How the Universe Works (2010) s07e04 Episode Script

How Black Holes Made Us

Black holes Long considered the bullies of the cosmos, but are they really so bad? Black holes aren't violent.
They are elegant.
They're incredibly powerful objects, but they're beautifully simple.
Simple but unpredictable.
Black holes rip planets to shreds, but they also give birth to stars.
Black holes are like the ultimate recycling-trash-bin combination.
They build galaxies and may have lit up the dark infant universe.
It's one of the biggest changes that happened.
Someone switched the lights on and transforms our universe.
They come in all sizes, from microscopic to ultramassive, controlling the fate of everything around them.
The story of the universe and how it's arranged is the story of black holes.
Black holes are the master architects of the universe, and without them, we would not exist.
Captions by vitac captions paid for by discovery communications Black holes We're riveted by their destructive power.
Black holes are dangerous.
Black holes are hazards.
Black holes are not friendly for their environments.
There's just no good end to anything that falls into a black hole.
Perhaps one of the most frightening objects in the universe.
But what exactly are these scary objects? Black holes are created when you get enough matter in a small region of space.
This happens when a massive star dies and collapses in on itself a supernova.
A black hole is the ultimate consequence of gravity.
It's an object that has so much mass crushed into such a small space that its escape velocity becomes greater than the speed of light.
They are a one-way street.
You go in.
Nothing escapes, not even light.
But do black holes really deserve their bad rap? In some ways, I think we set up black holes to be more villains than they actually are.
Black holes suffer a bit of a P.
R.
Problem.
I think they're a lot more menacing in science fiction and popular media than they really are.
There are trillions of galaxies in the known universe.
And most of them have a supermassive black hole at their center.
These monsters are millions of times the mass of our sun.
Their immense gravity can send stars flying.
They're instrumental in choreographing the dance of stars in their vicinity.
Supermassive black holes shoot out torrents of lethal radiation and violent cosmic winds and gobble up anything that comes close.
Now scientists are beginning to realize these cosmic giants may also have a creative side.
Most people think of black holes as being like giant vacuum cleaners in space, and basically everything falls into them, but that's not actually the case.
They're better thought of as the engines of cosmic change.
Although black holes are the end states of stars, they can actually influence the formation of stars, as well, in a bunch of different ways.
A galaxy's job is to make stars, but uncontrolled star growth isn't healthy.
Too many stars can drain a galaxy's gas supply.
Black holes are very important.
It appears that galaxy evolution is tied to black-hole evolution.
We don't know exactly how yet, but the marriage appears certain.
One idea is that supermassive black holes act as cosmic control mechanisms.
Black holes can act like a thermostat in your house.
If your house gets too hot, the thermostat will kick on the air conditioner, and if it gets too cold, it'll kick on the heater.
Black holes do the same things for galaxies.
Supermassive black holes regulate star formation by pulling gas in and shooting it back out into the galaxy.
When these black holes are consuming matter, they're drawing matter into themselves, but they're also spewing stuff out.
Basically, black holes eat like little babies Very sloppily, so a lot of what they eat comes flying back out again.
They eat stars.
They eat planets.
But most often, they eat giant clouds of gas.
The black hole drags gas and dust into an accretion disk around it.
This disk spins faster and faster.
Magnetic energy builds up.
With the accretion disk swirling around the black hole, there are also magnetic fields that are going on.
The material is moving so rapidly that the magnetic field sort of winds up, coils up, and forms a vortex like a tornado.
Astronomers call them jets.
These jets propagate outward like freight trains plowing through the galaxy over hundreds and thousands of light-years.
These are like death rays.
The jets disrupt the star-forming gas clouds, limiting excess star formation in the main body of the galaxy, but in the very outer reaches of the galaxy, they can spark star birth.
Things are more gentle out there.
You're not as close to the energetic heart, so stars, planets, and life can form out there partially because of the material that the black hole has moved out there.
So black holes can have outsize influence on the regions that they inhabit.
Right around them, they can prevent the formation of stars whereas, on very, very large scales, they can actually instigate the formation of stars.
2018 black holes hit the front page.
Scientists discovered black holes gobbling up gas so fast that they seem to be outgrowing their host galaxies.
It naturally makes the question come up How big can a black hole get? Now we have the answer.
They can reach size triple-XL, becoming ultramassive black holes.
Ultramassive black holes are so cool because it's just mind-boggling that black holes so large can exist.
Ultramassive black holes are very rare and typically have masses of more than 10 billion times the mass of the sun.
10 billion solar masses That's a 10 followed by nine zeros.
