All language subtitles for How.The.Universe.Works.S09E03.Birth.Of.The.Monster.Black.Holes.1080p.AMZN.WEB-DL.DDP2.0.H.264-alfaHD_track4_[eng]

NARRATOR:
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?

(ELECTRICITY BUZZING)

(EXPLOSION)

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.

CHIARA: This was 690 million years
after the Big Bang.

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

HAKEEM: 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.

PHILIP: 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.

ALEX: 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.

(EXPLOSION BLASTS)

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.

MAX: 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?

AMBER: 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.

GRANT: 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.

PHILIP: 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...

(EXPLOSION BLASTS)

..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, erm, making quite a show.

Recently, astronomers
were keeping an eye

on one extremely bright star
in the Fireworks Galaxy.

PHIL: 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?

PHIL: 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 shock wave

generated inside
a collapsing star can't escape.

MICHELLE: In some cases,
when the star is very massive,

the shock wave 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?

HAKEEM: 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.

ALEX: 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?

(OMINOUS MUSIC PLAYING)

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.

GRANT:
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.

Fifteen times the mass of the sun,

Cygnus X-1 is steadily feeding

off the material
that swirls around it.

CHIARA: 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 disk

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.

PHIL: A black hole growing
is a little bit

like a snowball rolling down a hill.

The bigger the snowball gets,

the more snow it can accumulate,

and so the bigger it gets.
It's a runaway effect.

But even if Cygnus X-1 follows
this runaway growth trajectory,

it still may never reach
supermassive status.

The black holes
of the early universe

must have fed
at a much faster rate.

The biggest issue is how do you have
enough time in the early universe

to go from a small black hole
that's born from a star

to something that's supermassive?

GRS 1915 is another
stellar mass black hole.

It's a greedy eater,

accreting at up to 40 times
the rate of Cygnus X-1,

and when something gobbles food
that quickly,

it can begin to overheat.

CHIARA: The black hole is accreting
a lot of material,

and as it's eating,
the accretion disc

really heats up to
very high temperatures.

And at those high temperatures,

you can get a lot of light
coming out of the system.

So the more material that
a black hole eats and swallows,

the brighter it shines.

This stellar black hole
sometimes eats so much so quickly,

its accretion disk
pushes out radiation

almost a million times
brighter than our sun...

..but this brightness
has a serious consequence.

It stops the black hole
from eating and growing larger.

If you wanted me to gain as much
mass as possible as quickly as
possible,

you would just keep feeding me
hamburgers nonstop or whatever,
but...

black holes have a problem
that when they eat a lot,

they tend to just gobble up a lot
of the food in the neighbourhood,

and then also, they start shining
out so much stuff

that it pushes away much of the
food.

The brightness, or luminosity,
gets so intense,

it pushes away incoming material,

a sort of safety valve
called the Eddington Limit.

So in many ways,
the Eddington rate could be

a kind of a speed limit
for the growth of black holes.

It could be a governor
that prevents black holes

from growing even faster

by just dumping more
and more gas onto it.

Eventually, you're gonna hit
that Eddington limit,

and that more gas
that you're dumping on

won't actually reach the black hole.

This cosmic method
of portion control

means that stellar black holes
in the early universe

couldn't have gained weight
fast enough

to become supermassive.

PAUL: Black holes need time to grow.

They need to feed. They need to eat.

Maybe you need to skip a few steps.

Maybe you need to start at
a medium size or bigger

in order to get to supermassive
by the time we observe it.

So was there another type
of black hole

in the early universe?

Something big enough
to grow supermassive

in the time available?

In 2017, astronomers studied
a dense star cluster

called 47 Tucanae on the
outskirts of our own galaxy.

They detected 25 pulsars,

bodies that spin
and emit radiation

like cosmic lighthouses.

These pulsars are all orbiting
a central object.

And even though we couldn't see
the central object itself,

we could watch the behaviour
in the orbits of all these pulsars

around it, and we could figure out
how big that central object was.

Well, when you do the math,
you come up with something

that is about 1,500 to 2,000 times
the mass of the sun

that's actually hidden
in the heart of that globular
cluster.

