Nova (1974–…): Season 48, Episode 17 - Universe Revealed: Age of Stars - full transcript

The Hubble Space Telescope and a heat-resistant solar probe reveal new clues about the sun's 5-billion-year history.

Are you wondering how healthy the food you are eating is? Check it -

In a universe that shines
with innumerable stars,

born from countless more stars

that have come
and gone before them,

rages the life-giving fire
of our sun.

The sun is the king of
the solar system.

It has essentially all the mass
and all the energy.

Familiar and yet unknown.

Even though we've looked at it
for a really long time,

the sun is still full
of mysteries.

Why is it hotter in its
atmosphere than on its surface?

What drives the solar wind?

Only now we take
our first steps closer

to understanding our star...

It is the first time

that we're actually going in
to touch the sun.

And it's already really started

to truly transform our

for how the sun works.

Uncovering the secret power
of all stars...

As you can imagine, when you
have a huge blob of flaming gas,

the core is usually the hottest.

And it is where the magic
is happening.

Perhaps even finding clues

to the stars that came
before it...

If we understand where the sun
comes from,

we can understand
a little bit more

about where life has come from.

And, ultimately, its fate.

It has about another 4.6 billion
years of nuclear fusion left.

And then it will start
to change.

It will start to evolve.

We really need to understand

what will happen to our own sun,

because that will impact Earth.

The sun is just one among

hundreds of billions of stars in
a galaxy among trillions.


We live in "The Age of Stars."

Right now, on "NOVA."


♪ See me when I float
like a dove ♪

♪ The skies above are lined
with trees ♪

♪ I'm on my knees,
begging please ♪

♪ Come and take me away ♪


93 million miles from Earth,

our nearest star, the sun.


A permanent fixture for life
on our planet.

Humans have always been
fascinated by the sun.

I think
because it is so constant

compared to our daily life.


It's been rising and setting
since the day that we were born.

We keep time by it,
we keep our calendars by it.

Without it, life wouldn't be
possible here on Earth.


The sun is just one of more than

a billion trillion stars
in the universe.

Why is it around our star
that life has emerged?

We want to know
where do we come from,

and what are our cosmic origins.

If we understand where
the sun comes from,

we can understand
a little bit more

about where life has come from.

But our star is an enigma.

The sun is still full of

Why is it hotter in its
atmosphere than on its surface?

What drives the solar wind?

We've spent millennia studying
from afar.

But only now are we getting
close enough

to truly reveal its secrets.


The sun's not a very nice

It's not easy to get up close
to the sun.


It's an enormous ball of

and it's putting out a
tremendous amount of energy.

Its surface is a bubbling
caldron of 10,000-degree plasma.

We can actually see cells
of hot gas

rising and falling,
it's incredible imagery.

And then above that,
you have this

very thin atmosphere that's
a million degrees.


Seeing these images is like
revealing something

that's been right in front of
us, but hidden for so long.

Occasionally you might see this
enormous coronal mass ejection

erupting from the star.

We now stand on the threshold

of being able to survive
a close encounter.


With a new heat-resistant probe

that's giving us
an up-close look

at our sun for the first time.

Status check.

Go Delta.


Minus 15.

Launch night,

I was sick to my stomach.

Five, four,

three, two, one, zero.

Lift off,

of the mighty Delta 4
heavy rocket with NASA's

Parker Solar Probe.

There we go.

The Delta 4 heavy
is a very slow rocket

compared to the other launches
I've seen.

So I just saw fireballs,

and was very, very frightened
for a while.

25 seconds into flight.

It is quite scary to think about
all that power in the rocket

underneath that, you know,

relatively small spacecraft
sitting on top.

Continue to look good on all
three boosters.

Then realizing that
this was all okay

as it slowly made its way up
into the sky.

Now 50 seconds into flight.

And we have jettisoned both
strap-on boosters.

Parker is just
an exquisite mission.

It will be the closest that
our species has thus far come

to literally touching the sun


The Parker Solar Probe
is traveling to a place

that has been completely
unexplored up close.

Until now.


NASA's Parker Solar Probe,

a daring mission to shed light

on the mysteries
of our closest star.

This is a journey into
Never-Never Land, you might say.

