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There's a killer lurking

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in our galaxy, a star ready
to explode into a supernova.

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These are the most
visually stunning

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events in the universe.

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Seen from Earth, it
would have a terrible beauty.

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But for us, it could be fatal.

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In a few seconds, it
can release as much energy

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as the sun will over
its entire lifetime.

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We're trying to hunt
it down, but it's lying low.

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We haven't seen a
supernova in the Milky Way

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in over 400 years.

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It could be anywhere.

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It is nearly impossible
to predict where and when

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the next supernova will happen.

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The hunt is on
to find the next supernova

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before it finds us.

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-== [ www.OpenSubtitles.org ] ==-

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October 2019, one of the
brightest stars in the sky

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looks dangerously unstable.

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If you look at the
constellation of Orion,

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one of the shoulders of Orion
is a star that is obviously red.

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This is Betelgeuse.

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I could go into my
backyard and see it.

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You could clearly see that
it was getting dimmer.

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Is this a warning?

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Is Betelgeuse about to die in
a massive cosmic explosion,

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a supernova?

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We've been studying this
star for hundreds of years.

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And one thing we're sure about
is that it's big, very big.

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Betelgeuse is a massive
star, maybe 15 or 20 times

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the mass of our sun.

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And it's near the
end of its life.

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It is a massive,
enormous, luminous star.

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And one day, it's
going to go boom.

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Betelgeuse is on our
list of supernova candidates

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because of this massive size.

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The bigger star
they are, actually the

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shorter the lifespan.

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The lifespan of a star depends

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on a delicate balance between
two competing forces...

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Gravity pulling in and heat
and pressure pushing out.

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Stars exist because
they're held up.

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They're not held up by pillars.

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They're held up by energy
flowing out of the core

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toward the surface of the star.

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That stops the
gravitational contraction.

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Stars get their energy

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from nuclear fusion
reactions right in the core.

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And the most basic one is
taking two hydrogen atoms

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and slamming them together
to form a helium atom.

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And you might think, OK,
the more hydrogen you have,

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the more stuff you have, maybe
the longer the start will live.

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Turns out it's exactly opposite.

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The reason... gravity.

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The more mass a star
has, the stronger

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its gravity, gravity
that crushes its hydrogen

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atoms closer together.

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As you crush
things more and more,

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the temperature gets hotter
and hotter and hotter.

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And the nuclear fusion
reactions burn faster.

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So bigger stars burn their
fuel very, very quickly

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and live short lives.

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Smaller stars burn their
fuel much more slowly

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and live long, protracted lives.

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So when you are a
big star, you live fast

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and you die young.

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Betelgeuse burns
brighter than 125,000 suns.

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But now it's running out
of its hydrogen fuel.

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So it's burning whatever it
has left just to stay alive.

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Stars are basically
factories for burning

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hydrogen into helium.

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And then, once the
helium is burned,

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they start burning heavier and
heavier elements, like carbon

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and nitrogen and oxygen.

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It's a little like, you
burn something, you get ash.

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But then if you
crush the ash enough,

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you could burn it again.

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And then you crush it some more,
and you can burn it yet again.

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But this process
can't go on forever.

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As the size of the atomic nuclei
being fused together grows,

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the amount of energy
released falls.

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The fuel the star needs to
resist the pull of gravity

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is running out.

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Unfortunately,
the amount of energy

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you can extract by putting
two nuclei together

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gets smaller and smaller the
bigger the nuclei are until you

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come to making iron,
and iron, it turns out,

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is the last thing you
can make that way.

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The problem with iron
is, when you fuse it,

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it doesn't make energy.

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It takes it away.

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So when the star builds up
that iron core, it's doomed.

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It can no
longer create energy in its core

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to flow out toward the
surface strong enough

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to keep it from collapsing.

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So collapse is what they do.

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In a fraction of a second,

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the star's core collapses
down from the size of a planet

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to about the size
of a small city.

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And when that happens,
all hell breaks loose.

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A huge amount of energy

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is suddenly released,
which forces

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the collapsing layers back out.

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The result... an enormous
explosion we call a supernova.

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The shockwave from a supernova

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rips out at thousands
of miles per second.

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And for a brief period
of time, they're

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brighter than an entire galaxy.

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A supernova could
devastate life on Earth.

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And the evidence can be found
at the bottom of our oceans.

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There are layers and layers

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of silt that have built up.

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And there seem to be a layer,
about 2.6 million years ago,

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that was enriched in a very
strange chemical element,

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something called iron-60.

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Iron-60 is a
radioactive isotope of iron,

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and it doesn't last very long,
just a few million years.

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And the only place that we
know of that can make iron-60

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is a supernova in
an exploding star.

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That means there must have
been a supernova close enough

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to the Earth within the
past couple of million years

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to have physically deposited
material on our planet.

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That freaks me out.

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The sign of this
shocking assault on our planet

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is a thin layer of this
very rare type of iron.

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We find it in the mud
of every ocean floor

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and always at the same depth.

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This interstellar dust
must have drenched

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our world in one enormous
burst 2.6 million years ago.

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It was a terrible time.

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A third of large animal species
in the sea suddenly died out.

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There were some
pretty amazing fish.

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Probably the most
amazing is the megalodon,

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a giant shark... teeth the size
of dinner plates and so on.

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But they went extinct
2.6 million years ago

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at the end of the Pliocene.

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What happened?

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A lot of sea creatures died.

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And a lot of them were
in shallow waters,

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whereas deep-water
animals tended to survive.

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That sounds kind of
like a supernova.

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That can do things that
would affect our atmosphere,

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would affect shallow water,
but not deeper water.

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Supernovas create
huge amounts of cosmic rays.

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When they crash
into other atoms,

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they break up and produce
showers of dangerous shrapnel

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called muons.

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These charged particles
are similar to electrons,

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only 200 times heavier.

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So they penetrate more
deeply and cause more damage.

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They can pierce
through our atmosphere,

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pierce through our
skin, get into a cell,

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and disrupt the DNA.

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They'll go right through
a mouse but deposit

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in the body of a larger animal.

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So the impact on an animal
the size of a megalodon,

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say, could be pretty extreme.

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Muons can shatter DNA,
causing mutations and cancer.

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But their power
weakens as they travel

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through water, which
may be why only

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deep sea creatures survived.

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The extinction really
tells us that we're not

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separate and apart from
the universe and the goings

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on up there, right?

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Supernova going off
and things like that...

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OK, it's a pretty light show.

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No.

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It is a direct impact
to life on Earth and us.

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So are we in
danger of extinction?

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Is Betelgeuse about to explode?

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When stars explode
as supernovas,

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they can devastate planets
hundreds of light years away.

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Betelgeuse is about 550
light years from Earth.

