Our universe is a place of infinite variety.
Two trillion galaxies...
..billions and billions of stars...
..and countless planets, worlds beyond imagination.
The universe is so vast, so incomprehensible, so terrifying,
that I think it's quite natural for us to choose to live out our lives
completely oblivious to it.
Perhaps that's why there's a sense of relief that rises with the dawn.
The brightening sky hides the stars and the questions that they pose.
After all, they are the biggest questions.
How did the universe come to be?
Why are we here?
And how will it all end?
We have to face those questions if we're ever to acquire
a truly deep understanding of ourselves.
You see, astronomy challenges us.
From one perspective, we're just grains of sand adrift
in an infinite and indifferent ocean.
But from another perspective, we are nature's most magnificent creation,
collections of atoms that can think and wonder about the universe
and choose to explore it.
OVERLAPPING LAUNCH COUNTDOWNS
We have liftoff... Zero...
In our quest for answers, we're venturing ever further from home,
far beyond the planets...
..and out to the stars.
Our spacecraft are sending back a stream
of extraordinary revelations...
..visions of alien worlds...
..with the ingredients to create life.
We've seen galaxies collide...
..black holes devouring star systems...
..and we may have glimpsed the origin of the cosmos itself.
With every new observation, every new piece of knowledge,
there is the opportunity to acquire a deeper understanding.
And as we answer question after question, we get ever closer
to being able to tell what is surely the greatest story ever told.
# Take me away. #
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.
Nasa's Parker Solar Probe is the first spacecraft to touch a star.
It's designed to fly through the sun's atmosphere...
..braving temperatures no spacecraft has ever endured.
The Parker Solar Probe is allowing us to know our star
as we've never known it before.
And it's also helping us to tell the story of all the stars.
Our sun is from a long line of stars dating back to the dawn of time...
..from fierce blue giants...
..which first lit up the universe...
..to later generations...
..whose deaths enriched the cosmos with precious elements...
..the building blocks of our solar system...
..and allowed our sun to create the thing
which brings meaning to the cosmos...
..life, you and me.
We have a strange relationship with the stars,
somewhere between awe and indifference.
I think we take our star, the sun, for granted,
partly because of its predictability.
Every day, it rises in the east and sets in the west...
..without any help or reverence from us.
But many ancient cultures deified the sun.
They treated it as a god.
And the sun gods were creators and destroyers of worlds.
So which is it?
Well, I think that the modern story of the stars, as told by science,
which is indisputably an epic story,
stretching back over 13 billion years to the origin of the universe,
places them firmly in the realm of the gods.
If we want to understand where these gods came from...
..we have to go back...
..to a time before the stars.
In the beginning, the universe was dark.
But it was not empty.
Something was lurking in the void...
..stretching out tendrils.
The cosmic web grew to become a vast structure...
..crisscrossing the entire universe.
It was formed by interlocking filaments of dark matter.
And it was at the places where these filaments met...
..the intersections...
..that the first stars, our sun's earliest ancestors, were born.
The cosmic web is the scaffolding of the universe,
the vast and intricate structure that spans the void.
The web is made primarily out of dark matter,
a mysterious substance that dominates the universe,
although we don't know what it is.
It's one of the great mysteries in modern physics.
It's probably some kind of particle
that interacts very weakly with itself and with light.
It doesn't interact with light.
You can't see it, which is why it's called dark matter.
But it does influence the universe through its gravity.
It was in the dark heart of the cosmic web
that gravity began to sculpt the early universe...
..drawing together the two simplest elements - hydrogen and helium...
..the raw material for the very first stars.
Hydrogen gas clings to the filaments of the web,
attracted there by the gravitational pull of the dark matter.
And where those filaments cross, the gas can become dense enough
to collapse under its own gravity to form great clusters of galaxies,
each filled with billions of stars.
The universe was approaching a turning point.
Hydrogen and helium poured into the regions
where the filaments crossed...
..gathering into ever denser clouds.
Gravity asserted its grip...
..and the clouds of gas began to collapse...
..becoming denser and denser.
And in the densest regions, the gas became so hot...
..that nuclear fusion reactions began.
And out of the maelstrom...
..the first gods emerged.
And there was light.
The stars illuminate the universe.
But that is the least interesting thing that they do.
The thing that makes the universe interesting,
that brings meaning to the universe is that -
life, you and me.
And life is just chemistry.
And chemistry requires complex chemical elements.
The only thing that existed in the universe before the stars
was hydrogen and helium.
Life requires carbon and oxygen and iron.
All those things were made in a process called nuclear fusion,
in the cores of stars or even, for the heavier elements like gold,
in the collisions of stars.
So, without the stars, the universe would be uninteresting.
