NARRATOR: They are
cosmic killers-- ROBERT KIRSHNER: They're
the end of stars. They're the deaths of stars. NARRATOR: --spectacular
stellar detonations-- ROBERT QUIMBY: 100 billion
times as bright as the sun. NARRATOR: --that for an instant,
outshine a whole galaxy. The most massive energetic
event in the universe since the Big Bang. NARRATOR: Out of this
exceptional cosmic catastrophe comes creation. But if one struck near here,
life on Earth would cease. The universe-- the cosmic
crime scene for a most violent and mysterious force-- supernovas. [music playing] Supernovas-- the sensational
and exceptional death of stars-- produce the biggest
blasts in the universe. Now, only a small minority
of stars actually explode, but those that do
just go ka-blam, blowing themselves
to smithereens. Releasing more
energy than the sun does in its entire lifetime,
by more than a billion. NARRATOR: The
spectacular detonation blasts vast amounts of lethal
radiation into the universe. STEFAN IMMLER: If a star at the
center of a planetary system would go supernova and
explode, it would probably wipe out all forms of life
in that planetary system. Radiation would basically
sterilize all forms of life on any planet in a
planetary system. NARRATOR: Like homicide
detectives poring over clues to a cosmic crime,
scientists use state of the art tools,
telescopes, and technology to find supernovas and to solve
the mystery of how and why they occur. ROBERT KIRSHNER: It's
an interesting thing because the
explosion-- the event-- has already taken place, and
then we get these clues, which we gather with our telescopes,
and try to figure out what happened. NARRATOR: As the stellar
investigators know, supernovas have a
dual personality. They have absolute power to
destroy, and at the same time, they are fundamental
to creation itself. ROBERT KIRSHNER: When
a supernova goes off, the explosion produces
a lot of light but it also produces
heavy elements out of the light one,
so for example, iron or calcium or sodium-- or any of the elements of the
periodic table-- those things came from exploding stars
that went off before the sun was formed. NARRATOR: The elements produced
in these enormous stellar explosions actually make
planets, plants, and people. The calcium in your bones
and the oxygen that you breathe were all cooked up in stars
and blown out into space. The shockwaves from
exploding stars can compress nearby
clouds of gas and trigger their gravitational
collapse, so that they begin the renewed process of
formation of new stars, planets, and ultimately, life. NARRATOR: Thanks to
circumstantial cosmic evidence collected, experts estimate
that a mighty supernova goes off somewhere
in the universe once every single second. So that's something
like 30 million per year, and that's been going on for
the last 10 billion years or so of the universe's existence. NARRATOR: Giving us a sense
of how big the universe is, in a typical galaxy,
like our Milky Way, a supernova suddenly occurs
only once or twice a century. However, nobody knows when
the next one might come. ROBERT QUIMBY: It's a
completely random process, so we have no idea when
the next one will occur. It could be tomorrow,
could be five minutes ago, could be another 100 years. We don't know. STEFAN IMMLER: If
it is very close, we would see a very
bright event in the sky. It could be even brighter than
the Venus, or the planets, or even the moon, or maybe even
the sun if it's bright enough. If a supernova is
too close to you, it can definitely destroy life. The flash disrupts the
atmosphere, burns things up. NARRATOR: Astronomers are
constantly policing the skies, keeping a wary eye
on at least two stars in the Milky Way that have the
potential to catastrophically explode close to Earth. One that threatens to blow lies
in the heart of the Eta Carinae Nebula, about 9,000
light years away. ROBERT KIRSHNER: Eta Carinae
is one that we know about, which is a very massive star-- maybe even 100 times
the mass of the sun-- has a very short
life, and it could be that the end of that life
will take place sometime very soon. NARRATOR: Another star
in danger of going supernova is Betelgeuse, a star
in the Orion constellation. This seething star is 15
times the size of the sun. This one is even closer
than Eta Carinae to Earth. ALEX FILIPPENKO: It's
roughly 500 light years away. It'll be a spectacularly
brilliant sight, visible even in the daytime. J CRAIG WHEELER:
There's no question Betelgeuse is going to blow up. It could be tonight. For all our ignorance, it could
be 10,000 years from now-- short on an
astronomical timescale-- but it could be tonight,
that we're sufficiently ignorant about it, so it is
worth looking at every night to see whether it's blown up. NARRATOR: Not only do the
massive supernova explosions create and destroy stars,
planets, and people, they also unleash
