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In the beginning,
there was darkness...
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and then, bang...
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giving birth to an endless
expanding existence...
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of time, space, and matter.
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Now, see further
than we've ever imagined...
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beyond the limits of our existence...
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in a place we call "The Universe. "
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They are cosmic killers.
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They're the end of stars.
They're the deaths of stars.
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Spectacular stellar detonations...
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A hundred billion times
as bright as the Sun.
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...that for an instant
outshine a whole galaxy.
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The most massive, energetic
event in the universe...
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since the Big Bang.
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Out of this exceptional cosmic
catastrophe comes creation.
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But if one struck near here,
life on Earth would cease.
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The universe,
the cosmic crime scene...
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for a most violent
and mysterious force:
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Supernovas.
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Supernovas, the sensational
and exceptional death of stars...
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produce the biggest blasts
in the universe.
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Now, only a small minority
of stars actually explode...
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but those that do
just go ka-blam...
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blowing themselves
to smithereens.
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Releasing more energy than
the Sun does in its entire lifetime...
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by more than a billion.
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The spectacular detonation blasts...
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vast amounts of lethal radiation
into the universe.
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If a star at the center
of a planetary system...
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would go supernova
and explode...
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it would probably wipe out
all forms of life...
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in that planetary system.
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Radiation would basically
sterilize all forms of life...
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on any planet
in the planetary system.
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Like homicide detectives poring
over clues to a cosmic crime...
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scientists use
state-of-the-art tools...
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telescopes, and technology
to find supernovas...
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and to solve the mystery
of how and why they occur.
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It's an interesting thing
because the explosion...
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the event,
has already taken place...
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and then we get these clues,
which we gather with our telescopes...
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and try to figure out
what happened.
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As the stellar
investigators know...
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supernovas have
a dual personality.
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They have absolute power
to destroy, and, at the same time...
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they are fundamental
to creation itself.
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When a supernova goes off,
the explosion produces a lot of light...
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but it also produces heavy elements
out of the light ones.
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So, for example,
iron or calcium or sodium...
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or any of the elements
of the periodic table...
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those things came
from exploding stars...
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that went off
before the Sun was formed.
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The elements produced in
these enormous stellar explosions...
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actually make planets,
plants, and people.
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The calcium in your bones
and the oxygen that you beathe...
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were all cooked up in stars
and blown out into space.
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The shockwaves
from exploding stars...
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can compress
nearby clouds of gas...
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and trigger
their gravitational collapse...
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so that they begin
the renewed process of formation...
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of new stars, planets,
and, ultimately, life.
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Thanks to circumstantial
cosmic evidence collected...
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experts estimate
that a mighty supernova goes off...
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somewhere in the universe
once every single second.
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So that's something
like thirty million per year...
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and that's been going on
for the last ten billion years or so...
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of the universe's existence.
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Giving us a sense
of how big the universe is...
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in a typical galaxy
like our Milky Way...
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a supernova suddenly occurs
only once or twice a century.
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However, nobody knows
when the next one might come.
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It's a completely
random process...
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so we have no idea
when the next one will occur.
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It could be tomorrow,
it could be five minutes ago...
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could be
another hundred years.
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We don't know.
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If it is very close...
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you would see
a very bright event in the sky.
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It could be even brighter
than Venus or the planets...
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or even the Moon...
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or maybe even the Sun
if it's bright enough.
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If a supernova is too close to you,
it can definitely destroy life.
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The flash disrupts the atmosphere,
burns things up.
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Astronomers are constantly
policing the skies...
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keeping a wary eye on
at least two stars in the Milky Way...
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that have the potential...
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to catastrophically explode
close to Earth.
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One that threatens to blow lies in
the heart of the Eta Carinae Nebula...
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about 9,000 light-years away.
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Eta Carinae is one
that we know about...
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which is a very massive star...
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maybe even a hundred times
the mass of the Sun...
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has a very short life...
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and it could be
that the end of that life...
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will take place
sometime very soon.
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Another star in danger of going
supernova is Betelgeuse...
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a star in the Orion constellation.
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This seething star is
fifteen times the size of the Sun.
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This one is even closer
than Eta Carinae to Earth.
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It's roughly 500 light-years away.
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It'll be a spectacularly brilliant sight,
visible even in the daytime.
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There's no question
Betelgeuse is going to blow up.
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It could be tonight,
for all our ignorance.
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It could be
10,000 years from now...
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short on an astronomical
time scale.
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But it could be tonight
if we're sufficiently ignorant about it.
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So it is worth looking at every night
to see whether it's blown up.
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Not only do the massive
supernova explosions...
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create and destroy stars,
planets, and people...
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they also unleash powerful energy
in the form of cosmic rays.
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These highly energetic
charged particles...
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strike our planet
each and every day.
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What's more, they have
the capacity to alter evolution.
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We live in what I call
a disturbed galactic ecology.
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It is a very eruptive,
energetic galaxy out there...
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and our planet is going
to get pummeled by that stuff.
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Experts say they can
and do change life as we know it.
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Well, we know that there are
genetic mutations...
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that take place when cosmic rays
hit living things.
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It disrupts the DNA inside cells.
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And if there were
a supernova nearby...
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there could be
a lot more cosmic rays...
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like a hundred or a thousand
or a million times more...
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than we ordinarily get.
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If you're the old species,
it might lead to your demise...
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but it also might lead
to new species being developed.
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So a supernova could be
an agent of change...
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and it could be for better
or for worse.
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Knowing that supernovas
have the power...
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to create and alter life...
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makes it imperative that
humankind unravel the riddle...
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of what makes
these stellar time bombs tick.
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What have you got here?
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All right, so this is
the supernova vectors.
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Supernova, uh...
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The key to unlocking the mystery
lies in detailed analysis...
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of what is ejected
into the cosmos by a supernova.
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I'm glad this one did
not escape our attention...
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'cause it was a winner.
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It's a great supernova.
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Nature has given us this puzzle.
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It says, "I make
these objects easily"...
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and we, as theorists, have
to figure out how nature does it.
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As with any crime scene...
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critical clues are contained
in what is left behind.
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Like a gunshot...
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hot gases and explosive debris
are propelled through space...
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by these deadly
stellar explosions.
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Just as these gunshots
are driving a shockwave...
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and you could hear this strong noise
from the shockwave...
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it's actually compressing
the matter and heating it up.
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A shockwave in a supernova
is doing the same thing.
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As these pieces of shrapnel are
hurtling very fast through space...
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they collide
with the material around it...
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and what forms is a shockwave.
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The fantastic stellar detonation...
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shoots vast amounts
of ballistic supernova evidence...
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cosmic debris called remnants,
into the universe.
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Though the remnants are
produced as this shockwave...
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keeps on moving out
through the universe...
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it actually produces
this very picturesque image...
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of the shock moving outward.
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The gases that made up that star...
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are ejected at tremendous velocities,
10,000 miles a second.
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And so they create
an expanding shell...
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and eventually that can
become very, very large.
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These things go
for thousands of years...
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or even tens of thousands of years.
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So sometimes we can see
the sight of a supernova explosion...
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tens of thousands of years
after the event has taken place.
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The high-speed collision
of stellar debris in the shockwave...
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produces intense heat and light...
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in wavelengths invisible
to the human eye.
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They include radio, infrared...
