All language subtitles for The Universe S01E09 Alien Galaxies

In the beginning, there was darkness,
and then, bang, giving birth to an

expanding existence of time, space, and
matter.

Now, think further than we've ever
imagined, beyond the limits of our

in a place we call the universe.

Our sun is one of billions of stars in
the Milky Way galaxy.

And our galaxy is one of hundreds of
billions, maybe a trillion, in the known

universe.

From the Hubble Space Telescope comes a
view of the universe that was.

A magnificent trip through the mists of
history and back nearly all the way to

the Big Bang.

Each smudge, each clump, each blob of
light.

A billion stars here, a trillion stars
there.

If you want to know our place in the
universe, take a look up and

far, far away to the realm of alien
galaxies.

is a universe of motion, expansion,
light,

and blackness.

We think the universe is about 13 .6
billion years old.

So just to put that in context, the
Earth and the solar system is just over

billion years old. So the universe is
just over three times older than the

Earth.

Across the vast reaches of the
interstellar void, distant stars are

together by the long reach of gravity's
unyielding grip.

Over billions of years, these stars have
come together to form galaxies.

A galaxy is a collection of 100 billion
or so stars.

Stars are by no means touching each
other or actually anywhere near each

compared to their sizes. They're very,
very far apart from one another.

The thing that blows my mind about
galaxies is what monsters they are. They

incredibly huge.

If the sun were the size of a period on
a page, the dot of an eye, our galaxy

would be the size of the continental
United States.

So they're gigantic.

Astronomers have always known there was
something special about the band of

stars and dust that seemed to encircle
the night sky above them.

It's our galaxy, a white smudge they
called the Milky Way.

That band of light is the collected
light of hundreds of thousands of stars

you can't see individually with your
eye. And that was named by the Greeks.

thought it looked like a milky river, so
they called it the Milky Way.

There are 100 billion stars in our
galaxy, and there are 100 billion

the observable universe.

That's more stars in the universe than
grains of sand on the beaches of the

Earth.

If you imagine a galaxy itself as the
size of a hockey puck, then the galaxies

are spaced.

from one to another about a few
diameters apart.

So if there's a puck here and a puck
over there, that's kind of the way that

galaxies are spaced in the universe.

Pictures from the Hubble Space Telescope
show the wide variety of alien

galaxies.

The Sombrero Galaxy, also known as M104.

One of the most massive objects in a
gigantic cluster of galaxies, the

Galaxy contains nearly 800 billion times
as much mass as our Sun.

Compared to the Milky Way, Sombrero has
a much larger bulge relative to its

highly wound disk.

This image of the Sombrero Galaxy is
also a prime example of what happens

three of the world's top space
telescopes join forces.

The Chandra X -ray Observatory, taking
an image of the high -powered X -rays

emitted by the Sombrero Galaxy.

The Hubble Space Telescope, snapping an
optical picture.

capturing the visual light that's made
the multi -million light -year journey

Earth.

And the Spitzer Space Telescope,
capturing an infrared version, looking

sombrero galaxy's heat signature.

Melded together, these three images
provide a stunning and unforgettable

a galaxy 28 million light -years away.

M51, the Whirlpool Galaxy.

Its spiral arms twisting like cotton
candy being spun.

The center of the Whirlpool Galaxy is so
densely packed with stars, anyone

living on planets there would be under a
constant bright sky, day or night.

Centaurus A.

a galaxy sending out massive amounts of
radio waves.

Think of it as an interstellar
broadcaster, beaming its signal

universe all day, every day.

It's the closest of the so -called
active galaxies, galaxies that pour out

tremendous amounts of energy from their
cores.

This is the Hubble Ultra Deep Field
image.

Created using the Hubble Faith
Telescope, it shows us how truly vast

the universe really is, and how those
far -off spaces are anything but empty.

When you look very deep in the universe,
you're looking back in time. So you're

looking back at galaxies right back to
when they were very, very young, when

they were only a few percent of their
current age.

So the Hubble Ultra Deep Field is really
like a time tunnel that gives us a

glimpse of galaxies as they were before
the Earth was in existence. The Earth is

4 billion years old. We're seeing
galaxies as they were 13 billion years

So the light left these objects before
there was any Earth at all.