It would be meaningless.
It would be just an infinite box of gas.
The first stars were monsters...
..hundreds of times as massive as our sun.
They burnt with such ferocity that they shone blue...
..with surface temperatures in excess of 100,000 degrees.
They were the largest stars ever to have lived...
..violent and volatile giants.
A star is essentially a balancing act.
The force of gravity is constantly trying to collapse it,
and that pushes its ingredients - primarily hydrogen, single protons -
closer and closer together.
Now, when those protons get close enough together,
another of the fundamental forces of nature, the strong nuclear force,
takes over and it can stick the protons together.
That releases energy, which creates a pressure which holds the star up.
Now, the more massive the star, the stronger the inward pull of gravity,
and the more energy has to be released to maintain the balance,
and so the faster the ingredients are used up.
These giant stars were in a struggle for survival...
..fighting the relentless pull of gravity...
..consuming more and more hydrogen fuel
to maintain their precarious equilibrium.
For most of its life, a star burns hydrogen -
the simplest chemical element, with one proton in its nucleus -
into helium, with two protons.
Now, when it runs out of hydrogen in the core,
the core starts to collapse and heat up,
and the star responds by building ever more complex elements.
So it makes carbon, with six protons,
and oxygen, with eight protons,
releasing more and more energy as it goes.
But when the star has assembled iron in its core,
with 26 protons in its nucleus,
no more energy can be released.
The star loses its battle against gravity.
It collapses
and in a final moment of creation,
salvaged, if you like, from its destruction,
it distributes those newly minted heavy chemical elements
out into the universe.
Imagine we could journey back in time
and watch the first star live out its brief, luminous life.
After only a million years,
the star used up all of its fuel...
..the core collapsed...
..the star imploded...
..and then rebounded in a colossal explosion -
a supernova.
In death, the first stars began to transform the cosmos,
enriching the ocean of hydrogen and helium,
which filled the universe with heavy elements,
to build new generations of more complex stars.
Over time, these elements gathered together...
..creating rich clouds of gas and dust.
Nurseries where new generations of stars were born.
And not just stars, but families of stars -
the first galaxies.
And around this time,
some of the early star systems formed
in our own galaxy, the Milky Way.
A new age of complexity was dawning in the universe.
Now there were stars of different sizes...
..and different colours...
..and, crucially, new bodies had appeared...
..planets.
Places where the rich chemical elements
built by previous generations of stars could finally find a home.
Countless billions of stars have come and gone
since those first giants illuminated the darkness,
each enriching the universe with the material
out of which the next generation formed.
Blue stars and white stars, single stars,
double stars, even triple star systems orbiting around each other.
The conditions were now right for those stars to drive the universe
into a new and profound age of complexity.
Our Sun was formed from the ashes of generations of ancestors.
Just one small star in a galaxy of billions of brilliant gods.
For the first million years of its life,
the Sun was virtually alone,
wreathed in clouds of gas and dust.
The dust slowly clumped together...
..forming clusters, the size of pebbles,
then boulders...
..and finally...
..planets.
But the planets were lifeless rocks.
Only the Sun had the power to turn them into worlds.
Some were too far away from the Sun.
Ice giants -
frozen, seemingly, into infertility.
Others formed too close to the Sun,
seared by a relentless light.
They became scorched desert worlds,
but there was a planet in the Sun's family
that quite by chance formed neither too close nor too far away.
An arcadia, where our star could breathe life into dust.
The planets are just the leftovers from the formation of stars.
The sort of debris, if you like.
It's just little specks orbiting around those magnificent flames,
but the planets are also the places in the universe
where gravity has concentrated the heavy elements
built by previous generations of stars.
And that makes the planets the canvas
on which the stars can create.
The canvas on which the stars can create,
what do I mean by that?
Well, just look around.
Everywhere you look on Earth, there is complexity.
Not only mountains and rivers,
but living things, animals and plants, human beings,
human civilisation,
the most complex thing we know of anywhere in the universe.
So you have to ask yourself, how can it be that such complexity
can emerge completely naturally in the universe?
Well, the answer, in fact, was known in the 19th century,
and it comes from the science of thermodynamics.
In the 19th century,
people were interested in the efficiency of steam engines,
and steam engines are, after all, the machines that powered
the factories that allowed people to build increasingly complex things.
And it turns out that the only thing that matters for a steam engine,
the thing that determines its efficiency,
the thing that allows it to do work and build things
is the temperature difference between the fire,
the furnace and the heart of the steam engine
and the cold environment surrounding it.
In the universe, the stars are hot spots in a cold sky.
We are sitting, in a very real sense,
inside a giant steam engine, powered by the furnace of the Sun.