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all the way to X-rays
and gamma rays.
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Fortunately for astronomers...
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sophisticated
space-based instruments...
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like Hubble...
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Spitzer...
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and the Chandra
X-ray Telescope...
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can help the cosmic detectives
see them all.
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So, basically, every instrument
in every way you can...
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gives you a somewhat different
perspective on what's going on.
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So then you try
to put all that together...
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as an intellectual enterprise.
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Like a fingerprint, each supernova
has a unique pattern...
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and they can be analyzed
in several different ways.
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One thing we can do is measure
how bright the supernova is...
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and that's what we call
the light curve.
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00:11:11,754 --> 00:11:13,004
The other thing
that we can measure...
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that is really helpful
is what we call the spectrum.
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We take the light
from a supernova at a telescope...
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spread it out into a little rainbow,
using a prism or a grating...
194
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and then measure
how much light there is...
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at each color or wavelength.
196
00:11:28,145 --> 00:11:32,524
Analysis of that line can tell us
lots of interesting things...
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like the chemical composition
of the supernova, the temperature...
198
00:11:35,736 --> 00:11:38,488
the pressures
and densities of the gases...
199
00:11:38,531 --> 00:11:41,074
how quickly
they're expanding, and so on.
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00:11:42,910 --> 00:11:46,079
Information gleaned
from the light curve and spectrum...
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reveals distinctions
between each supernova.
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So it is much like
a detective's job...
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where you get different clues
from the light curve...
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or from the spectrum...
205
00:11:56,841 --> 00:11:59,718
and try to figure out
what kind of star it was...
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00:11:59,760 --> 00:12:01,302
what made it explode...
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00:12:01,345 --> 00:12:03,471
what the products
of the explosion were...
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00:12:03,514 --> 00:12:05,974
and what the effects
of that explosion might be.
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00:12:07,893 --> 00:12:11,521
As time goes on,
we can see deeper and deeper...
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into what the star
originally was...
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00:12:13,899 --> 00:12:19,112
so we can actually get what
the composition of the star was...
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00:12:19,155 --> 00:12:21,614
at the time it exploded.
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00:12:21,657 --> 00:12:24,075
By comparing
the light curves and spectra...
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00:12:24,118 --> 00:12:27,287
from literally hundreds
of supernova cases...
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00:12:27,329 --> 00:12:32,208
scientists have been able to classify
supernovas into two main types.
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00:12:37,798 --> 00:12:41,468
Type 1 a supernovae
release no hydrogen.
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00:12:43,554 --> 00:12:47,140
The explosions are uniform
in size and luminosity.
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00:12:48,934 --> 00:12:53,438
Type ll supernova release
large amounts of hydrogen.
219
00:12:53,481 --> 00:12:56,983
The explosions vary greatly
in size and luminosity.
220
00:13:01,822 --> 00:13:05,492
But why would there be such
distinct types of exploding stars?
221
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Might they be blowing themselves
apart in different ways?
222
00:13:12,708 --> 00:13:17,796
Scientists focus their efforts on
uncovering the mammoth question:
223
00:13:17,838 --> 00:13:22,050
What drives these stellar
monsters to destroy themselves?
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00:13:26,931 --> 00:13:29,849
Like bounty hunters
looking for bandits...
225
00:13:29,892 --> 00:13:32,769
today's astronomers
scour the cosmos...
226
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looking for deadly supernovas.
227
00:13:36,565 --> 00:13:38,566
With their keen eyes on the sky...
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00:13:38,609 --> 00:13:43,029
they belong to a long lineage
of stellar observers.
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00:13:43,072 --> 00:13:46,407
In fact, the first supernova
ever witnessed by man...
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00:13:46,450 --> 00:13:52,288
occurred in China in 185 A.D.,
2,000 years ago.
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00:13:53,541 --> 00:13:57,335
The Chinese astronomers
kept very meticulous records...
232
00:13:57,378 --> 00:13:59,045
about what they saw in the sky.
233
00:13:59,088 --> 00:14:01,506
Specifically,
when something new appeared...
234
00:14:01,549 --> 00:14:05,009
they recorded how bright it was,
where it was...
235
00:14:05,052 --> 00:14:06,302
how long it was there.
236
00:14:08,055 --> 00:14:09,931
Using the royal Chinese records...
237
00:14:09,974 --> 00:14:12,892
stellar investigators today
have recently found...
238
00:14:12,935 --> 00:14:15,478
the remnant
of this ancient supernova.
239
00:14:17,231 --> 00:14:20,608
It is identified as RCW86...
240
00:14:20,651 --> 00:14:23,403
and is in
the constellation Centaurus...
241
00:14:23,445 --> 00:14:28,116
near two bright stars known
as Alpha and Beta Centauri.
242
00:14:28,158 --> 00:14:31,578
1,400 years
after the Chinese discovery...
243
00:14:31,620 --> 00:14:35,248
the first European observer
witnessed a supernova.
244
00:14:37,334 --> 00:14:39,961
On November 11, 1572...
245
00:14:41,422 --> 00:14:45,717
26-year-old Danish astronomer
Tycho Brahe was taking a walk...
246
00:14:45,759 --> 00:14:48,469
when he witnessed a shocking
stellar phenomenon...
247
00:14:48,512 --> 00:14:50,471
in the northern sky.
248
00:14:50,514 --> 00:14:52,265
It was right next to the "W"...
249
00:14:52,308 --> 00:14:55,935
etched by the brightest stars
in the constellation Cassiopeia.
250
00:14:58,898 --> 00:15:00,064
Even though he saw it...
251
00:15:00,107 --> 00:15:03,568
and even though he was
the leading astronomer of his age...
252
00:15:03,611 --> 00:15:06,446
he did not believe
the sense of his own eyes.
253
00:15:08,824 --> 00:15:11,743
A few years after
Tycho's remarkable sighting...
254
00:15:11,785 --> 00:15:14,954
his former pupil,
Johannes Kepler...
255
00:15:14,997 --> 00:15:18,791
made his own groundbreaking
observation of a new star.
256
00:15:19,585 --> 00:15:23,254
He measured from star to star
around it, the distance.
257
00:15:23,297 --> 00:15:24,547
And we can use that now...
258
00:15:24,590 --> 00:15:28,134
to recreate exactly the position
of where it exploded.
259
00:15:29,595 --> 00:15:31,387
When contemporary investigators...
260
00:15:31,430 --> 00:15:34,599
took a closer look
at Kepler's 1604 remnant...
261
00:15:34,642 --> 00:15:36,935
they found something
very strange about it.
262
00:15:39,313 --> 00:15:42,023
A detailed analysis
of the chemical composition...
263
00:15:42,066 --> 00:15:44,275
of the ejected
and expanding gases...
264
00:15:44,318 --> 00:15:48,655
indicated that there were
two stars that somehow conjoined...
265
00:15:48,697 --> 00:15:51,240
to produce a gigantic explosion.
266
00:15:54,328 --> 00:15:58,373
So how did this companion
cause the stellar catastrophe?
267
00:15:58,415 --> 00:16:00,416
Many stars are
in binary systems...
268
00:16:00,459 --> 00:16:03,795
so they have a partner
that is orbiting around them.
269
00:16:03,837 --> 00:16:10,134
And we think what happens is that
one star puts mass onto the other.
