How the Universe Works (2010) s07e01 Episode Script

Nightmares of Neutron Stars

Neutron stars.
Super heavy, super dense.
Gravitational, magnetic, hot.
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 by vitac 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 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 a 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, 1 mile less than the length of Manhattan.
Nailing down any physical characteristic is really important.
And if there's gonna 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 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 gonna 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.
This isn't a good neighborhood for a space traveler.
If you were to find yourself in the vicinity of a neutron star, it's gonna 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 then, 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.
'Cause 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 kilonova 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 100 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's so strong that it's almost perfectly smooth.
The biggest mountains on the surface are gonna 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 glue themselves together into exotic shapes.
First, they form clumps that look something like gnocchi, then, deeper, the gnocchi glue themselves together to form long strands that look like spaghetti.
Even deeper, the spaghetti fuse together to form sheets of lasagna.
And then, finally, the lasagna fuse together to become a uniform mass, but with holes in it.
So, it looks like penne.
This is pasta, nuclear style, simmering at a temperature of over one million degrees Fahrenheit.
Extreme gravity bends, squeezes, stretches, and buckles neutrons, creating a material 100,000 billion times denser than iron.
But the journey gets even more extreme.
Even deeper is more mysterious and harder to understand.
The core of a neutron star Which is very far away from these layers, which we call the "nuclear pasta" Is perhaps the most exotic form of matter.
So exotic it might be the last bastion of matter before complete gravitational collapse into a black hole.
Data from NASA's Chandra observatory suggests the core is made up of a super fluid A bizarre friction-free state of matter.
Similar super fluids produced in the lab exhibit strange properties, such as the ability to flow upwards and escape airtight containers.
Although our knowledge of the star's interior is still hazy, there's not mystery about its dazzling birth.
Forged into life during the most spectacular event the universe has to offer The explosive death of a massive star.
Neutron stars Manhattan-sized, but with a mass twice that of our sun.
So dense a teaspoon of their matter weighs a billion tons.
Mind-blowing objects that arrive with a bang.
Neutron stars spark into life amid the death of their parent star.
They're the ultimate story of resurrection, or of life from death.
It's all part of a cosmic cycle.
Stars are born from giant clouds of very cold gas.
Those clouds collapse under their own gravity, and the density of the core at the center of the collapse starts to increase.
A star is a huge nuclear fusion reactor.
The force of its gravity is so powerful that it fuses atoms together to make progressively heavier and heavier elements.
The star fuses hydrogen into helium.
Once it exhausts its hydrogen, then, if it's massive enough, it can start fusing helium at its core.
Fusion continues, forming carbon, oxygen, nitrogen, all the way up to iron.
Once a star has iron in the core, it's almost like you've poisoned it, because this extinguishes the nuclear reactions in the core of the star.
You fuse something into iron, and you get no energy.
All of a sudden, there's nothing to support the crush of gravity.
No radiation pressure pushing out means no pressure keeping the outer regions from falling in, and that's what they do.
As the star collapses in its death throes, its core becomes the wildest, craziest, and freakiest pressure cooker in the whole universe.
The ingredients are all in place.
It's time to start cooking up a neutron star.
If we were to scale up an atomic nucleus to be the size of a baseball, in a normal atom, the nearest electron would be way over in those trees, but in the extreme conditions that lead to the formation of a neutron star, those electrons can be pushed closer to the nucleus.
They can come zipping in from any direction.
And if the temperatures and pressures are high enough, they can even strike the nucleus and enter it, and they can hit a proton.
And when they do, they become converted into more neutrons.
So, in the formation of one of these objects, the protons and electrons disappear, and you're left with almost entirely pure neutrons, with nothing to stop them from cramming together and filling up this entire baseball with neutrons leading to incredibly high densities.
With the sea of electrons now absorbed in the atomic nuclei, the matter in the stars can now press together a lot tighter.
It's like squeezing 300 million tons of mass into a single sugar cube.
As the star collapses, enormous amounts of gas fall towards the core.
The core is small in size, but huge in mass.
Billions of tons of gas bounce off of it, then erupt into the biggest fireworks display in the cosmos A supernova.
