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White dwarfs,

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small stars that pack
a big punch.

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When white dwarfs
were first discovered,

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astronomers' reaction
was no, no, no, no,

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no, no, no, that can't be real.

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What's going on
inside these things

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can only be described
as seriously weird.

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They're the cooling
corpses of stars

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like our sun,

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but new research proves
white dwarfs are

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one of the driving forces of
our universe.

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They eat planets, they
flare out in high-energy light.

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They can<i> really</i> explode.

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And they can tell us literally

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about the nature of
the universe itself.

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And there's a dirty secret at

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the heart of
white dwarf science.

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We see dead stars exploding,

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and we still don't understand
why they're doing it.

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Have scientists finally
discovered how these small

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stars could be such massive
galactic players?

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December 2018.

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Astronomers spot
strange flares coming from

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a galaxy 250 million
light-years from Earth,

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GSN 069.

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We know that GSN 069 has
a supermassive black hole in

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its center, equal to about

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half a million
times the mass of the sun.

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That's a big black hole,

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and it blasts out X-rays in

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a very, very steady pace,

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every nine hours. Why?

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The flares are
so energetic and regular,

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the supermassive black hole
must be eating the mass of

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the planet Mercury
three times a day.

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The big question is what's
feeding this black hole

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such a huge dinner?

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In March 2020,
scientists found the answer.

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An unlucky star at the end of
its life

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had wandered into the death
zone of the black hole.

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A star getting
too close to a supermassive

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black hole is like
a glazed doughnut

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getting too close to me.

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That thing just is not
gonna make it.

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Stars to get too close
to a black hole

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get torn apart.

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They sort of get attacked
by the black hole,

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and some of that material
is also getting launched

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off in very powerful winds
and jets and streams

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getting out.

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Somehow, the star
survives its close

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encounter with
the supermassive black hole.

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Further investigation reveals
it's a small, compact star,

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a white dwarf.

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So what makes this tiny star
almost indestructible?

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The answer lies in how
it's formed.

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We get a clue if we look at
the life cycle of a star.

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It's burning hydrogen into
helium, that's causing nuclear

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fusion, and that causes a star
to stay stable.

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There's this delicate balance
between radiation pressure

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from that nuclear fusion pushing
out and gravitational pressure

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pulling in.

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But when stars like our sun
near the end of their life,

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they run out of hydrogen fuel.

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The sun-like star makes
more and more helium,

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which builds up in its center.

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Gradually, the immense weight of

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the star's outer layers crushes
the helium core.

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As the core ages,
it gets smaller and hotter,

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which increases the rate of
nuclear reactions.

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These nuclear fusion
reactions produce more energy,

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which pushes the outer layer,
or envelope, outwards.

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Because there's more energy
flowing through the envelope,

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the envelope swells up.

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The star expands to around
100 times its original size.

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The yellow star
becomes a red giant.

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Eventually, red giants shed
their outer layers,

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forming stunning gas shells
called planetary nebulas.

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Planetary nebulae are the most
beautiful objects in space.

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They're all spectacular.

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A star that ends its life in
one of these planetary nebulas

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leaves behind a white dwarf
at the center,

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and this white dwarf is
essentially a cinder,

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a stellar cinder.

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It's what's left after
nuclear fusion

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is no longer possible for that
particular star.

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All that remains,
a glowing white dwarf,

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the leftover core
of the dead star.

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But in galaxy GSN 069,

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the supermassive black hole
turbocharged the process.

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It stripped off the outer
layers of the red giant

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in a matter of days.

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The black hole has almost eaten

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all the juicy parts,
all the easy-to-get-at parts

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of star, leaving behind
the sort of

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bone or the leftovers
of the white dwarf.

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This white dwarf is just 1/5

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of the mass of the sun.

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How can such a small
star survive

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being so close to a black hole?

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You might think that
because a white dwarf is small,

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it's not gonna last very long,

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because there's not that much
stuff there to eat,

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but it turns out
it's quite the opposite.

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The pocket-sized white
dwarf is packed full of matter.

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If it were a normal star,
it would have been shredded

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long ago,
but because it's such a dense,

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tight ball of matter,
it survives.

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Imagine taking the sun
and crushing it down

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to just about the size
of the Earth.

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Same mass, but now packed way

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more tightly,
so a basketball-worth of this

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stuff would weigh as much
as 35 blue whales.

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The white dwarf's extreme
density protects it from

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the gravitational onslaught of
the supermassive black hole.

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Its orbit takes it near that
black hole every nine hours,

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and every time it encounters
the black hole, some of its

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material gets sipped off.

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They're playing a game
of interstellar

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tug of war with one another.

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The black hole is bigger,
so it's going to win.

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But the white dwarf is very
dense, so it's very tough,

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and it's able to hang in there
for quite a long time.

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It's gonna stay in orbit around

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a supermassive black hole for
billions of years.

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Talk about David and Goliath.

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When astronomers first
discovered white dwarfs,

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they thought
they shouldn't exist.

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How could something have
such an extreme density

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and not collapse under
its own weight?

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Quantum mechanics,
the science of atomic

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and subatomic particles
has the answer.

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We're used to the rules
of physics up here

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in the macroscopic world,

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but when you zoom down into
the subatomic world,

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things get weird.

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Here we have the electron,
one of the tiniest

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particles in the universe,

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and it's these little
electrons that are doing

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the work of supporting
an entire star.

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Electrons really don't like
being squashed

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into a small space.

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If you try to squash too many
of them into too small a space,

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they'll push back really hard,

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and this is an effect
called degeneracy pressure.

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These degenerate
electrons stop white dwarfs

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from collapsing,

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but they give these stars
strange qualities.

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White dwarfs behave

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very differently
than normal matter.

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Take planets and stars.

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They become bigger
when they gain mass.

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White dwarfs
are the exact opposite.

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As they gain mass,
they get smaller.

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The more massive a white dwarf,

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the tighter the electrons
squeeze together,

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and the smaller and denser
the star gets.

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The high density means

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the white dwarf's structure
is also strange.

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It has an extremely
thin atmosphere,

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made of hydrogen
or, occasionally, helium gas.

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If you were to take an Earth
skyscraper and put it on

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a white dwarf star,

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if you climb to the top of
that skyscraper,

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you'd be outside of the white
dwarf's atmosphere.

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You'd actually be in space.

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Beneath the thin
atmosphere lies a surface

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of dense helium
around 30 miles thick.

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It surrounds an interior made

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of superheated liquid carbon
and oxygen.

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A white dwarf at its surface

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can be a half a million degrees.

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It's even hotter in
the interior,

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and so that kind of material,

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it's not gonna behave
the way normal matter does.

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Eventually,
over billions of years,

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the center of the white dwarf
cools down into a solid.

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As the carbon
and oxygen atoms cool down,

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they form a crystal.

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Diamonds are actually crystals
of carbon,

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so at the center of
these cool white dwarfs

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could be a diamond the size
of the Earth.

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White dwarfs gradually
give off their remaining energy

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until there's just a cold,
dead ball of matter,

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a black dwarf.

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We've never seen what
we call a black dwarf,

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and there's a simple reason
for that.

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It takes a tremendous amount
of time,

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many tens of billions of years,
longer than the age of

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the universe,
to reach that point.

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This is the dark destiny
of most midsized stars,

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including our sun.

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This long, slow death may make
white dwarfs seem ordinary,

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but these tiny stars
could answer

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some big questions
about our universe.

