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♪
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narrator: Imagine a universe
with no stars --
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a dark, endless night.
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This is not some
sci-fi nightmare.
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This is our future.
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There will definitely be a point
in the future when, you look up,
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you will no longer
be able to see stars.
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Thaller: Things really will get
darker and darker,
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until there will be almost
no memory of light left.
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Narrator:
For billions of years, stars
brought life to the universe.
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The fact that you exist at all
is because of stars.
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Narrator: Now, they're dying out
in a star apocalypse.
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Stricker: The effect
could be tremendous.
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It can permeate
throughout the universe.
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Narrator:
What's causing the die-off,
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and what happens to life
when the lights go out?
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Eventually, the whole
entire universe
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starts to get
a little bit weird.
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-- Captions by vitac --
www.Vitac.Com
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captions paid for by
discovery communications
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narrator:
For over 4.5 billion years,
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the sun has bathed
our home planet with light.
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Its bright, stable glow
helps life flourish,
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but hidden in
the night sky,
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other planetary systems
haven't been so lucky.
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Thaller: Hanging right above
your head every night,
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we see up there
these dead corpses of stars.
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Narrator:
400 light-years from earth
lies a system called sdssj1228.
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A disk of debris orbits
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the faintly glowing leftovers
of a dead star.
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J1228 is a dead star.
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It is a core of a star
that had aged,
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blown off its outer layers,
revealed the core --
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which is about
the size of the earth,
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but has about half
the mass of the star in it.
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And we call these
"white dwarfs."
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narrator: May, 2018.
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Astronomers
investigated j1228
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using the world's largest
optical telescope --
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the gran telescopio canarias.
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They discovered what appears
to be a ball of iron
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orbiting the white dwarf.
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The lump of metal,
less than 400 miles across,
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could be the exposed core
of a destroyed planet.
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It's a clue to
this system's past.
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Thaller: It's always
a little poignant
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when you see evidence
of a planet around a dead star.
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You know, you think back of
when that star was shining,
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and could there have been life
in that solar system?
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Narrator: The j1228 system
is a cosmic graveyard.
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It might look different
than our solar system,
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but this is our future.
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This discovery of a dead planet
orbiting a dead star
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is like looking into
a crystal ball.
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And is it the future
of our own solar system?
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Yep.
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For a glimpse into your future,
you know,
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all you need to do
is look up.
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Narrator: Just like j1228,
our sun will die,
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killing off earth
in the process.
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This terrifying fate
will play out across the galaxy
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in a star apocalypse.
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Our sun is a fairly common type
of star in the milky way,
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and so, other stars
in the milky way
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will undergo the same sort
of fate as the sun.
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They will end up
as white dwarfs.
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And so, any other planets out
there orbiting sun-like stars
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will undergo
a similar fate.
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Once the stars like our sun
have died out,
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what's gonna happen?
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Could life still survive
around white dwarfs?
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Narrator: To understand the fate
of sun-like stars,
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we have to look
inside them.
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Buried within are clues to how
they live, and why they die.
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Plait:
The core, the very center,
that's where the action is.
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That's where the star
is fusing light elements
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into heavier elements.
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And that works like
a hydrogen bomb.
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It's the same thing.
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If you compress hydrogen enough,
it gets very hot,
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and the pressure
gets very high,
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and if fuses into helium,
and generates energy -- heat.
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And that's what's happening
in the core of every star.
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Narrator:
Because of their enormous mass,
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stars have huge
amounts of gravity.
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This gravity pushes inwards,
trying to collapse the star,
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but fusion energy from the core
stops that from happening.
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It's really this sort of
very balanced dance
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between gravity pushing in,
fusion energy pushing out.
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You can think of a star
as losing energy,
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continuously,
to the outside world/
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and gravity is saying,
"yes, I'm gonna take over."
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but, no, the nuclear reactions
inside a star
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replenish the energy
that's lost,
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and keep the star hot
and pressurized inside,
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so that the pressure-gravity
balance can be maintained.
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Narrator:
This balance
keeps sun-like stars alive
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for up to 10 billion years,
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until the star's gas tank
runs dry.
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Plait: It's gonna
run out of fuel.
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And when that happens,
it's going to die.
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But what is that
gonna look like?
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How is this
gonna happen?
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Narrator:
One hundred million years ago,
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things in the j1228 system
started to get ugly.
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First, the star grew large --
really large.
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Straughn: Once the center starts
fusing heavier elements,
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the outside will swell
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into what will eventually be
a red giant star.
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Narrator: J1228 transformed
into a red giant.
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Its outer layers blew off,
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extending out
over 40 million miles.
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When stars like our sun die,
it's not a quiet affair.
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It's very violent,
and ugly, and messy.
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They turn into
red giants,
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and they turn themselves
inside out,
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and vomit
all over the solar system.
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Narrator: When j1228 swelled
into a red giant,
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nearby planets
were stuck in a kill zone.
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The dying star engulfed them,
or fried them
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with temperatures of over
1,200 degrees fahrenheit.
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Atmospheres disappeared.
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Oceans boiled away,
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but one planet survived
j1228's death throes.
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Here's a case where a planet
survived, in some sense,
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the death of its own star,
and it's still hanging around,
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still hanging on,
hoping for something new.
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Narrator: The red giant's
expanding outer layers
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separated from
the star's core.
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With no active fusion, the core
collapsed into a white dwarf.
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The white dwarf's
dense gravity
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then went to work
on the one surviving planet.
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Flippenko:
The planet that might've been
orbiting the normal star
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can gradually spiral in
toward the white dwarf,
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and then, eventually, the
gravity of the white dwarf pulls
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on the near side of the planet
more than on the far side,
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and that tears it apart.
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Plait: What we're seeing here
is a dead star
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dining on
its own solar system.
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That's what is in the future
for the sun.
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Narrator: J1228 feasted on the
remains of its rocky worlds,
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leaving behind a disk of debris
and the planetary core.
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It's a glimpse
of earth's future.
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What happened here
around this white dwarf
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is gonna happen
to earth.
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It's gonna be stripped
of its atmosphere,
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its crust,
and its mantle,
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and the only thing that
will remain will be the core.
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Narrator: Fried and ripped apart
by a dying star --
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not a good way to go.
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Fortunately,
for life on earth,
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our own sun
isn't dying just yet.
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Plait:
The sun is middle-aged.
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It's 4.5 billion years old,
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and it's going to go on for
another 5 or 6 billion years.
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Sutter: We've got
a little bit of time
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before our sun pukes
all over the solar system.
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Narrator: Our home planet
may be safe for now,
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but systems like j1228
show us
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that sun-like stars
are destined to die,
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killing off any life
orbiting them.
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But sun-like stars
aren't the only stars
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dying across the cosmos.
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There are others out there,
and they're all doomed.
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There's a wonderful
rainbow of stars
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out there,
of all different shapes,
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all different sizes,
and all different colors.
