How the Universe Works

Supermassive black holes,

the engines that power our universe.

Supermassive black holes are one of the major players

in the evolution of galaxies.

With no supermassive black holes,

you have no Milky Way Galaxy, no sun, no Earth, no you.

They're the driving force at the heart

of nearly every galaxy in the cosmos.

They are the most monstrous and scary and bizarre aspects of

our world, which just fascinates me.

Now, a new mystery has emerged

about the oldest supermassive black holes.

We see supermassive black holes in

the very early universe.

And we don't understand how they grew so large so quickly.

We have clues about their formation.

But can we solve the mystery

of this supermassive growth spurt?

2017.

Scientists gazing deep into

the distant universe discover something

completely unexpected...

A vast supermassive black hole dating

from the earliest days of the universe.

This was 690 million years after the Big Bang.

The universe was about 5 or 6% of the age that it is now.

Finding a supermassive black hole in the early universe is

like finding an NFL defensive lineman playing

in peewee football.

Something that big shouldn't exist that young.

The supermassive black hole wasn't just super early.

It was super big, 800 million times the mass of our sun.

In just a few hundred million years,

the universe has somehow been able to collapse nearly

a billion suns' worth of

material into a giant black hole.

And we honestly just don't know how that's possible.

We measure black holes by the mass of our sun...

Solar masses.

Regular, or stellar, black holes are a few

to a hundred solar masses.

Supermassive black holes weigh from 100,000 to billions

of suns.

And scientists have now found over 100 of these monsters in

the early universe.

We were shocked to find even one of them existing so early

after the Big Bang.

It was kind of freakish, to be honest,

but then to find that there's whole populations

of these things that exist and are well

in place at the earliest times

that we can look at was truly shocking.

We believe supermassive black holes might

help explain the evolution and the destiny of the universe.

Astronomers are striving to understand them.

Understanding the origin

of supermassive black holes and how

they could form so early in the universe's history is

something that would change all of astronomy and astrophysics.

How do you get something that massive to

form in such a short amount of time?

It's a big question... To begin to answer it,

we have to start small, by asking

how regular stellar black holes form.

Black holes form through the collapse of stars.

Everyone knows that... You have a big enough star,

and it'll collapse to form a black hole.

A really massive star dies in a violent supernova explosion,

and if they have sufficient mass, what's left over

collapses into a black hole.

The bigger the star was,

the bigger the black hole is to start with.

Were the stars of the early universe

big enough to collapse into supermassive black holes?

The very early universe was much different than

the university you see around us today.

It was filled entirely with hydrogen and helium gas.

This gas amassed into giant clouds,

which collapsed under their own gravity.

Nuclear fusion ignited the dense cores,

and the first stars were born.

Now, we think that these earliest clouds of gas probably

made bigger stars than clouds

of gas do in our local or today's universe.

It was possible to get huge, giant stars that we call

Population III stars that were just utterly massive.

Population III stars are the oldest category of star.

Like stellar dinosaurs,

they dominated the universe a long time ago.

Now, they're extinct.

They'd be weird stars.

They would be incredibly bright in the ultraviolet

and have very unique signatures

that are very different from stars today,

but precisely because they're so big and so bright,

they would be very short-lived.

These first stars lived fast and died young...

...exploding in supernovas, leaving behind black holes.

But were they supermassive black holes?

When a star blows up, when it goes supernova,

most of the mass is ejected away.

It just goes flying out,

leaving a dense neutron star or perhaps a black hole.

But it won't have much mass, because

most of that mass was blown away.

Even though Population III stars in the infant universe

were very large,

they weren't big enough to leave a supermassive black hole

behind when they exploded.

Perhaps if we can skip the supernova step,

that might be one pathway to understanding how supermassive

black holes formed.

Could a dying star's entire mass collapse

into a black hole?

A clue may lie in a galaxy nicknamed the Fireworks Galaxy.

The Fireworks Galaxy has that

flashy name, because when you look at it,

there are all these supernova explosions going off

and, um, making quite a show.

Recently, astronomers were keeping an eye on

one extremely bright star in the Fireworks Galaxy.

This star is exactly the kind

that we know explodes as a supernova.

Astronomers expected it to explode,

but then it did something even weirder.

Astronomy is so wonderful, because sometimes you see things

right in front of your eyes that you can't explain.

We saw an entire star just disappear.

In 2007, the star looked like this.

By 2015, it had completely vanished.

There was no flare

or debris from a supernova explosion.

So what the heck is going on?

It turns out that not every massive star blows up

with all the fireworks of a normal supernova.

You can get what's called a failed supernova.

A supernova fails when the shockwave

generated inside a collapsing star can't escape.

In some cases, when the star is very massive,

the shockwave never has a chance to get all the way out of

the star by the time the star itself

collapses into a black hole,

then you have a failed supernova.

The Fireworks Galaxy star may have been massive enough to

smother its own explosion before collapsing

to form a black hole.

Everything collapses into the black hole.

You can actually have a black hole

with all the mass of the original star.

Back in the early universe,

could the enormous Population III stars have died

as failed supernovas,

leaving behind supermassive black holes?

These Population III stars don't seem to me to be

a good contender for the precursor to supermassive

black holes... they just would not have enough mass.

Even the most massive stars are only

a couple of hundred times more massive than our sun,

whereas a supermassive black hole is millions or billions of

times the mass of our sun.

Early supermassive black holes

can't have formed from collapsing stars.

Even giant stars aren't massive enough.

So is there some other path to being supermassive?

Were stellar black holes

cosmic bodybuilders on a fast-track bulking program?

How did supermassive black holes in

the early universe get so large so quickly?

We ruled out the idea that they were

created from the collapse of very large stars.

Maybe they started out as smaller,

stellar mass black holes and grew to be supermassive

by eating.

Black holes are not fussy eaters.

They'll consume anything that comes in their path.

You know, gas, planets, stars.

It doesn't matter, and everything that they

consume adds mass to the black hole.

We've spotted a stellar mass black hole

currently eating in our Milky Way Galaxy.

15 times the mass of the sun,

Cygnus X-1 is steadily feeding

off the material that swirls around it.

Some black holes are fed through things called

accretion disks.

It's kind of like the rings around Saturn.

There's this thick or thin disk of

material around the black hole that feeds it.

Cygnus X-1's secretion disc gets

constant refills from a nearby source,

a vast star 20 times the mass

of the sun called a blue supergiant.

The black hole has been feeding on gas

from this star for about five million years.

So if you ask, how do black holes eat or consume gas?

The answer is gravity, these are

very massive objects, and anything that comes within

their sphere of influence can be consumed by the black hole.

The more mass a black hole gains, the greater

its gravity and the more food it attracts.