During its seven year mission,

the Parker Solar Probe
will attempt a series of dives

towards the surface of the sun.

Its goal is to understand
how the sun sheds its energy.


Orbiting a total of 24 times...

Each pass taking it perilously


So close it will enter
the sun's atmosphere.


Braving temperatures no
spacecraft has ever endured.


And traveling faster

than any other human-made object
has before.



The mission is still
in its early days.

But in the coming years,
the Parker Solar Probe

will help us unlock not only the
secrets of our own sun

but all stars.

Including those that hold
the key to the sun's origins,

and our own.


We can look at the processes,
look at what's inside the sun,

and understand how it had
to become that.

What were the generations of
stars before that?

What was its ancestry?


The sun's story
can be traced back

to its most distant stellar

the very first stars
in the universe.

Almost 100 million years
after the Big Bang,

the universe is dark and cold...

Not a single star shining.

But this universe is far
from empty.


Something is growing
in the void.

Stretching out tendrils.

The early universe was largely
hydrogen and helium,

and only small amounts
of other materials.

None of the elements we see
these days,

no carbon, oxygen, iron,
none of that.

Even though the name
"the Cosmic Dark Ages"

suggests that there might not
have been

anything particularly
interesting going on,

it was really kind of laying
the groundwork

for the construction of

the cosmic web.

The cosmic web is literally

the structure of the universe


The cosmic web is unimaginable
in scale.

Huge clouds of gas are drawn

by the gravity of a mysterious,
invisible form of matter

called dark matter,

creating a great network
of filaments.

A web the size of the cosmos.


The gas in these tendrils

is made up of mostly hydrogen
and helium.


Where these great filaments

are the places where the first
stars will one day be born.


The cosmic web has been shaping
our universe

for 13.8 billion years.

And it's still doing so today.

But it's only recently

that we've actually been able
to see it.

The image that we have here
is absolutely amazing.

It's one of the most
fundamental pictures

that we can take
in our universe.

And it's actually a direct image

of some of the largest
structures that exist,

the filaments of the cosmic web.

Now the bright dots that you
see over here,

they're entire galaxies.

Now, if I take those away,

what you can see much more

is the faint glow of the
hydrogen and helium

that exists on the tendrils
of the cosmic web.

And it's on this cosmic web,

that the story of our sun

and the stars
in the night sky begins.


As time passes in the
early universe,

the cosmic web continues
to grow...

Gas, rushing along these
great tendrils,

traveling down towards
the intersections.

It is being pulled to these
points by gravity.

And as more gas joins, this
force becomes ever stronger,

creating great clouds
staggering in size.

They grow denser,


as gas is relentlessly added

until, at last, the conditions
become so extreme

that there is a sudden moment
of ignition.


The birth of the very first star
in the universe.


Born 17 times hotter
than the sun.


This star is a blue monster.



The first stars

were unlike anything we can see
around us today,

which is what makes them
so incredible.

When the very first
stars formed,

these stars ended up
with giant masses

of 500 to 600 times
the mass of the sun.

Stars today are perhaps as hot
as 100,000 degrees.

And these stars were nearly
twice as hot as that.

And the very hot color tends
to also make them look blue.


But this first star is not alone
for long.

At intersections
across the cosmic web,

it's soon joined by others.


An entire generation
of first stars...

lighting up the universe.


But this isn't all they do.


These stars are also forging
new elements,

creating the ingredients
for all the planets

and, ultimately,
even for life to exist.

The birth of the first stars

signaled a complete

in the makeup of the universe.

Before they existed, all we had
was hydrogen and helium,

but nuclear fusion completely
changed all of that.

The cores of the first stars
were so hot,

they reached more than
100 million degrees.

And that forced hydrogen atoms
to change.

Now under the very high
temperatures and pressures

that you find in the cores of
these stars,

they were smashed together,

fusing a heavier element,

But the first stars
didn't stop there.

After a few million years,

the hydrogen completely
runs out.

So instead, the helium atoms are
forced to be smashed together,

creating even heavier elements,

such as carbon, oxygen,
and iron.

The new elements these
first stars forged

are the elements that seed other
types of stars, planets,

and even us.


In other words,
the elements for life.