So what is the invisible object?

Whatever's lurking
at the centre of 47 Tucanae

has to be big, and it has to be
black.

Astronomers think
it's a large black hole.

At 1,500 times the mass of the sun,

the object is much bigger
than a regular stellar black hole,

but too small to be supermassive.

Could it be what's known
as an intermediate mass black hole?

It's extremely hard to find any of
these intermediate mass black holes.

This rare category of black hole

ranges between 100
and 100,000 solar masses.

At that size, they may have
been large enough to become

supermassive very quickly.

Intermediate mass black holes
could be what give

supermassive black holes
a head start in life.

Astronomers search
for intermediate mass black holes.

They may have been large
enough to act as seeds

for the first supermassive
black holes.

Yet so far,
they've escaped discovery.

They're like the missing link.

And I mean that for real.
They're missing.

Imagine you're an alien
who's arrived on the planet Earth,

and you know very little
about the human species,

and when you look around,

you only notice
tiny, tiny little children

and grown adults.
You don't see any adolescents,
right?

And intrinsically, you know
that the tiny little children

grow up to be full-size adults.

But you don't see
how they got there, right?

You don't see the intermediate
stages of growth.

That would be really,
really weird, right?

That is the case
for supermassive black holes.

So it's like a universe
without teenagers.

Or that's how it looked,
until September 2020.

Scientists studying
gravitational waves

picked up the signal
of an extreme event

in the distant universe.

What researchers are looking for
are things called gravitational
waves.

They're like ripples in space
itself.

Most signals sound
a little bit like a chirp.

It's a noise
that's very characteristic.

It goes a bit, like, sort of whoop!

(WHOOPING NOISE)

But this particular event
was so extreme

and so sudden, it just
sounded more like a thud.

(FAINT THUD)

This faint thud
from halfway across the universe

is music to the ears
of intermediate black hole hunters,

because its pitch
can mean only one thing.

This could only have been created

by two really massive black holes
colliding into each other

and producing a combined black hole

with a mass that's 142 times
the mass of our sun.

So that, is for the first time,

getting into this intermediate mass
black hole regime.

This is the first confirmed
observation

of an intermediate black hole.

Finding direct evidence like this

for an intermediate mass black hole
is absolutely fantastic.

Now that we're certain
intermediate black holes exist,

could they help explain the
origin of supermassive black holes

in the early universe?

These intermediate black holes
really could be the first seeds

of the supermassive black holes.

You would need something
like that to form really big,

really early to even begin to
explain these very massive,

supermassive black holes
that have formed

just a short time after the Big
Bang.

How do intermediate black holes
form in the first place?

The recently discovered one
came from the collision

of two smaller black holes.

They may also form
in giant clouds of gas.

It could be
that in the earlier universe,

you can just have large clouds of
gas that can lose enough energy

quickly enough to just
spontaneously collapse

and form a black hole of this size.

PHILIP: The enormous cloud of gas
contracts and gets denser and
denser,

the way it would
if it was starting to form stars.

But it's somehow able
to remain coherent

and collapse into one giant object

that forms an intermediate
mass black hole.

A giant gas cloud
undergoing a direct collapse

down to an intermediate
mass black hole

would be a rare sight.

You think it would go giant cloud,
slowly collapsing, black hole,

but instead, it's more like,
giant cloud, ahhhh! Black hole.

So one day, you see this
massive gas complex,

and then you blink,
and it's collapsed,

and now you're face-to-face
with a big black hole.

At least, that's the theory.

CHIARA: Getting a black hole
to form from the direct collapse

of a gas cloud is very tricky.

Gas clouds tend to split up
and collapse

into a multitude of stars...

Collapsing into one object
would take unique conditions.

One possible scenario
involves two neighbouring galaxies.

The first, a young
protogalaxy,

a gas cloud yet to form stars.

Next door sits a larger galaxy.

It's forming so many stars,

radiation is bursting out
all over its young neighbour.