And it's in that sense that the stars are the creators
of complexity in the universe.
But creating complexity is a subtle art.
You need an engine -
in this case, a star that's not too wild and flashy.
A star which is consistent enough for long enough
to kindle the sparks of life...
..and allow those sparks to flicker and flourish.
The most important property of a star,
if it's to nurture a civilisation,
is magnificent dependability.
No-one knows exactly how life on Earth emerged...
..but what we do know is that at some point,
primitive cells living in the ocean began using the Sun's energy
to power life-giving chemical reactions.
These cells formed a bridge between Earth and Sun,
delicate engines which harness the fires of our star,
using sunlight to turn carbon dioxide and water into food.
This process, known as photosynthesis,
unleashed the Sun's creative power...
..and drove the evolution of complexity...
..from primitive bacteria,
to plants and trees...
..and, ultimately,
to you and me.
Photosynthesis is a process that's very easy to describe in words.
The plants take energy from the Sun
then use it to react carbon dioxide and water together
to make sugars and a waste product, oxygen.
Really easy to say.
Very difficult to do.
I mean, there's a part of that photosynthetic machinery,
everything you see here,
every plant on the planet's got a photosystem, too.
It's comprised of 46,630 atoms,
all working together in an intricate machine.
Very efficient. It took billions of years of evolution.
Then we eat the plants, or we eat something that's eaten the plants
and we do the reverse reaction.
We take those sugars and we breathe in that waste product, oxygen,
react them together, release a bit of energy,
a bit of the stored sunlight, if you like,
and we use that energy to maintain our structure,
to grow, to live.
Trillions of stars have existed since the universe began...
..but ours has nurtured that most miraculous thing,
life.
And that makes the Sun a truly remarkable star.
That is the only star we know of
anywhere where there are collections of atoms in orbits around it,
you and me,
that have named it.
The Sun, our Sun.
We've worshipped it, deified it since the dawn of history.
In fact, it's been argued that the Sun lies at the foundation
of all religion, and there may be some truth in that.
In fact, I think there is a deep truth in that,
because we all owe our existence,
this brief time we have in the universe,
to that star.
In fact, in a deeper sense, to all the stars.
We don't need to invent imaginary gods to explain the universe.
We can replace them with the real thing.
Everyone we love...
..everything we value...
..our supreme accomplishments as a civilisation...
..were created and crafted...
..by stars.
There are over 200 billion stars in our galaxy...
..and there are two trillion galaxies in the observable universe.
We're living in the Age of Stars...
..an era of light and life in the cosmos.
From our fleeting human perspective, stars seem eternal...
..but even gods are not immortal.
Where there is light,
there is darkness.
Stars are creators...
..but they can be jealous guardians of their creations.
Many smaller stars don't die in spectacular explosions,
instead, they slowly. fade away.
They hang on to the precious elements they made,
becoming fossil stars...
..and as more fossils litter the universe,
more life-giving elements remain locked away,
starving the cosmos of the material needed
to make new generations of stars.
The Age of Stars may seem infinite,
but it had a beginning
and it will also have an end.
Imagine a timeline of the universe
and imagine that this is the origin of the universe,
the Big Bang, 13.8 billion years ago.
After 100 million years or so, the first stars formed.
On this scale, one centimetre is about 20 million years.
After four billion years, the peak rate of star formation occurred.
The maximum number of new stars were born.
After nine billion years,
our Sun was born.
And today we stand,
13.8 billion years later,
about halfway through the lifetime of our Sun.
Now, in about five billion years' time,
our Sun will die, but new stars will be born
and many of the oldest stars in the universe,
the smallest stars, will continue to shine.
In fact, we think that the last star will cease to shine,
the universe will go dark,
in around ten trillion years.
On this scale, that's about 5,000 metres away from the Big Bang.
But that's not the end of the universe.
As far as we know, the universe will continue expanding forever.
And so the Age of Starlight is the briefest moment of time
in the infinite history of the universe.
The Age of Darkness will go on and on and on.
Stars won't just disappear, of course.
They'll be here for aeons to come.
But over time, the universe, will grow darker,
colder and emptier.
There are stars around today that existed
close to the beginning of the Age of Stars...
..and some of them will also witness the end.
They're the longest lived stars in the universe,
red dwarfs.
TRAPPIST-1 is one of these ancients.
It's already more than seven billion years old,
almost twice as old as our Sun...
..but only around a tenth of the size...
..and less than 1% as bright.
It's a cool star, slow-burning...
..and that is the secret of its longevity.
Because they burn slowly,
red dwarfs live for a very long time...
..far longer than any other star.
Like the Sun, TRAPPIST-1 has its own planets -
seven rocky worlds,
each roughly the size of Earth.