It's massive.
It's bright.
It's imposing.
Supernova are among the most dramatic events to happen in the universe.
A single star dying One star dying Can outshine an entire galaxy.
And arising out of this cataclysm, a new and very strange cosmic entity.
When the smoke finally clears from the supernova explosion, you're left with one of the most real, fascinating, unbelievable monsters of the entire universe.
Humans have been witnessing supernovas for thousands of years, but we're only now just starting to understand what we've truly been witnessing The births of neutron stars.
But while supernovas are big and bright, neutron stars are small, and many don't even give off light.
So, how many neutron stars are out there? We know of about 2,000 neutron stars in our galaxy, but there probably are many, many, more.
I'm talking about tens of millions in the milky way alone, and certainly billions throughout the universe.
Neutron stars may be small, but some give themselves away, shooting beams across the universe Unmistakable, pulsing strobes of a cosmic lighthouse.
Our knowledge of neutron stars is expanding fast.
But we didn't even know they existed until a lucky discovery just over 50 years ago.
Cambridge, the Mullard radio observatory, Jocelyn bell, grad student, operating the new radio telescope.
Scanning the sky, doing all sorts of cool astronomy stuff, and sees what she calls "a bit of scruff" in the data.
This scruff is a short but constantly repeating burst of radiation originating 1,000 light years from earth.
It's so stable and regular that bell is convinced there's a fault with her telescope.
She returns to that spot, and finds a repeating, regular signal A single point in the sky that is flashing at us continually, saying "Hi.
" Blip, blip, blip.
Boom, boom, boom.
Pulse, pulse, pulse.
Nothing that we know of in the universe, has such a steady, perfectly-spaced in time, pulse.
It seemed so perfect that it must have been artificial.
It looks like someone is making that, but it turns out, it's not a person, but a thing.
What she discovered was called a "pulsar.
" A pulsar is a type of rapidly spinning neutron star.
Neutron stars had been theorized in the 1930s, but were thought to be too faint to be detected.
Neutron stars were hypothesized to exist, but not really taken seriously.
It was just a, "oh, that's cute.
Maybe they're out there, but probably not.
" The signal bell detected seemed like something from science fiction.
No one had ever seen this in astronomy before, and some people even speculated that it was an alien signal.
She even called them "LGM objects" "little green men.
" But then, bell found a second signal.
Little green men went back to being fiction, and pulsars became science fact.
The discovery of pulsars came out of the blue.
Nobody was expecting this.
So, it was an amazing breakthrough Really important.
Pulsars pulse because they are born to spin.
They burst into life as their parent star collapses during a supernova.
Any object at all that is undergoing any sort of compression event, if it has any initial angular momentum at all, it will eventually end up spinning.
As the star shrinks, it spins faster and faster.
They spin so quickly because the Earth-sized core of a massive star collapsed to something as small as a city.
So, because the size of the object became so much smaller, the rate of spin had to increase by a tremendous amount.
Neutron stars can spin really, really, fast.
Their surface is moving so fast.
It's moving at about 20% the speed of light, in some cases.
So, if you were to get on the neutron star ride No pregnant women, no bad backs, no heart issues, keep your arms and legs inside the ride at all times, because they are about to be obliterated.
And as they spin, they generate flashing beams of energy.
This beam is like a lighthouse beam.
You see these periodic flashes many times per second.
So, every time you see it Beam, beam, beam.
These beams are the pulsar's calling card.
They're generated by the elemental chaos raging inside a neutron star.
Although the star is predominantly a ball of neutrons, the crust is sprinkled with protons and electrons, spinning hundreds of times a second, generating an incredible magnetic field.
And with this strong magnetic field, you can create strong electric fields.
And the electric and magnetic fields can work off of each other and become radiation.
These neutron stars send jets Beams of radiation Out of their spinning poles.
And if their spinning pole is misaligned, if they're a little bit tilted, this beam will make circles, across the universe.
And if we're in the path of one of these circles, we'll see a flash A flash.
Just like if you're on a ship, and you observe a distant lighthouse in a foggy night, you can see pulsars across the vast expanse of space because they are immensely powerful beams of light.