The nearest large galaxy to ours, the
Andromeda Galaxy, is about 2 million

years away.

So the light from the Andromeda Galaxy
takes 2 million years to get here.

So if we're seeing it as it looked 2
million years ago. And that's one of the

more nearby galaxies.

As we look farther and farther out in
space then, we're looking farther and

farther back in time.

To get a better idea of the concept,
just visit one of the most spectacular

vistas on Earth, the majestic Grand
Canyon.

As you look down the layers, you get
older and older rocks, and we can tell

the different environments were.

So we can actually look at the geologic
history of this area over time and in

essence look back through the
environment that was located right here

hundreds of millions of years of the
Earth's history.

So by looking at stars that are further
and further away from the Earth,

astronomers can get an idea of the
evolution of the universe.

From the earliest days of galactic
astronomy...

Observers noticed galaxies came in a
variety of shapes and sizes.

The two main types of galaxies are
spiral galaxies, like our Milky Way,

have spiral arms in a thin disk, and
then elliptical galaxies, which are sort

more spherically or elliptically shaped,
and they don't have spiral arms.

The spiral galaxies have a lot of gas
and dust in them, from which new stars

forming right now.

whereas the elliptical galaxies seem to
have formed their stars long ago. They

don't have that much gas and dust, so
they're not forming stars right now.

There's also some irregular galaxies,
which generally have a lot of gas and

dust, but not in a nice spiral form.

Detecting these far -off accumulations
of stars is made easier when astronomers

search for the streaming, blasting
beacons found near the center of many of

them.

Violent and erratic hearts beat at the
center of many alien galaxies, sending

out so much energy they can overwhelm
the amount of energy produced by all of

the other stars within them.

These are the active galactic nuclei.

So we look at some galaxies and we find
that they have at their very center very

powerful engines that are producing a
tremendous amount of light.

We can tell that they're very far away,
and yet they're still very bright when

we look at them. So they must be
tremendously powerful, dumping a lot of

out every second.

Among the most violent and powerful of
the active galactic nuclei, the

mysterious phenomenon called quasars.

When we look at quasars, quasi -stellar
objects, and see how far away they are,

some of them are tremendously bright.

The brightest one of them is about a
trillion times as bright as our sun.

Spectacular streams of electromagnetic
energy, bright beacons lighting up the

sky for billions of miles.

These high -energy sources provide a
stunning reminder of the universe's

to illuminate.

A quasar itself can be brighter than an
entire galaxy.

So when we look at a quasar like 3C273,
the Hubble Space Telescope took some

images of this, and we found that it has
a big jet of material shooting out of

the side of it, almost the size of the
galaxy itself.

These are really weird things, these
active galactic nuclei.

As active galactic nuclei show, space is
a violent place.

And as it turns out, there's a massive
collision going on.

Right in our own backyard.

The culprit?

A galaxy called the Canis Major Dwarf
Galaxy.

As the name implies, dwarf galaxies are
small, making them even more difficult

to detect.

Now, the Canis Major Dwarf Galaxy is
taking aim at the Milky Way.

Two galaxies on a collision course from
which, thanks to gravity, there is no

escape.

When a small galaxy comes too close to a
large galaxy, the tidal

effects cause it to be stretched out and
distorted.

So the gravitational attraction of the
larger galaxy will actually pull and

stretch the stars in the smaller galaxy.

So a collection of galaxies that has a
relative spacing compared to their size,

about like the way these pucks are laid
out on the ice, all these galaxies would

be moving through space with respect to
one another.

But every once in a while, one of these
galaxies is going to bonk into another

one. Now when that happens, the shape of
the galaxies would actually become

distorted and stretched out.

Pucks are solid. Galaxies are made of
individual stars, each of which feels

gravity of all the others, and they
become distorted and torn into tidal

a big swooping arc of stars in either
direction.

And that's how the once far -off stars
from an alien galaxy, blazing through

space for millions upon billions of
miles, can end up blending

right in with our own.

But what caused these stars to clump
together in galaxies?