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Straughn: We're talking down to,
you know,
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fractions of the mass
of the sun,
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up to hundreds of times
the mass of the sun.
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Narrator:
When it comes to the star
apocalypse, size matters.
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The bigger and brighter
the star, the faster it dies.
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♪
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narrator:
Our universe is a vast expanse
of death and destruction.
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All of the stars are destined
to die, but not all at once.
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There's not going to be
one particular point
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where all the lights turn off
at the same time.
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It's more like
a power outage,
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where different grids go off
at different times, until,
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like, there's the one last
light bulb that'll just go off.
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Narrator: This is because stars
come in different sizes.
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The way a star dies
has everything to do with
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the amount of mass
it started life with.
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It carries that all the way
through its lifetime.
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Narrator: The sun is
a medium-sized star
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living a stable existence
for billions of years.
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Giant stars
are different.
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They live fast,
and die young.
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A star like the sun,
which is a medium-sized star,
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it lives about
10 billion years.
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The really massive stars,
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they live maybe
10 million years.
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Narrator:
Massive stars can be tens
or even hundreds of times
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more massive than the sun.
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When it comes to life span,
that's a problem.
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Flippenko:
A massive star has more fuel
to burn, in a nuclear sense.
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So, you might naively think
that it lasts longer,
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but it's the
exact opposite.
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Narrator:
Massive stars can only access
hydrogen fuel in their core.
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The rest is trapped
in the outer layers,
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and can't be used as fuel.
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Plait: If there's hydrogen
in the core, you're good.
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If there's hydrogen outside
of the core, it can't be used.
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If it's not in your fuel tank,
it's not doing you any good.
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Narrator:
Massive stars also have
more gravity than smaller stars,
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so they have to burn
their hydrogen fuel faster
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to prevent the star
from collapsing.
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They burn their candle
on both ends.
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Because of
their incredible mass,
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their fusion reactions
in the core
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happen at an
incredible rate.
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Stricker: Giant stars are
kind of fast and furious.
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They are bright.
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They live their life,
and they die very quickly.
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Narrator: When a giant star's
fuel runs out,
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the core collapses
catastrophically
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under the overwhelming
force of gravity.
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And then, boom,
supernova.
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Narrator:
The death of a giant star
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triggers one of the biggest
bangs in the universe.
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The blast would instantly
vaporize nearby planets.
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But these star deaths
are also critical for life.
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When massive stars die,
they release heavy elements
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they've been making through
the course of their lives.
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And sometimes,
they even make new ones.
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And it's these heavier elements
that are essential for life.
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We owe our existence
to stars
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that formed
billions of years ago.
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Narrator:
In may of 2018, we spotted
evidence of ancient stars
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creating the stuff of life.
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We picked up
an infrared light signal
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00:13:53,033 --> 00:13:59,304
from a distant galaxy
named macs1149-jd1.
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The signal was
ionized oxygen.
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00:14:06,613 --> 00:14:10,481
It's been traveling
for 13.3 billion years,
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00:14:10,483 --> 00:14:15,119
so the oxygen formed when
the universe was very young --
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00:14:15,121 --> 00:14:20,792
just 500 million years
after the big bang.
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This oxygen formed
in the hearts of massive stars.
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00:14:26,733 --> 00:14:28,299
Hopkins: The presence
of oxygen tells us
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00:14:28,301 --> 00:14:31,603
that there needed to be massive
stars in the early universe
240
00:14:31,605 --> 00:14:34,038
in order to synthesize
hydrogen and helium
241
00:14:34,040 --> 00:14:36,374
into heavier elements,
like oxygen,
242
00:14:36,376 --> 00:14:39,010
and then explode
to eject that oxygen
243
00:14:39,012 --> 00:14:42,814
back into the interstellar
and intergalactic medium.
244
00:14:44,918 --> 00:14:49,220
Narrator:
Extreme pressure in the cores
of the stars produces oxygen...
245
00:14:51,524 --> 00:14:55,927
...And other elements,
like carbon and nitrogen.
246
00:14:55,929 --> 00:15:00,164
Supernova blasts spread these
elements across the universe,
247
00:15:00,166 --> 00:15:04,535
helping to create
new generations of stars,
248
00:15:04,537 --> 00:15:08,806
and, most importantly, us.
249
00:15:08,808 --> 00:15:11,809
If there is one single fact
that you should care about
250
00:15:11,811 --> 00:15:15,413
in all of science --
and this is my favorite fact --
251
00:15:15,415 --> 00:15:18,683
is that you and I
are a consequence of star death.
252
00:15:22,455 --> 00:15:24,422
Bullock: Before you can have
life, you need to have
253
00:15:24,424 --> 00:15:27,325
the kind of elements
out of which life forms.
254
00:15:27,327 --> 00:15:29,294
You need carbon.
You need nitrogen.
255
00:15:29,296 --> 00:15:30,662
You need oxygen.
256
00:15:30,664 --> 00:15:32,530
You need the elements
that are the backbone
257
00:15:32,532 --> 00:15:36,134
to the biology
that makes us possible.
258
00:15:36,136 --> 00:15:37,602
Where did those elements
come from?
259
00:15:37,604 --> 00:15:38,903
Well, they came from stars.
260
00:15:38,905 --> 00:15:41,372
They came from stars that formed
in the early universe,
261
00:15:41,374 --> 00:15:44,175
before even
the sun existed.
262
00:15:44,177 --> 00:15:46,577
Narrator:
The huge size of massive stars
263
00:15:46,579 --> 00:15:49,547
quickly signs
their death warrants.
264
00:15:49,549 --> 00:15:56,020
Their explosive ends help create
new stars, and even life.
265
00:15:56,022 --> 00:16:01,225
The fact that you exist at all
is because of stars.
266
00:16:02,562 --> 00:16:05,830
Narrator: But, probing galaxies
across the universe,
267
00:16:05,832 --> 00:16:08,499
we've discovered
something else.
268
00:16:08,501 --> 00:16:12,403
The star apocalypse
isn't just killing stars.
269
00:16:12,405 --> 00:16:15,773
It's stopping them
from ever being born.
270
00:16:15,775 --> 00:16:17,508
Thaller:
Star formation is dying.
271
00:16:17,510 --> 00:16:19,978
And in fact,
it's dying rather quickly.
272
00:16:19,980 --> 00:16:22,080
The universe,
right before our eyes,
273
00:16:22,082 --> 00:16:24,115
is becoming
a darker place.
274
00:16:24,117 --> 00:16:25,850
It's running out of fuel.
275
00:16:25,852 --> 00:16:29,153
And eventually, no more stars
will be made at all.
276
00:16:43,069 --> 00:16:46,804
♪
277
00:16:46,806 --> 00:16:51,042
♪
278
00:16:51,044 --> 00:16:55,513
narrator: Life on earth follows
a series of regular patterns.
279
00:16:55,515 --> 00:16:59,150
Day after day,
the sun rises...