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They might be small,
and they might be dim,

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but they are essential for
our understanding of physics.

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New research into
white dwarfs may answer

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one of the biggest questions
of all...

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Can life survive the death
of its star?

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In the past,
we've underestimated

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white dwarfs,

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but now they're causing
a buzz among astronomers.

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One of the big questions
over the last

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decade is could a planet
survive around a white dwarf?

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The logical answer would be no.

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On their way to becoming
white dwarfs,

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stars evolve through
a red giant phase.

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They expand to become very huge.

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So we figured any planets around

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these stars might just
get eaten.

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In December of 2019,
evidence from the constellation

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of Cancer turned that idea
on its head.

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Astronomers spotted
a strange-looking white dwarf

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about 1,500 light-years
from Earth.

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Subtle variations in light
from the star

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revealed a mystery...

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The elements oxygen and sulfur
in amounts never

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before seen on the surface of
a white dwarf.

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We know what the chemical
signature of a white dwarf is,

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and this stuck out
like a sore thumb.

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Normally, hydrogen and helium

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make up the outer layers
of a white dwarf.

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Oxygen and sulfur

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are heavier than hydrogen
and helium,

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and they should have sunk
down, but we still see them

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there, so they must have
gotten there recently.

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Using ESO's Very Large
Telescope in Chile,

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astronomers took a closer look.

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They discovered a small,
Earth-sized white dwarf

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surrounded by a huge gas disc
roughly 10 times

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the width of the sun.

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The disc contained hydrogen,
oxygen, and sulfur.

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A system like this had
never been seen before,

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and so the next step was to
look at a profile of these

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elements and figure out where

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we'd seen something similar.

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And the amazing thing is,
we have.

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We've seen these elements in
the deeper layers of the ice

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giants of our solar system,

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Uranus and Neptune.

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Hidden in the gas ring
is a giant,

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Neptune-like icy planet.

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It's twice as large as the star,

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but the fierce 50,000-degree
heat from the white dwarf is

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slowly evaporating
this orbiting planet.

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The white dwarf

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is bombarding the planet with
high-energy radiation, X-rays,

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00:12:32,170 --> 00:12:33,230
UV rays.

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It's pulverizing the ice
molecules in its atmosphere

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and blowing them out into space,

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and the ice molecules are
streaming behind

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the planet like
the tail of a comet.

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The icy planet loses mass at

255
00:12:45,350 --> 00:12:49,050
a rate of over 500,000 tons
per second.

256
00:12:49,150 --> 00:12:52,690
That's the equivalent of
300 aircraft carriers

257
00:12:52,790 --> 00:12:55,260
- every minute.
- It sounds like

258
00:12:55,360 --> 00:12:56,836
that could be curtains
for the planet.

259
00:12:56,860 --> 00:12:59,190
But remember,
the planet is large,

260
00:12:59,290 --> 00:13:02,260
- and the star is cooling down.
- As it cools,

261
00:13:02,360 --> 00:13:05,000
it will stop blasting
the planet so intently,

262
00:13:05,100 --> 00:13:07,030
and that stream of
gas will cease.

263
00:13:07,140 --> 00:13:08,700
The planet will probably
end up losing

264
00:13:08,800 --> 00:13:11,740
only a few percent of
its total mass.

265
00:13:11,840 --> 00:13:13,510
So the planet should survive

266
00:13:13,610 --> 00:13:16,840
and continue orbiting
the white dwarf.

267
00:13:16,950 --> 00:13:18,910
But a mystery remains.

268
00:13:19,010 --> 00:13:22,080
Why didn't the closely
orbiting planet die

269
00:13:22,180 --> 00:13:25,690
when the star swelled
to a red giant?

270
00:13:25,790 --> 00:13:30,790
It had to have started
farther out and moved inwards.

271
00:13:30,890 --> 00:13:34,160
Our best guess is that other
ice giants were probably

272
00:13:34,260 --> 00:13:36,330
lurking somewhere
in the outer regions

273
00:13:36,430 --> 00:13:39,070
of the system and knocked
that planet inwards,

274
00:13:39,170 --> 00:13:42,140
towards the white dwarf,
sometime after the red giant

275
00:13:42,240 --> 00:13:45,410
phase in some kind of
cosmic pool game,

276
00:13:45,510 --> 00:13:46,610
if you will.

277
00:13:47,710 --> 00:13:50,440
This isn't the only white
dwarf with evidence of planets.

278
00:13:50,550 --> 00:13:54,050
About 570 light-years
from Earth,

279
00:13:54,150 --> 00:13:59,690
there's a white dwarf star
called WD 1145 017.

280
00:14:01,820 --> 00:14:04,230
After studying the star
for five years,

281
00:14:04,330 --> 00:14:08,060
researchers report that
the white dwarf is ripping apart

282
00:14:08,160 --> 00:14:11,330
and eating a mini rocky planet.

283
00:14:11,430 --> 00:14:13,230
So as the planet
is being torn up,

284
00:14:13,340 --> 00:14:16,240
we see this huge cloud of
dust blocking out 50% of

285
00:14:16,340 --> 00:14:18,640
the light of the star
and huge chunks of rock

286
00:14:18,740 --> 00:14:20,640
passing in front of the star.

287
00:14:20,740 --> 00:14:24,280
It's exciting to see
this planet being torn apart,

288
00:14:24,380 --> 00:14:27,550
because it's not often
that we get to see an event,

289
00:14:27,650 --> 00:14:29,750
we get to see something
in the process

290
00:14:29,850 --> 00:14:32,020
that we can observe
and we can learn from.

291
00:14:34,790 --> 00:14:36,360
There's more and more evidence

292
00:14:36,460 --> 00:14:38,430
that planetary systems
can survive

293
00:14:38,530 --> 00:14:42,900
the death of their star and
the formation of a white dwarf.

294
00:14:43,000 --> 00:14:45,900
It just depends on
the planet's composition

295
00:14:46,000 --> 00:14:47,370
and location.

296
00:14:47,470 --> 00:14:51,610
The distance from the planet to
the star is a critical factor,

297
00:14:51,710 --> 00:14:55,480
because as you move farther
and farther out from a star,

298
00:14:55,580 --> 00:14:59,610
the intensity of that solar
radiation decreases.

299
00:14:59,710 --> 00:15:02,680
So the farther you go out,
the less heat you have,

300
00:15:02,780 --> 00:15:05,550
the less high-energy particles
are reaching the surface of

301
00:15:05,650 --> 00:15:07,390
that planet.

302
00:15:07,490 --> 00:15:11,090
Also, rocky planets can
survive better than gas giants,

303
00:15:11,190 --> 00:15:13,350
because rocky planets can hold
onto their stuff better,

304
00:15:13,430 --> 00:15:15,660
whereas gas can be blown
away much more easily.

305
00:15:17,830 --> 00:15:19,100
These new discoveries raise

306
00:15:19,200 --> 00:15:21,940
questions about habitability
around stars.

307
00:15:23,410 --> 00:15:26,840
Could white dwarf systems
support life?

308
00:15:26,910 --> 00:15:28,980
If we limit
ourselves to only looking

309
00:15:29,080 --> 00:15:31,910
for life on planets
orbiting stars like our sun,

310
00:15:32,010 --> 00:15:35,220
we would be doing ourselves
a huge disservice.