270
00:16:10,177 --> 00:16:11,719
Experts have since found...
271
00:16:11,762 --> 00:16:15,139
that the companion, or binary,
scenario is the hallmark...
272
00:16:15,182 --> 00:16:18,643
of what is called
a Type 1 a supernova.
273
00:16:20,354 --> 00:16:24,482
The Type I supernovae, we think,
are the explosion of white dwarfs.
274
00:16:24,525 --> 00:16:28,069
So a star like the Sun
will produce a little, dense nugget...
275
00:16:28,112 --> 00:16:29,529
about the size of the Earth.
276
00:16:30,781 --> 00:16:35,076
When a star like the Sun dies,
it ejects its outer layers...
277
00:16:35,119 --> 00:16:38,830
and leaves behind just a small,
dense, burnt-out core...
278
00:16:38,872 --> 00:16:40,206
called a white dwarf.
279
00:16:42,042 --> 00:16:46,963
The ashes of the Sun will be
a carbon-and-oxygen white dwarf.
280
00:16:47,006 --> 00:16:48,673
Left to its own devices...
281
00:16:48,716 --> 00:16:51,384
that will just last forever
and cool off.
282
00:16:52,386 --> 00:16:56,055
But when a star has a companion,
like a partner in crime...
283
00:16:56,098 --> 00:16:58,016
it can lead to catastrophe.
284
00:16:58,934 --> 00:17:01,853
One star puts mass
onto that white dwarf...
285
00:17:01,895 --> 00:17:05,273
pushes its mass up to the point
where it becomes unstable...
286
00:17:05,315 --> 00:17:08,109
and there is burning
that takes place in the center.
287
00:17:08,152 --> 00:17:09,569
And very, very rapidly...
288
00:17:09,611 --> 00:17:13,406
the star goes from being
a kind of boring white dwarf...
289
00:17:13,449 --> 00:17:16,826
to being a tremendously
violent and brilliant supernova.
290
00:17:18,746 --> 00:17:22,415
But why do some white dwarfs
catastrophically explode?
291
00:17:25,502 --> 00:17:27,545
That was figured out in 1930...
292
00:17:27,588 --> 00:17:32,383
by a brilliant young astrophysicist,
Subrahmanyan Chandrasekhar...
293
00:17:32,426 --> 00:17:34,761
the Sherlock Holmes
of astrophysics...
294
00:17:34,803 --> 00:17:37,305
on a boat trip
from India to England.
295
00:17:38,599 --> 00:17:42,602
During this long voyage,
he used the newly developed fields...
296
00:17:42,644 --> 00:17:45,563
of quantum physics
and special relativity...
297
00:17:45,606 --> 00:17:47,148
to come up with the idea...
298
00:17:47,191 --> 00:17:53,112
that a white dwarf can have only
a certain maximum limiting mass.
299
00:18:00,579 --> 00:18:03,372
You cannot go beyond
a certain mass...
300
00:18:03,415 --> 00:18:06,793
about forty percent bigger
than that of our Sun...
301
00:18:06,835 --> 00:18:09,003
1.4 solar masses.
302
00:18:09,046 --> 00:18:12,090
And this came to be known
as the Chandrasekhar Limit.
303
00:18:12,132 --> 00:18:13,883
And at that point...
304
00:18:13,926 --> 00:18:18,888
an uncontrolled, runaway chain
of nuclear reactions ensues.
305
00:18:22,810 --> 00:18:26,896
But for decades, scientific
investigators remained puzzled...
306
00:18:26,939 --> 00:18:30,399
by just how this explosive
chain reaction worked...
307
00:18:31,693 --> 00:18:33,820
and what it looked like when it did.
308
00:18:35,239 --> 00:18:37,281
Computer models
could never recreate...
309
00:18:37,324 --> 00:18:39,534
what seemed to be happening
in nature.
310
00:18:41,120 --> 00:18:44,122
But then,
in 2006, astrophysicists...
311
00:18:44,164 --> 00:18:47,792
from the University of Chicago's
prestigious Flash Center...
312
00:18:47,835 --> 00:18:49,836
literally cracked the code.
313
00:18:52,881 --> 00:18:57,135
The Chicago team was the first
to create a supercomputer program...
314
00:18:57,177 --> 00:19:00,388
capable of processing
the vast amounts of data.
315
00:19:01,890 --> 00:19:05,309
It had to be to simulate
the complicated dynamics...
316
00:19:05,352 --> 00:19:08,604
involved in the explosion
of a whole star.
317
00:19:08,647 --> 00:19:10,773
We call this extreme computing.
318
00:19:10,816 --> 00:19:15,820
The computers we use, some of them
have 128,000 processors.
319
00:19:15,863 --> 00:19:21,242
So they're really 128,000
desktop computers all linked together.
320
00:19:21,285 --> 00:19:23,661
Even with all that power...
321
00:19:23,704 --> 00:19:27,081
it took almost 60,000 hours
of computing time.
322
00:19:28,208 --> 00:19:32,336
The astrophysicists decided not
to start their simulated explosion...
323
00:19:32,379 --> 00:19:35,631
exactly at the center of the star.
324
00:19:35,674 --> 00:19:38,092
The reason that we decided
to start slightly off-center...
325
00:19:38,135 --> 00:19:39,844
rather than right at the center...
326
00:19:39,887 --> 00:19:43,306
is that it's just
very, very improbable...
327
00:19:43,348 --> 00:19:47,977
that the flame will ignite exactly
or even really close to the center.
328
00:19:48,020 --> 00:19:49,437
There's just no volume there.
329
00:19:49,479 --> 00:19:51,814
There's no "there" there.
330
00:19:51,857 --> 00:19:54,150
According
to the remarkable simulation...
331
00:19:54,193 --> 00:19:59,030
in one second, a flame bubble
forms inside the star.
332
00:20:00,407 --> 00:20:02,867
So what you see right
in the center of the star...
333
00:20:02,910 --> 00:20:06,370
is the bubble rising quickly,
growing, expanding...
334
00:20:06,413 --> 00:20:08,122
as the burning takes place...
335
00:20:08,165 --> 00:20:10,583
and breaking through
the surface of the star.
336
00:20:12,002 --> 00:20:16,881
The molten bubble initially measures
approximately ten miles across...
337
00:20:16,924 --> 00:20:22,053
and rises more than 1,200 miles
to the surface of the star.
338
00:20:22,095 --> 00:20:26,390
It's spreading over the star
at about 3,000 miles a second...
339
00:20:26,433 --> 00:20:31,062
and it collides at the opposite point
on the surface of the star...
340
00:20:31,104 --> 00:20:35,149
and produces
extremely energetic jets...
341
00:20:35,192 --> 00:20:38,653
one that's moving outward
at about 40,000 miles a second...
342
00:20:38,695 --> 00:20:41,447
another jet that's
punching in towards the star...
343
00:20:41,490 --> 00:20:43,074
and that ignites
a detonation wave...
344
00:20:43,116 --> 00:20:45,785
which you've just seen
race through the star.
345
00:20:46,662 --> 00:20:50,373
Torrid temperatures, depicted
using a standard color scale...
346
00:20:50,415 --> 00:20:54,627
reach an unfathomable
three billion degrees Fahrenheit.
347
00:20:55,629 --> 00:20:57,797
And you can see the moment,
it's just detonated...