Because they're in close proximity,
the energy from the large galaxy

prevents the smaller galaxy
from forming its stars,

so that means that it will continue
to collapse in cloud form

before moving to star formation.

The gas cloud becomes large
and dense enough,

the gravity eventually pulls
it in on itself.

When it can't ignite into stars,

the collapse creates
an intermediate mass black hole.

PAUL: I think this idea
is very intriguing.

I don't know
if it's physically possible,

but then again, there's a lot we
don't know about the early universe.

2017,
scientists simulated another way

that intermediate-mass black holes
might form in the infant universe.

Under the influence of dark matter.

Dark matter was absolutely critical

for the evolution of structure
in the early universe.

Without dark matter,
there would be virtually nothing.

Dark matter is mysterious.

We know it has a gravitational pull
on ordinary matter.

One idea is that it helped form very
large stars in the early universe,

stars that later collapsed
into intermediate mass black holes.

MICHELLE:
The idea is something like this.

About a hundred million years
after the Big Bang,

dark matter which dominated
the gravitational early universe

was forming big clumps.

Then there might have been
these supersonic streams

of regular matter after the Big Bang

and they were directed into
these gravitational cores

where dark matter was
gathering everything together.

When scientists simulated this,

they found that dark matter's
strong gravity

could pull in huge clouds of gas.

You could actually accumulate
as much as, say,

34,000 times the mass of the Sun
into one gigantic star-like object.

That's big enough, it would
just collapse into a black hole.

A black hole of 34,000 solar
masses would sit squarely

in the intermediate-mass category.

It would be large enough
to potentially become

a supermassive black hole.

It's possible that dark matter
directing streams of gas together

about a hundred million years
after the Big Bang

was the seed for these
supermassive black holes.

Whichever way
intermediate mass black holes form,

they seem like a good way to start
explaining supermassive black holes

in the early universe.

The question is, then,
how do they grow?

How do you start
from this seed and end up,

you know, with something that's
a billion times the mass of the sun?

Maybe early intermediate
mass black holes

had enormous appetites,

gorging themselves
to a supermassive state,

feeding on the biggest meals
our universe can serve up.

(LIVELY MUSIC PLAYING)

Astronomers want to know how

the earliest supermassive
black holes got so big so quickly.

Could they have started
as intermediate mass black holes

that devoured super-sized meals?

PHILIP: It's possible that these
intermediate mass black holes

could form in an exceptionally
rare environment

where it can accrete new material
at an enormously high rate.

So far, we only have direct evidence
of one intermediate mass black hole,

and we can't yet detect
how it eats and grows.

But we could look at much
larger black holes for clues.

In 2019, astronomers searched
for supermassive black holes

that are actively feeding.

They pinpointed 12 quasars
from the beginning of the cosmos.

Quasars are among the brightest
objects we know of in the universe.

And they're what happens
when a supermassive black hole

at the centre of a galaxy is
swallowing up gas and dust,

and that generates
a tremendous amount

of energy and luminosity
that we can see.

Surrounding these early galaxies

are enormous gas reservoirs
called hydrogen halos.

PHIL: This is great, because
that acts as fuel

for those supermassive black holes.

Cold gas can stream into
those black holes and feed them.

These huge halos of cold gas
are also the building blocks of
stars.

GRANT: These enormous, pristine
halos of hydrogen around early
galaxies,

they're gonna be reservoirs
to power star formation.

Star formation is a violent process

that can create turbulence
in a galaxy.

That turbulence makes the gas
fall toward the black hole,

and then that makes
the black hole even bigger.

Hydrogen halos might have spoon fed
early supermassive black holes.

This process may have also helped

intermediate mass black holes
grow quickly.

Could the largest black holes
show us other,

more drastic ways to put on weight?

In October, 2019,
astronomers used telescopes

to explore a remarkably clear
galaxy called M77.

Because this galaxy is so near to
us,

we can study its central engine
in really exquisite detail

at very, very fine resolution.

PAUL: Not only do you see
the bright core, the bright nucleus,

but you can see spiral arms.

You can see structures
in the galaxy.

You can see how the whole
galaxy is arranged.