Ultramassive black holes are real beasts.
The black hole at the center of our galaxy is 4 million solar masses.
Imagine black holes that are 2,500 times bigger.
That's what we're talking about here.
An ultramassive black hole this big would be as wide as the solar system and weigh as much as all the stars in the milky way.
They're inside galaxies that aren't a whole lot bigger.
That really surprised the hell out of everybody.
And in 2018, scientists discover a 20-billion-solar-mass ultramassive black hole growing faster than any other black hole.
This ravenous behemoth devours the mass of our sun every two days.
These big black holes are really good at gobbling up other things.
They'll literally eat anything.
They're monsters of the universe.
This kind of voracious eating can have devastating consequences.
It blasts so much energy and turbulence into the galaxy that stars no longer form, and the bigger the black hole, the faster the galaxy dies.
The primary thing these ultramassive black holes do to galaxies is they shut down all star formation, and so in that sense, they kind of kill galaxies.
And so these things could even wipe out their host galaxies.
Ultramassive black holes are a problem for scientists, too.
They might be the fastest eaters, but that doesn't explain how they got so large.
With these ultramassive black holes, these black holes that are 10s of billions of times more massive than our sun, you can't just grow them from the slow accretion of gas over time.
There's just not enough gas, and there's just not enough time.
It gives us a new mystery to solve.
How do you make black holes that are just that big? There's not a clear answer so far as to how these ultramassive black holes were formed.
People wonder if there's some other mechanism by which you could make black holes.
A mechanism so violent it also throws supermassive black holes clean out of galaxies.
We now know that ultramassive black holes billions of times the mass of the sun exist, but we have no idea how they got so big.
We've detected lightweight stellar-mass black holes colliding.
They merged into a new larger black hole and generated huge amounts of energy.
But what about supermassive black holes? When galaxies merge, their central supermassive black holes will fall to the center of the newly formed galaxy.
Could these supermassive black holes caught up in galactic mergers combine to form an ultramassive black hole? In 2017, the Hubble space telescope spotted something strange in a distant galaxy called 3c186.
It detected an incredibly bright spot thousands of light-years from the galaxy center.
Scientists suspect it's a quasar.
A quasar is an incredibly bright, active galactic nucleus that's powered by a supermassive black hole.
We regularly spot black-hole-powered quasars, but always at the centers of galaxies, until now.
When we actually got this data from Hubble, we were absolutely stunned to discover that the quasar that we've long known to exist in the center of this galaxy wasn't actually at the center.
This black hole is offset from the center of the galaxy by about 35,000 light-years.
That's really weird.
What is an incredibly rare and bizarre event to find a quasar, a supermassive black hole, that is not at the center of the galaxy.
When scientists looked closer, they discovered that the quasar is hurtling through space away from the center of the galaxy.
Now, mind you, this is a black hole with the mass of about a billion times the sun, and it's screaming away at 4 million miles an hour.
This black hole, which was probably originally in the galaxy center, has somehow been shot out at high velocity by some incredibly violent event.
It's hard to imagine what kind of event would pump that much energy into such a huge object to shoot it away from the center of a galaxy.
Who kicked it out, how, and why? Scientists have an idea.
3c186 may be the remnant of a galaxy merger.
The merged galaxies' supermassive black holes circle each other, sending out blasts of energy in the form of gravitational waves.
Gravitational waves are all around us.
They're ripples in the fabric of space-time.
Every time mass moves, gravitational waves are produced, so if I wave my hand, I am making gravitational waves.
A hand produces imperceptible waves.
When objects as huge as supermassive black holes collide, the energy released as gravitational waves is phenomenal.
Scientists think these black holes might have been different sizes.
It's possible that if one of the black holes is really massive and the other one isn't quite as massive, that when they spiral around and merge, they send out gravitational waves in an asymmetric way.
This asymmetry has a catastrophic effect.
As the two black holes collide and merge, they shoot out a huge blast of gravitational waves, but only in one direction.
This blast of energy kicks the newly combined black hole out of the galactic center.
Think of a shotgun recoil, but supersized.
And there's so much energy in that emission that it acts like a rocket, and it actually pushes the merged black hole away.
It would have been one of the most energetic events ever witnessed.
They're so energetic, they are literally shaking the fabric of space.
We didn't witness the actual collision, but 3c186 could be evidence that supermassive black holes can collide and merge, building even larger black holes.
This would be a mechanism by which you would create, ultimately, an ultramassive black hole.
As for the ejected black hole, the gravitational recoil sent it on a one-way ride to oblivion.