powerful energy in the form of cosmic rays. These highly energetic,
charged particles strike our planet each and every day. What's more, they have the
capacity to alter evolution. We live in what I call a
disturbed galactic ecology. It is a very eruptive,
energetic galaxy out there, and our planet is going to
get pummeled by that stuff. NARRATOR: Experts say they can
and do change life as we know it. Well, we know that there
are genetic mutations that take place when cosmic
rays hit living things. It disrupts the
DNA inside cells, and if there were
a supernova nearby, there could be a lot more
cosmic rays, like 100 or 1,000 or a million times more
than we ordinarily get. If you're the old species,
it might lead to your demise, but it also might lead to
new species being developed. So a supernova could
be an agent of change and it could be for
better or for worse. NARRATOR: Knowing that
supernovas have the power to create and alter
life makes it imperative that humankind unravel
the riddle of what makes these stellar time bombs tick. What have you got here? All right, so this is the
supernova factory supernova. NARRATOR: The key to
unlocking the mystery lies in the detailed analysis of
what is ejected into the cosmos by a supernova. I'm glad this one did
not escape our attention, because it was a winner. Yeah. It's a great supernova. CHRIS FRYER: Nature has
given us this puzzle. It says I make these
objects easily, and we, as theorists, have to
figure out how nature does it. NARRATOR: As with
any crime scene, critical clues are contained
in what is left behind. Like a gunshot, hot gases
and explosive debris are propelled through space
by these deadly stellar explosions. CHRIS FRYER: Just
as these gunshots are driving a shockwave-- and
you can hear this strong noise from the shockwave-- it's
actually compressing the matter and heating it up. A shockwave in a supernova
is doing the same thing. UNA HWANG: As these
pieces of shrapnel are hurtling very
fast through space, they collide with the material
around it, and what forms is a shockwave. NARRATOR: The fantastic stellar
detonation shoots vast amounts of ballistic supernova evidence,
cosmic debris called remnants, into the universe. CHRIS FRYER: So the remnants are
produced as the shockwave keeps on moving out
through the universe. It actually produces this very
picturesque image of the shock moving outward. DON LAMB: The gases that
made up that star are ejected at tremendous velocities-- 10,000 miles a second-- and so they create
an expanding shell, and eventually, that can
become very, very large. ROBERT KIRSHNER: These things
go for thousands of years or even tens of
thousands of years, so sometimes, we can see the
sight of a supernova explosion tens of thousands of years
after the event has taken place. NARRATOR: The high speed
collision of stellar debris and the shockwave produces
intense heat and light in wavelengths invisible
to the human eye. They include radio, infrared,
all the way to X-rays, and gamma rays. Fortunately, for astronomers,
sophisticated space based instruments, like Hubble,
Spitzer, and the Chandra X-ray telescope can help the cosmic
detectives see them all. So basically, every
instrument and every way you can gives you a somewhat
different perspective on what's going on, so then you try
to put all that together as an intellectual enterprise. NARRATOR: Like a
fingerprint, each supernova has a unique pattern
and they can be analyzed in several different ways. One thing we can do is measure
how bright the supernova is, and that's what we
call the light curve. The other thing that we can
measure that is really helpful is what we call the spectrum. We take the light from a
supernova at a telescope, spread it out into a
little rainbow using a prism or a grating, and then
measure how much light there is at each color or wavelength. Analysis of that line can tell
us lots of interesting things, like the chemical composition of
the supernova, the temperature, the pressures and
densities of the gases, how quickly they're
expanding, and so on. NARRATOR: Information
gleaned from the light curve and spectrum
reveals distinctions between each supernova. ROBERT KIRSHNER: So it is much
like a detective job, where you get different clues
from the light curve or from the spectrum and try
to figure out what kind of star it was, what made
it explode, what the products of
the explosion were, and what the effects of
that explosion might be. DON LAMB: As time goes on,
we can see deeper and deeper into what the star
originally was, so we can actually get what
the composition of the star was at the time it exploded. NARRATOR: By comparing the
light curves and spectra from literally hundreds
of supernova cases, scientists have been able
to classify supernovas into two main types. Type Ia supernova
release no hydrogen. The explosions are uniform