When we examined M77's central
supermassive black hole,

we saw something extraordinary.

Its food was coming not from one,

but two accretion disks
spinning in opposite directions.

Normally around a black hole,
all of the gas is spinning in

roughly the same direction,

and that creates kind of a slow
in-fall of gas and slow feeding.

Here, we've got a case
where some of it's going one way,

the other is going the other way.

This is very unstable
and can create opportunities

for lots of gas to get gobbled up
by that black hole.

The material in the disks
is one enormous ready-to-eat meal...

..but dinner will not be served
until the outer disk slows down.

PHILIP: If there's a black hole
at the centre of a galaxy,

and you're orbiting around it
fast enough to maintain your orbit,

you're never going to fall in.

You're just going to orbit forever,
and you're just going to spin
around,

just like the way the Earth
is going around the sun.

What needs to happen
if you wanna fall in,

is to slow down your speed.

The outer accretion disk
will gradually slow down

and orbit more tightly
against the inner disk.

Dangerous collisions
of the counter-rotating material

will start to occur.

The double accretion disk
is like drinking

from two soda fountains
at the same time.

It's great while it lasts, but
you're building up some serious gas

that is just gonna blow
the whole thing away.

In just a few 100,000 years,

the double disks
will catastrophically collide,

and their entire contents will fall

into the central
supermassive black hole.

It will devour everything in one
gulp, generating a colossal cosmic
burp.

In February of 2020,
in the Ophiuchus Galaxy Cluster,

we saw the damage
a cosmic burp can do.

PHIL: The Ophiuchus Galaxy Cluster
is a collection

of a huge number of galaxies,
all bound together by gravity.

And there's gas in between
these galaxies.

And when astronomers
looked at that gas in detail,

what they found was
a huge arcing structure in it

that they realized
was the edge of a cavity.

PAUL:
There is a massive hole in the gas

that is over 15 times bigger
than the entire Milky Way Galaxy.

Something frightening had to happen
to carve this void out.

The size of this bubble
is kind of stomping my brain.

We are talking about a hole
in this gas

that is over
a million light-years wide.

The burp that created this cavity
must have been astoundingly powerful.

There are a lot of ideas about this,

but there's only one
that really can explain it.

And that's a supermassive black
hole.

A supermassive black hole
that suddenly got very greedy.

In order to drive
an energetic event like this,

the black hole needs to eat...
Not just one meal.

It needs to eat thousands of meals
at the exact same time.

It needs to go to an all-you-can-eat
intergalactic buffet.

Sometime in the distant past,

this black hole must have had
a huge episode of just gorging

on material falling in.
That got super-hot,

blew out a tremendous amount
of material in jets,

beams that shot out
from the poles of the disk.

And that's what basically
pushed its way out of that gas,

forming this enormous cavity.

The colossal cosmic burp
pushed food far away

from the supermassive black hole,

ending its all-you-can-eat
binge and stopping its growth.

If an intermediate mass
black hole was this greedy,

it would come to a similar end.

It's no way to gain weight
and become supermassive.

This is probably not the way

the earliest supermassive black
holes grew to such enormous size.

Is there another way supermassive
black holes could have formed

in the early universe
without having to overeat?

Maybe black holes smashed
their way to being giant-sized.

(EXPLOSION BLASTS)

November, 2018.

Astronomers scanning hundreds
of nearby galaxies in infrared light

spot something extraordinary.

Some galaxies had not one
supermassive black hole,

but two.

Are these pairs a clue
to how supermassive black holes

in the infant universe
got so big so fast?

Seeing these infrared images

showing pairs
of supermassive black holes

at the centres of galaxies and
showing that this could be very
common

just is mind-blowing to me.

The reason we see pairs
of supermassive black holes

is because two galaxies
merged together.

CHIARA: In our picture of how
the universe works,

galaxies start off as smaller
galaxies

and grow by merging
with other galaxies.

So they'll be whooshing
around each other

and tearing each other up.

It's actually quite violent.

When galaxies merge,

we think their central
supermassive black holes also merge,

smashing into each other
and combining to build

a larger black hole.