280
00:16:59,152 --> 00:17:02,220
And sets,
281
00:17:02,222 --> 00:17:06,924
and stars light up the darkness
of the night sky.
282
00:17:06,926 --> 00:17:09,894
The reason I got into astronomy
to begin with
283
00:17:09,896 --> 00:17:12,363
was because I grew up
in a rural part of the country,
284
00:17:12,365 --> 00:17:13,831
and the sky
was beautiful and dark.
285
00:17:13,833 --> 00:17:15,633
You go outside at night,
and you look up,
286
00:17:15,635 --> 00:17:18,403
and you could see
thousands of stars.
287
00:17:18,405 --> 00:17:20,805
But it won't be
that way forever.
288
00:17:23,309 --> 00:17:27,779
Narrator: 2016, a network
of telescopes across the world
289
00:17:27,781 --> 00:17:32,517
measured the energy outputs
of over 200,000 galaxies.
290
00:17:32,519 --> 00:17:34,519
♪
291
00:17:34,521 --> 00:17:37,588
they discovered that
in the past 2 billion years,
292
00:17:37,590 --> 00:17:40,958
the universe has lost
half its brightness.
293
00:17:42,429 --> 00:17:44,929
The night sky is getting darker
294
00:17:44,931 --> 00:17:49,233
as stars flicker
out of existence.
295
00:17:49,235 --> 00:17:50,768
About 10 billion years ago,
296
00:17:50,770 --> 00:17:52,837
the universe
kind of hit its peak,
297
00:17:52,839 --> 00:17:55,273
and lots of stars were shining.
298
00:17:55,275 --> 00:17:58,209
It was an incredibly
bright place,
299
00:17:58,211 --> 00:18:00,778
but in the last
couple billion years,
300
00:18:00,780 --> 00:18:04,615
it's really, overall,
become a less bright place.
301
00:18:04,617 --> 00:18:07,485
The darkening universe
isn't just a sign
302
00:18:07,487 --> 00:18:09,921
that stars are dying.
303
00:18:09,923 --> 00:18:15,460
It seems there's a problem
with star birth as well.
304
00:18:15,462 --> 00:18:17,595
Mingarelli: When we look
into the universe's past,
305
00:18:17,597 --> 00:18:19,197
what we find is that long ago,
306
00:18:19,199 --> 00:18:21,799
stars were forming
at a much higher rate.
307
00:18:21,801 --> 00:18:24,168
Right now what we see is
that really,
308
00:18:24,170 --> 00:18:27,972
stars are dying off faster
than they're being born.
309
00:18:27,974 --> 00:18:30,374
A milky way-type galaxy, today,
310
00:18:30,376 --> 00:18:32,810
produces about
seven stars per year.
311
00:18:32,812 --> 00:18:35,313
However, 11 billion years ago,
312
00:18:35,315 --> 00:18:38,850
a galaxy like our own would've
produced 10 times more stars.
313
00:18:40,453 --> 00:18:43,321
Narrator: In the early universe,
old stars died,
314
00:18:43,323 --> 00:18:46,290
and new ones formed
in their place
315
00:18:46,292 --> 00:18:48,526
from the material left over.
316
00:18:48,528 --> 00:18:51,696
It was a cycle that kept
the cosmos bright.
317
00:18:52,665 --> 00:18:54,799
Not anymore.
318
00:18:54,801 --> 00:18:58,803
Plait: It kind of sucks for us.
We like a bright universe.
319
00:18:58,805 --> 00:19:01,405
We like all this energy and life
320
00:19:01,407 --> 00:19:03,741
that's vibrating
through the universe,
321
00:19:03,743 --> 00:19:06,611
but that's just not always
going to be the case.
322
00:19:06,613 --> 00:19:09,914
The universe is already
winding down.
323
00:19:09,916 --> 00:19:12,483
♪
324
00:19:12,485 --> 00:19:15,653
straughn: One of the biggest
mysteries in galaxy evolution
325
00:19:15,655 --> 00:19:18,990
is figuring out how galaxies
stop forming their stars.
326
00:19:18,992 --> 00:19:21,092
And we really don't know
the answer yet,
327
00:19:21,094 --> 00:19:23,594
and it's really important
for us to figure out why
328
00:19:23,596 --> 00:19:27,365
because in the end,
stars really equal life.
329
00:19:27,367 --> 00:19:29,967
♪
330
00:19:29,969 --> 00:19:33,137
narrator: To find out what is
shutting off the stars,
331
00:19:33,139 --> 00:19:35,773
we study galaxy clusters.
332
00:19:35,775 --> 00:19:38,976
♪
333
00:19:38,978 --> 00:19:41,112
these giant regions of space
334
00:19:41,114 --> 00:19:45,816
contain hundreds of galaxies
bound together by gravity.
335
00:19:46,953 --> 00:19:51,255
Slowly, the clusters
pull new galaxies into them,
336
00:19:51,257 --> 00:19:55,526
causing something
strange to happen.
337
00:19:55,528 --> 00:19:59,430
What we see happening when
a galaxy falls into a cluster
338
00:19:59,432 --> 00:20:01,365
is that its star formation
is quenched.
339
00:20:01,367 --> 00:20:03,734
It's shut off.
340
00:20:03,736 --> 00:20:06,237
Narrator: The cause of this
quenching effect
341
00:20:06,239 --> 00:20:10,007
has baffled scientists
for decades.
342
00:20:10,009 --> 00:20:13,244
Then in October of 2018,
343
00:20:13,246 --> 00:20:15,880
an international team
of astronomers
344
00:20:15,882 --> 00:20:18,783
investigated this
long-standing mystery.
345
00:20:18,785 --> 00:20:20,651
♪
346
00:20:20,653 --> 00:20:23,387
they tracked variations
in quenching
347
00:20:23,389 --> 00:20:25,156
across 14 galaxy clusters
348
00:20:25,158 --> 00:20:29,126
and found
a possible explanation.
349
00:20:29,128 --> 00:20:32,063
Thaller: The ability a galaxy
has to make new stars
350
00:20:32,065 --> 00:20:35,399
is related to the larger
environment it finds itself in.
351
00:20:35,401 --> 00:20:38,169
In clusters of galaxies
where many galaxies
352
00:20:38,171 --> 00:20:39,770
are orbiting around each other,
353
00:20:39,772 --> 00:20:44,709
we see interactions that strip
gas and dust away from galaxies.
354
00:20:44,711 --> 00:20:46,577
The stuff that makes up stars
355
00:20:46,579 --> 00:20:49,046
literally just thrown off
into space.
356
00:20:50,917 --> 00:20:54,385
Narrator: Stars formed from
dense parcels of cold gas,
357
00:20:54,387 --> 00:20:56,254
something galaxies
are filled with.
358
00:20:58,091 --> 00:21:01,092
But when a galaxy is dragged
into a cluster,
359
00:21:01,094 --> 00:21:03,427
everything changes.