in size and luminosity. Type II supernova release
large amounts of hydrogen. The explosions vary greatly
in size and luminosity. But why would there be such
distinct types of exploding stars? Might they be blowing themselves
apart in different ways? Scientists focused their
efforts on uncovering the mammoth question-- what drives these stellar
monsters to destroy themselves? Like bounty hunters
looking for bandits, today's astronomers
scour the cosmos looking for deadly supernovas. With their keen eyes on the sky,
they belong to a long lineage of stellar observers. In fact, the first supernova
ever witnessed by man occurred in China in
185 AD, 2000 years ago. ROBERT QUIMBY: The
Chinese astronomers kept very meticulous records
about what they saw in the sky, specifically, when something
new appeared, they recorded how bright it was, where it
was, how long it was there. NARRATOR: Using the
royal Chinese records, stellar investigators today
have recently found the remnant of this ancient supernova. It is identified as RCW 86,
and is in the constellation Centaurus, near two bright
stars known as Alpha and Beta Centauri. 1,400 years after the
Chinese discovery, the first European observer
witnessed a supernova. On November 11, 1572,
26-year-old Danish astronomer Tycho Brahe was
taking a walk when he witnessed a shocking stellar
phenomenon in the northern sky. It was right next to the W
etched by the brightest stars in the constellation Cassiopeia. ROBERT KIRSHNER: Even
though he saw it, and even though he was the
leading astronomer of his age, he did not believe the
sense of his own eyes. NARRATOR: A few years after
Tycho's remarkable citing, his former pupil,
Johannes Kepler, made his own groundbreaking
observation of a new star. He measured from star to
star around it, the distance. And we can use that now to
recreate exactly the position of where it exploded. NARRATOR: When contemporary
investigators took a closer look at Kepler's 1604
remnant, they found something very strange about it. A detailed analysis of
the chemical composition of the ejected and
expanding gases indicated that there were two
stars that somehow conjoined to produce a gigantic explosion. So how did this companion
cause this stellar catastrophe? Many stars are
in binary systems, so they have a partner that
is orbiting around them. And we think what happens
is that one star puts mass on to the other. NARRATOR: Experts have since
found that the companion, or binary scenario, is
the hallmark of what is called a type Ia supernova. The type I
supernovae, we think, are the explosion of white
dwarfs, so a star like the sun will produce a
little dense nugget about the size of the earth. NARRATOR: When a
star like the sun dies, it eject its outer layers
and leaves behind just a small, dense, burnt out core
called a white dwarf. The ashes of the sun will be
a carbon and oxygen white dwarf. Left to its own
devices, that will just last forever and cool off. NARRATOR: But when a
star has a companion, like a partner in crime,
it can lead to catastrophe. One star puts mass
onto that white dwarf, pushes its mass up to the point
where it becomes unstable, and that there is burning that
takes place in the center. And very, very
rapidly, the star goes from being a kind of
boring white dwarf to being a tremendously violent
and brilliant supernova. NARRATOR: But why do some
white dwarfs catastrophically explode? That was figured out in
1930 by a brilliant young astrophysicist, Subrahmanyan
Chandrasekhar, the Sherlock Holmes of astrophysics,
on a boat trip from India to England. ALEX FILIPPENKO: During
this long voyage, he used the newly developed
fields of quantum physics and special relativity
to come up with the idea that a white dwarf can have
only a certain maximum limiting mass. You cannot go beyond
a certain mass-- about 40% bigger than that of
our sun, 1.4 solar masses-- and this came to be known
as the Chandrasekhar limit. And at that point, an
uncontrolled runaway chain of nuclear reactions ensues. NARRATOR: But for decades,
scientific investigators remain puzzled by just
how this explosive chain reaction worked, and what
it looked like when it did. Computer models could
never recreate what seemed to be happening in nature. But then in 2006,
astrophysicists from the University of Chicago's
prestigious Flash Center literally cracked the code. The Chicago team was the first
to create a supercomputer program capable of processing
the vast amounts of data. It had to be, to simulate the
complicated dynamics involved in the explosion
of a whole star. DON LAMB: We call this
extreme computing. The computers we use, some of
them have 128,000 processors, so they're really 128,000
desktop computers all linked together. NARRATOR: Even with
all that power, it took almost 60,000
hours of computing time. The astrophysicists