So gravitational waves kicked this supermassive black hole and sent it flying through space.
In 20 million years, it's expected to exit its galaxy.
The ejected supermassive black hole may eventually hit another galaxy and merge with its supermassive black hole.
These largest of black holes seem to throw their weight around, bullying galaxies and other black holes.
Now researchers have discovered a vampire black hole that's draining the lifeblood of its neighbor.
Ultramassive black holes seem to destroy their galaxies, while supermassive black holes seem to regulate star formation.
But are all supermassive black holes forces for good? Hundreds of galaxies surround the milky way, large and small, but most of the largest galaxies are red.
This is not a good omen.
In space, red means danger.
If you have active ongoing star birth, then you have massive stars, and massive stars tend to be blue, but they don't live very long, and they blow up.
Once you stop star formation, after some amount of time, the galaxy turns red.
The only stars left alive are small, long-lived red stars called red dwarfs.
A red galaxy with only red dwarfs is a dying galaxy.
The Sloan digital sky survey found an entire population of these luminous red galaxies that were no longer forming stars that were dead.
One galaxy around 340 million light-years away stood out.
It was named after a Japanese anime character, Akira.
It's very red.
All the stars in it are red, and that means they're old, so we know that Akira has not had any active star formation in a long time.
The Akira galaxy doesn't form stars because it doesn't have the cool, calm gas needed to build them.
Something is heating the gas, making it turbulent.
One of the ways in which a black hole can drive the evolution of the galaxy in which it resides is by simply powering a wind.
These are winds that are literally driven by light.
When a black hole feeds, it drags gas into an accretion disk.
The disk heats up and gives off light radiation.
The radiation pressure from the accretion disk around this black hole couples to the ambient gas and dust and pushes it outwards at very high velocity.
These winds that are driven out by the black hole essentially warm up the gas in the galaxy, preventing further star formation.
However, whatever's fueling the black hole in Akira is a mystery.
Here's a weird thing There is an outflow, a wind coming out of this galaxy, and that means there's gas feeding that black hole in the center, and it's blowing it out.
Where is this gas coming from? Ah, it's stealing it.
It has a small companion galaxy, which is nicknamed Tetsuo, and that has gas in it.
Akira's supermassive black hole pulls gas from Tetsuo and drags it into the center of the galaxy.
The black hole is taking the gas from this companion galaxy, and that's what's falling around the black hole and creating this wind, so Akira is actually sort of a dead galaxy, but it's being rejuvenated by its companion, Tetsuo.
Like a cosmic vampire, Akira's supermassive black hole feeds off Tetsuo.
The black hole drags gas and dust into its accretion disk, which spins faster and faster.
When these particles are rubbing against each other, well, that generates friction.
Friction may not seem like that big of a deal.
I mean, you can rub your hands together on a cold day to get warm, but imagine rubbing your hands together at very nearly the speed of light.
How much friction is that gonna generate? It's gonna make a lot of heat.
Over a million degrees Fahrenheit So hot the accretion disk lights up.
Its temperature goes up, and he starts emitting light.
It becomes incredibly bright.
Even though there's a black hole in the core, its surroundings are intensely bright.
This heats up the surrounding gas, generating a hot wind, which extends thousands of light-years from the black hole.
And those winds carry with them a lot of energy, and that energy, if it couples to the gas in the galaxy, can blow that gas out.
They inject energy into nearby gas clouds and heat them up and prevent them from forming stars.
Stars don't form The galaxy dies.
These dying galaxies are called red geysers.
Scientists think around 10% of the red galaxies we see around us died this way heated up by this galactic warming.
We think that the source of some of this galactic warming is in the growth of supermassive black holes themselves because when you grow a supermassive black hole, you must liberate an enormous amount of energy.
You can't grow a black hole for free, and that energy gets dumped back into the ambient surroundings and keeps this halo of gas hot.
It prevents it from cooling and forming stars.
Sagittarius a-star, the supermassive black hole at the heart of our galaxy, the milky way, could turn into a red geyser.
If you were suddenly to dump an enormous amount of gas onto Sagittarius a-star, you could have what is effectively a red-geyser effect, a very powerful wind driven by all of this energy.
Star formation would stop, and our milky way would become another dying red galaxy.
Now new research suggests that Sagittarius a-star has already affected the inner region of our galaxy, not by killing stars, but by transforming planets from gas giants into super-earths.
At the center of our galaxy lies a supermassive black hole, Sagittarius a-star.
We think it's calm, dormant, safe.
Relative to other supermassive black holes in the universe, ours is relatively quiet.