311
00:15:35,280 --> 00:15:39,090
Far more important is to look
for, around whatever star,

312
00:15:39,190 --> 00:15:40,890
the habitable zone,

313
00:15:40,990 --> 00:15:43,890
the Goldilocks zone,
the region around a star where

314
00:15:43,990 --> 00:15:46,530
a planet could support life.

315
00:15:48,300 --> 00:15:50,160
When it comes to
supporting life,

316
00:15:50,270 --> 00:15:53,930
white dwarfs have some
surprising advantages.

317
00:15:54,040 --> 00:15:55,940
Even though
there's no fusion happening,

318
00:15:56,040 --> 00:15:58,440
they have all of this internal
energy stored up that they

319
00:15:58,540 --> 00:16:01,480
release that warms
the nearby planets.

320
00:16:01,580 --> 00:16:04,780
Life might even prefer
hanging out around

321
00:16:04,880 --> 00:16:06,280
a white dwarf, because

322
00:16:06,380 --> 00:16:08,550
it doesn't change much over
the course

323
00:16:08,650 --> 00:16:10,180
of billions of years.

324
00:16:10,290 --> 00:16:13,720
With something like our sun,
there are flares and coronal

325
00:16:13,820 --> 00:16:16,260
mass ejections, and then
eventually, it's gonna die,

326
00:16:16,360 --> 00:16:17,960
and we have to deal with that.

327
00:16:18,060 --> 00:16:19,860
That's not a problem with
a white dwarf.

328
00:16:21,130 --> 00:16:23,760
So if life can gain a foothold,

329
00:16:23,870 --> 00:16:25,900
it has a nice, stable home.

330
00:16:27,970 --> 00:16:30,900
We now think 25 to 50% of

331
00:16:31,010 --> 00:16:33,570
white dwarfs
have planetary systems.

332
00:16:33,680 --> 00:16:36,110
Perhaps one day,
we'll find one with

333
00:16:36,210 --> 00:16:40,350
an Earth-like planet,
and maybe even life.

334
00:16:42,080 --> 00:16:45,020
But not all of these tough
little stars are good hosts.

335
00:16:46,490 --> 00:16:49,690
White dwarfs
have a volatile nature.

336
00:16:49,790 --> 00:16:53,190
They can explode in some of the
biggest bangs in the cosmos.

337
00:17:08,280 --> 00:17:12,080
White dwarfs are the dead
remains of stars like the sun.

338
00:17:13,550 --> 00:17:16,080
Most of these zombie
stars slowly

339
00:17:16,180 --> 00:17:18,250
cooled down
over billions of years.

340
00:17:20,420 --> 00:17:22,120
Most, but not all.

341
00:17:25,760 --> 00:17:28,560
Some go out in a spectacular
explosion known

342
00:17:28,660 --> 00:17:30,330
as a type 1a supernova.

343
00:17:31,930 --> 00:17:33,370
A type 1a supernova

344
00:17:33,470 --> 00:17:35,770
is one of the most
violent, powerful,

345
00:17:35,870 --> 00:17:38,110
energetic events
in the universe.

346
00:17:38,210 --> 00:17:41,140
We are talking about
a star exploding.

347
00:17:41,240 --> 00:17:43,610
They can outshine
entire galaxies.

348
00:17:43,710 --> 00:17:45,680
They can create devastation over

349
00:17:45,780 --> 00:17:47,480
hundreds and hundreds of
light-years.

350
00:17:47,580 --> 00:17:49,020
They're a big deal.

351
00:17:51,690 --> 00:17:54,420
We'd seen the aftermath
of these cosmic fireworks,

352
00:17:54,520 --> 00:17:57,560
but for over 60 years, we had
little direct evidence

353
00:17:57,660 --> 00:17:59,330
they came from white dwarfs.

354
00:18:01,630 --> 00:18:05,600
Then students from University
College London UK got lucky.

355
00:18:05,700 --> 00:18:09,600
While taking
routine photographs,

356
00:18:09,700 --> 00:18:11,910
they spotted
a supernova explosion

357
00:18:12,010 --> 00:18:14,810
in our own cosmic neighborhood.

358
00:18:14,910 --> 00:18:17,910
M82, the cigar galaxy,
is actually really

359
00:18:18,010 --> 00:18:19,980
close to us on cosmic terms.

360
00:18:20,080 --> 00:18:22,550
It's only about 12 million
light-years away.

361
00:18:22,650 --> 00:18:25,350
This makes it one of
the closest galaxies in the sky.

362
00:18:26,520 --> 00:18:29,290
The blast called
Supernova 2014J was

363
00:18:29,390 --> 00:18:33,260
the closest type 1a supernova
for over 20 years.

364
00:18:34,430 --> 00:18:36,260
Its proximity allowed us
to look for

365
00:18:36,360 --> 00:18:40,030
the signature of
a white dwarf supernova,

366
00:18:40,140 --> 00:18:42,040
a blast of gamma rays.

367
00:18:42,140 --> 00:18:47,140
Gamma rays are a type of light
that's incredibly energetic.

368
00:18:47,240 --> 00:18:49,780
They're the most energetic
type of rays,

369
00:18:49,880 --> 00:18:53,510
or photons, on
the electromagnetic spectrum.

370
00:18:53,620 --> 00:18:55,120
White dwarfs should release

371
00:18:55,220 --> 00:18:57,580
gamma rays when they explode.

372
00:18:57,690 --> 00:19:01,260
But dust in interstellar space
soaks up the rays,

373
00:19:01,360 --> 00:19:06,260
so unless an explosion is close
by, they're hard to detect.

374
00:19:06,360 --> 00:19:09,460
For years, astronomers had
been looking for the gamma rays

375
00:19:09,560 --> 00:19:12,130
that should be emitted by
a type 1a supernova,

376
00:19:12,230 --> 00:19:13,600
but no one had found them.

377
00:19:15,970 --> 00:19:18,040
Now, scientists had their chance

378
00:19:18,140 --> 00:19:20,770
and the technology to see
the elusive rays.

379
00:19:22,640 --> 00:19:24,810
Using ISA's integral satellite,

380
00:19:24,910 --> 00:19:26,950
they sifted through
the shockwaves sent out by

381
00:19:27,050 --> 00:19:29,520
the explosion in M82.

382
00:19:29,620 --> 00:19:32,550
It was tough, but finally,
they got a reading,

383
00:19:32,650 --> 00:19:35,320
the telltale signal of
gamma rays.

384
00:19:35,420 --> 00:19:38,290
It's the best evidence yet
for white dwarfs

385
00:19:38,390 --> 00:19:41,430
exploding in type 1a supernovas.

386
00:19:41,530 --> 00:19:46,500
The reason Supernova 2014J
was so cool is that this

387
00:19:46,600 --> 00:19:49,600
observation gave scientists
evidence, it's white dwarfs that

388
00:19:49,700 --> 00:19:53,140
explode to create this specific
type of supernova.

389
00:19:53,240 --> 00:19:55,680
So which white dwarfs fade out

390
00:19:55,780 --> 00:19:57,840
and which ones
go out with a bang?

391
00:20:00,820 --> 00:20:02,650
A survey of stars revealed

392
00:20:02,750 --> 00:20:07,290
around 30% of white dwarfs
live in binary systems,

393
00:20:07,390 --> 00:20:09,920
but white dwarfs are not
good neighbors.

394
00:20:10,020 --> 00:20:13,830
A white dwarf in a binary
system is... it's like a zombie.