decided not to start their simulated
explosion exactly at the center of the star. DON LAMB: The reason that
we decided to start slightly off center, rather than
right at the center, is that it's just very, very
improbable that the flame will ignite exactly, or even
really close to the center. There is just no volume there. There's no there there. NARRATOR: According to
the remarkable simulation, in one second, a flame
bubble forms inside the star. DON LAMB: So what you see
right in the center of the star is the bubble, rising
quickly, growing, expanding as the burning takes place, and
breaking through the surface of the star. NARRATOR: The molten
bubble initially measures approximately 10 miles across,
and rises more than 1,200 miles to the surface of the star. DON LAMB: It's spreading over
the star at about 3,000 miles a second, and it collides at the
opposite point on the surface of the star, and produces
extremely energetic jets-- one that's moving outward at
about 40,000 miles a second, another jet that's
punching in towards a star, and that ignites a detonation
wave, which you've just seen race through the star. NARRATOR: Torrid temperatures,
depicted using a standard color scale, reach an unfathomable
three billion degrees Fahrenheit. DON LAMB: And you can see the
moment it's just detonated, and going through the star
takes less than half a second. The whole burning phase takes
less than three seconds. NARRATOR: Expert analysis
reveals that each type Ia supernova is remarkably
similar in size and brilliance. DON LAMB: This explosion
is equivalent to completely detonating a mass
the size of the sun. NARRATOR: This groundbreaking
computer simulation illustrates, for the first time,
how the explosions could occur in a type Ia supernova. But type IIs seem to be a
radically different animal. By examining the stellar
debris, scientists have reasoned that type
II supernovas are not the result of
exploding white dwarfs, but rather the huge blasts
of massive dying stars, at least 10 times
the mass of the sun. But how do these
mega explosions work? The answer to the
cosmic conundrum would come in the middle
of the 20th century. That's when supernova gumshoes,
for the first time in history, pounded the intergalactic
pavements, systematically seeking gigantic
exploding stars. Like detectives on a stakeout,
cosmic investigators constantly scan the night sky. They're looking for the telltale
bright lights that are evidence of a supernova. To carry out their surveillance,
they use an impressive array of high tech telescopes
scattered across the globe. STEFAN IMMLER: Historically,
we discover supernovas with ground based telescopes,
either scanning the sky constantly to look for
new supernova explosions. NARRATOR: The cosmic supernova
hunt began in the 1930s. Maverick astrophysicist,
Fritz Zwicky, led the charge. He was the first to
methodically search, catalog, and quantify new
and exploding stars. ALEX FILIPPENKO: He was one of
the real pioneers in finding exploding stars, and then he
wanted to physically understand what they are. NARRATOR: The trailblazing
astrophysicist proposed that these enormous and
spectacular stellar events were the result of whole
stars exploding. ALEX FILIPPENKO: Zwicky
predicted that a certain kind of exploding star can occur when
a massive star's core collapses and then rebounds, creating
a colossal explosion. During the collapse, they
said, a compact remnant should be formed, a ball of
neutrons, a neutron star. Essentially, ordinary
matter is made out of protons and neutrons and electrons. In this collapse
of an iron core, the protons and electrons
that make up the iron atoms combine to make neutrons. ALEX FILIPPENKO: A neutron star
is an incredibly dense object. Now, if you were to
take a large building, like the Empire State
Building in New York, and compress it to the
density of a neutron star, it would be about
the size of a marble. They have a very high density. And in fact, a teaspoon
of neutron star material would weigh as much as
1 billion tons on Earth. NARRATOR: Scientists today
believe that only huge stars, at least 10 times
the mass of the sun, have the potential to generate
this core collapse type explosion. ROBERT KIRSHNER: A massive
star generates energy by fusing hydrogen to helium. It can fuse helium
into carbon and oxygen. And it keeps on going, all
the way up to make iron. Iron is the most
tightly bound nucleus, so when a star has
made iron, it's really at the end of the line,
and it's ready for disaster. NARRATOR: The iron core forms
in the last day of the star's life. ALEX FILIPPENKO: And then
it becomes so massive that essentially, it collapses
under its own weight. It just collapses
gravitationally, very quickly. ROBERT KIRSHNER: It
takes less than a second for the core of
the star to crunch down from something about