It's been active in the past, and it could flare up in the future.
It could be active tomorrow, for all we know.
All you need to do to light it up is start dumping some gas on it, and there is almost certainly a giant cloud of gas that we don't currently know of on its way to the center of our galaxy, and it will find itself one day in the vicinity of our supermassive black hole, and it will start to light up like a Christmas tree.
In February of 2018, scientists at Harvard simulated Sagittarius a-star during a feeding frenzy to understand the impact of an active supermassive black hole on its local environment.
They found that, as Sagittarius a-star gobbled up gas and dust, it belched out bright flares of high-energy radiation, which radically affected the region around the black hole.
The environment near the center of a galaxy that has an actively feeding black hole is the worst place in the universe.
You've got this tremendous object which is heating up this gas to millions of degrees.
This is no place that you want to be.
The model revealed what would happen to any planets in the line of fire.
Think about being in the way of one of these black-hole burps.
All of a sudden, there's a tremendous wind of radiation that comes through your solar system.
That could actually strip away the outer layers of gas of a planet like Neptune.
The high-energy radiation from the supermassive black holes would hit the gas planets and heat up their atmospheres.
Maybe this would actually strip away the outer layers, leaving the solid material in the middle.
You could actually turn a gas-giant planet into a terrestrial solid planet all because you're close to a black hole.
This radiation strips away the gas, leaving the core, now a new rocky planet but a giant one A super-earth.
Normally, you think of rocky planets being about the size of the earth, but this would be a way of making so called super-earths.
Super-earths are one of the most common type of planets discovered in our galaxy.
It's possible that any super-earths close to Sagittarius a-star were created by these blasts of energy.
Away from our galactic center, a much smaller stellar-mass black hole is also radically transforming its environment.
January 2017 Researchers discover something strange in a cloud of gas called W44.
W44 is a supernova remnant.
It's the debris the expanding cloud from a star that blew up.
The explosive shock wave from a supernova pushes gas and dust out from the dead star, forming a huge nebula.
We see a lot of these.
I mean, they're catastrophic, amazing, incredible events, but as far as they go, this one appears to be pretty standard, except for one weird thing.
In the heart of it, there's something very mysterious going on.
There seems to be something shooting out of the very center of this explosion.
A thin protrusion trillions of miles long streams out from the cloud.
It's moving at over 60 miles a second against the flow of the galaxy.
It's very strange that it's moving backwards against the rotation of the milky way.
When you see a giant, giant, very massive cloud of gas that is moving counter to the rotation of the milky way, it needed to be like a bullet from a gun fired against a headwind in the opposite direction.
So what is that gun? You know, what fired that bullet of gas? The tip of the bullet cloud is expanding at 75 miles a second.
That's 270,000 miles an hour, over 150 times faster than a bullet.
What in the cosmos has the power to accelerate gas to such high speed? Could that actually be a black hole moving very, very quickly? Researchers think a stellar-mass black hole hidden in the bullet cloud is powering the movement of the gas.
Gravity from this black hole is incredibly strong, and so it will latch onto this gas cloud as it passes through it, and it can completely disrupt the motions of this cloud.
This is a very interesting stream of gas that's somehow connected to a black hole, and we don't know whether it's there because the black hole is moving through the gas, and it's creating a wake, or whether somehow this black hole is spitting out a stream of material in some way.
The black hole could be dragging gas into an accretion disk around it.
The gas heats up and expands, giving the initial supernova explosion, W44, an extra kick, driving this bullet-like cloud out in front of it.
Or the black hole could be racing away from the nebula, dragging the gas behind it like a wake.
Ultramassive, supermassive, and stellar-mass black holes all play a role in shaping the cosmos, but there may be another type of black hole even more dangerous than the rest A microscopic black hole.
We have so far detected triple-XL ultramassive black holes, large supermassive black holes, medium-sized intermediate black holes, and small stellar-mass black holes.
Now scientists have another to add to the roster Microscopic black holes.
We know there are supermassive black holes at the centers of galaxies.
We know there are star-sized black holes from the deaths of stars.
That's what we know for sure.
It's possible there are much smaller black holes, microscopically small black holes.
Microscopic black holes are virtually invisible to the naked eye, but magnified, they look like regular stellar-mass black holes the definition of a black hole is an object that has so much mass crushed into such a small space that its escape velocity becomes greater than the speed of light, so it could be something the size of a star, the size of a galaxy.
It could also be the mass of a planet.
If you could crush the earth down far enough, it could become a black hole.
The density of a black hole is something that the human brain really doesn't wrap itself around very easily.