Why has the matter and mass of the
universe fused into these spectacular

structures?

To find the answer, we have to turn our
clocks back millions and

billions of years ago.

Go back far enough, and you reach a
point where all the matter and faith and

time become compressed and compacted
into an infinitely small point, a

gravitational singularity of infinite
dimension.

It's a point that exploded with a
spectacular big bang.

A long time ago, the matter and energy
that would make up every alien galaxy

wasn't far away.

Everything that ever became an alien
galaxy sprung forth from a gravitational

singularity that has come to be known as
the Big Bang.

If you run a film of the universe
backwards in your mind, eventually you

a point where the density would become
extremely high. If you go far enough,

the mass and energy that we have in the
universe would be in a single location

and you would find infinite density.

We think that the expansion of the
universe is telling us something very

profound, that the universe has a
beginning point in time.

In those moments after the Big Bang, the
rules of our universe and stars took

shape. And one of the biggest rules was
the law of gravity.

After the Big Bang, the universe, of
course, was expanding.

But there were some parts that were
denser than others.

Those denser parts started
gravitationally contracting, and they

galaxies.

Pockets of gas within those
gravitationally contracting clouds

because those pockets gravitationally
contracted even more than the general

cloud of gas.

It would take hundreds of millions of
years for the first galaxy to coalesce

into existence.

We don't know exactly when this
happened, but we can see Pretty mature

about a billion years after the Big
Bang, and the earliest objects that I

see are about 500 million years after
the Big Bang. So it's within this period

that we think the very earliest objects
switched on.

But we haven't yet found a time when
there were no galaxies at all.

To learn more about alien galaxies,

We need to solve the many mysteries of
our Milky Way's own place in the

universe.

When we want to look at the structure of
our galaxy, the difficulty that we run

into is that we're inside of it.

We can only see what we can see from
inside.

Moreover, there's dust and gas blocking
our lines of sight, so we can't see very

far from our position in our galaxy in
many different directions.

We think the Milky Way is a barred
spiral galaxy reaching about 100 ,000

years across with a 3 ,000 light years
thick core.

Most galaxies in the universe are
smaller.

The Milky Way and many alien galaxies.

are like cities with a central dense
core and less dense suburbs.

For spiral galaxies like our own Milky
Way, that means a trip to visit the

is not unlike a trip on the freeways.

All the stars in our galaxy are orbiting
around the center.

about 30 ,000 light years away from the
center. And it takes us about 250

million years to make one orbit around
the galaxy.

Now, the stars are all in their orbits.
They're all moving around the galaxy.

So what causes these beautiful spiral
arms that we see?

Well, they're sort of a density wave, an
area where the stars in the galaxy are

just a little bit denser, more packed
together than the rest of the galaxy.

Different stars move into the density
wave. Different stars move out.

The density wave stays there, and that's
the spiral arm.

It's a lot the same way that traffic
jams get started on the freeway.

Something happens that makes maybe one
star slow down, some sort of

gravitational interaction, and other
stars slow down in response to it. And

of a sudden, you've got a traffic jam.

So galaxies seem to naturally form these
spiral density waves.

Two and a half million light years away,
a menacing counterpart

to our galaxy sits and swirls, casting a
wary eye toward the Milky Way.

It's the dance partner for our galaxy,
our biggest neighbor and our biggest

nemesis.

It's called M31, better known as the
Andromeda Galaxy.

The Andromeda Galaxy is about the same
size as our Milky Way. It's about 100

,000 light years across.

It's a spiral galaxy.

It has perhaps a little bit less active
star formation going on right now than

our Milky Way, but otherwise it's quite
similar.

Andromeda is probably also the product
of several smaller galaxies that

coalesced or interacted over time.

One of those galaxies may be responsible
for Andromeda's double nucleus, two

huge clumps of stars found at its
center.

On Earth, we've been keeping an eye on
our trillion -star neighbor for

centuries.

Persian texts from the 10th century
mention this small cloud in the skies.

But at the time there was no way of
knowing that Andromeda was an entirely

separate galaxy, two and a half million
light years away.

That makes it the furthest object in the
universe you can see with the naked

eye.