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So, when it dramatically
dimmed in 2019,

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scientists were concerned.

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00:10:14,680 --> 00:10:16,181
But Betelgeuse
has dimmed before.

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Betelgeuse varies

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quite a lot over the years.

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There are some
cycles, and sometimes

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these cycles come together,
and you get a deep minimum.

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So dimming is part
of the star's natural cycle

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as it nears the end of its life.

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But to get a full picture, we
took Betelgeuse's temperature.

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If the star was dimming, that
would mean that the surface

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was cooling over time.

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We actually made measurements
of the temperature of Betelgeuse

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and found out that
wasn't happening.

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It hardly cooled at all.

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It cooled, like,
50 or 100 degrees.

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You might expect
a much, much more

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dramatic change in the
surface temperature

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if it were about to explode.

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So, if Betelgeuse wasn't cooling

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00:11:04,397 --> 00:11:06,464
much, what was making it dim?

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00:11:08,668 --> 00:11:12,904
To take a closer look, we
used a very large telescope

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00:11:12,972 --> 00:11:16,141
and an exoplanet
hunting instrument

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00:11:16,242 --> 00:11:20,011
called SPHERE and came up
with an extraordinary image.

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00:11:23,249 --> 00:11:27,218
When I first saw this image
of Betelgeuse, it blew me away.

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I almost gasped.

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00:11:28,754 --> 00:11:30,955
I may have said a
word I can't say on TV.

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00:11:32,725 --> 00:11:34,025
That was very exciting.

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00:11:35,761 --> 00:11:38,029
The image reveals
that, while the upper part

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00:11:38,130 --> 00:11:41,166
of Betelgeuse was
still bright, the lower

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00:11:41,267 --> 00:11:44,169
part was noticeably dimmer.

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00:11:44,270 --> 00:11:47,072
We had images of
Betelgeuse from before,

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00:11:47,173 --> 00:11:49,474
and we were able to compare
the new ones with it.

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00:11:49,575 --> 00:11:52,343
And so you could see
that half of Betelgeuse

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00:11:52,445 --> 00:11:53,878
looked pretty much the same.

209
00:11:53,979 --> 00:11:56,748
But the other half was
significantly dimmer.

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00:11:56,849 --> 00:12:00,018
And what could make a
star dim that quickly?

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00:12:00,119 --> 00:12:02,721
And remember how
big this star is.

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00:12:02,822 --> 00:12:04,956
Nothing happens on
Betelgeuse quickly.

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00:12:05,057 --> 00:12:07,659
So this must be something
happening right on the surface.

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00:12:10,863 --> 00:12:12,797
As heavier
material like silicone

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00:12:12,898 --> 00:12:16,067
emerges from the
surface of Betelgeuse,

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00:12:16,168 --> 00:12:19,304
it cools and condenses.

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00:12:19,405 --> 00:12:21,216
It's kind of like sticking
the hose in the wrong end

218
00:12:21,240 --> 00:12:22,307
of your vacuum cleaner.

219
00:12:22,408 --> 00:12:24,219
Instead of pulling stuff in,

220
00:12:24,243 --> 00:12:26,044
it blows all this
dust out into space.

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00:12:28,481 --> 00:12:31,783
Betelgeuse
has cosmic indigestion

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00:12:31,884 --> 00:12:36,621
and is belching dust, which
makes the star seem dim.

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00:12:36,722 --> 00:12:37,722
But it's not over.

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00:12:39,191 --> 00:12:42,393
All through 2020,
Betelgeuse first brightened

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00:12:42,495 --> 00:12:44,195
and then dimmed again.

226
00:12:45,998 --> 00:12:50,001
So astronomers are watching this
massive star with bated breath.

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00:12:52,171 --> 00:12:53,471
It's going to explode.

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00:12:53,572 --> 00:12:55,640
The question is, when?

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00:12:55,741 --> 00:12:58,376
It's probably sometime
in the next 100,000 years.

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00:12:58,477 --> 00:12:59,544
But it could be tomorrow.

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00:12:59,645 --> 00:13:01,189
It could have already
exploded and we're

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00:13:01,213 --> 00:13:03,515
just waiting to see the light.

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00:13:03,616 --> 00:13:06,751
With luck, if
Betelgeuse blows, all we'll see

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00:13:06,852 --> 00:13:08,086
is a beautiful light show.

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00:13:10,656 --> 00:13:13,691
At a distance of
550 light years,

236
00:13:13,793 --> 00:13:16,327
it's probably too far
to do serious damage.

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00:13:19,031 --> 00:13:22,634
But is there another star
we should worry about?

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00:13:26,472 --> 00:13:30,408
A closer star, just 150
light years from Earth,

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00:13:30,509 --> 00:13:34,946
could do us some major
damage, a star like IK Pegasi.

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00:13:37,416 --> 00:13:40,451
But it isn't this star which
we can see in our night

241
00:13:40,553 --> 00:13:41,986
sky that's the threat.

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00:13:44,056 --> 00:13:47,659
The main star is only about
1.6 times the mass of the sun.

243
00:13:47,760 --> 00:13:50,161
That's nowhere near enough
mass to go supernova.

244
00:13:50,262 --> 00:13:54,432
And yet, we think it is the
progenitor for a supernova.

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00:13:54,500 --> 00:13:55,500
How can that be?

246
00:13:56,802 --> 00:13:58,403
The main star isn't alone.

247
00:13:59,805 --> 00:14:02,540
It has a more
dangerous accomplice.

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00:14:05,411 --> 00:14:08,746
There's another star there
orbiting the larger star.

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00:14:08,848 --> 00:14:10,826
And this is what
we call a binary system...

250
00:14:10,850 --> 00:14:12,250
Two stars orbiting each other.

251
00:14:13,652 --> 00:14:15,253
Right now, the system is stable.

252
00:14:15,354 --> 00:14:17,499
But things aren't always going
to be the way they are now,

253
00:14:17,523 --> 00:14:20,358
and sometime in
the future, things

254
00:14:20,459 --> 00:14:21,993
are going to change a lot.

255
00:14:24,396 --> 00:14:26,264
IK Pegasi is really made up

256
00:14:26,365 --> 00:14:34,339
of IK Pegasi A, a large white
star, and its accomplice,

257
00:14:34,440 --> 00:14:41,812
a white dwarf called IK
Pegasi B. This tiny star

258
00:14:41,881 --> 00:14:43,248
is the real threat to Earth.

259
00:14:45,217 --> 00:14:49,721
You can think of a
white dwarf as a zombie.

260
00:14:49,822 --> 00:14:53,658
You know, it's a dead star,
and they can eat living stars.