GRANT: Galaxy-scale mergers
can be one of the most

efficient growth mechanisms
for supermassive black holes.

Maybe, in the early universe,

black holes of stellar
or intermediate mass

merged repeatedly,

getting heavier and heavier
until they became super massive.

AMBER: We don't really
know how common

supermassive black hole
mergers were in the early universe,

but we think they were more common
than they are today,

because galaxies were closer
together.

It would have taken
millions of mergers

to build up the largest
supermassive black holes we see
today,

which could have been a tall order.

There's another problem, too.

We've never witnessed a supermassive
black hole merger in the act.

We've seen supermassive black holes
on their way to merging,

and we've seen ones that we think
had gone through mergers.

But we haven't caught one
in the moment.

As supermassive black holes
start merging,

they spiral around each other,

getting faster and faster
the closer they get.

But for them
to finally merge together

into a single black hole,

they need to lose what
astronomers call orbital energy.

The merger of supermassive black
holes means that their orbits have
to decay

for them to get closer
and closer together.

So in order for an orbit to decay,

that orbital energy
has to go somewhere.

To lose energy,

the merging supermassive
black holes start disrupting

the orbits of nearby stars,

throwing them off their paths.

PHILIP: So something small and puny
that weighs just one sun

like our own star will often
get in the path of these two

and just get rocketed out,

potentially unbound and flung out
of the galaxy entirely.

Each time the supermassive
black holes fling out a star,

they lose more orbital energy.

They get closer and closer.

But eventually, they kicked out
all the stars. There's nothing left.

The merger stalls.

Like two sweethearts
at a high school prom...

..the supermassive black holes dance
as close as they can,

but physical contact is not allowed.

So these two black holes could
end up spiralling around each other

for billions and billions of years.

This is called
the final parsec problem.

CHIARA: In 1980, there was
a famous paper,

which addressed this issue
that supermassive black holes

can only get to within
about one parsec,

or three light-years, of each other

before they can't merge or they
stall.

We believe that supermassive
black holes must merge.

We know that galaxies merge,

and so if the black holes
didn't merge,

we'd see lots of black holes
floating around.

And we don't...
There's always one in the middle.

So how do they merge?

In 2019, we found something
that appears to solve

the final parsec problem...

A galaxy in the middle of a merger

that contains not two
supermassive black holes,

but three.

Three supermassive black holes.
Now that's really cool.

Sometimes you can have three
galaxies

that are merging together
in a galaxy cluster.

Then you have three
supermassive black holes.

At this point is,
it's virtually impossible

for there to be
a final parsec problem.

Here's how a third black hole
solves the final parsec problem.

Two of the black holes
orbit closer and closer,

ejecting stars to lose energy.

Black hole number three
joins the action.

Its gravitational pull takes even
more energy from the orbiting pair.

Eventually, they lose enough
orbital energy to collide.

HAKEEM: That third supermassive
black hole is just what's needed

to transfer energy away
from the two merging black holes

so that they can now merge into
one single supermassive black hole.

Triple black hole events may explain

how the earliest supermassive black
holes grew to such enormous size.

We've suspected that three black
holes

may be necessary in order
to get black holes to merge,

but we've never had
any evidence for it.

But now, this might provide
a direct picture

of three black holes
caught in the act itself.

If we have a picture
of this happening now,

then it certainly happened
in the early universe

and might explain how the biggest
black holes got so big so quickly.

Final proof will come when we
witness a merger being completed.

But tracking mergers as they
happen is challenging.

CHIARA: Supermassive black hole
mergers can take billions of years

and therefore,
it's impossible to witness

a supermassive black hole merger
in action.

Mergers may take
an incredibly long time

but the actual moment
the black holes join is very fast.

Compared to the billions of years
the black holes take to spiral
together,

they might merge together
in a matter of minutes or hours.

That means if we want to
witness a merger happening,

we have to watch the skies
very carefully.

No-one has ever seen a supermassive
black hole merger

but I imagine it would be
an absolutely spectacular event.