395
00:20:13,930 --> 00:20:16,700
It's the corpse of a star
that used to be alive.

396
00:20:16,800 --> 00:20:18,730
But now it is eating
the material

397
00:20:18,830 --> 00:20:21,200
from a star that is still alive.

398
00:20:21,300 --> 00:20:23,870
They very literally suck
the material

399
00:20:23,970 --> 00:20:25,710
and suck the life
out of that star

400
00:20:25,810 --> 00:20:28,410
by swallowing up all of
its outer layers.

401
00:20:30,080 --> 00:20:32,710
The white dwarf zombie
tendencies can backfire.

402
00:20:33,880 --> 00:20:36,850
Adding mass to
a white dwarf is like this.

403
00:20:36,950 --> 00:20:41,690
We keep adding mass from that
companion star

404
00:20:41,790 --> 00:20:45,360
a little bit of hydrogen
at a time,

405
00:20:45,460 --> 00:20:48,960
building up that atmosphere,
and for a long time,

406
00:20:49,060 --> 00:20:50,760
everything's fine.

407
00:20:50,870 --> 00:20:54,800
Until you add too much mass,
and you reach that critical

408
00:20:54,900 --> 00:20:57,070
threshold, and then...

409
00:21:00,480 --> 00:21:02,510
The real-world consequences of

410
00:21:02,610 --> 00:21:05,910
reaching the threshold
are devastating.

411
00:21:06,010 --> 00:21:09,620
The extra weight of gas stolen
from the companion star

412
00:21:09,720 --> 00:21:12,720
compresses carbon deep in
the core of the white dwarf.

413
00:21:14,490 --> 00:21:18,430
When the white dwarf reaches
1.4 times the mass of our sun,

414
00:21:18,530 --> 00:21:23,100
it hits a tipping point known
as the Chandrasekhar limit.

415
00:21:23,200 --> 00:21:25,630
You add up the mass little by
little by little until

416
00:21:25,730 --> 00:21:28,140
you get to that Chandrasekhar
limit and then blam,

417
00:21:28,240 --> 00:21:30,440
- there's a supernova.
- In a flash,

418
00:21:30,540 --> 00:21:33,010
carbon undergoes nuclear fusion,

419
00:21:33,110 --> 00:21:35,010
releasing a tremendous
amount of energy.

420
00:21:38,080 --> 00:21:39,580
If the white dwarf explodes

421
00:21:39,680 --> 00:21:41,150
at the Chandrasekhar limit,

422
00:21:41,250 --> 00:21:43,920
it's a little bit like
fireworks that all have

423
00:21:44,020 --> 00:21:45,690
the same amount of gunpowder.

424
00:21:45,790 --> 00:21:49,120
They'll all go off in the same
way, they'll be equally loud.

425
00:21:49,220 --> 00:21:51,290
Well, the supernovas
will be equally bright.

426
00:21:53,060 --> 00:21:55,300
This equal brightness
of all type 1a

427
00:21:55,400 --> 00:21:58,570
supernovas is vital to
our understanding of space.

428
00:21:59,770 --> 00:22:03,340
Type 1a's are known as
standard candles

429
00:22:03,440 --> 00:22:05,940
and are useful tools for
calculating fast

430
00:22:06,040 --> 00:22:07,940
cosmic distances.

431
00:22:08,040 --> 00:22:10,180
They were the key
to the Nobel Prize winning

432
00:22:10,280 --> 00:22:12,910
discovery that the expansion
of our universe

433
00:22:13,010 --> 00:22:14,480
is accelerating.

434
00:22:14,580 --> 00:22:20,290
But what kind of companion star
triggers type 1a supernovas?

435
00:22:20,390 --> 00:22:25,190
For decades, the number one
suspect was red giant stars.

436
00:22:25,290 --> 00:22:26,430
A red giant's

437
00:22:26,530 --> 00:22:30,330
a good candidate, because it's
a very big, puffy star.

438
00:22:30,430 --> 00:22:33,630
That material becomes easy
pickings for the white dwarf

439
00:22:33,740 --> 00:22:36,540
to siphon off until it gets
big enough to explode.

440
00:22:37,910 --> 00:22:40,040
To prove the theory,
we needed to find

441
00:22:40,140 --> 00:22:43,980
evidence in the debris left
behind after a supernova.

442
00:22:44,080 --> 00:22:47,350
Stars are surprisingly
hardy objects.

443
00:22:47,450 --> 00:22:50,750
They can survive an explosion
of a nearby star.

444
00:22:50,850 --> 00:22:53,250
Some of these companion stars
should still be there.

445
00:22:53,350 --> 00:22:55,560
A lot of them will be, you know,
worse for the wear,

446
00:22:55,660 --> 00:22:57,760
but they'll still exist.

447
00:22:57,860 --> 00:22:59,690
Scientists search
through the remains

448
00:22:59,790 --> 00:23:02,560
of 70 type 1a supernovas.

449
00:23:03,930 --> 00:23:05,870
Only one blast zone contained

450
00:23:05,970 --> 00:23:08,640
the glowing remains
of a red giant.

451
00:23:09,740 --> 00:23:12,940
The fact that we've only found
maybe this one example suggests

452
00:23:13,040 --> 00:23:15,210
that actually, they're not
quite the serial killers

453
00:23:15,310 --> 00:23:16,710
we thought.

454
00:23:16,810 --> 00:23:18,880
It's probably likely
that this is

455
00:23:18,980 --> 00:23:22,780
the minority of these types of
supernova explosions.

456
00:23:22,880 --> 00:23:26,320
Indeed, we now think that only
a small fraction of

457
00:23:26,420 --> 00:23:30,390
these white dwarf supernovas
involve a red giant,

458
00:23:30,490 --> 00:23:33,230
despite the fact that, in
the standard textbooks, for

459
00:23:33,330 --> 00:23:36,100
decades, that was
the preferred explanation.

460
00:23:37,400 --> 00:23:38,800
If red giants don't cause

461
00:23:38,900 --> 00:23:41,640
the majority of
type 1a supernovas,

462
00:23:41,740 --> 00:23:43,500
what does?

463
00:23:43,600 --> 00:23:45,140
New evidence suggests

464
00:23:45,240 --> 00:23:47,040
colliding white dwarfs,

465
00:23:47,140 --> 00:23:49,340
star mergers that could exceed

466
00:23:49,440 --> 00:23:51,180
the Chandrasekhar limit,

467
00:23:51,280 --> 00:23:54,380
producing explosions with
different brightness.

468
00:23:54,480 --> 00:23:57,180
But if the explosions
vary in brightness,

469
00:23:57,290 --> 00:23:58,990
can they still be used

470
00:23:59,090 --> 00:24:01,220
as standard candles?

471
00:24:01,320 --> 00:24:04,490
If we don't really know
what a type 1a supernova is,

472
00:24:04,590 --> 00:24:05,990
then when we use them to map out

473
00:24:06,090 --> 00:24:09,000
the universe and the way
the universe is expanding,

474
00:24:09,100 --> 00:24:12,470
we just can't be sure any longer
what it is we're looking at.

475
00:24:12,570 --> 00:24:14,100
If we're wrong about that,

476
00:24:14,200 --> 00:24:16,900
then we're wrong about so many
other things that our whole

477
00:24:17,000 --> 00:24:18,470
model of the universe
falls apart.

478
00:24:19,540 --> 00:24:22,640
Is our understanding of
the cosmos completely wrong?