261
00:14:53,759 --> 00:14:57,362
If there's a normal star like
the sun near a white dwarf,

262
00:14:57,463 --> 00:15:00,298
the white dwarf has very,
very intense gravity.

263
00:15:00,399 --> 00:15:03,401
It can literally pull
material off that normal star,

264
00:15:03,502 --> 00:15:06,104
and that material will
then pile up on the surface

265
00:15:06,205 --> 00:15:07,071
of the white dwarf.

266
00:15:07,172 --> 00:15:09,707
So it really is
eating a living star.

267
00:15:12,611 --> 00:15:14,746
These stars
orbit each other just

268
00:15:14,847 --> 00:15:18,049
18.5 million miles apart.

269
00:15:18,150 --> 00:15:21,552
That's closer than
Mercury is to our sun.

270
00:15:21,654 --> 00:15:26,457
But they're not interacting
with each other, yet.

271
00:15:26,558 --> 00:15:28,960
The problem is,
sometime in the future,

272
00:15:29,061 --> 00:15:31,329
that normal star is
going to run out of fuel.

273
00:15:31,430 --> 00:15:34,165
And when it does, it's going
to expand into a red giant.

274
00:15:36,268 --> 00:15:38,169
When it gets
to the end of its life,

275
00:15:38,270 --> 00:15:43,241
IK Pegasi A will cool and
swell up to become a red giant.

276
00:15:45,377 --> 00:15:48,613
And that's it, no big explosion.

277
00:15:48,714 --> 00:15:51,749
It won't become a supernova.

278
00:15:51,850 --> 00:15:57,055
But that's just when it's
accomplice, IK Pegasi B,

279
00:15:57,156 --> 00:15:58,156
will start to feed.

280
00:15:59,992 --> 00:16:02,460
A lot of that material
will gravitationally

281
00:16:02,561 --> 00:16:04,896
be attracted to the white dwarf
and fall under the surface.

282
00:16:06,632 --> 00:16:08,399
As the white
dwarf pulls material

283
00:16:08,500 --> 00:16:10,802
from its bloated
red giant neighbor,

284
00:16:10,903 --> 00:16:12,103
it gets more and more massive.

285
00:16:13,706 --> 00:16:16,441
It's gravitational
pull increases,

286
00:16:16,542 --> 00:16:17,976
so it feeds even faster.

287
00:16:21,880 --> 00:16:24,782
Eventually, it can no longer
support its own weight.

288
00:16:26,919 --> 00:16:29,087
The core of the star
is actually very dense.

289
00:16:29,188 --> 00:16:31,289
In fact, if you had, like,
a teaspoon of material,

290
00:16:31,390 --> 00:16:34,058
it would weigh about as
much as an 18-wheel truck.

291
00:16:34,159 --> 00:16:36,661
And it's basically right at
the limit of normal matter

292
00:16:36,762 --> 00:16:38,863
being able to hold
up at that density.

293
00:16:38,964 --> 00:16:41,132
You dump more and
more stuff onto it,

294
00:16:41,233 --> 00:16:43,568
and eventually there's
a limit that's reached.

295
00:16:43,669 --> 00:16:47,538
And it either collapses
or, more generally, blows up.

296
00:16:53,612 --> 00:16:56,948
When, this
happens IK Pegasi will

297
00:16:57,016 --> 00:17:00,752
be brighter than the
full moon in our sky

298
00:17:00,853 --> 00:17:03,554
because it's only
150 light years away.

299
00:17:07,292 --> 00:17:10,595
Having a supernova 150 light
years sounds like a bad idea,

300
00:17:10,696 --> 00:17:11,696
and it is.

301
00:17:11,730 --> 00:17:13,264
That's close enough
that it might

302
00:17:13,399 --> 00:17:15,199
have some physical
effects on the Earth.

303
00:17:19,038 --> 00:17:21,873
Right now, IK
Pegasi is about as far

304
00:17:21,974 --> 00:17:25,043
from Earth as the
supernova suspected

305
00:17:25,144 --> 00:17:26,511
of killing off the megalodon.

306
00:17:29,281 --> 00:17:31,916
So how worried should we be?

307
00:17:33,919 --> 00:17:36,220
The good news is
the IK Peg system

308
00:17:36,321 --> 00:17:38,489
is moving away from
the sun and the Earth

309
00:17:38,590 --> 00:17:40,892
right now at a decent clip.

310
00:17:40,993 --> 00:17:43,494
So if it's not going to blow
up for a while, that means

311
00:17:43,595 --> 00:17:47,398
it could be on the other side of
the galaxy by the time it does.

312
00:17:47,466 --> 00:17:49,767
By that time, we'll
be completely safe.

313
00:17:49,868 --> 00:17:52,437
As an astronomer and an
astronomer who has studied

314
00:17:52,538 --> 00:17:55,106
supernovas professionally,
having them

315
00:17:55,207 --> 00:17:58,042
far away is fine with me, close
enough that we can study them

316
00:17:58,143 --> 00:18:00,511
well but not so close
that I can study

317
00:18:00,612 --> 00:18:03,314
them personally on a physical
level on my own body.

318
00:18:03,415 --> 00:18:04,415
Yeah, no.

319
00:18:09,688 --> 00:18:12,757
A close supernova
would be devastating for life

320
00:18:12,858 --> 00:18:13,858
on Earth.

321
00:18:14,927 --> 00:18:19,597
Will there be any
warning signs before one

322
00:18:19,698 --> 00:18:22,667
of our prime suspects
is about to blow?

323
00:18:40,119 --> 00:18:42,720
To find a supernova
warning signal,

324
00:18:42,821 --> 00:18:46,424
we need to know what's
happening deep inside the core

325
00:18:46,525 --> 00:18:47,625
of an exploding star.

326
00:18:49,361 --> 00:18:51,796
At the very beginning
of a supernova explosion,

327
00:18:51,897 --> 00:18:54,465
the core of a massive
star is collapsing.

328
00:18:54,533 --> 00:18:56,434
There's no more nuclear
fusion going on,

329
00:18:56,535 --> 00:18:59,170
and it is compressing to
higher and higher densities.

330
00:19:00,706 --> 00:19:02,373
The star's gravity crushes

331
00:19:02,474 --> 00:19:05,510
protons and electrons
so close together

332
00:19:05,611 --> 00:19:07,311
they merge to form neutrons.

333
00:19:09,181 --> 00:19:12,850
The star's core becomes one
of the densest materials

334
00:19:12,951 --> 00:19:14,585
in the universe.

335
00:19:14,686 --> 00:19:17,688
It's like a gigantic
atomic nucleus...

336
00:19:17,789 --> 00:19:22,460
Roughly half a million Earths
compressed into the volume,

337
00:19:22,561 --> 00:19:24,262
the size of a city.