360
00:21:03,429 --> 00:21:06,697
Clusters of galaxies contain
a lot of hot gas,
361
00:21:06,699 --> 00:21:09,267
whereas you need cold gas
inside of a galaxy
362
00:21:09,269 --> 00:21:10,901
in order to form stars,
363
00:21:10,903 --> 00:21:14,171
and when a galaxy is moving
through this hot gas,
364
00:21:14,173 --> 00:21:17,742
then the cold gas inside
is stripped away.
365
00:21:19,178 --> 00:21:20,911
Narrator:
If this new study is right,
366
00:21:20,913 --> 00:21:25,182
and galaxy clusters are
stripping away star-forming gas,
367
00:21:25,184 --> 00:21:28,486
new starlight will become rare.
368
00:21:29,656 --> 00:21:32,056
Looking over the history
of the universe
369
00:21:32,058 --> 00:21:35,359
and how much gas was out there
and how much is still left,
370
00:21:35,361 --> 00:21:38,195
I think it's fair to say
that most of the stars
371
00:21:38,197 --> 00:21:41,299
that will ever be made
already have been made.
372
00:21:41,301 --> 00:21:43,100
They've already been born.
373
00:21:44,504 --> 00:21:47,338
Narrator: Thanks to the shortage
of star-forming gas,
374
00:21:47,340 --> 00:21:50,975
stars won't just be dying
in the universe.
375
00:21:50,977 --> 00:21:52,977
They'll go extinct,
376
00:21:52,979 --> 00:21:56,814
and the first to go
will be the largest.
377
00:21:56,816 --> 00:21:59,016
Plait:
As the universe runs out of gas
378
00:21:59,018 --> 00:22:01,218
and fewer of these stars
are being made,
379
00:22:01,220 --> 00:22:03,387
eventually sometime
in the future,
380
00:22:03,389 --> 00:22:06,657
all the high-mass and even
medium-mass stars like the sun,
381
00:22:06,659 --> 00:22:08,159
they'll be gone.
382
00:22:08,161 --> 00:22:10,628
What does that mean for life?
383
00:22:10,630 --> 00:22:13,798
♪
384
00:22:13,800 --> 00:22:16,067
narrator:
Some of the brightest stars
385
00:22:16,069 --> 00:22:17,468
will disappear forever,
386
00:22:17,470 --> 00:22:20,571
begging the question,
can life survive
387
00:22:20,573 --> 00:22:23,874
the monsters
that dead stars leave behind?
388
00:22:24,911 --> 00:22:29,980
The long-term fate of the
universe is not a pretty sight.
389
00:22:29,982 --> 00:22:34,285
Some very interesting creatures
can start to appear.
390
00:22:34,287 --> 00:22:37,922
♪
391
00:22:48,935 --> 00:22:50,868
♪
392
00:22:50,870 --> 00:22:52,636
narrator:
In the star apocalypse,
393
00:22:52,638 --> 00:22:56,040
the first stars to fade away
will be the brightest --
394
00:22:56,042 --> 00:23:01,679
the giant stars,
followed by the mid-sized suns.
395
00:23:02,849 --> 00:23:07,218
The universe will become
unrecognizable.
396
00:23:07,220 --> 00:23:09,854
The far future will be
a very dim universe,
397
00:23:09,856 --> 00:23:11,956
especially for creatures
like us.
398
00:23:11,958 --> 00:23:16,093
If there's no more gas,
no more new stars, it gets dark.
399
00:23:17,630 --> 00:23:19,130
Narrator:
Scared of the dark?
400
00:23:19,132 --> 00:23:21,665
You will be...
401
00:23:21,667 --> 00:23:24,135
Because 100 billion years
from now,
402
00:23:24,137 --> 00:23:27,238
in the shadows
of this new universe,
403
00:23:27,240 --> 00:23:30,508
monsters will come out to play.
404
00:23:30,510 --> 00:23:34,245
Now we find ourselves in the era
of stars and starlight.
405
00:23:34,247 --> 00:23:36,313
What comes after
you can think of
406
00:23:36,315 --> 00:23:38,916
as the era of the dead corpses
of old stars.
407
00:23:40,420 --> 00:23:43,154
Narrator: We already see
the corpses of dead stars
408
00:23:43,156 --> 00:23:46,257
scattered
throughout the cosmos --
409
00:23:46,259 --> 00:23:52,129
black holes,
pulsars, white dwarfs.
410
00:23:52,131 --> 00:23:57,735
What happens when more stars die
out and the dead take over?
411
00:23:57,737 --> 00:24:00,004
Can life survive?
412
00:24:00,006 --> 00:24:03,407
Thaller:
It's actually possible that life
in the universe will survive,
413
00:24:03,409 --> 00:24:05,576
but we're going to have
to get more creative.
414
00:24:06,913 --> 00:24:09,980
Narrator: January 2019.
415
00:24:09,982 --> 00:24:14,852
The gaia satellite studied
15,000 white dwarfs
416
00:24:14,854 --> 00:24:18,088
within 300 light-years of earth.
417
00:24:18,090 --> 00:24:22,593
These are the corpses
of sunlight stars.
418
00:24:22,595 --> 00:24:25,162
Plait: White dwarfs are
the remnants, the cores,
419
00:24:25,164 --> 00:24:27,264
of stars like the sun
after they die.
420
00:24:27,266 --> 00:24:30,234
There's no more fusion going on
inside of a white dwarf.
421
00:24:30,236 --> 00:24:32,803
So it's just kind of
sitting there cooling off,
422
00:24:32,805 --> 00:24:36,240
but it turns out
there's a slight reprieve.
423
00:24:37,543 --> 00:24:41,512
Narrator: The white dwarf
corpses usually cool off and dim
424
00:24:41,514 --> 00:24:44,114
over tens of billions of years.
425
00:24:44,116 --> 00:24:47,618
Gaia's data showed something
different,
426
00:24:47,620 --> 00:24:50,621
something
we've never seen before.
427
00:24:50,623 --> 00:24:54,558
Some of the older dead stars
aren't dimming at all.
428
00:24:56,395 --> 00:24:57,895
O'dowd: We used to think
that white dwarfs
429
00:24:57,897 --> 00:24:59,763
could really only dim over time.
430
00:24:59,765 --> 00:25:02,233
After all, there's no source
of fusion,
431
00:25:02,235 --> 00:25:04,668
no source of energy
in their interiors,
432
00:25:04,670 --> 00:25:07,972
but new studies with
the gaia satellite have shown
433
00:25:07,974 --> 00:25:10,908
that there must be
some other energy source
434
00:25:10,910 --> 00:25:14,078
keeping those older
white dwarfs shining bright.
435
00:25:14,080 --> 00:25:16,080
♪
436
00:25:16,082 --> 00:25:19,850
something is giving these
white dwarf corpses a spark,
437
00:25:19,852 --> 00:25:24,421
bringing them back from the dead
as zombies.