But the era of blue giants
can't last.

Fusion at the center of a star

eventually ends as it runs
out of fuel,

so the process can't go on


When fusion stops,

you lose that internal pressure
which pushes against gravity.

You lose a tug of war,

and the gravity starts to push
down on the star.


You know that saying,
"Live fast, die young"?

That really applies
to stars, right?

So the most massive,
luminous stars

have the shortest lifetimes.

Even though they have much more
hydrogen fuel

than an ordinary star
like our sun,

they burn it so quickly that
they only live

a few million years
before they burn out.

And a few million years,
in astronomy time,

that's the blink of an eye.

With its fuel spent,
fusion reactions stop.

And gravity takes over.


The core collapses.


Gas suddenly falls inwards.


And then rebounds

in a colossal explosion called
a supernova.


A shockwave of energy,

followed by material hurtling
outwards into space.

Supernovae explosions
rocked the universe.

They are amongst the most
explosive events

that we now know about.

Briefly, a single supernova
can outshine an entire galaxy.

This was a very important moment
in the history of the universe.

It allowed the universe to kind
of start evolving.

After the first stars exploded,

the material that has been
forged in their interiors

was spewn out into space.

They seeded the universe
with these heavy elements

and paved the way for subsequent
generations of stars.

Generations of stars that
we can see in the night sky.

The Hubble Space Telescope

has been studying them
for more than 30 years.


Showing us this epic cycle
of cosmic death and renewal.


It’s not only the first stars
which enriched the universe.

As you go on for the second,
the third,

the fourth generation of stars,

they're all creating more
and more heavy elements

which get expelled into
the universe.


Hubble reveals to us how stars
have evolved

from a primitive universe
dominated by blue stars

to our universe today,

populated by stars of every
color, size, and configuration.


Neutron stars

violently spinning up
to 700 times a second,

spitting out jets of radiation.

Stars so huge,

that more than a billion suns
could fit inside them.

There are many types of stars.

Wolf-Rayet stars, red giant
stars, white dwarf stars.

All of them have their
own unique characteristics.


And some that aren't alone.

They are kept company
by systems of planets,

including rocky worlds
built of ingredients

like carbon, silicon, and iron.

So stars really are the engines

of higher-order complexity
in the universe, right?

They're the factories that
make up the heavier elements

that are the seeds of things

like planets.

Stars have changed the entirety
of the universe,

filling it with all manner
of wondrous celestial objects,

and ultimately paving the way
for a star

that has all the
right conditions to make us.

The sun must have relied
on many, many generations

of previous stars for the

that's there today in our
solar system.

Probably thousands
of other stars

that would have had to explode.


Nine billion years after
the birth of the first star.

The universe has been enriched

with dozens of new elements.

Here, gravity draws one cloud

and our own star is born.


But not all of the material
is used to create the sun.


Some remains in orbit.

And it's from these leftovers

that eight extraordinary planets
form our solar system.

The sun has a very tight

with all the planets
in the solar system.

Not just because of
its enormous gravity,

but because of the light that
it provides.

Some of these worlds seem just
too far away from the sun

for complex life to take hold.

Deprived of light, they may be
devoid of any life at all.


These are the gas
and ice giants.


In contrast, others
are too close to the sun.

They are relentlessly blasted...

Until they become
scorched deserts.

But there is a sweet spot.


Neither too far
nor too close to the sun.

It's in this place...

that the chemical legacy

of generations
of long-gone stars

would form something

We are, on the Earth, on kind of

this special, sweet zone.

They call it
the Goldilocks zone.

This exciting distance
from a star

where a planet could conceivably

liquid water on its surface.

Water is the medium that

the biochemical reactions

that are responsible for life.

Earth's relationship
with the sun

is the most important
relationship there is.


The sun is constantly reaching
out to our planet,

something the Parker Solar Probe
is helping us understand.

What makes Parker so great is
the fact that

it has a great set of
instruments that work together

in order to look in all

So there's this sun-facing part
of the probe

that peeks above the heat shield

and literally looks directly
at the sun.

The Parker Solar Probe is
spotting holes

in the sun's atmosphere...

Vents that release

a blizzard of charged particles

at more than a million miles
an hour.