338
00:19:24,363 --> 00:19:27,198
That's really,
really dense stuff.

339
00:19:27,299 --> 00:19:29,367
If you had about a
teaspoon full of material,

340
00:19:29,468 --> 00:19:31,669
that would be about as
much mass as Mount Everest.

341
00:19:36,909 --> 00:19:39,644
Forcing protons
and electrons together

342
00:19:39,745 --> 00:19:42,914
releases a huge amount
of energy in the form

343
00:19:43,015 --> 00:19:47,985
of tiny, elusive, subatomic
particles called neutrinos.

344
00:19:49,755 --> 00:19:51,235
Neutrinos are one
of the most abundant

345
00:19:51,290 --> 00:19:52,423
particles in the universe.

346
00:19:52,524 --> 00:19:54,604
But they don't interact with
things very much at all.

347
00:19:56,795 --> 00:19:59,076
Neutrinos are
often called ghost particles

348
00:19:59,131 --> 00:20:00,665
because they do what ghosts do.

349
00:20:00,766 --> 00:20:02,466
They walk through walls.

350
00:20:02,568 --> 00:20:04,468
But neutrinos walk through us.

351
00:20:04,570 --> 00:20:05,647
They walk through the planet.

352
00:20:05,671 --> 00:20:07,471
They walk through stars.

353
00:20:07,573 --> 00:20:09,140
They're super ghosts.

354
00:20:11,443 --> 00:20:14,011
At first, these
neutrinos can fly straight

355
00:20:14,112 --> 00:20:15,846
out of the core of the star.

356
00:20:15,948 --> 00:20:19,450
But, as the star
collapses, it gets so dense

357
00:20:19,551 --> 00:20:21,752
that some neutrinos
get trapped and

358
00:20:21,853 --> 00:20:25,089
their energy turned into heat.

359
00:20:25,190 --> 00:20:28,392
And that creates a shockwave
that rips the star apart.

360
00:20:28,493 --> 00:20:31,796
And the ensuing explosion is
brighter than billions of stars

361
00:20:31,897 --> 00:20:32,897
all put together.

362
00:20:36,301 --> 00:20:40,471
This light show may
be spectacular, but it's only 1%

363
00:20:40,572 --> 00:20:43,040
of the energy released
in a supernova.

364
00:20:43,141 --> 00:20:47,378
The rest is in the form of a
massive burst of neutrinos.

365
00:20:47,479 --> 00:20:52,550
So neutrinos could act as a
supernova early warning system.

366
00:20:52,651 --> 00:20:54,218
At least that's the idea.

367
00:20:57,422 --> 00:21:02,293
On February 24th, 1987,
that idea was tested.

368
00:21:05,063 --> 00:21:08,032
An astronomer was doing a
routine survey of a dwarf

369
00:21:08,133 --> 00:21:09,734
galaxy close to ours.

370
00:21:12,004 --> 00:21:15,206
He was taking pictures of
it, develops the pictures,

371
00:21:15,307 --> 00:21:17,608
and says, hey,
there's a star here

372
00:21:17,709 --> 00:21:19,710
that wasn't there yesterday.

373
00:21:22,881 --> 00:21:25,516
He basically got up, walked
outside, and looked and went,

374
00:21:25,617 --> 00:21:27,485
oh, there's that star.

375
00:21:27,586 --> 00:21:30,655
And it turns out he had
discovered a supernova.

376
00:21:32,924 --> 00:21:34,502
Because it
was the first supernova

377
00:21:34,526 --> 00:21:41,065
spotted that year, it was
called Supernova 1987A.

378
00:21:41,166 --> 00:21:45,836
1987A a was an amazing event
in the world of astronomy.

379
00:21:45,937 --> 00:21:50,041
Essentially, a supernova
went off in our own backyard.

380
00:21:50,142 --> 00:21:52,209
It was very close to us,

381
00:21:52,311 --> 00:21:55,746
occurring in a neighbor
galaxy of the Milky Way.

382
00:21:55,847 --> 00:21:59,750
And so it was the brightest
thing seen in our skies

383
00:21:59,851 --> 00:22:01,852
since the invention
of the telescope.

384
00:22:04,923 --> 00:22:08,659
Supernova 1987A
blazed with the power

385
00:22:08,760 --> 00:22:10,461
of 100 million suns.

386
00:22:11,797 --> 00:22:14,365
But that wasn't the
most exciting part.

387
00:22:14,466 --> 00:22:17,668
For the first time, we
received an early warning

388
00:22:17,769 --> 00:22:20,938
that a supernova was about
to appear three hours

389
00:22:21,039 --> 00:22:22,940
before it lit up our night sky.

390
00:22:24,409 --> 00:22:27,578
Neutrino observatories
around the world

391
00:22:27,679 --> 00:22:31,515
saw a sudden surge in neutrinos
from the same direction

392
00:22:31,616 --> 00:22:32,616
on the sky.

393
00:22:38,223 --> 00:22:41,759
Neutrinos' ability
to zip across the galaxy,

394
00:22:41,860 --> 00:22:45,062
slipping through stars
and planets like ghosts,

395
00:22:45,163 --> 00:22:48,032
gives them an unbeatable head
start during a supernova.

396
00:22:50,268 --> 00:22:53,938
The neutrinos are released
in the very earliest moments

397
00:22:54,039 --> 00:22:55,473
of this supernova blast.

398
00:22:55,574 --> 00:22:58,709
And they slip through the
atmosphere of the star

399
00:22:58,810 --> 00:23:01,078
before it goes boom.

400
00:23:03,582 --> 00:23:06,717
Neutrinos can escape
in as little as 10 seconds.

401
00:23:08,787 --> 00:23:10,888
But it can take hours
for the shockwave

402
00:23:10,989 --> 00:23:15,192
to travel right through the star
and blast off the outer layers,

403
00:23:15,293 --> 00:23:17,261
revealing the light.

404
00:23:17,362 --> 00:23:19,530
The result is that
we see neutrinos

405
00:23:19,631 --> 00:23:22,633
from a supernova explosion
before we see the actual light.

406
00:23:28,540 --> 00:23:31,642
So if we want to spot the
next supernova explosion,

407
00:23:31,743 --> 00:23:34,645
we've got to be paying
attention to the neutrinos.

408
00:23:38,016 --> 00:23:40,684
Astronomers set
up the SuperNova Early

409
00:23:40,786 --> 00:23:46,190
Warning System, a network
of neutrino detectors

410
00:23:46,291 --> 00:23:47,291
all around the world.

411
00:23:49,361 --> 00:23:51,595
It should give astronomers
several hours notice

412
00:23:51,730 --> 00:23:53,164
of an impending supernova.

413
00:23:56,401 --> 00:23:58,869
But, so far, nothing.