348
00:20:57,839 --> 00:21:01,509
and going through the star
takes less than half a second.
349
00:21:01,551 --> 00:21:04,553
The whole burning phase
takes less than three seconds.
350
00:21:06,431 --> 00:21:10,434
Expert analysis reveals
that each Type 1 a supernova...
351
00:21:10,477 --> 00:21:13,729
is remarkably similar
in size and brilliance.
352
00:21:14,731 --> 00:21:17,525
This explosion is equivalent...
353
00:21:17,567 --> 00:21:21,862
to completely detonating a mass
the size of the Sun.
354
00:21:23,991 --> 00:21:26,450
This groundbreaking
computer simulation...
355
00:21:26,493 --> 00:21:28,494
illustrates for the first time...
356
00:21:28,537 --> 00:21:32,540
how the explosions could occur
in a Type 1 a supernova.
357
00:21:35,794 --> 00:21:39,130
But Type lls seem to be
a radically different animal.
358
00:21:41,717 --> 00:21:44,135
By examining the stellar debris...
359
00:21:44,177 --> 00:21:47,013
scientists have reasoned
that Type ll supernovas...
360
00:21:47,055 --> 00:21:49,724
are not the result
of exploding white dwarfs...
361
00:21:51,143 --> 00:21:54,895
but rather the huge blasts
of massive dying stars...
362
00:21:54,938 --> 00:21:57,940
at least ten times
the mass of the Sun.
363
00:22:00,235 --> 00:22:03,154
But how do these
mega-explosions work?
364
00:22:04,656 --> 00:22:06,574
The answer
to the cosmic conundrum...
365
00:22:06,616 --> 00:22:09,785
would come in the middle
of the 20th century.
366
00:22:09,828 --> 00:22:14,248
That's when supernova gumshoes,
for the first time in history...
367
00:22:14,291 --> 00:22:16,917
pounded
the intergalactic pavements...
368
00:22:16,960 --> 00:22:20,755
systematically seeking
gigantic exploding stars.
369
00:22:26,887 --> 00:22:29,347
Like detectives on a stakeout...
370
00:22:29,389 --> 00:22:34,018
cosmic investigators
constantly scan the night sky.
371
00:22:34,061 --> 00:22:36,562
They're looking
for the telltale bright lights...
372
00:22:38,023 --> 00:22:40,232
that are evidence
of a supernova.
373
00:22:43,653 --> 00:22:45,363
To carry out their surveillance...
374
00:22:45,405 --> 00:22:48,574
they use an impressive array
of high-tech telescopes...
375
00:22:48,617 --> 00:22:50,284
scattered across the globe.
376
00:22:52,204 --> 00:22:55,873
Historically, we discover supernovae
with ground-based telescopes...
377
00:22:55,916 --> 00:22:57,917
either scanning the sky constantly...
378
00:22:57,959 --> 00:23:00,127
to look for new
supernovae explosions.
379
00:23:01,880 --> 00:23:06,092
The cosmic supernova hunt
began in the 1930s.
380
00:23:07,677 --> 00:23:11,972
Maverick astrophysicist Fritz Zwicky
led the charge.
381
00:23:12,015 --> 00:23:14,475
He was the first
to methodically search...
382
00:23:14,518 --> 00:23:18,938
catalog, and quantify
new and exploding stars.
383
00:23:21,900 --> 00:23:25,903
He was one of the real pioneers
in finding exploding stars.
384
00:23:25,946 --> 00:23:28,531
And then he wanted to physically
understand what they are.
385
00:23:31,660 --> 00:23:33,744
The trailblazing astrophysicist...
386
00:23:33,787 --> 00:23:37,665
proposed that these enormous
and spectacular stellar events...
387
00:23:37,707 --> 00:23:40,751
were the result
of whole stars exploding.
388
00:23:42,462 --> 00:23:47,007
Zwicky predicted that
a certain kind of exploding star...
389
00:23:47,050 --> 00:23:51,095
can occur when a massive
star's core collapses...
390
00:23:51,138 --> 00:23:55,433
and then rebounds,
creating a colossal explosion.
391
00:23:55,475 --> 00:23:57,101
During the collapse, they said...
392
00:23:57,144 --> 00:23:59,562
a compact remnant
should be formed...
393
00:23:59,604 --> 00:24:02,148
a ball of neutrons,
a neutron star.
394
00:24:04,526 --> 00:24:05,693
Essentially, ordinary matter...
395
00:24:05,735 --> 00:24:07,611
is made out of protons
and neutrons and electrons.
396
00:24:07,654 --> 00:24:09,780
In this collapse
of an iron core...
397
00:24:09,823 --> 00:24:13,534
the protons and the electrons
that make up the iron atoms...
398
00:24:13,577 --> 00:24:14,785
combine to make neutrons.
399
00:24:16,830 --> 00:24:19,915
A neutron star
is an incredibly dense object.
400
00:24:19,958 --> 00:24:22,334
Now, if you were to take
a large building...
401
00:24:22,377 --> 00:24:25,129
like the Empire State Building
in New York...
402
00:24:25,172 --> 00:24:27,965
and compress it to the density
of a neutron star...
403
00:24:28,008 --> 00:24:30,634
it would be
about the size of a marble.
404
00:24:31,470 --> 00:24:34,013
They have a very high density.
405
00:24:34,723 --> 00:24:37,892
And, in fact, a teaspoon
of neutron star material...
406
00:24:37,934 --> 00:24:40,269
would weigh as much
as one billion tons on Earth.
407
00:24:44,191 --> 00:24:47,234
Scientists today believe
that only huge stars...
408
00:24:47,277 --> 00:24:50,154
at least ten times
the mass of the Sun...
409
00:24:50,197 --> 00:24:54,200
have the potential to generate
this core-collapse-type explosion.
410
00:24:56,786 --> 00:25:01,874
The massive star generates energy
by fusing hydrogen to helium.
411
00:25:01,917 --> 00:25:05,336
It can fuse helium
into carbon and oxygen.
412
00:25:05,378 --> 00:25:09,131
And it keeps on going
all the way up to make iron.
413
00:25:09,174 --> 00:25:11,217
Iron is the most
tightly bound nucleus.
414
00:25:11,259 --> 00:25:13,177
So when a star
is made of iron...
415
00:25:13,220 --> 00:25:17,515
it's really at the end of the line,
and it's ready for disaster.
416
00:25:17,557 --> 00:25:21,560
The iron core forms
in the last day of the star's life.
417
00:25:23,188 --> 00:25:24,688
And then it
becomes so massive...
418
00:25:24,731 --> 00:25:27,983
that, essentially, it collapses
under its own weight...
419
00:25:28,026 --> 00:25:31,070
just collapses gravitationally,
very quickly.
420
00:25:32,280 --> 00:25:34,198
It takes less than a second...
421
00:25:34,241 --> 00:25:36,534
for the core of the star
to crunch down...
422
00:25:36,576 --> 00:25:38,702
from something
about the size of the Earth...
423
00:25:38,745 --> 00:25:42,998
to a neutron star, which is
maybe ten or fifteen miles across.
424
00:25:45,252 --> 00:25:48,546
But this dense iron core
doesn't settle down peacefully...
425
00:25:48,588 --> 00:25:51,257
into its new life
as a neutron star.