But sometimes, pulsars get an extra push that accelerates the spin even more.
The way you make it spin even faster is by subsequently dumping more material onto it.
That's called "accretion," and you end up spinning it up even faster than it was already spinning.
Like stellar vampires, pulsars are ready to suck the life out of any objects that stray too close.
Gravity is bringing that material in, which means that any spin it has is accelerated.
It spins faster and faster.
These millisecond pulsars spin at around 700 revolutions per second.
They are the ultimate kitchen blender They will chop, they will slice, they will even julienne fry.
So, what stops neutron stars from simply tearing themselves apart? Neutron stars are incredibly exotic objects with immense, immense forces that bind them together, and so, they can be held rigid even against these incredibly fast rotation speeds.
They have incredibly strong gravity, and this is what allows them to hold together even though they're spinning around so fast.
The speed of the spin is hard to imagine.
On earth, a day is 24 hours long.
On a neutron star, it's a 700th of a second long.
Super-speeding pulsars are not the only weird stars that scientists are coming to grips with.
There is one other type of neutron star, that has the most powerful magnetic field in the universe.
This magnetic monster is called a "magnetar.
" Astronomers monitoring pulsing neutron stars have noticed something very odd.
On very rare occasions, they can suddenly speed up.
That's amazing.
I mean, you've got this incredibly dense object, and suddenly, it's spinning faster.
It happens Instantly.
They'll suddenly change frequency.
It would take an amazing amount of power to do that.
What's doing it? These sudden changes in speed are called "glitches.
" One leading idea for what causes these glitches is that the core material latches onto the crust, and this affects the way it can spin around.
Excess material beneath the crust cracks it open, causing the glitch.
This process releases a tremendous amount of radiation, a blast of x-rays, causes the face of the neutron star to rearrange itself, and for the rotation speed to change.
But there's another possible explanation.
Glitches could also be caused by starquakes.
Sometimes, the crust gets ruptured.
Anything that basically changes the geometry of the pulsar can change the rate at which it spins.
So, what could be powerful enough to cause these starquakes? It's hard to believe that there's any force in the universe that could deform the matter inside of a neutron star, which is undergoing tremendous gravity.
But when it comes to a neutron star, if there's one thing that can do it, it's magnetism.
Extreme magnetic fields within the star can get so twisted they can rip the crust wide open.
And so, the surface can restructure itself, and constantly reshape.
And just a tiny reconfiguration of the surface of a neutron star, on the order of a few millimeters, would be associated with an enormous release of energy.
The neutron star's immense gravity smooths over the star's surface almost instantaneously.
It's like the glitch never happened.
When it comes to neutron stars, there is no end to magnetic mayhem.
Meet the reigning champion in the universal "strongest magnetic field" competition The magnetar.
1 in 10 neutron stars formed during a supernova becomes a magnetar.
The thing about magnetars, as is implied in their name The magnetic field on them is so strong, that even somebody who is used to using big numbers Like, say, an astronomer Is still kind of in awe of these things.
Magnetars have a magnetic field one thousand trillion times stronger than that of earth's.
This amount of magnetism will seriously mess up anything that comes close.
Any normal object that we are familiar with, if it got close to a magnetar, it would just be shredded.
Any charged particle with any movement at all, would just be torn from its atom.
It would be just an insane situation.
Magnetars burn brightly, but their lives are brief.
We think magnetars These intensely magnetized neutron stars Can only be really short-lived.
Their magnetic field is so powerful that it should decay over very rapid time scales, only on the order of a few ten thousand years.
It seems their very strength leads to their downfall.
That magnetic field is so strong that it's picking up material around it, and accelerating it.
Well, that acts like a drag, slowing it down.
So, over time, the spin of the neutron star slows, and the magnetic field dies away.
During their lives, magnetars operate very differently than pulsars.
They don't have beams.
Their magnetic fields shoot out gigantic bursts of high-intensity radiation.
But recently, astronomers have spotted one neutron star that's hard to classify.
It behaves like a stellar Jekyll and Hyde.
So, this particular neutron star is a really weird example.