the size of the earth to a neutron star, which is
maybe 10 or 15 miles across. NARRATOR: But this
dense iron core doesn't settle down
peacefully into its new life as a neutron star. ALEX FILIPPENKO: But instead
of reaching an equilibrium configuration right
away, the neutron star rebounds off of itself, just
as the gymnast rebounds off of the trampoline and
goes upward again. Well, this rebounding neutron
star collides with the material surrounding it and imparts some
of its energy to that colliding material, thus
initiating an ejection. NARRATOR: However, unlike
a gymnast, for whom gravity ultimately prevails,
pulling him back to earth, in a core collapse scenario,
something else continues to drive the ejection outward. The question became, what
was this mysterious force driving the blast into space? Experts calculated that in
order for a successful explosion to occur, one more
ingredient was needed. They suspected something
called neutrinos-- ghostly, energy
bearing particles that had been predicted
but never observed. Astrophysicists believe that
during the core collapse, when the electrons are pushed
so close to protons in the nuclei of
atoms, that they combine to become neutrons. In the process, they release
these tiny, mysterious neutrino particles. ROBERT KIRSHNER:
The neutrinos are kind of interesting particles. They don't have any
electric charge, so they don't
interact with light. They only interact by what
physicists call the weak force, and the weak force
is aptly named. It means that these particles
can go right through the earth. They can go through
long chunks of matter, so they're like ghosts. They just go through things. NARRATOR: For centuries,
modern astronomers have been studying the
remnants of supernovas in faraway galaxies
from the distant past. But in 1987, they would get a
front row seat to an explosion of their very own. ALEX FILIPPENKO: It was the
brightest supernova scene in nearly four centuries,
long after the development of the telescope, so we
could use our full arsenal of equipment to study
this fantastic blast. NARRATOR: In 1987, the most
fantastic stellar event near our galaxy, since the
invention of the telescope, occurred. The first to witness it was
young Chilean astronomer Oscar Duhalde. His and astronomy's good fortune
came on the night of February 23, 1987. ROBERT KIRSHNER: A telescope
operator at the Las Campanas Observatory, Oscar Duhalde,
put water on for coffee and went outside to
take a look at the sky. And when Oscar
went out there, he looked at the large
Magellanic Cloud, which he knows very well,
and he noticed that there was an extra star. STEFAN IMMLER: So he discovered
this supernova explosion by basically running outside
the telescope building and saw it with his own eyes. NARRATOR: When a star
explodes, astrophysicists, like investigators looking
for clues to a crime, know that the first few
hours after the stellar death are the most critical. So in 1987, when the closest
supernova in nearly 400 years appeared, they knew
they had to act fast. It was only about
170,000 light years away. A mere stone's throw,
for an astronomer. Supernova 1987A was
in a small galaxy called the large
Magellanic Cloud, a dwarf galaxy that orbits
around our much bigger Milky Way galaxy. NARRATOR: Being the first
supernova of that year, the exceptional and
nearby exploding star was simply labeled SN
1987A, but this time, dozens of seasoned astronomers
all over the planet were ready for action. Armed with sophisticated
tools and telescopes, they turned their minds
and machines to the heavens and closely scrutinized
Supernova 1987A. Knowing that an
exploding star is at its hottest in
the first few hours and is emitting lots of light
at ultraviolet wavelengths, the astral detectives
sprung into action. At the time of the explosion,
we saw the fastest moving stuff was coming toward us at a
tenth of the speed of light, so that was the actual
star blowing up. NARRATOR: Scientists had their
explosion, now they wanted to know the name of the victim. They dug through a catalog
that lists all known stars and their positions in the
sky when they struck paydirt. They found the
star that exploded. It was tagged SK-69202. They also determined that
it was a huge star, 20 times the mass of the sun. Examining the spectral
evidence, scientists could see strong lines of
hydrogen. SN 1987A bore the hallmarks of a type II
core collapse supernova, but to confirm their suspicions,
and prove the core collapse theories, experts
had to have one more piece of physical evidence. They needed neutrinos,
those ghostly particles that scientists predicted would
be unleashed during the blast. In the early 1980s, scientists
had built a handful of neutrino detectors around the world. They consisted of
tanks, deep underground, filled with tons of pure
water, but these detectors had yet to capture a