While the Milky Way may be able to
absorb the impact of a colliding dwarf

galaxy,

A clash with the Andromeda Galaxy is not
only inevitable, but will forever

change the local galactic landscape.

The universe's most prolific power is
the force that's pulling Andromeda and

Milky Way closer and closer.

And someday, in the far -off future,
these two spiral titans will collide.

If you look at the Milky Way galaxy and
the Andromeda galaxy, the nearest large

galaxy to us, they're actually
approaching each other at a fairly

rate, several hundred kilometers every
second.

They're very far apart right now, but in
the next few billion years, sometime,

they will be right up against each
other. And so a collision is, in a

imminent.

Probably no stars will physically hit
each other.

There's just so much space between the
stars.

But when Andromeda collides with us, it
will have a huge impact on the Milky

Way.

Some things will get thrown into the
black hole in the middle. Some stars

get ripped off, thrown away into space.

So it'll be dramatic.

And the entire night sky will change.

The constant motion of alien galaxies
and the time frames involved may be

hard to comprehend.

Andromeda is close enough to the Milky
Way that their gravitational attraction

brings them closer together.

But elsewhere, almost all of the alien
galaxies we see are moving away from

us.

experience, like an exploding bomb.

Everything explodes away from a center.

Now, is there an empty center to our
universe? Are we on a shell of galaxies

flying away from wherever the original
explosion was? No. And that's the

thing.

In our universe, space itself is
expanding.

Every little bit of space.

The space right here between my hands.

has a pressure to expand.

It's this expansion, first detected by
astronomer Edwin Hubble, that laid the

foundation for much of modern astronomy.

The universe expands with time, and
space itself is actually expanding.

Now, if you take a one -dimensional
example of the universe here, here's a

hypothetical universe where I've got
these ping -pong balls, which are the

galaxies.

on this rubber hose, I can expand that
hose and all the galaxies move away from

the others.

See that?

And in fact, if we focus our attention
on this one here, the ones that are

farther away from that move faster than
the ones that are closer in because

there's more space, there's more tube
between this one here and the distant

than between this one and the nearby
one.

So that, in a sense, is a good model for
Hubble's observation that at a given

time, the more distant galaxies move
faster than the nearby galaxies.

Notice also that no galaxy can claim
that it's the unique center of the

universe. Sure, from this one's
perspective, all the others are moving

But if I were to put myself on this one
here,

I would say that all the galaxies are
moving away from that one as well.

So no matter which galaxy you're on, you
see the others moving away from you.

That's what happens in a uniformly
expanding universe.

There is no galaxy that can say that
it's the unique center of the universe.

If you think back to earlier times, it
was thought that the Earth was the

of everything, the center of the
universe, and the planets and the sun

orbited around the Earth, and the stars
every day made one trip around the

Earth. Then we discovered that our sun
was one of many stars, and that our sun

was cruising around through the universe
as we knew it.

But this discovery by Hubble told us
that not only was our...

planet one of many planets, and our
star, our sun, one of many stars, but

galaxy was one of many galaxies,
presumably like any other.

It really changed our worldview and our
place in the universe to think that our

galaxy is an ordinary galaxy.

So, just what's in our galactic
neighborhood?

Meet the Local Group of Galaxies, a
group with ever -increasing membership.

Our Local Group of Galaxies is a small
group or cluster of about three dozen

galaxies.

Our Milky Way and the Andromeda Galaxy,
M31, are the two dominant galaxies.

Most of the galaxies in our Local Group
are small dwarf galaxies.

These galaxies each have collections of
small satellite galaxies that are in

their thrall, that orbit around them.

And these big galaxies all feel the
influence of each other's mass and orbit

around each other. So all of these
galaxies, the small galaxies are

big galaxies, and the big galaxies are
all sort of orbiting each other. It's a

group of about 30 or so galaxies that
are all sort of orbiting around a common

center of mass.

The most well -known dwarf members of
the local group, two galaxies known as

Large and Small Magellanic Clouds.

Scientists now think the clouds orbit
the Milky Way thanks to the tidal

influence of our galaxy.