It behaves both like a radio pulsar, and also a highly-magnetized magnetar.
It has the extreme magnetic fields, it can have these magnetic outbursts, but it also has this strong jet of radiation coming out of its poles.
It's almost like it has a split personality.
When first sighted in 2000, this star was emitting radio waves Typical pulsar behavior.
Then, 16 years later, it stopped pulsing, and suddenly started sending out massive X-ray bursts The actions of a magnetar.
Scientists were baffled.
We don't know if this thing is a pulsar turning into a magnetar, or a magnetar turning into a pulsar.
One theory is that these X-ray bursts happened because the star's magnetic field suddenly twisted.
The stress became so great, the star cracked wide open, releasing the X-rays from the fractured crust.
A neutron star is the densest material that we know of in the universe.
And yet, we've seen things that actually make it shift and pull apart.
This neutron star is actually ripping itself apart under the forces of the magnetic field.
If this is the case, placid neutron stars turn into raging magnetars, growing old disgracefully.
When you think about the life cycle of a human being, we seem to kind of slow down over age, become a little more calmer.
Neutron stars do the opposite.
They can be spinning faster than they were when they were formed, and the magnetic field can get stronger over time.
It's sort of a reverse aging process.
But these strange changes are extremely rare.
Most pulsars are as regular as clockwork.
Pulsars are normally incredibly regular.
You can literally set your watch to the timing of their pulse.
And it's this stability that we may use in our future exploration of the universe.
You know, if you're a starship captain, what you need is a galactic GPS system.
Well it turns out, neutron stars may be the answer.
Astronomers often compare the steady flash of spinning neutron stars, called "pulsars," to cosmic lighthouses.
These flashes are not only remarkably reliable, each pulsar has its very own distinct flickering beam.
Each one has a slightly different frequency.
Each one has a slightly different rate.
Anyone in the galaxy, no matter where you are, can all agree on the positions of these pulsars.
The unique signature of pulsars opens up intriguing possibilities for the future of space travel.
We would basically be using pulsars to be able to sort of triangulate where we're at.
And because those pulses are so precise, we can use that in a similar way that we use GPS satellites that are stationed above the Earth.
Using pulsars as navigational aids is not a new idea.
It was recognized by the NASA voyager mission in the 1970's.
Affixed to the surface of those spacecraft is a golden record.
And on the plate that covers that record is a pulsar map, which in principle could tell an advanced alien civilization how to find earth, because it uses the position of earth relative to 14 known pulsars, as, effectively, a way to triangulate the position of our planet relative to all of these pulsars.
Aliens haven't made contact, but NASA still uses pulsar maps.
NASA recently launched a satellite called "nicer sextant" that exists on the international space station, that is being used to test these types of theories.
They've used pulsars to figure out the location of an object orbiting around the Earth at 17,000 miles an hour, and they were able to pinpoint its location to within three miles.
That's pretty incredible.
By recognizing their position relative to known pulsars, future space missions could navigate the universe.
Neutron stars are gonna take us on this incredible journey Something as necessary as knowing where you are in the galaxy.
We could be many hundreds of light years away, but neutron stars can actually show us where in the milky way we are.
I read a lot of science fiction, and I love the idea of being able to go from star to star, planet to planet.
It's kind of weird to think that, in the future, as a galactic coordinate grid, we might wind up using these gigantic atomic nuclei, these rapidly spinning, bizarrely-constructed, magnetic, fiercely gravitational objects like neutron stars.
Neutron stars have come a long way since being mistaken for little green men.
Once overlooked as astronomical oddities, they've now taken center stage as genuine stellar superstars.
What's really exciting about neutron stars is that, we're at the beginning of studying them.
We're not at the conclusion.
We've learned a lot, but there's a lot more to be learned.
From the humble neutron comes the most powerful, the most rapid, the strongest magnetic field, the most exotic objects in the cosmos.
I love the idea of a Phoenix, something actually rising from its own ashes.
You think something dies, and that's the end of the story, but something even more beautiful, even more fascinating, comes afterwards.
I told you at the beginning, and you didn't believe me, but now, I hope you do Neutron stars are the most fascinating astrophysical objects in the universe.