

From Einstein's theories,

we learned how to release
the energy inside an atom.

Now science
is trying to simulate

a star's energy source

to control the power
of fusion in a lab.

Inside this laboratory
near Oxford, England,

there's an 80,000-pound machine.

Every day,
Andy Kirk and his team

transform it into a star...

On Earth.

This machine
is called a tokamak.

It's effectively
a large magnetic bottle...

a cage to hold
a very hot plasma.

We're able to re-create
the conditions within a star.

Inside the tokamak,

hydrogen atoms
naturally repel each other.

To smash
hydrogen atoms together,

the tokamak heats them to more
than 300 million degrees.

At these temperatures,
the energized hydrogen atoms

are moving so fast,

they can't avoid smashing
into each other.

If you heat it up,
heat is motion.

And the motion of hot particles

will be enough to overcome
the repulsive force.

All personnel,
be prepared to leave.

Come off the machine area.

When everything goes right,

the result is the single best
power plant in the universe...

nuclear fusion.

Traveling at 1,000 miles
a second,

the hydrogen atoms smash
into each other and fuse...

...creating a new element...
helium...

...and a small amount
of pure energy.

The hydrogen gas weighs
slightly more than the helium.

You lost mass
in the process of burning.

That mass that you lost,
the missing mass,

turns into energy.

The tokamak
can only maintain fusion

for a fraction of a second.

But inside a real star,

fusion continues
for billions of years.

The reason is simple... size.

The engine
which drives a star is gravity.

That's why stars are big.

Stars are huge.

You need that amount of gravity
in order to compress the star

to create fantastic amounts
of heat

sufficient to ignite
nuclear fusion.

That is the secret of the stars.

That's why stars shine.

Fusion at the core of a
star generates the explosive force

of a billion nuclear bombs
every second.

A star is
a gigantic hydrogen bomb,

so why doesn't it
simply blow apart?

It's because gravity
is compressing the outer layers

of the star.

Gravity and fusion
lock horns in an epic battle.

We have this constant
tension between gravity,

which wants to crush a star
to smithereens,

and, also, the energy released
by the fusion process,

which wants
to blow the star apart.

And that tension,
that balancing act,

creates a star.

This power struggle plays out

over the entire life
of a star...

two awesome forces of nature
in a dynamic standoff.

As that battle rages, the star
blasts out light and heat

but also something
far more destructive.

Each beam of starlight
makes an epic journey.

Light travels
at 670 million miles an hour.

A beam of light
could travel around the Earth

seven times in one second.

Nothing in the universe
moves faster.

Yet most stars are so far away,

their light takes hundreds,
thousands, millions,

even billions of years
to reach us.

So, when
the Hubble space telescope

looks into the far corners
of our universe,

it sees light that's been
traveling for billions of years.

The light we see today
from Eta Carinae

left that star
when our ancestors

first farmed the land
8,000 years ago.

Light from Betelgeuse
has been traveling

since Columbus discovered
America 500 years ago.

Even light from our own sun
takes eight minutes to reach us.

But even before light starts
its journey through space,

it's already been traveling
for thousands of years.

When the Sun fuses hydrogen
into helium in its core,

it creates a photon of light,
a particle of light.

That new ray of light
has a long way to go

just to reach
the star's surface.

There's a whole star in its way.

And so when the photon
is created,

it doesn't get very far

before it immediately slams
into another atom...

another proton,
another neutron, something.

It gets absorbed and then
shot off in another direction.

And so it's sort of randomly
moving around inside of the Sun,

and it has to work its way out.

For the photons,
it's a wild ride,

smashing into atoms of gas
billions of times

as they struggle to escape
from inside the star.

What's funny
about this whole process

is that it takes the photon
thousands and thousands of years

to get from the core of the Sun
to the surface.

And yet
once it hits the surface,

it's only an eight-minute trip
from there to here.

Photons are the
source of light and heat,

but they also cause something
far more destructive...

the solar wind.

As they reach the surface,

photons heat up
the outer layers of the Sun...

...sending it hurtling
around the star,

creating extreme turbulence
and intense shock waves.