single supernova neutrino. ROBERT KIRSHNER: We've had this
story for a long time that most of the energy of a
supernova explosion-- a core collapse
supernova explosion-- goes into neutrinos, but we'd
never seen those neutrinos. NARRATOR: As luck would have
it, on February 23, 1987, they got their neutrinos. Two detectors, one beneath
the city of Kamioka, Japan, and the other under
Lake Erie in Ohio, captured a dozen of
the elusive particles. ROBERT KIRSHNER: There were
light detectors on this volume of water that were used to
see this little flash caused by the neutrino, interacting
with matter, inside the tank. NARRATOR: For the first time
ever, scientists on Earth saw tangible evidence of the
mysterious neutrino particles generated in the core
of an exploding star. Astronomers now knew the
theories first proposed in the 1930s were right. Supernova 1987A showed,
beyond a shadow of a doubt, that the massive iron core
of a very massive star collapsed and formed a neutron
star, because in that process, a lot of neutrinos
should be emitted. NARRATOR: With the deployment
of powerful space based telescopes,
astronomers today have built on the astonishing
discoveries made in the wake of Supernova 1987A. In 2006, 30-year-old
astronomer, Robert Quimby, would once again turn
conventional thinking on its head, and revolutionize
the way astronomers searched for supernovas. ROBERT QUIMBY: Most
supernova searches, they just want to find as
many supernovae as possible, so they'll look once every
two weeks every one week, just so you can find them, and so you
can look at as many fields as possible and get as many
supernovae as possible. So I decided to look at a
limited number of fields and look at them
as often as I can. NARRATOR: The enterprising
cosmic gumshoe programmed his robotic telescope
to systematically sweep the targeted field every night. Like an interstellar
search light, it honed in on and
methodically scanned the same small dark
corner of the cosmos, looking for supernova suspects. ROBERT QUIMBY: I had software
that can very quickly process the data and tell me if there's
anything there that wasn't there before, and
when it happens, if I think it could
be a supernova, I'll get a spectrum of it. And then that spectrum
of it will tell me exactly what it is. Is it a supernova, what
type is it, et cetera. NARRATOR: On September 18,
2006, Quimby got his big break. He found the brightest
supernova ever. This is my fourth supernova. I didn't think that
I should be so lucky. And others looked
at the spectra, and they started taking
their own measurements of the photometry--
how bright it was-- and they figured out
that, in fact, 2006gy was brighter than any
other published supernova. J CRAIG WHEELER: Very slowly. Took over two months, 70
days, to get the maximum light and then faded again. So it was a supernova unlike
anything we'd ever seen before, discovered by this fourth
year graduate student at the University of Texas. NARRATOR: Analysis
of the remnant indicated that the star,
before it exploded, was 100 times the size of the
sun, and with lots of hydrogen showing in its spectrum,
the brightest supernova ever recorded bore the stamp
of a type II event. Then Quimby topped himself. When he finally analyzed
a seemingly insignificant supernova he found
earlier, called SN 2005ap, he made a stunning discovery. ROBERT QUIMBY: It was something
like 100 billion times as bright as the sun, as compared
to-- for a type Ia supernova-- the peak may be only six billion
times as bright as the sun. NARRATOR: It was even
brighter than SN 2006gy. Like circumstantial evidence,
astonishing discoveries of new, ultra bright supernovas,
like 2005ap and others, have opened up a whole
new avenue of inquiry into exploding
stars and their M.O. The basic idea we have is
that, perhaps this is connected somehow to gamma ray bursts. NARRATOR: Gamma rays are
the most powerful form of light known in the universe. By analyzing supernovas,
investigators are getting closer
than ever to solving some of the most confounding
riddles in the cosmos. How one of them makes gamma
rays and the other makes an ordinary supernova is still
one of the big mysteries. Nobody really knows
how that works. NARRATOR: What astronomers
do know is that supernovas, and the gamma ray bursts
associated with them, are the brightest
beacons in the universe. On the galactic highway
that is the cosmos, supernovas serve as
celestial signposts, pointing astronomers to the
beginning and the end of time and space. NASA's powerful Swift
satellite, launched in 2004, was designed specifically
to sweep the sky and detect gamma ray
bursts in the universe. Like cosmic first
responders, astrophysicists at NASA's Goddard Space Flight
Center in Baltimore, Maryland are standing by 24/7, waiting
for a 911 call from Swift. STEFAN IMMLER: Basically, less
than two minutes after Swift discovered a gamma ray burst,