479
00:24:35,990 --> 00:24:39,960
White dwarfs explode in
spectacular type 1a supernovas.

480
00:24:41,500 --> 00:24:44,230
They're a crucial tool for
measuring the universe,

481
00:24:44,330 --> 00:24:46,170
but there is a problem.

482
00:24:48,100 --> 00:24:50,340
The standard model
says that white dwarfs

483
00:24:50,440 --> 00:24:54,270
gradually steal mass
from a red giant star

484
00:24:54,380 --> 00:24:56,180
until they reach a tipping point

485
00:24:56,280 --> 00:24:57,910
called the Chandrasekhar limit.

486
00:25:00,650 --> 00:25:03,620
But recent observations
proved this doesn't explain

487
00:25:03,720 --> 00:25:06,350
how most type 1a
supernovas occur.

488
00:25:07,920 --> 00:25:12,030
The majority of type 1a
explosions remain a mystery.

489
00:25:12,130 --> 00:25:14,690
We call the explosions from
white dwarfs standard candles,

490
00:25:14,800 --> 00:25:16,106
but they're really not
that standard.

491
00:25:16,130 --> 00:25:18,600
We actually think there's
different types of explosions.

492
00:25:18,700 --> 00:25:21,230
It may be imperative
to our understanding

493
00:25:21,340 --> 00:25:23,170
of the entire universe
that we really get

494
00:25:23,270 --> 00:25:25,710
this straight, because
the reason we think

495
00:25:25,810 --> 00:25:27,970
the expansion rate of
the universe is accelerating

496
00:25:28,080 --> 00:25:30,410
is based on the brightness of
type 1 supernovas

497
00:25:30,510 --> 00:25:33,910
all being the same,
and maybe that's not the case.

498
00:25:34,020 --> 00:25:36,680
Researchers suspected
a theoretical type of

499
00:25:36,780 --> 00:25:38,520
merger could be responsible

500
00:25:38,620 --> 00:25:42,020
for more type 1a supernovas,

501
00:25:42,090 --> 00:25:45,790
the result of two white dwarfs
crashing together.

502
00:25:45,890 --> 00:25:48,800
But this messes with the math.

503
00:25:48,900 --> 00:25:51,930
The Chandrasekhar limit says
white dwarfs should

504
00:25:52,030 --> 00:25:53,170
explode when they reach

505
00:25:53,270 --> 00:25:56,700
1.4 times the mass of our sun.

506
00:25:56,800 --> 00:26:00,040
Two white dwarfs colliding
can exceed this mass,

507
00:26:00,140 --> 00:26:02,540
and more mass means
a bigger bang

508
00:26:02,610 --> 00:26:05,150
and a brighter explosion.

509
00:26:07,450 --> 00:26:08,350
You're not adding gas

510
00:26:08,450 --> 00:26:10,050
little by little,
you're adding a whole

511
00:26:10,150 --> 00:26:12,390
other white dwarf...
That will go off.

512
00:26:12,490 --> 00:26:14,150
It will look like
a type 1 supernova,

513
00:26:14,260 --> 00:26:15,690
but it won't be
the standard candle.

514
00:26:15,790 --> 00:26:17,320
It'll be brighter than
we expect.

515
00:26:17,430 --> 00:26:22,460
But no white dwarf mergers
have been found, because

516
00:26:22,560 --> 00:26:26,630
detecting one after it happens
is virtually impossible.

517
00:26:26,730 --> 00:26:28,840
If two white dwarfs
merge together,

518
00:26:28,940 --> 00:26:32,370
it's almost impossible to tell,
because the DNA of the two

519
00:26:32,470 --> 00:26:35,280
systems is all mixed together,
and it's all identical.

520
00:26:35,340 --> 00:26:38,410
You can't tell that there was
a separate companion in

521
00:26:38,510 --> 00:26:39,710
the first place.

522
00:26:39,810 --> 00:26:42,620
So we can't just look at
when there's a bright flash.

523
00:26:42,720 --> 00:26:44,950
We have to go look for
the ticking time bombs in

524
00:26:45,050 --> 00:26:46,590
the galaxy.

525
00:26:46,690 --> 00:26:50,160
Astronomers
investigating a strange shaped

526
00:26:50,260 --> 00:26:52,890
cloud of gas made
a breakthrough.

527
00:26:52,990 --> 00:26:56,830
Using ESO's Very
Large Telescope,

528
00:26:56,930 --> 00:27:02,270
they focused in on a planetary
nebula called Henize 2-428.

529
00:27:02,370 --> 00:27:05,540
Planetary nebulas are
normally symmetric,

530
00:27:05,640 --> 00:27:07,210
because red giants shed

531
00:27:07,310 --> 00:27:11,340
their outer layers evenly
as they become white dwarfs.

532
00:27:11,450 --> 00:27:14,210
But this one is lopsided.

533
00:27:14,320 --> 00:27:16,950
We think, in this case, there
might be the presence of

534
00:27:17,050 --> 00:27:21,550
a companion star that shapes
and twists and sculpts

535
00:27:21,660 --> 00:27:23,560
that planetary nebula.

536
00:27:25,630 --> 00:27:26,860
Researchers peeled back

537
00:27:26,960 --> 00:27:30,630
the gaseous layers and
discovered something shocking,

538
00:27:30,730 --> 00:27:33,730
a two-star system made up of

539
00:27:33,830 --> 00:27:36,440
the most massive orbiting
white dwarf pair

540
00:27:36,540 --> 00:27:37,640
ever discovered.

541
00:27:39,610 --> 00:27:43,540
Each star is 90%
as massive as our sun,

542
00:27:43,640 --> 00:27:45,310
and they're so close together,
they take

543
00:27:45,410 --> 00:27:47,350
just four hours
to orbit each other.

544
00:27:47,450 --> 00:27:50,680
And they're getting closer.

545
00:27:50,790 --> 00:27:54,850
If you've ever seen
a car crash about to happen,

546
00:27:54,960 --> 00:27:58,190
you know that sense of
inevitability

547
00:27:58,290 --> 00:27:59,690
as you witness that.

548
00:27:59,790 --> 00:28:01,760
That's what we're seeing in
this system.

549
00:28:01,860 --> 00:28:06,100
We see these two massive white
dwarfs spiraling closer

550
00:28:06,200 --> 00:28:10,970
and closer and closer, and we
know that disaster is coming.

551
00:28:11,070 --> 00:28:13,010
In around 700 million years,

552
00:28:13,110 --> 00:28:15,410
these stars will
merge and explode

553
00:28:15,510 --> 00:28:17,680
in a type 1a supernova.

554
00:28:22,220 --> 00:28:24,780
Now, thanks to the discovery
of more systems

555
00:28:24,890 --> 00:28:26,650
like Henize 2-428,

556
00:28:26,750 --> 00:28:29,420
we think white dwarf
collisions could be responsible

557
00:28:29,520 --> 00:28:32,190
for the majority of
type 1a supernovas.

558
00:28:34,630 --> 00:28:38,200
Two white dwarfs
can merge together.

559
00:28:38,300 --> 00:28:40,600
And if the sum of their masses
is greater than

560
00:28:40,700 --> 00:28:42,170
1.4 solar masses,

561
00:28:42,300 --> 00:28:44,300
then you can get
a Super-Chandra type 1a.