It's so violent,
we can actually hear it.

Picked up
by the orbiting SOHO satellite,

this is the sound of the Sun.

The speeding gases also generate
powerful magnetic fields.

As the star rotates,

the fields clash
and burst through the surface.

Giant magnetic loops
erupt into space.

Some are so large,

the Earth could pass
right through them

with thousands of miles
to spare.

They are spectacular,
and they are deadly,

blasting a stream of electrical
particles deep into space.

This is the solar wind.

It can damage
spaceships and satellites,

even put astronauts' lives
in jeopardy.

To discover how the magnetic
loops trigger the solar wind,

a team of scientists at CalTech
re-create the surface of a star

right here on Earth.

It's very exciting to be able
to create in a laboratory

the same sort of physics
that are on the solar surface.

We can't go there.
We can't even send probes there.

But we can try to study
what's happening there.

An airless chamber
simulates the vacuum of space.

An enormous electric current

produces a pair
of man-made magnetic loops.

The main difference

between the plasma loops
we make in the lab

and the ones
on the surface of the Sun

is just their size.

The ones we make in lab
are, you know, about this big,

and the ones
on the surface of the Sun

can be many times
the size of the Earth.

Their experiment reveals

that when magnetic
loops clash in the lab,

they trigger a massive
burst of energy.

When giant loops collide
on the surface of a star,

the energy released
sends temperatures soaring

from 10,000
to 10 million degrees.

That extreme heat
triggers the solar wind,

sending millions of tons
of particles

streaming out into space.

The bigger the star,
the more deadly the wind.

If we were orbiting a star
like Eta Carinae

at the same distance,

it would be hell on earth,
quite literally.

The amount of energy
blasting down on the Earth

would strip away our atmosphere,

boil our oceans,
melt the surface.

Understanding how stars
work could help us protect ourselves

by predicting
their most destructive forces.

But there's nothing we can do

to protect ourselves
when a star dies.

In its final moments,

it annihilates
everything around it.

From the moment of its birth,

every star is destined to die.

Its fuel will run out.

Then gravity
will win the battle with fusion,

triggering a chain of events
that will destroy the star.

Our sun is no exception.

Every second, it burns
through 600 million tons

of the hydrogen
fueled in its core.

At that rate,
the hydrogen will run out...

In about seven billion years.

As the hydrogen gets used up,

it slows down the fusion
at the star's core.

This gives gravity the edge.

With less fusion
pushing outward,

gravity crushes the star
in on itself.

But fusion fights back,
heating the star's outer layers.

When you heat up
a gas, it expands.

And so the Sun
will actually expand up.

Instead of being a million miles
across like it is now,

it'll swell up until it's about
100 million miles across.

Our sun will become a red giant.

Lmagine a sunrise 7 billion A.D.

It's not just
a little, yellow disk

coming up all cheerful and nice.

What you would see is a huge,
swollen, bloated, red disk

slowly reaching up
over the horizon.

And when the Sun
is fully up in the sky,

it's blasting down heat
on the Earth.

It would be like sticking your
head in an oven set to "broil."

Temperatures here on Earth
will reach thousands of degrees.

The oceans will boil,
the mountains will melt,

and we'll have the last nice
day on the planet Earth.

Then the bloated star
will engulf the Earth.

But the giant red star
is self-destructing.

Its core becomes
dangerously unstable.

With no hydrogen left
to fuel it,

the star begins burning helium
and fusing it into carbon.

The star is now destroying
itself from the inside out,

blasting violent surges
of energy

from its core to its surface.

These energy waves blow away
the star's outer layers.

Slowly, it disintegrates.

The star is dead.

All that remains
is an intensely hot, dense core.

The red giant
has become a white dwarf.

By the time a star
reaches the white-dwarf stage,

the fusion process has stopped.

The engine
has finally come to rest.

Our sun will end
its life as a white dwarf

no larger than the Earth
but a million times denser.

A white dwarf
is a pretty amazing object.

It's incredibly dense.

If you could take

a sugar-cube-sized chunk
of white dwarf

and put it on the surface
of the Earth,

it would be so dense,

it would fall
right through the ground.