the satellite sends down emails directly to our Blackberries. NARRATOR: When a recent
supernova, recorded as SN 2006aj, appeared,
the Swift satellite caught the shocking
gamma rays it generated. STEFAN IMMLER: And that gamma
ray burst was very interesting because first of all, it was
a very long duration gamma ray burst. Usually, gamma ray bursts are
very short-lived phenomena, only fractions of a
second, a few seconds, but this gamma ray burst was
visible for like 35 minutes. We saw, three days later, a
supernova explosion going off at the exact same location. And this solved one of the
important mysteries of gamma ray bursts because we found
out at least parts of gamma ray bursts are due to massive
stars that are exploded. NARRATOR: Astronomers today
can see hundreds of supernovas and the deadly gamma ray
bursts they generate. On the cosmic
highway, scientists use these stellar headlights
to ascertain the bounds and breadth of the universe. CHRIS FRYER: You
can use supernova to probe the universe,
because if they're very dim, you know they were
very far away, and then you can study the
curvature of space, time, and all the cosmology that
you can study with them. ROBERT KIRSHNER: For example,
if you're on a desert highway and you're looking out at
the lights of the cars, you can tell which
are nearby and which are far away from the apparent
brightness of the lights. The ones that are
nearby look bright. The ones that are
far away look dim. J CRAIG WHEELER: Measuring
how far away things are, very systematically, will tell
you about the size, the age, the shape, the history,
the future of the universe. NARRATOR: It turns out that
type Ia supernovas are the best suited for this purpose. ROBERT KIRSHNER: One of
the things that's really interesting about the
type Ia supernova-- the ones that are
exploding white dwarfs-- is that there is
this fixed mass-- this Chandrasekhar mass-- that
sets how big the explosion is, how much stuff is involved,
and the consequence of that is that many of these have very
nearly the same brightness. If the explosion produces
the same amount of light, then we can measure
how much light we see, and figure out how far
away the supernova is. NARRATOR: This is known as
the standard candle principle. Type Ia supernovae are
like standard candles. They all have about the same
peak power, the same peak luminosity, so if you look at
them from different distances, they appear different
apparent brightnesses. They look dimmer if
they're farther away and brighter if they're more
nearby, so if we find type Ia supernovae in distant
galaxies and measure their apparent brightness and
compare that with the known power of a nearby
type Ia supernova, we can determine the distance
of that supernova and hence, of the galaxy in
which it's located. NARRATOR: The
trailblazing technique has also led astro-investigators
to some radical conclusions. Basically, you can use
the distances to supernovae to figure out what the universe
is doing, how old it is, and we now know that from
various lines of evidence, that it's a little less
than 14 billion years old, but in particular,
found out the universe was accelerating when we
thought it was decelerating in the grip of the
gravitational materials in it. That's just caused an
intellectual revolution, like throwing a ball
up towards the ceiling and rather than having it come
back down in your hand it goes faster and faster and
faster towards the ceiling. It's completely
counterintuitive. ROBERT QUIMBY: Basically,
all the texts-- astronomy textbooks
out there all said that the universe should be
decelerating, that its gravity should be slowing down
the expansion rates, but what this result showed is
that instead of slowing down, it was actually expanding
faster and faster and faster. NARRATOR: While the
examination of supernovas has helped scientists unravel
many monumental cosmic mysteries, experts believe
that if they continue to follow the clues left behind
when huge stars explode, they'll be able to answer the
biggest unanswered questions. Today, scientists know
that someday soon, we could each witness for ourselves
a marvelous and almighty force of a supernova. ROBERT KIRSHNER: Our galaxy
is 100,000 light years across, so that means there is light
from 1,000 supernovae that's on its way to us now. NARRATOR: It could even happen
in our very own Milky Way. STEFAN IMMLER: In our
galaxy, we are expected to have an average
about two supernova explosions per century. The problem is that the
last supernova that we saw in our galaxy was almost 400
years ago, so our galaxy is long overdue. NARRATOR: If it did happen
in our own galaxy, we, like the titans of
space and time-- Tycho, Kepler,
Chandrasekhar, and Zwicky-- would bear witness to
the most destructive and the most creative
force in the universe-- the supernova.