Gravity, of course, is a two -way
street.

It's believed the gravitational pull
from these clouds has also distorted

of our own galactic disk.

By measuring the energy that emits from
the stars in the small and large

Magellanic clouds, astronomers believe
they are made of different stuff than

galaxy.

The clouds are richer in hydrogen and
helium than the Milky Way and with fewer

metals.

Scientists think this means the stars
are younger in the clouds.

The gravitational dance between the
clouds and the Milky Way has likely been

going on for billions of years.

But all the while, a different and much
more mysterious battle is going on back

in the center of the Milky Way.

Because when you head for the center of
our galaxy, Once you get through all the

dust and gas and older stars, you'll
find something so insanely frightening,

normal rules of time and space do not
apply.

For lurking at the heart of the Milky
Way, and perhaps every alien galaxy, is

massive beast with a ravenous appetite.

A beast from which there is no escape.

There is a region at the core of our
galaxy, the Milky Way, where nothing

escapes.

This is the point of no return.

A supermassive black hole.

A black hole is an astrophysical object
that has so much mass in such a small

volume that the gravitational force is
so strong that even light doesn't have

enough energy to escape it.

Black holes can form either when a
massive star explodes at the end of its

and the core of the star collapses

into a black hole.

Or you can have supermassive black holes
at the centers of galaxies.

How massive?

Try nearly four million times the mass
of our sun.

Sometimes, black holes swallow entire
stars, creating fierce explosions called

gamma ray bursts.

In order to emit a gamma ray, an object
has to be billions of degrees in

temperature, or even trillions.

So we're seeing something incredibly
hot.

In some cases, the galaxies were as much
as 10 billion light years away.

And the gamma ray bursts just had been
so bright that...

If you had a pair of binoculars and you
were actually looking at the right part

of the sky at the right time, you would
have been able to see a visible light

afterglow from the gamma rays.

That's using binoculars to see something
that's on the other side of the

universe, 10 billion light years away.

Can you imagine what sort of explosion
that was?

So if there's a supermassive black hole
at the center of our galaxy, might

similar black holes lurk at the center
of all alien galaxies?

When we look at neighboring galaxies,
and this is a recent result, we find

most galaxies appear to have very
massive black holes in their center,

from millions to even billions of times
as massive as our sun.

It appears to be a very common, ordinary
aspect of a galaxy.

Black holes swallow matter.

But less than one half of one percent of
our universe is believed to be made up

of observable matter.

such as stars, planets, gas, and dust.

So what accounts for the rest of the
stuff created in the aftermath of the

Bang?

What really fills up alien galaxies?

Scientists' best guess is a mysterious
substance called...

Dark matter is fantastic stuff.

We know that it exists. We know that it
gravitationally pulls on things.

One of the best pieces of evidence for
the existence of dark matter is that

spiral galaxies are spinning more
quickly than they would be spinning

there were extra unseen material causing
them to spin that fast.

Caltech professor Richard Ellis has
pioneered a new technique to create a

-dimensional map of the universe,
including the dark matter.

This is the first hint from dynamical
data that there's a lot of dark matter

the universe.

We can also detect dark matter by a
really remarkable phenomenon which was

predicted by Einstein and is now in
great use in astronomy, which we call

gravitational lensing.

Dark matter bends the light passing
through it, much like a curved piece of

glass.

So light rays are bent by material, and
where we can see the signature of this

bending of the light rays, we can infer
that there's a lot of dark matter

present.

We don't have to see the dark matter
directly, it doesn't shine, it doesn't

scatter light, but we can infer its
presence from the effect it has on light

rays that are coming through.

clumps of dark matter so we know that
the dark matter is there we can make

of how it's distributed even if we can't
see it directly so one further

advantage of gravitational lensing is
it's just like a magnifying glass so

you look through it things are bigger
and brighter than they would be if you

didn't have it so if you think about it
it's like a natural telescope in space

While dark matter plays a central role
in the birth and evolving life of

galaxies, there's another dark force
partly responsible for their growth.

On a cosmic scale, the galaxies are
rushing away from us due to the

expansion of the universe.