It's also possible
that the merger is dark,

that there's no fireworks,

that there's nothing really special
that happens

in terms of light being emitted
from the system.

It could be a dark merger.

Whether dark or bright,

finally seeing a merger
will help answer

how the very first supermassive
black holes got so big so quickly.

AMBER: We think that mergers
of supermassive black holes

in the early universe are one key
way that galaxies and their black
holes

could have grown
in the early universe.

They're probably not the only way.

There are other ways that black
holes could grow as well.

Scientists are also
investigating invisible forces

at the beginning of the universe.

Did something we can't see

boost the size of the first
supermassive black holes?

There's still so much we don't know
about the early universe.

PAUL: The further out
we look in the universe,

the less familiar
the universe becomes.

And so the more and more
interesting and new physics

you need to involve
in order to explain

these very strange observations.

The puzzle of fast-growing,
supermassive black holes

in the infant universe

now takes physicists
somewhere new,

to the little understood realm
of magnetic fields.

The thing about magnetic fields is
they're hard.

They're hard to calculate,
they're hard to understand.

They're sort of the elephant
in the room for astronomers.

We know they're there, but we'd
really rather not talk about them.

It's only recently that
people are incorporating

magnetic fields into their models
of galaxy formation,

and therefore, maybe it's under
the influence of these fields

that somehow these supermassive
black holes are formed.

To investigate
how magnetic fields influenced

early supermassive black holes,

we must look back
at the very beginning.

Soon after the Big Bang,

the first particles form, cool,

and become electrically charged.

Things were very different,
radically different than they are
now.

Particles were whizzing
by each other.

Everything was charged. It was
just a very different landscape.

There are no stars yet,
not even atoms.

But some scientists think

moving charged particles
created the first magnetic fields.

Magnetic fields were essentially
everywhere in the early universe.

Those magnetic fields would have
extended extremely large distances,

like a very finely spun web
all through the early universe.

Gradually, atoms form
and gather into clouds of gas.

These will become
the first galaxies

and their supermassive black holes.

During this time,
magnetic fields change.

They bunch together
around the forming galaxies.

But we don't know how.

The thing with magnetic fields is
they're extremely hard to predict,

and you need to do really
hard calculations that, even now,

we're only just starting to do.

2017, scientists design
a ground-breaking computer model

that simulates patterns of
magnetism developing over time.

The images show lines
of magnetic force getting stronger

and more focused
across a vast region of space.

Some astronomers think
these emerging magnetic field lines

help shape early galaxies

and the supermassive
black holes at their cores.

Magnetic fields have this ability
to push material around.

So one possibility is
they could actually help push

or funnel material in
towards a growing black hole

and help it grow faster
than it would do otherwise.

In today's universe, we know
magnetic fields around planets

can deflect dust particles.

On much larger scales,
matter may also

have been channelled into the
centres of galaxies

of the early universe.

Were the magnetic fields
of these early galaxies a conduit

that you could get matter dumped
more and more into the middle

and maybe build up
a really big black hole?

Scientists are just starting
to figure out

the effects of magnetism
at the beginning of the universe,

but it could have been one
of several mechanisms

that influenced the size
of early supermassive black holes.

ANDREW: We have lots of ideas
for how you might be able to form

supermassive black holes,

but until we see
actual mechanisms in action,

we just can't really say which of
them are the most important routes.

Maybe some other mechanism
we haven't even thought of

explains how the early supermassive
black holes got so big so fast.

Hopefully, one day,
these monsters of the cosmos

will reveal their secrets to us.

Supermassive black hole research
is utterly mind-blowing to me.

I mean, this is so cool.

CHIARA: It's important to explain

how these early supermassive black
holes formed

in order to have a really
concrete understanding

of how the universe works.

Supermassive black holes are
the great engines of cosmic
change...

they're enormous points of matter,

and because they're just so massive,

they can sculpt
the evolution of galaxies.

They're the master key

to most of the unsolved
mysteries in physics.

We have a chance here to understand
super massive black holes

so that we can understand
the formation of galaxies,

the generation of stars
like our sun,

and maybe even the appearance of
life.

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