414
00:23:58,970 --> 00:24:01,172
No supernovas have
occurred near enough

415
00:24:01,273 --> 00:24:02,306
for the system to detect.

416
00:24:04,576 --> 00:24:07,411
Neutrinos are like the
friend that never comes.

417
00:24:07,512 --> 00:24:09,079
We're sitting here
waiting for him.

418
00:24:09,181 --> 00:24:11,261
But we don't know when it's
going to actually happen.

419
00:24:14,319 --> 00:24:18,389
But when they do
come, we might be in trouble

420
00:24:18,490 --> 00:24:21,826
because some supernovas are
armed with the most powerful

421
00:24:21,927 --> 00:24:23,227
weapon in the universe...

422
00:24:25,130 --> 00:24:26,130
Gamma rays.

423
00:24:38,076 --> 00:24:41,178
Our hunt for the Milky
Way's next supernova

424
00:24:41,279 --> 00:24:43,514
has identified some
potential suspects...

425
00:24:45,217 --> 00:24:50,888
Very massive, lonely stars and
stars with smaller sidekicks.

426
00:24:53,391 --> 00:24:58,162
In 2018, astronomers
found a system called Apep

427
00:24:58,263 --> 00:25:04,635
8,000 light years away with two
very massive stars, each one

428
00:25:04,736 --> 00:25:06,237
about as massive as Betelgeuse.

429
00:25:08,573 --> 00:25:13,677
These are giant stars
nearing the end of their lives

430
00:25:13,778 --> 00:25:19,083
with massive outer layers of
gas that continually contract

431
00:25:19,184 --> 00:25:21,318
and heat up again and again.

432
00:25:23,054 --> 00:25:24,332
They become really

433
00:25:24,356 --> 00:25:26,957
huge and bloated and
swollen, and they're

434
00:25:27,058 --> 00:25:28,993
prone to huge outbursts.

435
00:25:31,863 --> 00:25:35,900
These unstable stars
are called Wolf-Rayet stars.

436
00:25:39,838 --> 00:25:44,608
They're very rare and so hot and
bright they emit more radiation

437
00:25:44,709 --> 00:25:47,611
than a million sunlike stars.

438
00:25:47,712 --> 00:25:51,348
This intense energy is
blasting their outer layers off

439
00:25:51,449 --> 00:25:52,449
into space.

440
00:25:53,685 --> 00:25:56,587
Mass loss has been
occurring from the star,

441
00:25:56,688 --> 00:26:00,658
so much so that you've
actually lost all the hydrogen

442
00:26:00,759 --> 00:26:03,127
that wasn't burned into helium.

443
00:26:03,228 --> 00:26:06,096
So now you have a star
that's made entirely

444
00:26:06,197 --> 00:26:08,432
of helium and heavier elements.

445
00:26:08,533 --> 00:26:11,168
With no hydrogen
left, these massive stars

446
00:26:11,269 --> 00:26:13,070
are running low on usable fuel.

447
00:26:15,640 --> 00:26:18,208
They're like ticking
time bombs, made

448
00:26:18,310 --> 00:26:22,012
even more dangerous because
they're spinning so fast.

449
00:26:24,049 --> 00:26:26,417
It's spinning so
quickly, it's on the verge

450
00:26:26,518 --> 00:26:28,419
of ripping itself apart.

451
00:26:28,520 --> 00:26:30,955
And this means that,
when this thing blows,

452
00:26:31,056 --> 00:26:32,323
it's going to blow hard.

453
00:26:34,125 --> 00:26:38,395
When a star goes
supernova, its core collapses.

454
00:26:38,496 --> 00:26:40,698
The smaller it gets,
the faster it spins.

455
00:26:42,400 --> 00:26:47,037
Some cores collapse into
fast, spinning neutron stars.

456
00:26:47,138 --> 00:26:51,208
Heavier ones, like Apep,
collapse into even denser

457
00:26:51,309 --> 00:26:52,910
and more mysterious objects...

458
00:26:54,245 --> 00:26:55,245
Black holes.

459
00:26:58,049 --> 00:27:01,385
The immense gravity within
Apep's collapsing core

460
00:27:01,486 --> 00:27:05,689
will drag back some of the gas
and dust into a spinning disk.

461
00:27:08,660 --> 00:27:11,495
As the material
falls on to the core,

462
00:27:11,596 --> 00:27:14,198
it compresses and it speeds up.

463
00:27:15,700 --> 00:27:17,534
The dying star spins faster

464
00:27:17,636 --> 00:27:19,603
and faster as it collapses.

465
00:27:21,473 --> 00:27:25,309
And this incredible
rotation drives the creation

466
00:27:25,410 --> 00:27:29,413
of massive magnetic fields
that are capable of funneling

467
00:27:29,514 --> 00:27:32,983
material around and
up and out in the form

468
00:27:33,084 --> 00:27:35,419
of huge beams of radiation.

469
00:27:38,423 --> 00:27:41,158
So the energy from
the supernova collapse,

470
00:27:41,259 --> 00:27:44,361
instead of being admitted
spherically in every direction,

471
00:27:44,462 --> 00:27:46,930
comes at us in a
tightly focused beam.

472
00:27:48,266 --> 00:27:50,734
Like a laser from
the Death Star,

473
00:27:50,835 --> 00:27:52,803
it is pointed in one direction.

474
00:27:56,174 --> 00:27:58,075
This is a gamma ray burst.

475
00:28:00,178 --> 00:28:02,546
It is the single scariest thing

476
00:28:02,647 --> 00:28:04,515
the universe has to offer.

477
00:28:04,616 --> 00:28:08,719
This is an explosion so
powerful that, in a few seconds

478
00:28:08,820 --> 00:28:11,789
or minutes, it can
release as much energy

479
00:28:11,890 --> 00:28:14,792
as the sun will over
its entire lifetime.

480
00:28:16,528 --> 00:28:20,364
You do not want to get
caught in a gamma ray burst.

481
00:28:20,465 --> 00:28:21,545
Let's just put it that way.

482
00:28:27,372 --> 00:28:29,039
The impact of a nearby gamma ray

483
00:28:29,140 --> 00:28:31,842
burst on our home
planet is almost

484
00:28:31,943 --> 00:28:33,210
too terrible to think about.

485
00:28:34,546 --> 00:28:37,181
It would be a very
bad day for Earth.

486
00:28:40,585 --> 00:28:43,287
Earth's atmosphere could
be partly blown away,

487
00:28:43,388 --> 00:28:44,888
and there could be
chemical reactions

488
00:28:44,989 --> 00:28:46,356
in the atmosphere
that would form

489
00:28:46,458 --> 00:28:48,325
all kinds of noxious products.