438
00:25:24,423 --> 00:25:25,789
The leading contender
439
00:25:25,791 --> 00:25:28,592
is that the insides of
white dwarfs
440
00:25:28,594 --> 00:25:30,794
actually crystallize.
441
00:25:32,331 --> 00:25:35,199
Narrator: Up to 6 billion years
after dying,
442
00:25:35,201 --> 00:25:38,903
the hot carbon and oxygen matter
inside the white dwarf
443
00:25:38,905 --> 00:25:42,773
cools and crystallizes,
becoming solid,
444
00:25:42,775 --> 00:25:46,443
giving the dead star a lifeline.
445
00:25:46,445 --> 00:25:49,547
This actually releases energy.
446
00:25:49,549 --> 00:25:51,715
As the star cools,
it winds up releasing
447
00:25:51,717 --> 00:25:54,251
a little bit more energy
than it otherwise would.
448
00:25:54,253 --> 00:25:59,823
Narrator:
This unusual heat source could
warm up a nearby frozen planet,
449
00:25:59,825 --> 00:26:03,294
giving life a second chance.
450
00:26:03,296 --> 00:26:07,064
Thaller:
There will be some extra energy
available from these objects.
451
00:26:07,066 --> 00:26:08,766
So this is the time that we have
452
00:26:08,768 --> 00:26:10,834
to cuddle up
close to the zombies.
453
00:26:12,338 --> 00:26:16,807
Narrator: Crystallization
can rejuvenate old white dwarfs,
454
00:26:16,809 --> 00:26:19,043
and the process
could even provide
455
00:26:19,045 --> 00:26:22,713
a spectacular setting
for an orbiting planet.
456
00:26:22,715 --> 00:26:24,715
We have a special name
457
00:26:24,717 --> 00:26:27,518
for cooled-down crystallized
carbon and oxygen.
458
00:26:27,520 --> 00:26:29,420
We call them diamonds.
459
00:26:29,422 --> 00:26:32,089
The long-term fate
of our universe
460
00:26:32,091 --> 00:26:35,960
will be sprinkled with
all these glittering diamonds.
461
00:26:37,930 --> 00:26:41,398
A zombie that comes to life
and shines like a diamond
462
00:26:41,400 --> 00:26:43,233
might be pretty to look at,
463
00:26:43,235 --> 00:26:47,338
but it's still no guarantee
that life could survive here.
464
00:26:48,841 --> 00:26:51,842
You can kind of think
of these white dwarfs
465
00:26:51,844 --> 00:26:55,479
as maybe making a little
more energy for the universe,
466
00:26:55,481 --> 00:26:58,082
but even that's going
to eventually run out.
467
00:26:58,084 --> 00:27:01,885
The whole thing becomes
a gigantic crystal and, again,
468
00:27:01,887 --> 00:27:04,755
it's just going to
start cooling and fading away.
469
00:27:05,891 --> 00:27:09,159
Narrator: The zombie fizzles out
into a dark cinder,
470
00:27:09,161 --> 00:27:12,963
giving off almost
no light at all,
471
00:27:12,965 --> 00:27:17,401
but there's another monster
lurking in the cosmos.
472
00:27:20,673 --> 00:27:23,807
Thaller: When a star that's much
more massive than the sun dies,
473
00:27:23,809 --> 00:27:25,009
it explodes violently,
474
00:27:25,011 --> 00:27:27,745
and during that explosion,
the core collapses
475
00:27:27,747 --> 00:27:31,015
and becomes an incredibly dense,
small object,
476
00:27:31,017 --> 00:27:35,419
one of the most wonderful
real monsters in the universe.
477
00:27:37,123 --> 00:27:39,456
This is a pulsar...
478
00:27:39,458 --> 00:27:44,261
Psr b0329+54,
479
00:27:44,263 --> 00:27:47,364
3,000 light-years away from us.
480
00:27:47,366 --> 00:27:50,034
The pulsar has the mass
of the sun,
481
00:27:50,036 --> 00:27:52,436
but is just 12 miles across.
482
00:27:52,438 --> 00:27:57,374
Its rapid spin generates beams
of radiation from its poles,
483
00:27:57,376 --> 00:28:00,477
bringing the zombie to life.
484
00:28:01,714 --> 00:28:07,851
Now, we've discovered an alien
world orbiting this zombie star.
485
00:28:07,853 --> 00:28:10,587
Mingarelli:
In 2017, a new planet
486
00:28:10,589 --> 00:28:12,890
was discovered around a pulsar.
487
00:28:12,892 --> 00:28:15,926
They're about twice
the mass of the earth,
488
00:28:15,928 --> 00:28:18,429
and that's really incredible.
489
00:28:18,431 --> 00:28:21,699
Narrator: The pulsar planet
sounds intriguing,
490
00:28:21,701 --> 00:28:25,002
but the prospects
for life aren't good.
491
00:28:25,004 --> 00:28:29,807
Orbiting a pulsar would be
a brutal environment for life.
492
00:28:29,809 --> 00:28:32,743
Mingarelli: It's highly unlikely
that there's life
493
00:28:32,745 --> 00:28:35,946
because the radiation from this
system would be overwhelming
494
00:28:35,948 --> 00:28:39,116
and likely blow away
the atmosphere.
495
00:28:40,186 --> 00:28:42,820
Narrator: As for sustaining life
in the universe,
496
00:28:42,822 --> 00:28:47,157
none of these options
is what you'd call a safe bet.
497
00:28:47,159 --> 00:28:49,226
♪
498
00:28:49,228 --> 00:28:52,796
these are momentary reprieves
from the inevitable.
499
00:28:52,798 --> 00:28:55,032
No matter what you do,
eventually,
500
00:28:55,034 --> 00:28:57,601
you're going to run out
of these gimmes.
501
00:28:57,603 --> 00:29:00,404
You're going to run out of the
get-of-jail-free cards.
502
00:29:00,406 --> 00:29:04,508
Inevitably, everything is going
to cool and fade away.
503
00:29:04,510 --> 00:29:07,244
♪
504
00:29:07,246 --> 00:29:09,913
narrator: This might be
game over for stars
505
00:29:09,915 --> 00:29:12,850
and even for life.
506
00:29:12,852 --> 00:29:17,621
But there is still a glimmer
of hope hidden in the cosmos,
507
00:29:17,623 --> 00:29:20,791
a star that isn't dying.
508
00:29:20,793 --> 00:29:24,595
It appears blessed
with eternal life,
509
00:29:24,597 --> 00:29:27,197
and its color is red.
510
00:29:27,199 --> 00:29:31,034
Red dwarfs -- we are literally
surrounded by them,
511
00:29:31,036 --> 00:29:33,237
but they are largely
invisible to us.
512
00:29:44,316 --> 00:29:46,683
♪
513
00:29:46,685 --> 00:29:49,787
narrator: Illuminating
every corner of our night sky
514
00:29:49,789 --> 00:29:52,956
is the light of stars...