562
00:28:44,410 --> 00:28:46,840
We've now observed

563
00:28:46,940 --> 00:28:48,880
nine Super-Chandra explosions,

564
00:28:50,510 --> 00:28:52,210
and to complicate
matters further,

565
00:28:52,310 --> 00:28:55,980
we've spotted another form of
white dwarf supernovas,

566
00:28:56,080 --> 00:28:58,020
Sub-Chandra type 1as.

567
00:28:59,890 --> 00:29:03,190
These mysterious white dwarfs
that we don't quite understand

568
00:29:03,290 --> 00:29:06,690
die off much quicker than
regular white dwarf supernovas.

569
00:29:08,560 --> 00:29:10,830
The explosions are less
violent than normal

570
00:29:10,930 --> 00:29:14,030
type 1a supernovas
and fade away faster.

571
00:29:14,140 --> 00:29:16,400
But we don't know why.

572
00:29:18,270 --> 00:29:19,970
Maybe it has something to
do with

573
00:29:20,070 --> 00:29:22,310
the properties of the star
or the rotation,

574
00:29:22,410 --> 00:29:24,610
but the Chandrasekhar limit
may not be so exact.

575
00:29:24,710 --> 00:29:27,210
It's kind of
a Chandrasekhar range.

576
00:29:27,310 --> 00:29:30,150
The physics textbooks are
now being sort of rewritten,

577
00:29:30,250 --> 00:29:34,550
or at least modified, because
we know that not all type 1a

578
00:29:34,660 --> 00:29:38,020
supernovas come from Chandra
mass white dwarfs.

579
00:29:38,130 --> 00:29:42,000
There's actually a variety of
type 1a supernovas,

580
00:29:42,100 --> 00:29:46,370
a variety of white dwarf masses
and configurations

581
00:29:46,470 --> 00:29:47,630
that can explode.

582
00:29:49,140 --> 00:29:52,210
These new discoveries
mean researchers now study

583
00:29:52,310 --> 00:29:55,380
the chemistry and duration of
type 1a supernovas,

584
00:29:55,480 --> 00:29:57,340
not just their brightness.

585
00:30:01,120 --> 00:30:05,080
The deeper we investigate,
the more mysteries we uncover,

586
00:30:05,190 --> 00:30:08,790
like rogue white dwarfs
streaking across the galaxy

587
00:30:08,890 --> 00:30:13,990
and tiny stars that explode
over and over again.

588
00:30:14,090 --> 00:30:16,500
Can these odd white dwarfs
shed more

589
00:30:16,560 --> 00:30:19,630
light on the mystery of type
1a supernovas?

590
00:30:30,580 --> 00:30:31,480
White dwarfs are

591
00:30:31,580 --> 00:30:33,810
surprisingly difficult
to understand.

592
00:30:35,620 --> 00:30:38,480
They behave in completely
unexpected ways.

593
00:30:40,250 --> 00:30:43,190
But these oddballs may
help answer

594
00:30:43,260 --> 00:30:46,860
the remaining questions about
type 1a supernovas.

595
00:30:46,960 --> 00:30:49,230
These are white dwarfs,
but not as we know them.

596
00:30:50,460 --> 00:30:55,400
2017... astronomers spot
a rebellious star

597
00:30:55,500 --> 00:30:57,870
raising hell in
the Little Dipper constellation.

598
00:30:59,640 --> 00:31:02,480
It's like a zombie, but this
isn't one shambling down

599
00:31:02,580 --> 00:31:04,840
the road,
it runs like Usain Bolt.

600
00:31:04,950 --> 00:31:07,610
This thing is screaming
through the galaxy at a much

601
00:31:07,720 --> 00:31:10,020
higher speed than you'd expect
for a star like it.

602
00:31:12,090 --> 00:31:15,150
The white dwarf called LP 40-365

603
00:31:15,260 --> 00:31:16,990
is moving incredibly fast

604
00:31:17,090 --> 00:31:18,690
towards the edge
of the Milky Way.

605
00:31:18,790 --> 00:31:24,300
It's not the only star
behaving oddly... in 2019,

606
00:31:24,400 --> 00:31:27,400
we spotted three more
white dwarfs racing across

607
00:31:27,500 --> 00:31:28,870
the galaxy.

608
00:31:28,970 --> 00:31:30,870
Finding one white dwarf
blasting its way

609
00:31:30,970 --> 00:31:32,670
through space is weird enough.

610
00:31:32,770 --> 00:31:35,710
But to find three more, that's
telling you that something is

611
00:31:35,810 --> 00:31:37,210
going on, and whatever it is

612
00:31:37,310 --> 00:31:40,080
that's going on happens a lot.

613
00:31:40,180 --> 00:31:41,850
So what sent these renegades

614
00:31:41,950 --> 00:31:44,120
racing across the galaxy?

615
00:31:44,220 --> 00:31:47,990
LP 40-365 and these other
weird white dwarfs

616
00:31:48,090 --> 00:31:51,090
could be the results
of failed supernovas.

617
00:31:51,190 --> 00:31:52,930
People have theorized that maybe

618
00:31:53,030 --> 00:31:54,990
these things didn't
finish exploding.

619
00:31:55,100 --> 00:31:56,330
And if so, we should find

620
00:31:56,430 --> 00:31:59,470
some unburnt fractions
wandering around the galaxy.

621
00:32:01,070 --> 00:32:04,640
In the last 20 years,
we've spotted some unusually dim

622
00:32:04,740 --> 00:32:07,070
supernovas that could have sent

623
00:32:07,170 --> 00:32:11,210
LP 40-365 and friends flying.

624
00:32:11,310 --> 00:32:14,950
So what looks like happened is
that in a binary pair,

625
00:32:15,050 --> 00:32:16,950
there was stuff dumping
onto a white dwarf,

626
00:32:17,050 --> 00:32:19,590
and we were about to have
a type 1 supernova.

627
00:32:19,690 --> 00:32:22,620
But the type 1 supernova
didn't go off symmetrically.

628
00:32:22,720 --> 00:32:25,890
Some of it actually exploded,
and some of it didn't.

629
00:32:25,990 --> 00:32:29,260
That energy didn't go out in
all directions.

630
00:32:29,360 --> 00:32:31,970
And one of the things that
occurred is that these stars

631
00:32:32,070 --> 00:32:35,270
got sent hurling across space
at these incredible speeds.

632
00:32:39,210 --> 00:32:42,080
We call them
type 1ax supernovas.

633
00:32:42,180 --> 00:32:45,710
They could make up between
10 and 30%

634
00:32:45,810 --> 00:32:48,280
of type 1a supernovas.

635
00:32:48,380 --> 00:32:50,880
Many could throw out
a runaway star.

636
00:32:52,450 --> 00:32:55,860
But we still don't know why
the supernova fails.

637
00:32:55,960 --> 00:32:58,990
A funny thing
about science is things

638
00:32:59,090 --> 00:33:02,130
that fail still teach you
what's going on.

639
00:33:02,230 --> 00:33:04,560
Why are these ones different?
Were they not massive enough?

640
00:33:04,670 --> 00:33:06,700
Where they too massive?
Was the companion star

641
00:33:06,800 --> 00:33:08,900
not feeding them the material
the right way?

642
00:33:09,000 --> 00:33:11,670
Something happened there to
make these stars

643
00:33:11,770 --> 00:33:14,940
not basically blow
themselves to bits.

644
00:33:15,040 --> 00:33:17,080
And that's telling us
something about

645
00:33:17,180 --> 00:33:19,850
the way type 1as do explode.