490
00:28:51,930 --> 00:28:53,370
A gamma ray burst from Apep

491
00:28:53,431 --> 00:28:56,300
might last only 10
seconds, but its impact

492
00:28:56,434 --> 00:28:57,434
would last for decades.

493
00:28:58,570 --> 00:29:03,040
The generation of nitrogen
oxide from a gamma ray burst

494
00:29:03,141 --> 00:29:04,541
would be disastrous.

495
00:29:04,642 --> 00:29:06,143
In the upper
atmosphere, it would

496
00:29:06,244 --> 00:29:07,878
eat away at our ozone layer.

497
00:29:07,979 --> 00:29:12,683
In the lower atmosphere, it
would come out as acid rain.

498
00:29:12,817 --> 00:29:15,953
And the acid rain would
destroy our crops.

499
00:29:18,323 --> 00:29:22,025
Nitrogen dioxide
also filters out sunlight,

500
00:29:22,127 --> 00:29:24,895
turning the skies dark and
cooling the Earth enough

501
00:29:24,996 --> 00:29:26,930
to trigger a new Ice Age.

502
00:29:30,502 --> 00:29:34,104
Any life on the land, in
the shallow parts of the sea,

503
00:29:34,205 --> 00:29:37,441
or that live near the sea
surface would be done.

504
00:29:37,542 --> 00:29:40,911
In fact, it would ultimately
result in extinction.

505
00:29:45,183 --> 00:29:49,219
Blasted by ultraviolet
radiation from our sun,

506
00:29:49,320 --> 00:29:53,690
freezing cold and
hungry, humanity's future

507
00:29:53,792 --> 00:29:54,792
would be bleak.

508
00:29:58,029 --> 00:30:02,132
So we really need to know,
when Apep goes supernova

509
00:30:02,233 --> 00:30:06,937
and produces its deadly
beam of gamma rays,

510
00:30:07,038 --> 00:30:08,238
are we in its line of fire?

511
00:30:10,542 --> 00:30:12,910
The good news is
that we are probably

512
00:30:13,011 --> 00:30:16,446
not right in the direct
firing line of Apep.

513
00:30:16,548 --> 00:30:19,817
The axis of
rotation of the Apep system

514
00:30:19,918 --> 00:30:22,820
is pointed 30
degrees away from us.

515
00:30:22,921 --> 00:30:26,390
So if it does blow, it's
likely that the jets

516
00:30:26,491 --> 00:30:28,025
are going to miss us.

517
00:30:28,126 --> 00:30:30,727
It makes me feel
better that this gamma

518
00:30:30,829 --> 00:30:32,429
ray burst isn't pointing at us.

519
00:30:32,530 --> 00:30:35,732
But, of course, there are
many other cosmic catastrophes

520
00:30:35,834 --> 00:30:38,168
potentially waiting to get us.

521
00:30:38,269 --> 00:30:42,506
Apep is on the edge
of an enormous explosion.

522
00:30:42,607 --> 00:30:45,209
Its huge gravity
and incredible spin

523
00:30:45,310 --> 00:30:48,178
should produce a
spectacular supernova.

524
00:30:51,015 --> 00:30:55,385
But what if some stars
are too big to blow?

525
00:31:11,202 --> 00:31:18,375
Galaxy NGC 6946... a local galaxy
just 20 million light years

526
00:31:18,476 --> 00:31:23,046
away and well known to
supernova detectives.

527
00:31:23,147 --> 00:31:26,216
It's the fireworks galaxy
because it has produced so many

528
00:31:26,317 --> 00:31:28,485
supernovas in the past century.

529
00:31:28,553 --> 00:31:30,654
And they notice that
one star that they

530
00:31:30,755 --> 00:31:34,124
thought would become a
supernova instead blinked out.

531
00:31:36,294 --> 00:31:37,995
The star under investigation

532
00:31:38,096 --> 00:31:45,035
is N6946-BH1, a
cosmic heavyweight 25

533
00:31:45,136 --> 00:31:46,870
times the mass of our sun.

534
00:31:49,040 --> 00:31:51,742
That's way more than the
eight solar masses we

535
00:31:51,843 --> 00:31:53,777
thought guaranteed a supernova.

536
00:31:55,113 --> 00:31:57,347
This is a very
massive, very luminous

537
00:31:57,448 --> 00:32:00,851
star, the prototype
of what you expect

538
00:32:00,952 --> 00:32:03,921
to explode as a supernova.

539
00:32:04,022 --> 00:32:05,833
And over
the last couple of years,

540
00:32:05,857 --> 00:32:07,524
its brightness
has been changing.

541
00:32:07,625 --> 00:32:10,327
Maybe the star was beginning
to go a bit unstable.

542
00:32:10,428 --> 00:32:12,329
But then, right in
front of our eyes,

543
00:32:12,430 --> 00:32:15,365
this star just
completely disappeared.

544
00:32:20,204 --> 00:32:22,005
This is a huge mystery.

545
00:32:22,106 --> 00:32:23,307
Why didn't this thing blow up?

546
00:32:24,943 --> 00:32:27,311
How could a star just disappear?

547
00:32:28,613 --> 00:32:30,147
There had to be
something left behind.

548
00:32:32,884 --> 00:32:35,953
So astronomers began
a search for evidence

549
00:32:36,054 --> 00:32:37,354
and found a crucial clue.

550
00:32:39,791 --> 00:32:41,458
When you look in
the infrared, you

551
00:32:41,559 --> 00:32:42,893
can still see some light there.

552
00:32:42,994 --> 00:32:44,962
So there was something
happening there.

553
00:32:45,063 --> 00:32:46,063
But what?

554
00:32:47,699 --> 00:32:50,867
We think the infrared
light is heat coming off

555
00:32:50,969 --> 00:32:52,569
the debris of the dead star.

556
00:32:56,007 --> 00:32:59,042
Something is pulling
it inwards, something

557
00:32:59,143 --> 00:33:02,646
powerful but also invisible...

558
00:33:02,747 --> 00:33:03,747
A black hole.

559
00:33:05,750 --> 00:33:07,517
The outer stuff
from the star is still

560
00:33:07,618 --> 00:33:09,753
falling on to that
black hole, and it's

561
00:33:09,854 --> 00:33:11,288
powering a little bit of light.

562
00:33:11,389 --> 00:33:13,457
A little bit of the infrared
light still gets out.

563
00:33:18,029 --> 00:33:19,563
How can a giant star become

564
00:33:19,664 --> 00:33:23,600
a black hole without exploding
into a supernova first?

565
00:33:26,537 --> 00:33:30,273
The answer lies in how
dying stars burn their fuel.

566
00:33:32,310 --> 00:33:35,479
For stars that are about, say,
20 times the mass of the sun,

567
00:33:35,613 --> 00:33:37,681
you're actually going to
burn things convectively.