515
00:29:52,958 --> 00:29:58,061
But what we see with a naked eye
doesn't tell the whole story.
516
00:29:58,063 --> 00:30:00,197
♪
517
00:30:00,199 --> 00:30:03,367
thaller:
The stars that you're seeing
are mainly stars like the sun
518
00:30:03,369 --> 00:30:05,736
or even more massive
and even hotter than the sun.
519
00:30:05,738 --> 00:30:08,639
They're bright. You can see them
from a distance,
520
00:30:08,641 --> 00:30:11,308
but amazingly, the most
common form of star,
521
00:30:11,310 --> 00:30:14,344
by far, are
the red dwarf stars.
522
00:30:14,346 --> 00:30:16,513
They're up there right now
in the sky,
523
00:30:16,515 --> 00:30:19,616
but they're just too small
and too faint to see.
524
00:30:19,618 --> 00:30:23,387
Narrator: Red dwarfs are up to
10 times smaller than the sun,
525
00:30:23,389 --> 00:30:26,123
and they burn less brightly.
526
00:30:26,125 --> 00:30:29,092
Right now,
hidden in the night sky,
527
00:30:29,094 --> 00:30:33,564
over three-quarters of the stars
in our galaxy are red dwarfs...
528
00:30:33,566 --> 00:30:38,335
And while the larger stars
are dying out,
529
00:30:38,337 --> 00:30:41,338
we've never seen
a red dwarf die,
530
00:30:41,340 --> 00:30:44,141
making them
the best bet for life
531
00:30:44,143 --> 00:30:47,211
to survive the star apocalypse.
532
00:30:47,213 --> 00:30:51,315
When the most massive stars
eventually go out
533
00:30:51,317 --> 00:30:54,151
and are not replaced,
what will be left
534
00:30:54,153 --> 00:30:58,422
are much, much dimmer stars
like red dwarf stars.
535
00:30:58,424 --> 00:31:01,925
Narrator: We've seen star death
across the universe,
536
00:31:01,927 --> 00:31:04,294
so why not red dwarfs?
537
00:31:04,296 --> 00:31:06,697
Turns out their size
538
00:31:06,699 --> 00:31:10,400
gives them a crucial advantage
over larger stars.
539
00:31:10,402 --> 00:31:13,270
Thaller: The more massive a star
is, the hotter it burns.
540
00:31:13,272 --> 00:31:15,672
A red dwarf star burns
at a lower temperature.
541
00:31:15,674 --> 00:31:17,574
So it doesn't burn through
it's fuel
542
00:31:17,576 --> 00:31:19,710
quite as quickly
as a mid-mass star does.
543
00:31:19,712 --> 00:31:22,713
These are like the economy
cars of the universe.
544
00:31:22,715 --> 00:31:25,449
They're just sipping
on their nuclear fuel,
545
00:31:25,451 --> 00:31:28,185
and they can coast along.
546
00:31:28,187 --> 00:31:31,355
Narrator: Not only that,
despite being smaller,
547
00:31:31,357 --> 00:31:34,057
they have access to more fuel.
548
00:31:35,327 --> 00:31:38,595
Our mid-size sun
is split into three layers --
549
00:31:38,597 --> 00:31:41,331
a core, a radiation zone,
550
00:31:41,333 --> 00:31:43,500
and a convective layer.
551
00:31:43,502 --> 00:31:47,304
The radiation zone prevents
hydrogen in the top layer
552
00:31:47,306 --> 00:31:50,707
from ever becoming available
for the core to burn.
553
00:31:50,709 --> 00:31:52,976
So the sun can only access
554
00:31:52,978 --> 00:31:57,114
about 10 percent
of its total hydrogen fuel.
555
00:31:57,116 --> 00:32:01,251
Once the hydrogen
in our sun's core runs out,
556
00:32:01,253 --> 00:32:04,254
its days are numbered.
557
00:32:04,256 --> 00:32:06,490
In some ways,
these mid-sized stars
558
00:32:06,492 --> 00:32:08,158
end up starving themselves.
559
00:32:08,160 --> 00:32:11,561
Narrator: The smaller red dwarfs
are different.
560
00:32:11,563 --> 00:32:15,065
They can access all
the hydrogen they want.
561
00:32:15,067 --> 00:32:18,568
Plait: In low-mass stars,
outside of the core,
562
00:32:18,570 --> 00:32:21,505
this outer layer
is fully convective.
563
00:32:21,507 --> 00:32:25,375
What that means is, stuff near
the core rises to the surface
564
00:32:25,377 --> 00:32:28,312
and then drops back down
all the way to the core,
565
00:32:28,314 --> 00:32:30,514
and that means if you have
hydrogen somewhere
566
00:32:30,516 --> 00:32:33,150
outside of the core,
eventually, it's going to make
567
00:32:33,152 --> 00:32:35,619
its way down there,
and it can be used for fuel.
568
00:32:35,621 --> 00:32:37,854
Hopkins: The red dwarf has
access to everything
569
00:32:37,856 --> 00:32:39,189
at the all-you-can-eat buffet.
570
00:32:39,191 --> 00:32:41,758
It can grab stuff from
the distant regions
571
00:32:41,760 --> 00:32:44,795
at the surface of the star
and bring it all the way
572
00:32:44,797 --> 00:32:48,098
down the gullet
to the heart of the star.
573
00:32:49,201 --> 00:32:52,436
Narrator: This all-you-can-eat
hydrogen buffet
574
00:32:52,438 --> 00:32:56,540
extends the life span of red
dwarfs to incredible lengths.
575
00:32:56,542 --> 00:33:00,344
The universe is over 13 billion
years old,
576
00:33:00,346 --> 00:33:04,114
but any red dwarf
that age is a toddler.
577
00:33:05,517 --> 00:33:07,384
A red dwarf, even if it was born
578
00:33:07,386 --> 00:33:09,319
at the very beginning
of the universe
579
00:33:09,321 --> 00:33:11,054
when red dwarfs
could first form,
580
00:33:11,056 --> 00:33:14,725
even today, it's just
a tiny fraction of its lifespan.
581
00:33:14,727 --> 00:33:17,294
They can last for trillions
of years,
582
00:33:17,296 --> 00:33:20,564
thousands of times
the current age of the universe.
583
00:33:20,566 --> 00:33:22,632
Sutter:
Thirteen billion years old --
584
00:33:22,634 --> 00:33:24,801
that seems like a long time,
585
00:33:24,803 --> 00:33:26,603
but a small red dwarf,
586
00:33:26,605 --> 00:33:28,805
it's barely out of diapers.
587
00:33:28,807 --> 00:33:30,607
♪
588
00:33:30,609 --> 00:33:33,043
narrator:
Red dwarf stars will not die out
589
00:33:33,045 --> 00:33:36,580
for 10 trillion years or more...
590
00:33:36,582 --> 00:33:40,484
And we're discovering
they have another trump card
591
00:33:40,486 --> 00:33:42,252
that's good news for life.
