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 superpowers 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, creator of our most precious elements and life itself, 130.

Million light years from 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.

Gravitational wave is a distortion of space-time that's caused by usually some

kind of very traumatic gravitational event.

Events such as supernovas, or the collision of black holes, were 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.

Then, 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's

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's not just the gravitational waves, there's not just the gamma rays,

there's the 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 in 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 the 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, you know, 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, 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 and 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 stars' 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 into one of the most mysterious objects in the universe.

Trying to imagine what a neutron star is really like really challenges our imagination.

It also challenges our theoretical physics.

We have to go to our computer models, our mathematics, to have some estimate of what this might be like.

Now, scientists don't have to rely on their imaginations.

They can use hard data from the kilonova to work out what makes neutron stars tick.

There's so much information we got from observing

that one single event, that one colliding neutron star pair.

Now, for the first time, we have an accurate estimate of the mass of the neutron star and the diameter.

We can finally begin to piece together how neutron stars really work.

They calculate the diameter is just 12.4 miles.

One mile less than the length of Manhattan.

Nailing down any physical characteristic is really important.

And if there's going to be one, the radius is a big one because from

there, if you know the mass, you can get the density.

And if you know the overall density, you can start to figure out what the layering inside of a neutron star is like.

For physicists, the interior of a neutron star is the same.

The interior of a neutron star is one of the most intriguing places in the universe.

You have to realize that the conditions inside a neutron star are very,

very different than the conditions that exist here on Earth.

We're talking about material that's so dense that even the nuclei of atoms can't hold together.

With a neutron star, you're taking something that weighs more than the sun

and compressing it down to be smaller than a city.

It's so dense that if you tried to put it on the ground, it would fall right through the Earth.

High density means high gravity.

Gravity 200 billion times greater than on Earth.

Imagine climbing up on a table on the surface of a neutron star and jumping off.

You're going to just get flattened instantly and just spread out on that surface.

So don't even think about trying to do push-ups.

Added to the intense gravity are hugely powerful magnetic fields, awesome X-ray

radiation, electric fields 30 million times more powerful than lightning bolts and blizzards of high-energy particles.

For a space traveler, this is not a good neighborhood.

If you were to find yourself in the vicinity of a neutron star, it's going to be bad news.

First, you would be torn apart by the incredibly strong magnetic fields.

Then, the X-ray radiation would blast you to a crisp.

And as it pulled you closer, its intense gravity would stretch out your atoms and molecules into a long, thin stream.

You would build your speed faster and faster, and you would finally impact the

surface, splatter across it, and that process would release as much energy as a nuclear bomb.

If I had the choice between falling into a neutron star versus a black hole,

I think I'd pick the black hole, because I don't really feel like being

torn apart by a magnetic field and blasted with x-rays.

On a cosmic scale, neutron stars may be pint-sized, but they sure pack a serious punch.

The secret to all this pent-up power is what's going on below the surface.

Armed with the new kilonovid data, we can now take a virtual journey into the heart of a neutron star.

First, we must pass through its atmosphere.

Now, it's not like the Earth's atmosphere, which goes up like a hundred miles.

On a neutron star, the atmosphere is about this deep, and it's extremely dense compared to the air around us.

Below the compressed atmosphere is a crust of ionized iron, a

mixture of crystal iron nuclei, and free-flowing iron electrons.

Now, the gravity is so strong that it's almost perfectly smooth.

The biggest mountains on the surface are going to be less than a quarter of an inch high.

A quarter inch mountain range may sound odd.

But things get even stranger as we go below the surface.

This is home to the strongest material in the universe.

It's so weird, scientists liken it to nuclear pasta.

As we dive beneath the crust of a neutron star, the neutrons themselves start to