426
00:25:52,425 --> 00:25:56,220
But instead of reaching an equilibrium
configuration right away...
427
00:25:59,057 --> 00:26:01,725
the neutron star
rebounds off of itself...
428
00:26:01,768 --> 00:26:04,812
just as the gymnast rebounds
off of the trampoline...
429
00:26:04,854 --> 00:26:06,647
and goes upward again.
430
00:26:09,276 --> 00:26:11,610
Well, this rebounding
neutron star...
431
00:26:11,653 --> 00:26:14,738
collides with the material surrounding
it...
432
00:26:14,781 --> 00:26:19,827
and imparts some of its energy
to that colliding material...
433
00:26:19,869 --> 00:26:22,580
thus initiating an ejection.
434
00:26:25,458 --> 00:26:27,293
However, unlike a gymnast...
435
00:26:27,335 --> 00:26:31,380
for whom gravity ultimately prevails,
pulling him back to Earth...
436
00:26:32,924 --> 00:26:34,592
in a core-collapse scenario...
437
00:26:34,634 --> 00:26:38,345
something else continues
to drive the ejection outward.
438
00:26:40,056 --> 00:26:41,307
The question became...
439
00:26:41,349 --> 00:26:45,978
what was this mysterious force
driving the blast into space?
440
00:26:51,318 --> 00:26:55,863
Experts calculated that in order
for a successful explosion to occur...
441
00:26:55,905 --> 00:26:57,698
one more ingredient was needed.
442
00:26:58,491 --> 00:27:01,285
They suspected
something called neutrinos...
443
00:27:01,328 --> 00:27:03,329
ghostly, energy-bearing particles...
444
00:27:03,371 --> 00:27:06,332
that had been predicted,
but never observed.
445
00:27:10,045 --> 00:27:13,339
Astrophysicists believe
that during a core collapse...
446
00:27:13,381 --> 00:27:16,175
when the electrons are pushed
so close to protons...
447
00:27:16,217 --> 00:27:17,968
in the nuclei of atoms...
448
00:27:18,011 --> 00:27:21,055
that they combine
to become neutrons.
449
00:27:21,097 --> 00:27:25,768
In the process, they release these tiny,
mysterious neutrino particles.
450
00:27:27,103 --> 00:27:29,438
The neutrinos are kind
of interesting particles.
451
00:27:29,481 --> 00:27:31,482
They don't have
any electric charge...
452
00:27:31,524 --> 00:27:33,525
so they don't interact with light.
453
00:27:33,568 --> 00:27:37,488
They only interact by what physicists
call the weak force...
454
00:27:37,530 --> 00:27:39,323
and the weak force
is aptly named.
455
00:27:39,366 --> 00:27:42,534
It means that these particles
can go right through the Earth.
456
00:27:42,577 --> 00:27:45,621
They can go through
long chunks of matter.
457
00:27:45,664 --> 00:27:47,790
So they're like ghosts.
458
00:27:47,832 --> 00:27:49,792
They just go through things.
459
00:27:54,255 --> 00:27:56,507
For centuries,
modern astronomers...
460
00:27:56,549 --> 00:27:59,009
have been studying
the remnants of supernovas...
461
00:27:59,052 --> 00:28:02,805
in faraway galaxies
from the distant past.
462
00:28:02,847 --> 00:28:06,350
But in 1987,
they would get a front-row seat...
463
00:28:06,393 --> 00:28:09,269
to an explosion
of their very own.
464
00:28:10,522 --> 00:28:14,858
It was the brightest supernova
seen in nearly four centuries...
465
00:28:14,901 --> 00:28:17,444
long after the development
of the telescope.
466
00:28:17,487 --> 00:28:20,114
So we could use
our full arsenal of equipment...
467
00:28:20,156 --> 00:28:22,282
to study this fantastic blast.
468
00:28:26,079 --> 00:28:30,874
In 1987, the most fantastic
stellar event near our galaxy...
469
00:28:30,917 --> 00:28:33,836
since the invention
of the telescope occurred.
470
00:28:38,633 --> 00:28:40,217
The first to witness it...
471
00:28:40,260 --> 00:28:43,387
was young Chilean astronomer
Oscar Duhalde.
472
00:28:44,514 --> 00:28:46,932
His and astronomy's good fortune...
473
00:28:46,975 --> 00:28:51,395
came on the night
of February 23, 1987.
474
00:28:53,398 --> 00:28:57,609
A telescope operator at
the Las Campanas Observatories...
475
00:28:57,652 --> 00:29:00,904
Oscar Duhalde,
put water on for coffee...
476
00:29:00,947 --> 00:29:03,157
and went outside
to take a look at the sky.
477
00:29:03,199 --> 00:29:05,117
And when Oscar went out there...
478
00:29:05,160 --> 00:29:07,244
he looked at
the Large Magellanic Cloud...
479
00:29:07,287 --> 00:29:08,287
which he knows very well...
480
00:29:08,329 --> 00:29:10,998
and he noticed
that there was an extra star.
481
00:29:12,542 --> 00:29:15,127
So he discovered
this supernova explosion...
482
00:29:15,170 --> 00:29:17,463
by basically running
outside the telescope building...
483
00:29:17,505 --> 00:29:18,756
and saw it with his own eyes.
484
00:29:22,635 --> 00:29:25,596
When a star explodes,
astrophysicists...
485
00:29:25,638 --> 00:29:28,599
like investigators
looking for clues to a crime...
486
00:29:28,641 --> 00:29:31,602
know that the first few hours
after the stellar death...
487
00:29:31,644 --> 00:29:33,145
are the most critical.
488
00:29:37,859 --> 00:29:40,986
So in 1987,
when the closest supernova...
489
00:29:41,029 --> 00:29:43,363
in nearly 400 years appeared...
490
00:29:43,406 --> 00:29:45,783
they knew they had to act fast.
491
00:29:47,160 --> 00:29:50,954
It was only about
170,000 light-years away...
492
00:29:50,997 --> 00:29:53,332
a mere stone's throw
for an astronomer.
493
00:29:54,793 --> 00:29:58,629
Supernova 1987A
was in a small galaxy...
494
00:29:58,671 --> 00:30:00,798
called the Large Magellanic Cloud...
495
00:30:00,840 --> 00:30:06,678
a dwarf galaxy that orbits around
our much bigger Milky Way galaxy.
496
00:30:08,264 --> 00:30:10,974
Being the first supernova
of that year...
497
00:30:11,017 --> 00:30:13,519
the exceptional
and nearby exploding star...
498
00:30:13,561 --> 00:30:17,439
was simply labeled SN1987a.
499
00:30:20,902 --> 00:30:23,821
But this time, dozens
of seasoned astronomers...
500
00:30:23,863 --> 00:30:26,406
all over the planet
were ready for action.
501
00:30:27,951 --> 00:30:31,286
Armed with sophisticated tools
and telescopes...
502
00:30:31,329 --> 00:30:33,872
they turned their minds
and machines to the heavens...
503
00:30:33,915 --> 00:30:38,168
and closely scrutinized
Supernova 1987a.
504
00:30:41,381 --> 00:30:43,340
Knowing that an exploding star...
505
00:30:43,383 --> 00:30:46,385
is at its hottest
in the first few hours...
506
00:30:46,928 --> 00:30:50,430
and is emitting lots of light
in ultraviolet wavelengths...