646
00:33:21,520 --> 00:33:23,820
It seems that life
in a binary star system

647
00:33:23,920 --> 00:33:25,920
can be rough for white dwarfs,

648
00:33:26,020 --> 00:33:29,260
but for some lucky stars,
their lives can

649
00:33:29,360 --> 00:33:31,190
be more mellow.

650
00:33:31,290 --> 00:33:33,390
Just because a white dwarf

651
00:33:33,490 --> 00:33:35,290
has a normal star companion that

652
00:33:35,400 --> 00:33:38,830
it's stealing material from
does not spell a death sentence

653
00:33:38,930 --> 00:33:40,230
for that white dwarf.

654
00:33:40,330 --> 00:33:43,270
February 2013.

655
00:33:43,370 --> 00:33:46,770
Astronomers discover a star in
the Andromeda galaxy

656
00:33:46,870 --> 00:33:50,980
that flashes over and over
and over again.

657
00:33:51,080 --> 00:33:52,150
With each flare,

658
00:33:52,250 --> 00:33:55,950
it shines a million times
brighter than our sun

659
00:33:56,050 --> 00:33:58,280
before dimming to its
normal state.

660
00:33:58,390 --> 00:34:03,360
It's called M31N 2018-12a.

661
00:34:06,130 --> 00:34:09,430
This is not a supernova,
it's its little sibling,

662
00:34:09,530 --> 00:34:10,930
a nova.

663
00:34:11,030 --> 00:34:13,600
But what's weird about this
one is that it happens

664
00:34:13,700 --> 00:34:14,870
every year.

665
00:34:14,970 --> 00:34:18,500
Astronomers have known for
a long time that there are these

666
00:34:18,610 --> 00:34:21,370
cases of these nova that go off,

667
00:34:21,480 --> 00:34:23,380
you know, somewhat regularly,
every 10 years,

668
00:34:23,480 --> 00:34:24,680
every 100 years.

669
00:34:24,780 --> 00:34:26,410
But finding one that goes off

670
00:34:26,510 --> 00:34:29,050
every year is
a remarkable discovery.

671
00:34:30,580 --> 00:34:31,980
Much like supernovas,

672
00:34:32,090 --> 00:34:34,250
novas occur in a close
binary system,

673
00:34:34,350 --> 00:34:37,290
where a white dwarf and
another star orbit each other.

674
00:34:39,960 --> 00:34:41,830
The white dwarf pulls in
hydrogen

675
00:34:41,930 --> 00:34:43,700
from the companion star.

676
00:34:43,800 --> 00:34:46,170
The gas falls onto its surface.

677
00:34:46,270 --> 00:34:48,730
And so as
that hydrogen piles up,

678
00:34:48,840 --> 00:34:50,940
eventually, it gets to
the point where

679
00:34:51,040 --> 00:34:54,210
it can fuse into helium
and goes bang.

680
00:34:55,980 --> 00:34:56,880
In supernovas,

681
00:34:56,980 --> 00:35:00,180
fusion happens deep inside
the star's core,

682
00:35:01,550 --> 00:35:05,350
but in novas, fusion only
occurs on the surface.

683
00:35:05,420 --> 00:35:09,420
An explosion flares across
the white dwarf's exterior,

684
00:35:09,520 --> 00:35:13,530
hurling unburned hydrogen
out into space.

685
00:35:13,630 --> 00:35:17,660
The result... an object
called a remnant.

686
00:35:17,730 --> 00:35:23,400
The remnant from Nova M31N
is 400 light-years wide.

687
00:35:23,500 --> 00:35:25,140
This particular remnant is much

688
00:35:25,240 --> 00:35:27,910
bigger than even
supernova remnants.

689
00:35:28,010 --> 00:35:29,540
It's much larger, much denser

690
00:35:29,640 --> 00:35:31,480
and brighter than most
normal remnants are.

691
00:35:31,580 --> 00:35:32,580
But that makes sense

692
00:35:32,680 --> 00:35:34,810
if the star flares up so often.

693
00:35:34,920 --> 00:35:38,380
Think about the star flaring
away for millions of years.

694
00:35:38,490 --> 00:35:42,590
You build up a gigantic
nova remnant.

695
00:35:42,690 --> 00:35:44,120
The repeating flares explain

696
00:35:44,220 --> 00:35:45,590
the huge size of the remnant.

697
00:35:45,690 --> 00:35:48,960
But why does the nova explode
so frequently?

698
00:35:49,060 --> 00:35:53,200
Classically, we thought that
when a nova went off

699
00:35:53,300 --> 00:35:54,400
on the surface of

700
00:35:54,500 --> 00:35:58,240
a white dwarf star that
the white dwarf star's mass

701
00:35:58,340 --> 00:35:59,510
didn't change very much.

702
00:35:59,610 --> 00:36:01,310
Or maybe it got
a little smaller.

703
00:36:01,410 --> 00:36:04,680
Now we think that after a nova,

704
00:36:04,780 --> 00:36:07,450
the white dwarf
gains a bit of mass.

705
00:36:09,050 --> 00:36:12,750
Recurrent novas, like
M31N, steal more mass from

706
00:36:12,850 --> 00:36:15,920
their companion star than they
blow off in each explosion.

707
00:36:17,120 --> 00:36:18,890
Some gain more and more mass,

708
00:36:18,990 --> 00:36:21,860
exploding more frequently
until they reach

709
00:36:21,960 --> 00:36:24,000
the Chandrasekhar limit

710
00:36:24,100 --> 00:36:27,000
and go full-on supernova.

711
00:36:27,100 --> 00:36:29,500
M31N may very well be

712
00:36:29,600 --> 00:36:32,100
the missing link that shows us

713
00:36:32,210 --> 00:36:35,270
that some nova systems
eventually become

714
00:36:35,380 --> 00:36:36,640
supernova systems.

715
00:36:36,740 --> 00:36:39,010
Working out how novas become

716
00:36:39,110 --> 00:36:42,080
supernovas and why some
supernovas fail

717
00:36:43,980 --> 00:36:47,690
might help us understand what
makes white dwarfs explode.

718
00:36:50,490 --> 00:36:52,760
But just when we think
we get a break,

719
00:36:52,860 --> 00:36:55,090
white dwarfs hit us
with another bombshell...

720
00:36:55,200 --> 00:36:57,400
death rays.

721
00:37:09,740 --> 00:37:12,810
White dwarfs can explode
in violent supernovas,

722
00:37:15,750 --> 00:37:18,520
but that's not
their only deadly trick.

723
00:37:18,620 --> 00:37:20,750
They might also create the most

724
00:37:20,850 --> 00:37:24,790
magnetic and terrifying beast
in the universe...

725
00:37:24,890 --> 00:37:27,160
A magnetar.

726
00:37:27,260 --> 00:37:30,360
Magentars are scary.
They just are.

727
00:37:30,460 --> 00:37:31,576
I mean, it's even in the name.

728
00:37:31,600 --> 00:37:33,900
The word magnetar sounds scary.

729
00:37:34,000 --> 00:37:35,470
They're the reigning champion of

730
00:37:35,570 --> 00:37:37,700
the largest magnetic field in
the universe.

731
00:37:40,210 --> 00:37:44,840
The magnetic fields
around magnetars are so strong

732
00:37:44,950 --> 00:37:48,980
that they can stretch
and distort individual atoms.