When you think about something the size of the earth, how small would the earth have to be to be a black hole? And the answer is something on the order of a marble.
So think about taking the entire earth and compressing it down to the size of just a marble.
So where do these strange little black holes come from? These very small black holes can only be formed in the exotic conditions of the incredibly early universe.
Our universe might get flooded with these small black holes that simply persist to the present day.
It's the only time in the history of the universe where you could take a small amount of matter and crush it down so tightly that it could become a black hole.
Those conditions don't exist anymore, so if these things exist, they would be primordial.
They would be as old as the universe itself.
These primordial black holes may be ancient, but they still pack a punch.
When it comes to black holes, the smaller black holes are actually more dangerous because their mass is concentrated into such a small volume.
In fact, a tiny black hole would be lethal.
If it were to pass in front of me, very quickly, almost instantly, I would be ripped apart head to toe, stretched into a long, thin stream of fundamental particles that would then wind their way into the black hole.
It would actively feast on me in a matter of seconds.
But if Paul or an interstellar robotic probe visited a supermassive black hole or even an ultramassive black hole, they wouldn't be immediately ripped to shreds.
One of the most fun questions about black holes is, how close could you get to a black hole before the gravity would rip you apart? And that actually depends on the volume of the black hole.
If the black hole is very large, you could get very, very close.
The more massive they are, the slightly softer they are in how they tear things apart, so a supermassive black hole, actually You can cross within the event horizon and not really notice it.
You're never gonna get back out, but you won't necessarily be stretched to your death while you cross inside.
So a probe could visit a supermassive black hole and not be destroyed until it crossed the event horizon and traveled deep inside.
Then it would be torn to pieces.
But microscopic black holes are currently just a theory.
Microscopic black holes have been the focus for some researchers for many years, but currently there's no evidence to support their existence.
Microscopic primordial black holes may or may not have been around since the big bang.
Now scientists have discovered supermassive black holes from the very early universe.
They're shedding light on one of the most mysterious eras, the cosmic dark ages.
Black holes don't just shape the universe now.
They've been shaping it from almost the dawn of time.
Scientists think black holes may have triggered one of the universe's greatest transformations Turning from dark and foggy to transparent and light.
At the beginning of time, the universe was a tiny ball of super-hot energy The big bang.
Shortly after our big bang, our universe was shining bright because it was full of hot, glowing gas.
Then it cooled off and entered the so-called dark ages until eventually something lit it up again.
It's one of the biggest changes that happened in our universe.
Someone switched the lights on and transformed the universe.
During the dark ages, the universe was blanketed in a thick fog.
Then something lit it up in a process called reionization.
We still don't really know for sure whether reionization was mainly caused by young stars or whether it was mainly black holes that ate stuff and spewed out a bunch of radiation.
Then in December of 2017, researchers in Chile scan a region of space so far away it takes light 13 billion years to reach us.
They spot an object from just 690 million years after the big bang when the universe was only 5% of its current age.
It's called quasar J1342+0928.
The thing that's so amazing about this farthest quasar is we may actually have seen the boundary of these dark ages.
This particular supermassive black hole/quasar tells us something about the formation of the early universe.
It's thought that quasars helped drag the universe out of the dark ages.
They gobbled up so much hydrogen gas and belched out jets of energy and cleared up the fog.
Those jets could have actually put so much energy into the universe that it made it clear again.
We may actually be seeing the moment where something punches through this boundary of the dark ages.
Pockets of reionization opened up throughout the early universe.
They came in different sizes, depending on what created them.
While our universe was being reionized, there was kind of, like, all these holes that kept growing.
If the reionization was made by a large number of little stars, you would have many, many small holes, much like a sponge, whereas if you had a small number of monster black holes doing it, you'd have a lot of big holes, like in Swiss cheese.
At present, we can't measure the ionized pockets to determine if it was stars or black holes that lit up the early universe.
Perhaps it was both Black holes and stars working together.
The more we investigate black holes, the more we learn about their role as architects of the universe.
I think scientists of my generation are very lucky to be able to be at the beginning of this revolution.
We used to portray black holes as monsters.
Now we know that, without them, the universe would be a very different place.
They made life possible.
Without black holes, we probably wouldn't exist.
We're discovering just how black holes shaped the universe, but the more we learn, the more questions they pose.
I've spent my career studying black holes, and I want to spend the rest of my career studying black holes, and I guarantee you that, at the end of my career, on the day I retire, I will probably have more questions about black holes than I do today.
This is an incredibly exciting time for black-hole science.
Who knows what we're gonna discover?