So if the universe is expanding, what's
driving it?

The only answer scientists can come up
with for now, a mysterious... Dark

is even stranger in some ways than dark
matter.

Dark energy is causing the universe to
expand right now

faster and faster with time.

This expansion, set in motion at the
universe's conception, has accelerated

the last few billion years.

because the dark energy that creates the
movement has increased over time.

By nature, the gravitational force that
binds galaxies together decreases over

time as the space between them
increases.

So instead of having a gravitational
pull, instead of slowing down the

of the universe, dark energy is speeding
up.

the expansion of the universe and it's
been doing that for the past four or

billion years in perhaps a billion

trillion more years the fate of the
universe and the impact its black holes

matter and dark energy have on mankind
will finally be known

When a star gets too close to the black
hole at the heart of an alien galaxy,

chaos erupts.

That's one of the findings from the
Galaxy Evolution Explorer mission, or

The Galaxy Evolution Explorer is an
ultraviolet telescope that observes the

universe at ultraviolet wavelengths.

And at these wavelengths, you're very
sensitive to studying young stars and

formation in galaxies back to half the
age of the universe,

billions of years ago.

However, we also look in the ultraviolet
for these luminous flares for when a

star is swallowed by a black hole.

The star can't hold itself together
anymore, and it's ripped apart, and the

from the star plunges into the black
hole.

Some of the gas will be ejected from the
system at high velocities, but some

fraction of the gas will plunge into the
black hole, and in that process, will

heat up to very high temperatures and
give off a luminous flare of ultraviolet

and X -ray radiation.

Thanks to GALX, Sufi Ghazari and other
researchers were able to watch it all

happen 4 billion light years away.

GALX, Hubble, and the Spitzer Space
Telescope.

will soon be getting a new neighbor
designed to help capture images of alien

galaxies.

The James Webb Space Telescope is due to
launch in 2013, designed to

explore the infrared spectrum like never
before.

Using the Webb Telescope, scientists
hope to be able to see through the dust

stars that block our view of the Milky
Way Center.

and provide a more complete picture of
not just our galaxy, but of all alien

galaxies.

The James Webb Space Telescope differs
from the Hubble Space Telescope in two

respects. Firstly, it's more powerful,
it's a bigger mirror.

Secondly, it is actually working at
slightly longer infrared wavelengths.

What Hubble and Webb have in common?

is the power to see beyond atmospheric
turbulence that prevents astronomers

getting picture -perfect images from 99
% of the sky.

Earth's atmosphere is turbulent.

It blurs out images from stars.

So if the Earth had no atmosphere, we'd
see stars as basically really perfect

dots of light.

But what happens is that because as the
light passes through the atmosphere,

it's distorted, it turns into a fuzzy
blob.

It turns out there are two ways to fix
this. One way is to go into space.

The other way is to instead fix the
telescope on the ground so that it

the effects of this turbulence. And
that's a technology known as adaptive

optics.

Adaptive optics measures the image of a
galaxy.

by the way its light reflects off
another lighted object, like a nearby

star.

To do adaptive optic sensing, you need a
very bright star because, of course,

you're making measurements of the
atmosphere hundreds or thousands of

second. So you need something bright to
look at.

Most stars are not bright enough to do
this.

At observatories like Keck in Hawaii,
adaptive optics uses a laser beam to

create the light needed for the
snapshots.

You can point it anywhere you want on
the sky, and so instead of looking at

1 % of the sky, you can look at most of
the sky with very, very high resolution,

very sharp images.

In this way, you can make images 10 to
20 times sharper from the ground than

could without adaptive optics.

It's just another tool in the kit, of
course, designed to bring the fantastic

reaches of alien galaxies back down to
Earth.

The universe, of course, is home to many
things larger than our small planet

Earth, larger than our solar system,
larger than our galaxy.

To think that our Milky Way is just one
of hundreds of billions of galaxies in

the observable universe, it really makes
you feel like you're a part of

something much larger than our small
planet Earth.

Like it or not, this is our place in the
universe.

A speck on a speck on a speck. Just one
tiny blue -green oasis of life

swimming in a vast ocean of alien
galaxies.