What we call the solar wind.

We can tell how the energy

where the wind is coming off,

how much of the wind
is coming off.

The solar wind travels
billions of miles,

bombarding the planets
with radiation.

The charged particles in the
solar wind

can be detrimental to life.

On Earth, we're protected
by the Earth's magnetic field,

which deflects the particles.

So it's kind of like we have
our shields up,

and our shield is
our magnetic field.

Earth has defenses
that protect life

from our star's violent

But the sun also provides

something essential
to our planet.

At the core of it,

the sun is forging hydrogen
into helium,

which is what is releasing
the energy

that we get here on Earth.

The photons,

these packets of energy,
when they are formed,

they don't go straight
from the center

rushing through to the surface.

They go through
a very bumpy ride.

They get tossed from one atom
to the other.

They get absorbed and spit out,
absorbed and spit out.

So it takes a really convoluted
path out of that sun,

and that can
take millions of years.

Once these photons arrive
at the surface,

they're liberated as sunshine.


The light races across
the solar system.


it flashes past the planets

at 180,000 miles per second.

If you could take all the energy
that humans are producing

and store it in batteries,

the entire civilization,
for 50,000 years,

you could make the sun shine
for one second.


It takes just over eight minutes

for the sun's light
to reach Earth.

That stream of light is like
an umbilical cord of energy

coming down to us here on the

And it's been pretty much
constant and unbroken

for nearly five billion years.

And it's this combination
of the stability of light,

stability of energy
over billions of years,

that means complex life
that we see around us

here on the Earth has been
able to form

and has been able to thrive.



We don't know exactly how life
emerges on early Earth.

But what we do know is that
primitive cells,

living in the ocean,
begin to use the sun's energy

to power life-giving chemical


These cells are the bridge
between sun and Earth.

Tiny machines that harness
the power of our star.

The cells use sunlight to turn
carbon dioxide and water

into food in the form of sugar.

This process, photosynthesis,

is a direct use
of the sun's power.


It has driven the evolution
of complexity on Earth...


From primitive bacteria,

to plants and trees...

An unbroken line of living

All connected to the
power source in the sky.

Everything from the little blade
of grass

to the biggest oak tree,

they use the sunlight

to photosynthesize
and produce the energy

that we later consume

to sustain ourselves.

So in a way,

we have been feeding on


Trillions of stars have existed
since the universe began.

But ours is the only one
we know of

that has nurtured
that wonderful thing, life.

Not only nourished
by the sun's light,

but also granted protection
and the time to grow and change,

eventually creating
complex life.

The sun is connected to our
very existence.

It provides the light

and the energy that's necessary
to sustain life.

There would absolutely be no
life on Earth

if there was no sun.


The sun is a creator...

Bringing together atoms

forged in generations
of ancient stars.


To create us,

beings capable
of exploring the cosmos.


And uncovering our own
stellar ancestry.

It's a wonderful thing,

how we share this intimate
connection with stars,

because they are part of our
cosmic heritage.

We are the children
of these stars.


There are up to 400 billion
stars in our galaxy.

And there are two trillion
galaxies in our universe.

But it wasn't always that way.

We are living in the
age of stars.


An era of light in the universe.

Stars have always been
important to us.

They have helped us navigate
the land

and the open seas for millennia.


If you just think back at
the countless sonnets and poems

and songs, there is always
some kind of

celestial connection.


One of the reasons why

looking up into the stars is so

is because we realize that
others are doing

the same exact thing,
and so in a very real way,

we feel connected to people
both past and present.

From our fleeting,
human perspective,

the stars seem everlasting.

A constant in our night sky.

But seen across
the age of the universe,

the picture changes.

Because this era cannot last.

The stars will eventually wane.


And as they go,

they once again change
the character of the universe.

Their cores, where fusion once
raged, cool.


And eventually solidify,

locking precious elements away
beneath the surface.

And starving the universe
of the material needed

to make new stars and planets.


The chance

that a star is going to be born

is, is much, much lower
than it was

billions of years in the past.

Just as there was a very first
star in the universe,

there will come a time

when the era of stars
will come to an end.

The age of stars is not
as enduring as it might seem.