733
00:37:49,080 --> 00:37:52,850
They can turn an atom into
a long, thin pencil shape.

734
00:37:52,950 --> 00:37:56,360
Once you start stretching
atoms out into this shape,

735
00:37:56,460 --> 00:37:59,690
they can't bond together
in the usual ways anymore.

736
00:37:59,790 --> 00:38:01,430
And so you can just throw out

737
00:38:01,530 --> 00:38:04,530
every chemistry textbook
in the world.

738
00:38:04,630 --> 00:38:06,870
If an astronaut were
unlucky enough to get close to

739
00:38:06,970 --> 00:38:08,330
a magnetar, say, within

740
00:38:08,440 --> 00:38:11,900
600, 700 miles,
the whole body of the astronaut

741
00:38:12,010 --> 00:38:13,290
would be completely obliterated.

742
00:38:13,370 --> 00:38:15,640
They would more
or less dissolve.

743
00:38:15,740 --> 00:38:18,510
The origin of these
fearsome creatures is a mystery,

744
00:38:18,610 --> 00:38:21,380
but it must be something
very violent.

745
00:38:21,480 --> 00:38:24,580
We think they send out
a clue as they form,

746
00:38:24,690 --> 00:38:28,750
powerful blasts of energy
shooting across the cosmos.

747
00:38:28,860 --> 00:38:32,760
In the past few decades,
we've noticed these very odd,

748
00:38:32,860 --> 00:38:35,230
very confusing and very brief

749
00:38:35,330 --> 00:38:39,570
flashes of intense radio energy.

750
00:38:39,670 --> 00:38:42,940
They're known as fast
radio bursts, or FRBs.

751
00:38:44,100 --> 00:38:47,010
Some FRBs don't repeat.
They're one and done.

752
00:38:47,110 --> 00:38:48,910
So you're talking about
an incredible amount

753
00:38:49,010 --> 00:38:51,440
of energy released in less
than a second,

754
00:38:51,550 --> 00:38:52,880
then it's over.

755
00:38:52,980 --> 00:38:55,250
Because these
non-repeating FRBs are

756
00:38:55,350 --> 00:38:59,490
so powerful, we think they could
come from a huge collision.

757
00:38:59,590 --> 00:39:02,250
The heavier and denser
the objects colliding,

758
00:39:03,920 --> 00:39:05,020
the bigger the bang.

759
00:39:06,430 --> 00:39:10,460
New research suggests a white
dwarf star hitting a dense,

760
00:39:10,560 --> 00:39:13,930
heavy neutron star could be
enough to birth

761
00:39:14,030 --> 00:39:16,000
a magnetar,

762
00:39:16,100 --> 00:39:19,110
sending out FRBs in the process.

763
00:39:19,210 --> 00:39:22,610
A neutron star is
like a white dwarf.

764
00:39:22,710 --> 00:39:26,110
Even more so...
It is the leftover core

765
00:39:26,210 --> 00:39:28,380
of a giant star.

766
00:39:28,480 --> 00:39:31,150
They're effectively giant
balls of neutrons

767
00:39:31,250 --> 00:39:32,250
squeezed together

768
00:39:32,290 --> 00:39:34,790
into things about the size
of a city.

769
00:39:34,890 --> 00:39:37,790
You have a neutron star,
an incredibly nasty,

770
00:39:37,890 --> 00:39:40,860
complicated exotic object
and a white dwarf,

771
00:39:40,960 --> 00:39:43,560
an incredibly nasty,
ugly, complicated object,

772
00:39:43,660 --> 00:39:45,900
crashing headlong into
each other.

773
00:39:47,600 --> 00:39:49,740
As the two stars
orbit more closely,

774
00:39:49,840 --> 00:39:52,510
the neutron star strips gas
from the white dwarf.

775
00:39:53,970 --> 00:39:57,740
This material spirals
onto the neutron star,

776
00:39:57,810 --> 00:40:00,210
causing it to spin faster
and faster.

777
00:40:02,650 --> 00:40:06,090
The rapid rotation amplifies
its magnetic fields

778
00:40:07,450 --> 00:40:10,660
until the two stars collide,

779
00:40:10,760 --> 00:40:13,760
creating
a very magnetic monster,

780
00:40:13,860 --> 00:40:15,760
a magnetar.

781
00:40:15,860 --> 00:40:17,700
It's a turbulent situation.

782
00:40:17,800 --> 00:40:19,800
You could think of it as
a newborn baby coming into

783
00:40:19,900 --> 00:40:22,100
the world,
kicking and screaming.

784
00:40:22,200 --> 00:40:23,570
The turbulence produces

785
00:40:23,670 --> 00:40:26,470
a powerful blast of
electromagnetic radiation.

786
00:40:28,880 --> 00:40:32,950
It races out of the collision
site at the speed of light

787
00:40:33,050 --> 00:40:36,820
until we detect it
as a fast radio burst.

788
00:40:38,520 --> 00:40:41,590
We can hear the screams of
agony from millions

789
00:40:41,690 --> 00:40:42,790
of light-years away,

790
00:40:42,890 --> 00:40:46,930
and those screams are
the fast radio bursts.

791
00:40:47,030 --> 00:40:48,930
This could be the most
difficult childbirth in

792
00:40:49,030 --> 00:40:50,030
the cosmos.

793
00:40:55,300 --> 00:40:58,140
Few suspected
that white dwarfs could create

794
00:40:58,240 --> 00:41:00,610
something as violent as
a magnetar.

795
00:41:03,580 --> 00:41:06,050
White dwarfs are emerging
from out of

796
00:41:06,150 --> 00:41:08,980
the shadows and taking
their rightful place

797
00:41:09,080 --> 00:41:11,820
as one of the most
fascinating objects

798
00:41:11,920 --> 00:41:13,550
in the universe.

799
00:41:13,650 --> 00:41:16,220
When we first observed white
dwarfs, they were weird.

800
00:41:16,320 --> 00:41:19,360
They were curious,
but just like a sideshow.

801
00:41:19,460 --> 00:41:21,560
But now white dwarfs
are showing us

802
00:41:21,660 --> 00:41:23,560
what they're truly capable of.

803
00:41:23,630 --> 00:41:25,360
White dwarfs can sort of be seen

804
00:41:25,470 --> 00:41:27,230
as these underdogs
of the universe,

805
00:41:27,330 --> 00:41:30,370
but it's really become
an exciting and cutting edge

806
00:41:30,470 --> 00:41:32,840
area of research.

807
00:41:32,940 --> 00:41:34,310
Now we think
these objects may have

808
00:41:34,410 --> 00:41:37,010
a lot of exciting science
to deliver, things like,

809
00:41:37,110 --> 00:41:38,740
will the universe
expand forever?

810
00:41:38,850 --> 00:41:40,580
What is the ultimate fate of
the universe?

811
00:41:40,680 --> 00:41:44,820
All of that may be waiting for
us inside a white dwarf.

812
00:41:44,920 --> 00:41:47,520
Discount these things
at your own risk,

813
00:41:47,620 --> 00:41:48,820
because honestly,

814
00:41:48,920 --> 00:41:51,260
they are one of the driving
forces in the universe.

815
00:41:51,360 --> 00:41:54,330
Just because it's little
don't mean it ain't bad.

816
00:41:54,430 --> 00:41:56,260
Don't underestimate
a white dwarf.

817
00:41:56,310 --> 00:42:00,860
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