592
00:33:42,254 --> 00:33:46,423
♪
593
00:33:46,425 --> 00:33:48,759
February 2017.
594
00:33:48,761 --> 00:33:51,495
Nasa announced
the discovery of a system
595
00:33:51,497 --> 00:33:55,165
in the aquarius constellation
called trappist-1
596
00:33:55,167 --> 00:34:00,570
where seven earth-sized
planets orbit a red dwarf star.
597
00:34:01,707 --> 00:34:04,975
Plait: It turns out that red
dwarfs, apparently,
598
00:34:04,977 --> 00:34:07,444
are really good
at making planets,
599
00:34:07,446 --> 00:34:10,747
including planets that are
roughly the size of the earth.
600
00:34:10,749 --> 00:34:16,186
That's really cool because
these stars last a long time.
601
00:34:16,188 --> 00:34:18,688
If they have planets
orbiting them with life,
602
00:34:18,690 --> 00:34:22,692
they could outlast our solar
system by trillions of years.
603
00:34:23,762 --> 00:34:28,465
Narrator: Sounds promising, but
red dwarfs have an ugly side.
604
00:34:30,235 --> 00:34:32,569
In October 2018,
605
00:34:32,571 --> 00:34:35,305
astronomers turned
the hubble space telescope
606
00:34:35,307 --> 00:34:38,608
to a series of young
red dwarf stars
607
00:34:38,610 --> 00:34:41,845
in the tucana-horologium
association.
608
00:34:41,847 --> 00:34:47,851
They witnessed these infants
throwing daily stellar tantrums.
609
00:34:47,853 --> 00:34:49,920
Thaller: Even though they're
the smallest stars,
610
00:34:49,922 --> 00:34:52,389
they actually have
some of the strongest flares
611
00:34:52,391 --> 00:34:54,357
and storms on them.
612
00:34:54,359 --> 00:34:56,893
Narrator:
Red dwarfs can emit flares
613
00:34:56,895 --> 00:35:00,597
10,000 times more powerful
than the sun.
614
00:35:00,599 --> 00:35:04,634
These flares would cook
any nearby planets.
615
00:35:05,637 --> 00:35:07,370
Oluseyi:
When a red dwarf star forms,
616
00:35:07,372 --> 00:35:09,005
they're rotating very rapidly,
617
00:35:09,007 --> 00:35:11,408
and this creates
a lot of magnetic activity
618
00:35:11,410 --> 00:35:14,578
which creates flares
and mass ejections.
619
00:35:14,580 --> 00:35:16,947
Narrator:
For life to exist,
620
00:35:16,949 --> 00:35:21,251
it would have to wait for infant
red dwarfs to grow up.
621
00:35:22,754 --> 00:35:24,821
Oluseyi:
As a red dwarf gets older,
622
00:35:24,823 --> 00:35:27,457
there's drag between
the magnetic fields
623
00:35:27,459 --> 00:35:30,127
in space as it rotates,
and that has the effect
624
00:35:30,129 --> 00:35:32,129
of slowing down
its rate of rotation.
625
00:35:32,131 --> 00:35:34,431
And so this means
the activity settles down.
626
00:35:34,433 --> 00:35:38,034
So maybe later, in this life
of a red dwarf star,
627
00:35:38,036 --> 00:35:40,570
they can support
planets with life.
628
00:35:42,908 --> 00:35:47,177
Narrator: Red dwarf stars will
dominate the future universe
629
00:35:47,179 --> 00:35:50,914
and may give life
a chance to survive.
630
00:35:50,916 --> 00:35:55,118
These small red stars
are extremely long-lived,
631
00:35:55,120 --> 00:35:57,754
but no star is immortal.
632
00:35:57,756 --> 00:36:01,324
Even though they're really going
through their nuclear fuel
633
00:36:01,326 --> 00:36:06,329
very slowly, there's just not
enough fuel to last forever.
634
00:36:07,599 --> 00:36:10,800
Narrator: These little stars
will die out eventually.
635
00:36:10,802 --> 00:36:16,106
Unlike their larger stellar
siblings, they'll go quietly.
636
00:36:16,108 --> 00:36:18,241
Well, it actually just gets
hotter,
637
00:36:18,243 --> 00:36:21,178
and the color of a star
depends on its temperature.
638
00:36:21,180 --> 00:36:24,214
So as the red dwarf gets hotter,
it turns bluer.
639
00:36:24,216 --> 00:36:27,150
So sometime
in the very distant future,
640
00:36:27,152 --> 00:36:28,485
some of these red dwarfs
641
00:36:28,487 --> 00:36:31,254
are actually going
to become blue dwarfs.
642
00:36:31,256 --> 00:36:35,725
Narrator:
The universe isn't old enough
for blue dwarfs to exist yet.
643
00:36:35,727 --> 00:36:38,228
But trillions of years from now,
644
00:36:38,230 --> 00:36:43,133
a dim blue glow will
complete the star apocalypse.
645
00:36:44,236 --> 00:36:48,205
There will be a last star,
one last red dwarf,
646
00:36:48,207 --> 00:36:51,608
maybe now turning blue
as it warms up,
647
00:36:51,610 --> 00:36:55,712
but it too will eventually
cool off, fade away.
648
00:36:56,848 --> 00:36:59,416
And there will be no more stars
in the universe.
649
00:36:59,418 --> 00:37:01,418
It is inevitable.
650
00:37:01,420 --> 00:37:03,453
♪
651
00:37:03,455 --> 00:37:06,556
narrator:
In this dark, starless universe,
652
00:37:06,558 --> 00:37:09,826
prospects for life
seem impossible.
653
00:37:09,828 --> 00:37:14,064
But will something else
take the place of stars?
654
00:37:14,066 --> 00:37:16,700
Oluseyi: As we get to the end of
the universe,
655
00:37:16,702 --> 00:37:19,869
things get really cold,
but they also get really weird.
656
00:37:35,854 --> 00:37:39,155
Narrator: Trillions of years
from now, the star apocalypse
657
00:37:39,157 --> 00:37:42,692
will leave the universe
empty and dark,
658
00:37:42,694 --> 00:37:45,295
a never-ending night.
659
00:37:46,331 --> 00:37:47,964
The universe at this time
660
00:37:47,966 --> 00:37:49,866
is nothing like
the universe of today.
661
00:37:49,868 --> 00:37:55,372
There's no light, and it's
really cold and very lonely.
662
00:37:55,374 --> 00:37:59,209
When all of the stars die
and the light goes away,
663
00:37:59,211 --> 00:38:01,211
anything that relies on the heat
664
00:38:01,213 --> 00:38:04,414
and the processes from
these stars will start to die.
665
00:38:04,416 --> 00:38:06,283
♪
666
00:38:06,285 --> 00:38:08,585
sutter:
Once all the lights go out,
667
00:38:08,587 --> 00:38:12,389
the only things that will remain
will be the leftovers.