I have here a timeline
of the universe,

and I'm here at the start when
the universe formed

13.8 billion years ago during
the Big Bang.

Now it took a while
for the first stars to form...

In fact,
a few hundred million years.

Let's call that
400 million years.

So on my scale,
stars start to form here,

and those stars carried on

and then we reach this point

four billion years since
the Big Bang,

and a time when the most stars
are forming in the universe.

Our sun, though, didn't form

until nine billion years
had passed.

And that's my marker here.

And then we move forward again,
and we get to this point here,

which is the present day,

13.8 billion years since
the formation of the universe.

Now our sun won't live forever,

and in fact it will start to die
and end its life

in around five billion years'

But the sun will be outlived

by the least massive stars
in the universe.

They have lifetimes of
a few hundred billion years,

and that's about 200 meters
on my scale.

But even when those stars die,

that doesn't mark
the end of the universe.

The universe could live forever,

with the timeline stretching far
off into the distance.

And that means that
the age of starlight

that I've mapped out here

is like the blink of an eye
to the universe.

It's the age of darkness
that goes on and on and on.


Stars won't suddenly disappear,
of course.

They'll be here
for hundreds of billions,

perhaps even trillions,
of years to come.

But slowly over time,

the universe will become darker.


As it expands,

the distances between these
little islands of light

become greater and greater.

Until one day, only one type
of star will remain.


Red dwarfs...

The longest lived of all stars
in the universe.

Trappist 1 is one of these
near immortals.

This ancient star is likely more
than seven billion years old,

almost twice as old as our sun.


But Trappist is tiny,

a similar size to Jupiter.

And less than one percent
as bright as our sun.

It is a cool star, slow burning.


And that is the secret
of its longevity.

The lifetime of a star
is determined

by its reservoir of hydrogen,
of nuclear fuel.

As long as it has something
to burn,

it will continue to survive.

But paradoxically,

the stars with the least amount
of hydrogen live the longest.

And that's because they
are miserly.

They spend their fuel so slowly.

And so it's those smaller, more
quiescent, less energetic stars

that ultimately become

the greatest historians
of the universe.

It's especially exciting
because this particular star

is going to continue fusing

into helium in its core
and continue shining

for potentially hundreds
of billions of years.


Like the sun,

Trappist has its own planets.

Seven worlds, each roughly the
size of Earth.


Some may have atmospheres,

and even oceans.

But there the similarities end.

Because these
are strange worlds.

Just as one side of the moon
always faces Earth,

these planets may be what we
call "tidally locked"

in their orbits...

One side permanently looking

the red dwarf Trappist 1,

soaking up what light and warmth
it can from the faint star;

the other side permanently

facing the cold void of space.

These planets are witnesses

to much of the life of the

They were born near the start,

and they will survive to near
the end of the age of stars.


They will see entire galaxies

and eventually begin to fade in
their night skies.


They watch as countless stars
come and go.

Bearing witness to the time,

about five billion years from

when a distant star begins
to fade...

And vanishes from the night sky

as our sun finally exhausts
its fuel and disappears forever.

Ultimately, once the fusion
process is over in the sun,

it will begin to expand

into what astronomers call
a red giant,

and the outer envelope of the
sun will expand.

It's going to gulp up some of
the planets around it.

Earth is one of them.

And as the sun dies, so too
will many others like it.

The age of stellar creation
in the universe is waning.

The universe is like a
slow-motion fireworks show.

And we're kind of watching
the end of it.


It's unlikely that Trappist 1

will be the very last star
in the universe.

But we do believe the last star
will be a red dwarf.


As its fuel runs out,

fusion comes to an end.


The last star

slowly cools,

and fades away.


With its passing,

the universe becomes cold
and dark.

Without light and, most likely,

without life.

When the last red dwarf
stars die out,

that will be the end of stars
in the universe.

And it was starlight

that really lit up its story.


A universe without light may be
unfathomable to us humans.

Stars made us and our planet.

They define the universe
as we know it today.

It was like a gift given
to humanity,

that it took a cosmos
to make you.


A cosmos eventually defined more
by darkness than by light.

But for now,
we exist and learn and grow

as tiny sparks within the bright

and light-filled childhood
of our universe.

We live in "The Age of Stars."