At the heart of a white dwarf,

astronomers believe
there's a giant crystal

of pure carbon.

A cosmic diamond
thousands of miles across.

The idea
that the Sun will become

this sort of cool, dark lump
of cinder material

is kind of sad.

But that really will be

sort of a trillion-trillion-
trillion-karat diamond.

Think of that...
a diamond in the sky.

But stars can create something

much more precious
than a massive diamond.

When stars
much bigger than our sun die,

their death
is much more violent.

But in dying, they create
the building blocks of life.

Giant stars live fast,
burn bright, and die hard.

But from their destruction
comes life.

The death of massive stars

creates the building blocks
of the universe...

The seeds of life itself.

Less than 600 light-years
from Earth,

the monster star Betelgeuse
is near death...

well, in space years.

It's younger than our sun...

millions,
not billions of years old.

But the fusion at its core
is far more intense.

Betelgeuse is a different
beast from the Sun entirely.

It's a red supergiant.

And the reason is because
Betelgeuse is more massive.

It has 20 times
the mass of the Sun,

and that means
what's going on in its core

is very different than
what's going on in the Sun's.

Massive stars generate
pressures and temperatures

greater than anywhere else
in the universe.

The gravity of Betelgeuse
is so powerful,

it can smash together
bigger and bigger atoms.

The core of a massive star
is a kind of factory,

manufacturing heavier
and heavier elements...

...which is what also leads
to the star's destruction.

Once it makes the element iron,
the star is doomed.

In the world of science fiction,
there are many ideas

about what a star-killer
machine might be like.

Strangely enough, it's as run of
the mill as something as iron.

To a star,

iron is the most dangerous
element in the universe.

It's poison.

Iron absorbs energy.

From the moment
a massive star creates iron,

it has only seconds to live.

The star is trying to dump
energy into that iron ball

and trying to make it fuse,
but it can't.

And so that ball
is robbing the star of energy,

and it's that energy that
is supporting the star itself.

So, as soon as that iron starts
to be created in the core,

the star has written
its own death sentence.

The battle between
gravity trying to crush the star

and fusion trying
to blow it apart is over.

With iron,
fusion hits a dead end.

Gravity always wins.

The iron core collapses.

The outer layers of the star
slam down into it,

and a huge explosion
is generated.

It's the single most
violent event in the universe...

a supernova.

In just a few seconds,

supernovas create more energy
than our sun ever will.

Within a couple seconds
after beginning to make iron,

the star explodes
in a supernova.

So, think about that

when you're holding
one of your iron frying pans.

The iron killed a star
in just a few seconds...

dangerous stuff.

Telescopes around the world
scan the skies for supernovas.

In 1987,
a brilliant light appeared

in a nearby galaxy
170,000 light-years away.

These pictures record the events

following the death
of a massive star

as a fireball
trillions of miles wide

hurtles out into space.

But there's no record
of the actual moment of death

when the star
first ripped itself apart.

The only way to know
what happens

inside a massive star
when it explodes

is to make our own supernova.

What's amazing
when these stars explode

is that they almost
turn inside out.

Here in this lab
in Rochester, New York,

scientists are making
a supernova with a giant laser.

Telescopes can't see
inside the dying star.

With this laser,
we can detect the processes

that occur as the star explodes.

Working with these tools

is the most exciting thing
I can imagine doing.

This massive machine
amplifies the power

of a single laser beam
1,000 million million times.

That's enough power to supply
30 cities the size of Detroit.

And all that energy
will be directed

toward an area
the size of a pinhead.

Look at this tiny target
as a star's core.

The laser simulates

the most violent explosion
in the universe.

This would not be a safe place
to be when the laser was fired.

If a human were struck
by all these laser beams,

they would drill a hole
right through them.

Now going to closed access
in the laser bay.

Main doors locked.

Final preparations are complete.

5... 4... 3... 2... 1...

The target
is vaporized by the laser.

The explosion lasts
just 1/100,000 of a second.

But a high-speed camera

captures the shock wave
expanding outwards.