507
00:30:50,473 --> 00:30:53,392
the astro-detectives
sprung into action.
508
00:30:55,103 --> 00:30:56,812
At the time of the explosion...
509
00:30:56,855 --> 00:30:59,523
we saw the fastest-moving stuff
was coming toward us...
510
00:30:59,566 --> 00:31:00,774
at a tenth of the speed of light...
511
00:31:00,817 --> 00:31:03,485
so that was
the actual star blowing up.
512
00:31:07,657 --> 00:31:10,075
Scientists had their explosion.
513
00:31:10,118 --> 00:31:12,786
Now they wanted to know
the name of the victim.
514
00:31:15,748 --> 00:31:18,876
They dug through a catalog
that lists all known stars...
515
00:31:18,918 --> 00:31:21,336
and their positions
in the sky...
516
00:31:21,379 --> 00:31:23,297
when they struck pay dirt.
517
00:31:25,258 --> 00:31:27,384
They found the star that exploded.
518
00:31:28,595 --> 00:31:32,264
It was tagged SK-69202.
519
00:31:34,851 --> 00:31:37,895
They also determined
that it was a huge star...
520
00:31:37,937 --> 00:31:40,480
twenty times
the mass of the Sun.
521
00:31:42,066 --> 00:31:44,401
Examining the spectral evidence...
522
00:31:44,444 --> 00:31:47,237
scientists could see
strong lines of hydrogen.
523
00:31:48,531 --> 00:31:51,867
SN1987a bore the hallmarks...
524
00:31:51,910 --> 00:31:54,786
of a Type ll
core-collapse supernova.
525
00:31:58,708 --> 00:32:03,045
But to confirm their suspicions
and prove the core-collapse theories...
526
00:32:03,087 --> 00:32:06,340
experts had to have one more
piece of physical evidence.
527
00:32:07,967 --> 00:32:10,260
They needed neutrinos...
528
00:32:10,303 --> 00:32:13,096
those ghostly particles
that scientists predicted...
529
00:32:13,139 --> 00:32:15,349
would be unleashed
during the blast.
530
00:32:21,606 --> 00:32:24,149
In the early 1980s,
scientists had built...
531
00:32:24,192 --> 00:32:26,902
a handful of neutrino detectors
around the world.
532
00:32:28,863 --> 00:32:31,573
They consisted of tanks
deep underground...
533
00:32:31,616 --> 00:32:33,617
filled with tons of pure water.
534
00:32:35,536 --> 00:32:40,457
But these detectors had yet to
capture a single supernova neutrino.
535
00:32:40,500 --> 00:32:43,001
We've had this story
for a long time...
536
00:32:43,044 --> 00:32:46,797
that most of the energy
of a supernova explosion...
537
00:32:46,839 --> 00:32:50,384
a core-collapse supernova explosion,
goes into neutrinos.
538
00:32:50,426 --> 00:32:52,302
But we had never seen
those neutrinos.
539
00:32:54,180 --> 00:32:55,555
As luck would have it...
540
00:32:55,598 --> 00:33:00,310
on February 23, 1987,
they got their neutrinos.
541
00:33:00,353 --> 00:33:04,398
Two detectors-one beneath
the city of Kamioka, Japan...
542
00:33:04,440 --> 00:33:06,984
and the other
under Lake Erie in Ohio...
543
00:33:07,026 --> 00:33:10,028
captured a dozen
of the elusive particles.
544
00:33:12,699 --> 00:33:16,034
There were light detectors
on this volume of water...
545
00:33:16,077 --> 00:33:20,288
that were used to see this little flash
caused by the neutrino...
546
00:33:20,331 --> 00:33:23,291
interacting with matter
inside the tank.
547
00:33:24,460 --> 00:33:29,214
For the first time ever, scientists
on Earth saw tangible evidence...
548
00:33:29,257 --> 00:33:31,633
of the mysterious
neutrino particles...
549
00:33:31,676 --> 00:33:35,220
generated in the core
of an exploding star.
550
00:33:38,558 --> 00:33:40,183
Astronomers now knew...
551
00:33:40,226 --> 00:33:45,188
the theories first proposed
in the 1930s were right.
552
00:33:45,231 --> 00:33:49,192
Supernova 1987a showed
beyond a shadow of a doubt...
553
00:33:49,235 --> 00:33:53,321
that the massive iron core
of a very massive star...
554
00:33:53,364 --> 00:33:55,949
collapsed and formed
a neutron star...
555
00:33:55,992 --> 00:33:57,784
because, in that process...
556
00:33:57,827 --> 00:33:59,786
a lot of neutrinos
should be emitted.
557
00:34:01,039 --> 00:34:04,332
With the deployment of powerful
space-based telescopes...
558
00:34:04,375 --> 00:34:08,086
astronomers today have built
on the astonishing discoveries...
559
00:34:08,129 --> 00:34:11,757
made in the wake
of Supernova 1987a.
560
00:34:18,097 --> 00:34:23,393
In 2006, 30-year-old astronomer
Robert Quimby would once again...
561
00:34:23,436 --> 00:34:25,729
turn conventional thinking
on its head...
562
00:34:25,772 --> 00:34:29,775
and revolutionize the way
astronomers searched for supernovas.
563
00:34:32,945 --> 00:34:33,987
Most supernova searchers...
564
00:34:34,030 --> 00:34:35,864
they just want to find
as many supernovas as possible...
565
00:34:35,907 --> 00:34:39,201
so they'll look once every two weeks,
every one week...
566
00:34:39,243 --> 00:34:41,411
just so you can find them...
567
00:34:41,454 --> 00:34:43,580
and so you can look at
as many fields as possible...
568
00:34:43,623 --> 00:34:45,874
and get as many supernovae
as possible.
569
00:34:45,917 --> 00:34:48,752
So I decided to look
at a limited number of fields...
570
00:34:48,795 --> 00:34:50,545
and look at them
as often as I can.
571
00:34:52,298 --> 00:34:56,051
The enterprising cosmic gumshoe
programmed his robotic telescope...
572
00:34:56,094 --> 00:35:00,597
to systematically sweep
the targeted field every night.
573
00:35:00,640 --> 00:35:02,641
Like an interstellar searchlight...
574
00:35:02,683 --> 00:35:05,143
it honed in on
and methodically scanned...
575
00:35:05,186 --> 00:35:08,063
the same small, dark corner
of the cosmos...
576
00:35:08,106 --> 00:35:10,649
looking for supernova suspects.
577
00:35:12,652 --> 00:35:15,695
They had software that can
very quickly process the data...
578
00:35:15,738 --> 00:35:19,449
and tell me if there's anything there
that wasn't there before.
579
00:35:19,492 --> 00:35:23,078
And when that happens,
if I think it could be a supernova...
580
00:35:23,121 --> 00:35:24,329
then I'll get a spectrum of it.
581
00:35:24,372 --> 00:35:26,790
And then that spectrum of it
will tell me exactly what it is.
582
00:35:26,833 --> 00:35:29,459
Is it a supernova?
What type is it? Et cetera.
583
00:35:29,502 --> 00:35:35,423
On September 18, 2006,
Quimby got his big break.
584
00:35:35,466 --> 00:35:39,094
He found
the brightest supernova ever.
585
00:35:39,137 --> 00:35:41,555
And this was my fourth supernova.