568
00:33:37,782 --> 00:33:41,318
That means the gases inside
the core are moving around.

569
00:33:41,419 --> 00:33:45,355
A good analogy is water
in a boiling pot of water.

570
00:33:45,456 --> 00:33:47,157
You've got your
potatoes up here.

571
00:33:47,258 --> 00:33:48,525
You're trying to boil them.

572
00:33:48,626 --> 00:33:51,795
You've got convective cells
of water that are heated.

573
00:33:51,896 --> 00:33:53,930
Bring the heat up to the top.

574
00:33:54,032 --> 00:33:55,432
Get the potatoes hot.

575
00:33:55,533 --> 00:33:59,403
And then those blobs of water
cool down, become denser,

576
00:33:59,504 --> 00:34:01,071
and settle down to
the bottom again

577
00:34:01,172 --> 00:34:02,539
where they're heated once more.

578
00:34:04,876 --> 00:34:06,777
As fusion turns hydrogen

579
00:34:06,878 --> 00:34:11,014
to helium and then to
carbon, convection mixes

580
00:34:11,115 --> 00:34:12,616
the carbon so it burns up.

581
00:34:15,620 --> 00:34:18,388
Convection cells work inside

582
00:34:18,489 --> 00:34:21,958
of a star like
massive elevators that

583
00:34:22,060 --> 00:34:24,961
take hot gas from
the central regions,

584
00:34:25,063 --> 00:34:28,365
bring it up to the surface,
allow it to cool, and then

585
00:34:28,466 --> 00:34:30,734
pull that material back down.

586
00:34:30,835 --> 00:34:35,338
They're constantly churning
back and forth inside of a star.

587
00:34:37,675 --> 00:34:40,510
But stars more
massive than roughly 20 times

588
00:34:40,611 --> 00:34:45,482
the mass of the
sun, like N6946-BH1,

589
00:34:45,583 --> 00:34:47,084
don't burn carbon this way.

590
00:34:49,520 --> 00:34:51,621
Instead of mixing,
the heavier atoms

591
00:34:51,722 --> 00:34:54,991
created by the fusion reactions
just start to pile up.

592
00:34:57,562 --> 00:34:58,882
That means there's
a layer of very

593
00:34:58,963 --> 00:35:02,065
dense material building up on
just the surface of the core.

594
00:35:02,166 --> 00:35:04,034
All of the stuff is
just ready to collapse.

595
00:35:06,504 --> 00:35:08,772
It's possible that, if
you have enough mass sitting

596
00:35:08,873 --> 00:35:11,007
around, the collapse
is so powerful

597
00:35:11,109 --> 00:35:13,143
that it actually collapses
into a black hole

598
00:35:13,244 --> 00:35:15,912
before any supernova goes off.

599
00:35:16,013 --> 00:35:18,615
That, then, is a
failed supernova.

600
00:35:18,716 --> 00:35:20,717
It's a star that
pretty much directly

601
00:35:20,818 --> 00:35:22,385
collapses to form a black hole.

602
00:35:26,591 --> 00:35:30,827
If many of the massive
stars we expect to go supernova

603
00:35:30,928 --> 00:35:33,029
won't, that's a problem.

604
00:35:36,601 --> 00:35:39,402
We used to think we had the
basics of supernovas cracked.

605
00:35:39,504 --> 00:35:41,624
Any time you have a star
more massive than eight times

606
00:35:41,706 --> 00:35:43,373
the mass of the
sun, it was destined

607
00:35:43,474 --> 00:35:45,175
to explode as a supernova.

608
00:35:45,276 --> 00:35:47,911
And then along comes a star
that screws everything up.

609
00:35:50,515 --> 00:35:52,616
To make things
worse, we found no clear

610
00:35:52,717 --> 00:35:55,051
distinction between
stars that go out with

611
00:35:55,153 --> 00:35:56,887
a bang and those that don't.

612
00:35:59,824 --> 00:36:05,462
As many as 30% of massive stars
could die without exploding.

613
00:36:05,563 --> 00:36:08,131
Our search for the
next killer supernova

614
00:36:08,232 --> 00:36:09,232
is getting even harder.

615
00:36:10,568 --> 00:36:12,869
Stars blow up
when we don't expect them to.

616
00:36:12,970 --> 00:36:15,605
They don't blow up
when we expect them to.

617
00:36:15,706 --> 00:36:17,741
They can have several
stars orbiting each other,

618
00:36:17,842 --> 00:36:19,686
and the one that blows up
isn't necessarily the one

619
00:36:19,710 --> 00:36:20,710
you think it will.

620
00:36:23,714 --> 00:36:27,050
So right now we
can't identify a prime suspect,

621
00:36:27,151 --> 00:36:28,285
but the hunt continues.

622
00:36:30,755 --> 00:36:31,999
As far as we know, there

623
00:36:32,023 --> 00:36:34,257
are no life-threatening
stars out there,

624
00:36:34,358 --> 00:36:37,928
but we haven't done
a complete survey.

625
00:36:38,029 --> 00:36:41,398
So please keep funding astronomy
so we can keep looking.

626
00:36:43,668 --> 00:36:44,935
Supernovas destroy.

627
00:36:47,138 --> 00:36:49,105
But can they also create?

628
00:36:52,476 --> 00:36:56,580
Did a supernova spark
humanity's rise to dominate

629
00:36:56,681 --> 00:36:59,416
our world and our solar system?

630
00:37:11,462 --> 00:37:19,202
Supernovas are spectacular,
devastating, and frightening.

631
00:37:21,806 --> 00:37:24,608
But without them,
we wouldn't exist.

632
00:37:26,277 --> 00:37:28,712
The iron in your blood and
the calcium in your bones

633
00:37:28,813 --> 00:37:32,983
was literally forged inside of
a star that exploded billions

634
00:37:33,084 --> 00:37:35,018
of years ago as a supernova.

635
00:37:35,119 --> 00:37:38,054
And I think this is one of the
most beautiful and the most

636
00:37:38,155 --> 00:37:40,991
profound things that we've
learned in astronomy,

637
00:37:41,092 --> 00:37:44,894
that we're literally viscerally
connected to the cosmos

638
00:37:44,996 --> 00:37:46,730
and the cosmos is
connected to us.

639
00:37:49,767 --> 00:37:52,369
With every breath,
we are inhaling

640
00:37:52,470 --> 00:37:55,205
oxygen that was created
in a supernova explosion.

641
00:37:59,210 --> 00:38:02,979
This is almost literally
a cosmic cycle of life.