Some of the inner material
comes out

and trades places
with the outer material,

and that turning inside out

is just what happens
in a stellar explosion.

Material
from deep inside a star's core

surfs the shock wave
out into space.

In the extreme heat and turmoil
of the explosion,

heavier elements are forged.

Among them,
gold, silver, and platinum.

And because there's so little
time for the elements to form,

they are the rarest and most
valuable in the universe.

Silver, gold,
everything else are created

by the explosion of the star,
by the immense energy released,

and that's how they come to us.

But even after the
universe's most violent explosion,

there's something left behind.

We scientists used to believe

that after
a supernova explosion,

a star would literally
blow itself to bits,

and there'd be nothing left.

Well, we were wrong.

There's a corpse... a corpse
of a supernova explosion.

Some of the most ex otic matter
known to science

called a neutron star...
solid nucleonic matter,

the most fantastic state
of matter in the universe.

The superdense core
is now a neutron star.

It's around 20 miles across
and unbelievably heavy.

It's incredibly dense.

Just a cubic centimeter,

just the size of a sugar cube
of neutron-star material

would weigh as much
as all the cars

in the United States
of America combined.

The dying star

doesn't just leave the corpse
of a neutron star.

It blasts the new elements
far out into space.

These clouds
contain the building blocks

of the universe.

Everything we know and love
is built from this stardust.

Only a supernova has enough
energy to fuse these elements,

which are so essential for life.

Without supernovae,
there's no life.

There's no you,
and there's no me.

When massive stars die...

...they seed the universe
with stardust...

...full of elements
like hydrogen...

carbon...

o xygen...

silicon...

and iron.

The raw materials
to build new stars,

solar systems, planets,
and, of course, us.

Everything we see around us

once blasted out
from the core of a star.

You may wonder what stardust is.

Well, you're stardust
because every atom in your body

was produced
inside the fiery core of a star.

The atoms in your left hand
may come from a different star

from the atoms
in your right hand,

but you are literally
a star child.

Long-dead stars
provided the stardust

to create our solar system,
the planets,

and everything on them.

So, you're made of
carbon, you're made of o xygen.

There's iron in your blood.

All of those things
had to be generated

inside the core of a star.

There's no other way
to get them.

So, when you think about
star stuff, look around you.

Everything that you're made of,

everything in the world
around you is made of

had to come
from the belly of a star

that blew up a long time ago.

Even the atoms
in our own sun are recycled.

They're third
or fourth generation...

leftover debris shot into space
by dying stars a long time ago.

Our sun is our stepmother.

Our true mother died
in a supernova explosion

to give birth to the elements
which made up our body.

But how come the poets
and the songwriters,

how come they don't write
poems to our true mother?

It's perhaps they don't
understand physics

and the laws
of stellar evolution.

We live in an age of stars.

But it will come to an end.

There's only so much hydrogen
in the universe.

Trillions of years from now,
it'll all be used up.

And when there's
no hydrogen left,

there'll be no new stars.

We live in a very brief period
in the history of the universe.

Well, we still have stars
illuminating the sky,

stars creating life
as we know it,

but it's not gonna last forever.

Sooner or later, the stars
will begin to blink out.

First,
the massive stars will burn out,

then midsized stars
like our sun,

leaving only the smallest.

Trillions of years later,
they, too, will fade away.

Slowly, inex orably,

the universe
will get colder and darker

until the last star burns out

and the universe
becomes dark once again.

The age of stars will be over.

Honestly, the future of
the universe looks kind of grim,

but you can take
something positive out of that.

This is the best time
to be alive.

This is the time where life
can flourish, stars can form.

We are in the golden age
of the universe right now.

We live in a season for
life in the universe, if you will,

that lasts
for a few billion years.

And that makes me, at least,

appreciate the way
things are right now

because they weren't
always that way,

and they won't always be.

We live in the stage

where stars glow
and illuminate the night sky,

when stars create life
as we know it.

We live in the best
of all stages of the universe.

For now, stars will
continue to shape our universe,

generating the building blocks
of new worlds,

creating new stars and filling
the darkness with light.

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