586
00:35:41,597 --> 00:35:44,307
I didn't think that
I should be so lucky.
587
00:35:45,434 --> 00:35:47,894
And others looked
at the spectra...
588
00:35:47,937 --> 00:35:49,938
and they started taking
their own measurements...
589
00:35:49,981 --> 00:35:52,607
of the photometry,
how bright it was.
590
00:35:52,650 --> 00:35:55,277
And they figured out that,
in fact, 2006gy...
591
00:35:55,319 --> 00:35:58,196
was brighter than any other
published supernova.
592
00:36:02,702 --> 00:36:05,662
Very slowly, it took
over two months, seventy days...
593
00:36:05,705 --> 00:36:08,290
to get to the maximum light,
and then faded again.
594
00:36:08,332 --> 00:36:11,334
So it was a supernova unlike anything
we'd ever seen before...
595
00:36:11,377 --> 00:36:14,004
discovered by
this fourth-year graduate student...
596
00:36:14,046 --> 00:36:15,589
at the University of Texas.
597
00:36:16,632 --> 00:36:19,551
Analysis of the remnant
indicated that the star...
598
00:36:19,594 --> 00:36:24,431
before it exploded,
was 100 times the size of the Sun.
599
00:36:24,473 --> 00:36:27,017
And with lots of hydrogen
showing in its spectrum...
600
00:36:27,059 --> 00:36:32,397
the brightest supernova ever recorded
bore the stamp of a Type ll event.
601
00:36:33,399 --> 00:36:36,151
Then Quimby topped himself.
602
00:36:36,194 --> 00:36:37,485
When he finally analyzed...
603
00:36:37,528 --> 00:36:40,864
a seemingly insignificant
supernova he found earlier...
604
00:36:40,907 --> 00:36:47,495
called SN2005ap,
he made a stunning discovery.
605
00:36:47,538 --> 00:36:50,415
It was something like
a hundred billion times...
606
00:36:50,458 --> 00:36:53,126
as bright as the Sun
as compared to-
607
00:36:53,169 --> 00:36:54,711
For a Type 1 a supernova...
608
00:36:54,754 --> 00:36:58,048
the peak may be only
six billion times as bright as the Sun.
609
00:36:59,842 --> 00:37:04,095
It was even brighter
than SN2006gy.
610
00:37:08,017 --> 00:37:09,601
Like circumstantial evidence...
611
00:37:09,644 --> 00:37:13,230
astonishing discoveries
of new ultrabright supernovas...
612
00:37:13,272 --> 00:37:16,149
like 2005ap and others...
613
00:37:16,192 --> 00:37:18,902
have opened up
a whole new avenue of inquiry...
614
00:37:18,945 --> 00:37:22,030
into exploding stars and their M.O.
615
00:37:24,450 --> 00:37:25,533
The basic idea we have...
616
00:37:25,576 --> 00:37:28,578
is that perhaps this is connected
somehow to gamma-ray bursts.
617
00:37:29,288 --> 00:37:31,831
Gamma rays are
the most powerful form of light...
618
00:37:31,874 --> 00:37:33,250
known in the universe.
619
00:37:36,170 --> 00:37:37,921
By analyzing supernovas...
620
00:37:37,964 --> 00:37:40,465
investigators
are getting closer than ever...
621
00:37:40,508 --> 00:37:44,135
to solving some of the most
confounding riddles in the cosmos.
622
00:37:45,221 --> 00:37:46,763
How one of them
makes gamma rays...
623
00:37:46,806 --> 00:37:48,390
and the other makes
an ordinary supernova...
624
00:37:48,432 --> 00:37:50,141
is still one
of the big mysteries.
625
00:37:50,184 --> 00:37:52,018
Nobody really knows
how that works.
626
00:37:53,854 --> 00:37:56,773
What astronomers do know
is that supernovas...
627
00:37:56,816 --> 00:37:59,526
and the gamma-ray bursts
associated with them...
628
00:37:59,568 --> 00:38:01,903
are the brightest beacons
in the universe.
629
00:38:04,031 --> 00:38:06,992
On the galactic highway
that is the cosmos...
630
00:38:07,034 --> 00:38:09,995
supernovas serve
as celestial signposts...
631
00:38:10,037 --> 00:38:15,500
pointing astronomers to the beginning
and the end of time and space.
632
00:38:22,842 --> 00:38:27,762
NASA's powerful Swift satellite,
launched in 2004...
633
00:38:27,805 --> 00:38:30,598
was designed specifically
to sweep the sky...
634
00:38:30,641 --> 00:38:33,351
and detect gamma-ray bursts
in the universe.
635
00:38:40,109 --> 00:38:42,152
Like cosmic first responders...
636
00:38:42,194 --> 00:38:45,196
astrophysicists at NASA's
Goddard Space Flight Center...
637
00:38:45,239 --> 00:38:49,659
in Baltimore, Maryland,
are standing by 24/7...
638
00:38:49,702 --> 00:38:52,662
waiting for a 911 call from Swift.
639
00:38:56,125 --> 00:38:57,792
Basically, less than two minutes...
640
00:38:57,835 --> 00:39:00,211
after Swift
discovered a gamma-ray burst...
641
00:39:00,254 --> 00:39:04,716
the satellite sends down e-mails
directly to our Blackberries.
642
00:39:04,759 --> 00:39:10,013
When a recent supernova,
recorded as SN2006aj, appeared...
643
00:39:10,056 --> 00:39:13,725
the Swift satellite caught
the shocking gamma rays it generated.
644
00:39:16,228 --> 00:39:18,646
And that gamma-ray burst
was very interesting...
645
00:39:18,689 --> 00:39:19,689
because, first of all...
646
00:39:19,732 --> 00:39:22,275
it was a very long-duration
gamma-ray burst.
647
00:39:22,318 --> 00:39:24,486
Usually, gamma-ray bursts are
very short-lived phenomena...
648
00:39:24,528 --> 00:39:27,030
only fractions of a second
or a few seconds...
649
00:39:27,073 --> 00:39:30,158
but this gamma-ray burst
was visible for, like, 35 minutes.
650
00:39:30,201 --> 00:39:32,535
We saw, three days later...
651
00:39:32,578 --> 00:39:36,164
a supernova explosion going off
at the exact same location.
652
00:39:36,207 --> 00:39:38,625
And this solved one
of the important mysteries...
653
00:39:38,667 --> 00:39:39,959
of gamma-ray bursts...
654
00:39:40,002 --> 00:39:43,338
because we found out at least
parts of gamma-ray bursts...
655
00:39:43,381 --> 00:39:45,882
are due to massive stars
that are exploding.
656
00:39:47,843 --> 00:39:50,720
Astronomers today can see
hundreds of supernovas...
657
00:39:50,763 --> 00:39:53,556
and the deadly gamma-ray bursts
they generate.
658
00:39:55,309 --> 00:39:56,559
On the cosmic highway...
659
00:39:56,602 --> 00:39:59,354
scientists use
these stellar headlights...
660
00:39:59,397 --> 00:40:04,025
to ascertain the bounds
and breadth of the universe.
661
00:40:04,068 --> 00:40:05,985
You can use supernovae
to probe the universe...
662
00:40:06,028 --> 00:40:09,322
'cause if they're very dim,
you know they were very far away.