668
00:38:12,391 --> 00:38:15,191
Narrator: With stars as we know
them long gone,
669
00:38:15,193 --> 00:38:17,961
could something else
spark into existence
670
00:38:17,963 --> 00:38:20,363
in this cosmic wasteland?
671
00:38:20,365 --> 00:38:23,300
You'd think that's it,
no more star formation.
672
00:38:23,302 --> 00:38:27,203
But the universe still
has a few tricks up its sleeve.
673
00:38:27,205 --> 00:38:29,873
Narrator: Over the history
of the universe,
674
00:38:29,875 --> 00:38:32,642
generations of stars
have lived and died.
675
00:38:32,644 --> 00:38:36,112
They released heavy metal
elements into the universe,
676
00:38:36,114 --> 00:38:39,749
building materials
for a new kind of star,
677
00:38:39,751 --> 00:38:42,285
and stars born from these
new materials
678
00:38:42,287 --> 00:38:46,823
can do things
their ancestors could not.
679
00:38:46,825 --> 00:38:50,894
As you enrich the universe,
as more and more metals
680
00:38:50,896 --> 00:38:52,629
get produced over time,
681
00:38:52,631 --> 00:38:56,333
you can lower
the temperature needed
682
00:38:56,335 --> 00:38:58,935
for fusion reactions in a star.
683
00:38:58,937 --> 00:39:02,639
Narrator: With lower
temperatures needed for fusion,
684
00:39:02,641 --> 00:39:06,376
stars have
become smaller and smaller.
685
00:39:06,378 --> 00:39:08,978
O'dowd: Currently, the smallest
possible star
686
00:39:08,980 --> 00:39:11,648
is a little under 10 percent
the sun's mass.
687
00:39:11,650 --> 00:39:14,084
But eventually it may
be possible to form stars
688
00:39:14,086 --> 00:39:16,686
that have around 4 percent
the sun's mass.
689
00:39:18,256 --> 00:39:21,725
Narrator: Hundreds of trillions
of years in the future,
690
00:39:21,727 --> 00:39:24,461
a new star may dominate
the universe,
691
00:39:24,463 --> 00:39:30,567
built from scraps left over
from generations of dead stars,
692
00:39:30,569 --> 00:39:32,669
a star so small
693
00:39:32,671 --> 00:39:36,039
that it burns cold
instead of hot.
694
00:39:37,476 --> 00:39:39,342
One of the weirdest types
of stars
695
00:39:39,344 --> 00:39:42,178
that scientists hypothesize
might exist in the far future
696
00:39:42,180 --> 00:39:43,880
is the frozen star.
697
00:39:45,417 --> 00:39:49,586
Sutter: You can start forming
stars that are very, very small
698
00:39:49,588 --> 00:39:52,922
and very cold,
where nuclear fusion
699
00:39:52,924 --> 00:39:57,494
is happening in the core,
but the surfaces are cold.
700
00:39:57,496 --> 00:40:00,830
♪
701
00:40:00,832 --> 00:40:02,866
narrator:
These small, cold objects
702
00:40:02,868 --> 00:40:04,968
will be thousands of times
dimmer
703
00:40:04,970 --> 00:40:08,471
than the faintest star
we see today.
704
00:40:08,473 --> 00:40:11,875
So cold, the temperatures
on the surface
705
00:40:11,877 --> 00:40:15,478
could reach just 32 degrees
fahrenheit...
706
00:40:15,480 --> 00:40:19,783
And ice clouds may form
in the star's atmosphere.
707
00:40:19,785 --> 00:40:23,420
They are so much cooler
than stars now.
708
00:40:23,422 --> 00:40:27,924
They could actually have ice,
water ice, on their surface,
709
00:40:27,926 --> 00:40:31,494
even though
they are technically stars.
710
00:40:31,496 --> 00:40:36,099
Sutter: It's literal water-ice
covering the surface of a star,
711
00:40:36,101 --> 00:40:39,602
the same ice that you can use
for ice-skating
712
00:40:39,604 --> 00:40:41,571
or ice racing or curling.
713
00:40:41,573 --> 00:40:43,306
You could do all of this
714
00:40:43,308 --> 00:40:46,476
on the surface of a star
in the far future.
715
00:40:47,646 --> 00:40:50,046
Narrator: It's hard to predict
if life could arise
716
00:40:50,048 --> 00:40:53,316
on planets
orbiting frozen stars.
717
00:40:55,454 --> 00:40:59,689
We won't know
until one appears...
718
00:40:59,691 --> 00:41:03,827
And that
won't be for a very long time.
719
00:41:05,497 --> 00:41:07,330
The universe is far too young
720
00:41:07,332 --> 00:41:09,632
for even the first one
of these things
721
00:41:09,634 --> 00:41:11,468
to even be a glimmer of an idea.
722
00:41:11,470 --> 00:41:14,103
So if you want to wait,
you know, a quadrillion years,
723
00:41:14,105 --> 00:41:15,939
then we can find out.
724
00:41:15,941 --> 00:41:18,775
Narrator:
Stars helped create us,
725
00:41:18,777 --> 00:41:21,077
building and spreading
the ingredients
726
00:41:21,079 --> 00:41:23,146
for life to develop,
727
00:41:23,148 --> 00:41:25,181
but the coming star apocalypse
728
00:41:25,183 --> 00:41:27,851
may mean the end of life,
729
00:41:27,853 --> 00:41:30,186
just not for a while.
730
00:41:31,656 --> 00:41:36,359
Small red stars will continue
to illuminate the darkness...
731
00:41:36,361 --> 00:41:41,064
Safe havens for life to survive
and even flourish.
732
00:41:41,066 --> 00:41:42,799
As for us on earth,
733
00:41:42,801 --> 00:41:46,236
we should be
most thankful for one star
734
00:41:46,238 --> 00:41:50,473
because without it,
we simply wouldn't exist.
735
00:41:50,475 --> 00:41:53,643
Thaller:
I really want you to never
experience a sunny day again
736
00:41:53,645 --> 00:41:55,011
and not think about this.
737
00:41:55,013 --> 00:41:57,380
The sun, someday, will burn out,
738
00:41:57,382 --> 00:41:59,549
and so will all of
the other stars.
739
00:41:59,551 --> 00:42:03,620
We are in this wonderful era
of light and warmth
740
00:42:03,622 --> 00:42:05,154
coming out of the sky,
741
00:42:05,156 --> 00:42:09,058
and everything is going to go
dark, absolutely everything,
742
00:42:09,060 --> 00:42:11,160
everywhere in the universe.
743
00:42:11,162 --> 00:42:14,430
So for the time being, you know,
enjoy the light.
744
00:42:14,432 --> 00:42:16,533
Step outside, enjoy the sun,
745
00:42:16,535 --> 00:42:19,669
and think about how lucky we are
to live in this time.
746
00:42:19,671 --> 00:42:23,473
♪
747
00:42:23,475 --> 00:42:27,844
♪