Some may have atmospheres
and even oceans...
..but there the similarity ends...
..because these are strange worlds.
Every one of these planets is locked in its orbit,
one side facing TRAPPIST-1,
the other side frozen,
permanently exposed to the cold void of space.
If you could stand on the surface of one of these ancient worlds...
..as the aeons passed...
..you could watch the future of the cosmos slowly unfold.
And one day, five billion years from now,
you'd see our Sun flicker and fade away forever.
The death of our Sun will probably go unremarked.
We had hope that we'll be around to see it.
Maybe some alien astronomer on a world far away
across the Milky Way will see it through the end of their telescope,
but I don't think they'll give it a second thought.
We've seen hundreds of stars die
and we don't give them a second thought.
But I think the death of our Sun will matter here locally
in this little corner of the galaxy,
because it will mark the end of a glorious time
in the history of our galaxy,
where meaning, where science and literature
and art and poetry and music existed here.
And that does matter.
Why does meaning have to be eternal?
It's the fragility of our lives that makes them valuable.
I think the wonderful thing is that our star
has taken the laws of nature here on this planet
and crafted such a magnificent expression of them.
You, me and all this.
Stars like TRAPPIST-1 will linger on long after the death of our Sun.
We will never know the name of the last star...
..but we know that the last star to shine...
..will be a red dwarf.
The last star will slowly cool
and fade away.
With its passing, the universe will become, once again,
a void,
without light
or life
or meaning.
The stars illuminate the universe
and create its most intricate structures,
and one day they will all be gone.
The stars are gods, but they are mortal gods.
And when that time comes when the last stars have faded
and all possibility of life and meaning in the universe
has faded with them,
they will have left the most profound legacy
because for a moment in the long history of the universe,
the stars illuminated the dark
and allowed us to illuminate it, too.
MUSIC: Who Knows Where The Time Goes? by Fairport Convention
# For who knows where the time goes?
# Who knows where the time goes? #
We want to study the Sun because it teaches us a lot about stars.
It teaches us a lot about all the other millions and billions
of stars in our galaxy and beyond.
There was a moment when we were putting the spacecraft together
that I just took a moment and looked at the spacecraft
and realised this is going into a star.
And to realise how special it was
to be able to have worked on this
and that humanity decided this was something we wanted to do.
Status check.
Go, Delta. Go, PSP.
Minus 15.
Launch night, I was sick to my stomach.
Five, four, three,
two, one,
zero.
Liftoff of the mighty Delta IV Heavy rocket
with Nasa's Parker Solar Probe.
There we go.
The spacecraft is the first that NASA has named after a living
person because Eugene Parker is really such, you know,
an eminent physicist in our field.
The Delta IV 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.
Temp pressures continue to look good on all three boosters.
Then realising that this was all OK,
as it slowly made its way up into the sky.
Now, 50 seconds into flight.
Parker Solar Probe is so revolutionary
because it's the first time that we're actually going in
to touch the Sun.
We're going 94% of the way from the Earth to the Sun
to actually experience the solar corona, the Sun's atmosphere.
I think at closest approach,
it'll be about eight solar radii from the Sun,
which is just mind-blowingly close.
So we were expecting things to be very hot,
over 2,500 Fahrenheit,
but in a soup of a million degree plasma.
That's a real challenge for the spacecraft
to survive that environment.
So in order to do that, there's a very large heat shield
on the front of the spacecraft,
which protects the majority of the instruments
which are sat behind on the spacecraft body.
What makes Parker so great is the fact that it has a set
of instruments that work together in order to look in all directions,
in order to solve those big mysteries about the solar wind.
The solar corona has been mysterious to us since we've known about it,
so it's a very strange thing.
The surface of the Sun is sort of 6,000 degrees,
and then above that, you have this very thin atmosphere
that's a million degrees, super hot.
And the way that's heated, we know it has something to do
with magnetic fields, but we don't know exactly how it works.
That's where the solar wind is generated.
We don't know quite exactly how that works, either.
Other things that have come out of this are coronal mass ejections.
When we originally did the proposal,
we were thinking that we would see five
in the entire seven year mission, if we were lucky.
We ended up seeing around four to five in the first year,
so there has been just a total switch
in terms of how active the Sun is
or what we classify as coronal mass ejections.
Maybe a little bit of both.
It is a joy to see all the data coming back.
It's a joy to share it with others
and to see them be as curious as I have been for the last decade.
So Parker's just begun its mission, really,
and it's already really started to truly transform our understanding
for how the Sun works.
Next time...
..we had deeper into the galaxy...
..on the hunt for alien worlds...
..and perhaps the first signs of life.
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MUSIC: Who Knows Where The Time Goes? by Fairport Convention
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