How the Universe Works

Neutron stars.

Super heavy, super dense.

Extreme.

Gravitational, magnetic, hot.

Scary.

They destroy planets.

They can even destroy stars.

A cosmic conundrum.

They're very, very massive,

but they're also really, really small.

Tiny cosmic super powers

long overshadowed by black holes... Until now.

Neutron stars have been thrust very much

to the forefront of modern astrophysics.

The world's astronomers know that something is happening.

Something's up, it's new, and it's different.

Neutron stars are the most interesting

astrophysical object in the universe.

Now firmly in the limelight,

neutron stars, creators of our most precious elements

and life itself.

captions paid for by discovery communications

130 million light years form earth,

a galaxy called "NGC-4993."

Two dead stars trapped in a rapidly diminishing spiral.

It's like listening to the ringing of the cosmos itself.

The sound of that collision, if you will,

imprinted on the fabric of space and time itself.

Livingston, Louisiana, the advanced LiGO observatory.

Its mission... To detect gravitational waves

generated in space.

A gravitational wave is a distortion of space time

that's caused by, usually,

some kind of very traumatic gravitational event.

Events such as a supernova,

or the collision of black holes, or massive stars.

2015... LiGO makes history by detecting gravitational waves

for the first time,

100 years after Einstein's prediction.

It's the signature of the crash of black holes.

It's almost like listening to the sound

of a distant car crash that you didn't witness.

But you're so clever,

and the sound of this car crash is such a unique signature,

that you are able to use your computers to model

exactly the type of cars that must have collided together.

In 2017, LiGO picks up a different kind of signal.

The unfolding of the August 2017 event

was nothing short of extraordinary.

So, the signal comes in, and the signal is strange.

It has a long-lasting signal.

It's over 100 seconds.

Less than two seconds later, a gamma-ray telescope

detected a flash of gamma rays

from that same part of the sky.

And very quickly, the world's astronomers

know that something is happening.

Something's up, it's new, and it's different.

This combination of a long gravitational wave signal

and a blaze of gamma rays...

Acts as a beacon for astronomers.

When they saw this event,

they sent out a worldwide alert

to astronomers across the globe, saying,

"hey, we saw something interesting,

and it came from a particular patch of sky.

Then, all the chatter started

amongst the astronomical community,

and everyone starting pointing their telescopes

at this one part of the sky.

Within hours, thousands of astronomers

and physicists across the globe are frantically

collecting data on this mysterious event.

There is not just the gravitational waves,

there is not just the gamma rays.

There's a visible light, there's infrared light,

there's ultraviolet light.

And all these signals together tell us a story.

And this was the very first time

we've seen these two multiple messengers at once...

Gravitational waves and regular light.

So, that was a groundbreaking moment for astronomy.

Scientists realize

this isn't another black-hole collision.

This is something different.

When you see an explosion in the universe,

there aren't exactly a lot of candidates.

There's not a lot of things in the universe that blow up.

But the length of the signal is the smoking gun.

The collision of two black holes was quick.

This one was the longer, slower, death end-spiral

of two neutron stars.

Spiraling in, closer and closer, speeding up.

And then, when they finally collide,

when they finally touch, releasing a tremendous

amount of energy into the surrounding system.

The collision throws up huge clouds of matter,

which may have slowed down the light very slightly.

The light and gravitational waves

travel for 130 million years,

arriving at earth almost simultaneously.

It's the first time astronomers see neutron stars collide.

They call it a "kilonova."

And this spectacular cosmic event

doesn't just release energy.

The aftermath of this neutron-star collision,

this kilonova, created a tremendous amount of debris,

which blasted out into space.

And this may finally have provided us

the evidence of where some very special

heavy elements are created.

Through the destruction of a neutron star comes the seeds

for the essential ingredients of life itself.

We breathe oxygen molecules... O2.

Water is hydrogen and oxygen.

Most of our body is made up of carbon compounds

that include nitrogen, phosphorus.

One of the big questions in science

over the history of humanity has been,

"what are the origins of these elements?"

And it turns out that neutron stars play a critical role

in creating many of the heavy elements.

Most of the elements on earth are made in stars.

But how the heaviest elements are made

has been one of science's longest-running mysteries.

For a long time, we knew there was a problem

with making these heavier atoms...

Things like gold and platinum, all the way out towards uranium.

And really, the most energetic thing we had

in the universe was supernova explosions.

So, they had to be created somehow in supernovas.

But when scientists ran computer simulations,

virtual supernovas failed to forge these oversized atoms.

In 2016, astronomer Edo Berger explained

a potential solution to the mystery.

If you open any one of these books,

and flip to the page that tells you where gold came from,

it will tell you that gold came from supernova explosions.

But it was becoming clear that the textbooks were out of date.

To form heavy elements requires a lot of neutrons,

and so, another possible theory was that

the heaviest elements were produced in the mergers

of two neutron stars in a binary system.

But at the time, no one had actually seen

a neutron-star collision.

It was difficult to convince the community

that this was a potential channel

for the production of heavy elements.

The proof is to actually see this process

happening in the universe.

The 2017 kilonova

provides the perfect opportunity.

It generates thousands of hours of data.

Scientists notice a pattern...

Subtle changes in the color of the kilonova remnants.

In space, when you have an event that is very bright,

it emits a certain amount of light,

and it emits it at certain wavelengths...

What we think of as colors.

Different colors in a pyrotechnics display

indicate the use of different chemicals in fireworks.

In the same way, scientists can uncover the elements

in the kilonova by the colors in the explosion.

As the kilonova turns red, they realize it's the result

of newly-created heavy elements

starting to absorb blue light.

As we watched this remnant change...

The explosion change in color, expand and cool...

We could estimate what sort of elements were being produced.

The light from the debris shifts

from blue and Violet to red and infrared.

The color change provides clues

about the presence of certain heavy metals.

Well, this neutron-star collision, this kilonova,

produced brightness and a color spectrum

that are consistent with models of predictions

that produce gold and platinum.

This model is called "The R-process,"

short for "rapid neutron capture."

That is a bit of a complicated term

that describes how we make atoms heavier than iron.

You need a really neutron-rich environment.

And as you might imagine, a neutron-star collision

is a very neutron-rich environment.

If these models are correct...

And this blows me away...

This collision, this kilonova,

produced several dozen times the mass of the Earth

in just gold.

The 2017 kilonova not only reveals

the origin of key elements,

it sheds light on the neutron star's interior...

The strongest material in the universe

creating a magnetic field

a trillion times greater than that of earth.

Two neutron stars caught in a death spiral.

This massive kilonova explosion not only sheds light

on the creation of heavy elements,

such as gold and platinum,

it also provides scientists with a unique insight