How the Universe Works

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.

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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