642
00:38:09,620 --> 00:38:11,187
And the supernova may even

643
00:38:11,289 --> 00:38:14,758
be responsible for the
dawning of our intelligence

644
00:38:14,859 --> 00:38:17,894
by causing lightning.

645
00:38:17,995 --> 00:38:19,275
It might sound
rather incredible,

646
00:38:19,363 --> 00:38:21,575
but a supernova might actually
influence, directly, weather

647
00:38:21,599 --> 00:38:22,732
right here on the Earth.

648
00:38:22,833 --> 00:38:26,503
The cosmic rays from a
supernova will create charges

649
00:38:26,604 --> 00:38:28,371
in the lower atmosphere.

650
00:38:28,472 --> 00:38:30,840
That energy will
break apart molecules,

651
00:38:30,941 --> 00:38:34,678
excite atoms and molecules,
and it will ionize them.

652
00:38:34,779 --> 00:38:38,748
And an ionized
atmosphere means that now

653
00:38:38,849 --> 00:38:40,550
it can conduct electricity.

654
00:38:40,651 --> 00:38:43,453
So it probably increased
lightning across the planet.

655
00:38:46,991 --> 00:38:49,893
It's possible the
same gamma ray burst that caused

656
00:38:49,994 --> 00:38:54,264
a mass extinction
2.6 million years ago

657
00:38:54,365 --> 00:38:58,168
also affected
Earth's atmosphere,

658
00:38:58,269 --> 00:39:01,571
triggering tremendous
bursts of lightning,

659
00:39:01,672 --> 00:39:04,841
which caused forest fires.

660
00:39:06,477 --> 00:39:09,212
We have
evidence of widespread fires

661
00:39:09,313 --> 00:39:10,313
at this time.

662
00:39:10,414 --> 00:39:12,882
So it could be that
lightning was increased,

663
00:39:12,983 --> 00:39:14,918
and that created more fires.

664
00:39:15,019 --> 00:39:18,054
And those fires could have
leveled forests and savannas,

665
00:39:18,155 --> 00:39:19,422
creating grasslands.

666
00:39:21,092 --> 00:39:25,195
So how could this
change/boost our intelligence?

667
00:39:25,296 --> 00:39:29,599
With their forest homes burnt,
our ancestors, early hominids,

668
00:39:29,700 --> 00:39:33,937
had to adapt to life out in the
open, which meant standing up.

669
00:39:35,072 --> 00:39:36,183
You're living in a savanna

670
00:39:36,207 --> 00:39:39,075
where there's lions and
leopards and cheetahs,

671
00:39:39,176 --> 00:39:41,244
and the savanna is
mostly grassland.

672
00:39:41,345 --> 00:39:44,214
It's a lot more efficient,
perhaps, on two feet.

673
00:39:44,315 --> 00:39:45,148
You can run.

674
00:39:45,249 --> 00:39:46,493
And moving on two
feet might have

675
00:39:46,517 --> 00:39:48,651
been the survival mechanism.

676
00:39:50,154 --> 00:39:52,956
Standing upright also
triggered the most important

677
00:39:53,057 --> 00:39:54,124
change in our history.

678
00:39:56,093 --> 00:39:57,533
Walking around on two feet

679
00:39:57,628 --> 00:40:00,864
freed our hands to be able
to start doing things.

680
00:40:00,965 --> 00:40:03,165
And as you... you know, of
course, you can imagine that,

681
00:40:03,200 --> 00:40:05,468
as you start doing things,
that drives your brain to more

682
00:40:05,569 --> 00:40:06,980
complexity as you're
trying to figure

683
00:40:07,004 --> 00:40:08,171
out how to manipulate things.

684
00:40:08,272 --> 00:40:09,939
And this is perhaps the biggest

685
00:40:10,040 --> 00:40:12,842
evolutionary leap,
because, without it, we

686
00:40:12,943 --> 00:40:13,943
don't get tool use.

687
00:40:14,044 --> 00:40:15,178
We don't get fire.

688
00:40:15,279 --> 00:40:16,780
We don't get intelligence.

689
00:40:18,749 --> 00:40:20,850
As our ancient ancestors adapted

690
00:40:20,951 --> 00:40:24,053
to their new habitat, they
took their first steps

691
00:40:24,155 --> 00:40:25,488
toward world domination.

692
00:40:27,258 --> 00:40:28,858
At least, that's the theory.

693
00:40:30,528 --> 00:40:33,830
The idea presented here
is this would be the dawn

694
00:40:33,931 --> 00:40:36,032
of modern humans as we see it.

695
00:40:36,133 --> 00:40:38,435
And we would owe
that to lightning

696
00:40:38,536 --> 00:40:40,937
created from a gamma ray burst.

697
00:40:41,038 --> 00:40:42,038
That's nuts.

698
00:40:45,509 --> 00:40:48,711
Supernovas are extraordinary.

699
00:40:48,813 --> 00:40:50,547
They launched our
journey into the cosmos.

700
00:40:51,916 --> 00:40:54,651
And in time, a
supernova may end it.

701
00:40:57,621 --> 00:41:01,658
We're searching hard to
spot which one it could be.

702
00:41:01,759 --> 00:41:04,894
But, for now, the only
way we'll know for sure

703
00:41:04,995 --> 00:41:06,596
is when it lights up our sky.

704
00:41:09,433 --> 00:41:13,570
While a supernova might appear
to be the death of a star,

705
00:41:13,671 --> 00:41:16,239
the beauty of it is
that it's really a story

706
00:41:16,340 --> 00:41:17,407
about beginnings, as well.

707
00:41:23,347 --> 00:41:26,082
Supernovae giveth,
and they taketh away.

708
00:41:26,183 --> 00:41:28,518
Without supernovae, the
Earth wouldn't exist

709
00:41:28,619 --> 00:41:29,719
and we wouldn't exist.

710
00:41:32,323 --> 00:41:35,158
I actually do imagine standing
out on a nice winter night,

711
00:41:35,259 --> 00:41:36,926
looking up at
Betelgeuse, and actually

712
00:41:37,027 --> 00:41:38,761
seeing the thing explode.

713
00:41:38,863 --> 00:41:40,864
There would be
this bright light.

714
00:41:40,965 --> 00:41:42,765
I can imagine my
face lighting up.

715
00:41:42,867 --> 00:41:44,133
I would really lose it.

716
00:41:47,438 --> 00:41:48,782
I would love to see
a supernova up close,

717
00:41:48,806 --> 00:41:49,506
Right?

718
00:41:49,607 --> 00:41:50,740
I mean, what a light show.

719
00:41:50,841 --> 00:41:52,809
But there's no way I would
want to be that close

720
00:41:52,910 --> 00:41:54,811
because I don't want to die.

721
00:41:54,835 --> 00:41:56,835

722
00:41:57,305 --> 00:42:57,864
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