663
00:40:09,365 --> 00:40:11,408
And then you can study
the curvature of space-time...
664
00:40:11,450 --> 00:40:14,244
and all of the cosmology
that you can study within it.
665
00:40:14,286 --> 00:40:16,538
For example,
if you're on a desert highway...
666
00:40:16,580 --> 00:40:18,415
and you're looking out
at the lights of the cars...
667
00:40:18,457 --> 00:40:21,167
you can tell which are nearby
and which are far away...
668
00:40:21,210 --> 00:40:22,752
from the apparent brightness
of the lights.
669
00:40:22,795 --> 00:40:24,546
The ones that are nearby
look bright.
670
00:40:24,588 --> 00:40:27,382
The ones that are far away
look dim.
671
00:40:27,883 --> 00:40:30,969
Measuring how far away
things are very systematically...
672
00:40:31,011 --> 00:40:35,598
will tell you about the size,
the age, the shape...
673
00:40:35,641 --> 00:40:38,309
the history,
the future of the universe.
674
00:40:40,312 --> 00:40:43,273
It turns out that
Type 1 a supernovas...
675
00:40:43,315 --> 00:40:45,650
are the best suited
for this purpose.
676
00:40:47,194 --> 00:40:48,945
One of the things
that's really interesting...
677
00:40:48,988 --> 00:40:50,947
about the Type 1 a supernovae...
678
00:40:50,990 --> 00:40:53,116
the ones that are
exploding white dwarfs...
679
00:40:53,159 --> 00:40:56,744
is that there is this fixed mass,
this Chandrasekhar Mass...
680
00:40:56,787 --> 00:41:00,957
that sets how big the explosion is,
how much stuff is involved.
681
00:41:01,000 --> 00:41:04,961
And the consequence of that
is that many of these...
682
00:41:05,004 --> 00:41:07,797
have very nearly
the same brightness.
683
00:41:07,840 --> 00:41:10,967
If the explosion produces
the same amount of light...
684
00:41:11,010 --> 00:41:13,636
then we can measure
how much light we see...
685
00:41:13,679 --> 00:41:16,681
and figure out how far away
the supernova is.
686
00:41:18,476 --> 00:41:22,061
This is known as
the standard candle principle.
687
00:41:22,104 --> 00:41:25,857
Type 1 a supernovae
are like standard candles.
688
00:41:25,900 --> 00:41:28,818
They all have about
the same peak power...
689
00:41:28,861 --> 00:41:30,862
the same peak luminosity.
690
00:41:31,655 --> 00:41:34,324
So, if you look at them
from different distances...
691
00:41:34,366 --> 00:41:36,910
they appear different
apparent brightnesses.
692
00:41:36,952 --> 00:41:39,496
They look dimmer
if they're farther away...
693
00:41:39,538 --> 00:41:41,831
and brighter
if they're more nearby.
694
00:41:41,874 --> 00:41:45,835
So if we find Type 1 a supernovae
in distant galaxies...
695
00:41:45,878 --> 00:41:48,796
and measure
their apparent brightness...
696
00:41:48,839 --> 00:41:51,341
and compare that
with the known power...
697
00:41:51,383 --> 00:41:53,760
of a nearby Type 1 a supernova...
698
00:41:53,802 --> 00:41:56,846
we can determine the distance
of that supernova...
699
00:41:56,889 --> 00:41:59,516
and, hence, of the galaxy
in which it's located.
700
00:42:00,392 --> 00:42:03,811
The trailblazing technique has
also led astro-investigators...
701
00:42:03,854 --> 00:42:05,939
to some radical conclusions.
702
00:42:07,900 --> 00:42:10,276
Basically, you can use
the distances to supernovae...
703
00:42:10,319 --> 00:42:13,863
to figure out what the universe
is doing, how old it is.
704
00:42:13,906 --> 00:42:16,157
And we now know that,
from various lines of evidence...
705
00:42:16,200 --> 00:42:18,701
that it's a little less
than fourteen billion years old.
706
00:42:18,744 --> 00:42:22,413
But, in particular, we found out
the universe was accelerating...
707
00:42:22,456 --> 00:42:24,082
when we thought
it was decelerating...
708
00:42:24,124 --> 00:42:26,709
in the grip
of the gravitational materials in it.
709
00:42:26,752 --> 00:42:29,045
That just caused
an intellectual revolution...
710
00:42:29,088 --> 00:42:30,922
like throwing a ball up
towards the ceiling...
711
00:42:30,965 --> 00:42:32,715
and rather than it having come
back down into your hand...
712
00:42:32,758 --> 00:42:35,385
it goes faster and faster
and faster towards the ceiling.
713
00:42:35,427 --> 00:42:38,179
It's completely counterintuitive.
714
00:42:38,222 --> 00:42:40,723
Basically, all the astronomy textbooks out
there...
715
00:42:40,766 --> 00:42:44,811
all said that the universe
should be decelerating...
716
00:42:44,853 --> 00:42:49,190
that is, gravity should be
slowing down the expansion rate.
717
00:42:49,233 --> 00:42:52,569
But what this result showed
is that instead of slowing down...
718
00:42:52,611 --> 00:42:56,030
it was actually expanding
faster and faster and faster.
719
00:43:01,287 --> 00:43:04,414
While the examination of supernovas
has helped scientists...
720
00:43:04,456 --> 00:43:07,959
unravel many
monumental cosmic mysteries...
721
00:43:08,002 --> 00:43:10,920
experts believe that if they
continue to follow the clues...
722
00:43:10,963 --> 00:43:13,548
left behind
when huge stars explode...
723
00:43:15,384 --> 00:43:18,970
they'll be able to answer
the biggest unanswered questions.
724
00:43:23,142 --> 00:43:26,227
Today, scientists know
that someday soon...
725
00:43:26,270 --> 00:43:28,438
we could each witness
for ourselves...
726
00:43:28,480 --> 00:43:32,150
the marvelous and almighty
force of a supernova.
727
00:43:33,986 --> 00:43:37,405
Our galaxy is
100,000 light-years across.
728
00:43:37,448 --> 00:43:40,158
So that means there's light
from a thousand supernovae...
729
00:43:40,200 --> 00:43:42,952
that's on its way to us now.
730
00:43:42,995 --> 00:43:46,623
It could even happen
in our very own Milky Way.
731
00:43:47,708 --> 00:43:50,501
In our galaxy, we are expected
to have an average...
732
00:43:50,544 --> 00:43:53,338
of about two supernova
explosions per century.
733
00:43:53,380 --> 00:43:54,964
The problem is
that the last supernova...
734
00:43:55,007 --> 00:43:57,800
that we saw in our galaxy
is almost 400 years ago...
735
00:43:57,843 --> 00:43:59,844
so our galaxy is long overdue.
736
00:44:01,555 --> 00:44:03,973
If it did happen
in our own galaxy...
737
00:44:04,016 --> 00:44:06,934
we, like the titans
of space and time-
738
00:44:06,977 --> 00:44:11,731
Tycho, Kepler, Chandrasekhar,
and Zwicky...
739
00:44:11,774 --> 00:44:14,651
would bear witness
to the most destructive...
740
00:44:14,693 --> 00:44:18,738
and the most creative force
in the universe:
741
00:44:18,781 --> 00:44:20,490
The supernova.
63382
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