37x15 - Hunting the Edge of Space: The Mystery of the Milky Way

[bunniefuu]

NARRATOR:
Today's vast and powerful telescopes

are taking us
on an unimaginable quest

to unlock the secrets
of the cosmos.

They are going to tell us
in detail

what our universe is made of,
how it was born,

how our universe is evolving.

NARRATOR:
They take us back to the dawn of time,

to the very birth
of the universe,

show us giant clouds where
stars and planets are born.

MAN:
Each time a new telescope looks in a different way

at the universe

we learn something new and
profound about the universe.

NARRATOR:
In stunning clarity, we can now watch stars exploding,

galaxies colliding,
and the violence of black holes.

There's a whole hidden universe
out there.

We see the universe continuously
changing and evolving.

NARRATOR:
Revolutions in technology and ever larger telescopes

are pushing forward
the frontiers of space.

Every time we try and explore
a new part of the universe,

we have these great discoveries
and these great surprises.

NARRATOR:
But where did this race begin?

Where will it take us?

This is the remarkable journey
through 400 years

of an extraordinary device

that is changing everything
we thought we knew.

Telescopes have revolutionized
our understanding of ourselves

and our place in the cosmos
and our mindset about who we are

and where we came from.

NARRATOR:
"Hunting the Edge of Space," up now on NOVA.

Major funding for NOVA is
provided by the following...

Supporting NOVA and promoting
public understanding of science.

And the Corporation
for Public Broadcasting

and by PBS viewers like you.

Additional funding from:

Inspiring tomorrow's engineers
and technologists.

Additional funding
for "Hunting the Edge of Space"

is provided by:

Supporting original research

and public understanding
of science, technology,

engineering, and mathematics.

And:

(narrator)
Giant doors 8 stories high slide apart.

These twin eyes are preparing
to look into deepest space.

They belong to the
large binocular telescope.

It is one of the most
powerful telescopes on Earth,

costing over $120 million.

These 28-foot-wide mirrors
collect light from objects

millions of times fainter
than anything our eyes can see.

600 tons of machinery
turn the mirrors

to look more than
13 billion light-years away

to the very edges of
the visible universe.

Super telescopes like this
are taking real images

that illuminate the
darkest corners of our skies.

Billowing clouds
of gas and dust

are buffeted by supersonic winds

and lit up by thousands
of energetic new stars.

57 trillion miles high,

these giant clouds of gas
and dust are stellar nurseries,

hiding the very birthplaces
of stars and planets.

Suddenly,
a star's expl*sive death

sends its super heated gas

ripping through space at
hundreds of miles per second,

and in faraway galaxies
we can take images

of invisible jets of energy

screaming out from one
of the most mysterious objects,

a supermassive black hole;

all because of
hi-tech telescopes.

The telescope
has changed the way

we as a species
think about ourselves.

With a new telescope,

you're always going
to find something new

because you always add
to your ability to see more.

(narrator) These breathtaking
images are only possible

because extraordinary telescopes
like these are staring out

night after night
across the globe and in space.

Over the past 4 centuries,
revolutions in technology

have transformed this
groundbreaking instrument.

So where did it all begin?

The journey starts with
one man and 2 pieces of glass.

It is the summer of 1609.

Mathematics professor,
Galileo Galilei, is building

his own version of an
extraordinary new invention.

It is the telescope,

a name that means "far-seeing"
in ancient Greek.

The invention has spread
like wildfire across Europe

from a small town in Holland.

Spectacle makers working on

the most precise glass lenses
of the day

discovered that
2 different types of lenses

held at just
the right distance

produce a surprising
optical effect.

They act like a magnifying glass
for distant objects.

This is the birth
of the telescope.

Galileo immediately sees
the potential of the invention.

(man) Galileo's a practical
mathematician, that's his trade.

He designs instruments,

he teaches the use of these
instruments,

and these instruments
are often used for warfare.

(narrator)
Galileo works out how to increase

the magnifying power
of the telescope

to 8 times what
our naked eyes can see,

and he hits on
a military use for it.

It would be
a particular advantage

if you could see the enemy
before he can see you.

(narrator)
The Venetian military buys this new device

as a spyglass for
spotting enemy ships.

But then Galileo
turns his telescope

from the Earth to the sky
and starts a revolution.

By turning the
telescope to the heavens,

Galileo enters a whole
new regime of practice

where this, this instrument
can be used to discover things

we didn't know
before about the world.

(narrator)
All astronomers knew of the heavens before Galileo

was what they could
see with the naked eye,

the stars and the moon.

But today,
even amateur astronomers

can see much, much more.

Alexandra hall spends her nights

gazing up at the night sky
from her backyard.

(Alexandra)
I never get bored of looking at the night sky above our heads.

It's like 2000 diamonds
sprinkled across black velvet.

And then the moon arises,

and watching the moon
go through its phases,

I mean, it looks different
every time you look at it.

(narrator)
To the naked eye,

5 stars sometimes appear
brighter than the rest,

and watched
over the course of nights,

they seem to move against the
backdrop of the other stars.

(Alexandra)
They don't just stay in the same place

like all the rest of the stars;
they move around.

Sometimes they're visible;
sometimes they're not.

(narrator)
Each of these bright stars is a planet,

a name that simply means
"wanderer" in Greek.

Venus, the evening star,
skims the horizon at sunset.

Mars glows red.

Jupiter and Saturn outshine
everything around them.

We now know that these wandering
stars are actually other worlds,

like the Earth, planets
as we understand them today.

But in Galileo's time, everyone
believes they are just stars.

There is only one world
in the universe, our Earth,

and it sits at the
very center of everything.

The sun appears to circle
the Earth during the day,

and over the long
course of the night,

the moon and stars also appear
to rotate across the heavens,

circling the Earth
in giant orbits.

When you stand outside, even
just for a few hours at night,

you suddenly notice that
all the stars and the planets

and the moon; everything is
wheeling around your head.

It's like you're at
the center of things!

Really quite a powerful feeling.

(narrator)
But Galileo is about to show that this is just a feeling.

He starts to shake
the known world order

when he looks at the moon.

The belief in his day was

that all the heavenly bodies
were flawless.

In the old cosmology,

the moon was a heavenly body

and therefore perfect.

(narrator)
But looking across a quarter of a million miles of space,

Galileo sees
something very different

from the smooth sphere
he expects.

He sees instead a moon scarred

with craters and valleys.

It must've been an
extraordinary moment

for Galileo to peer
with his little

itty-bitty crummy telescope
at the moon and see craters,

mountain ridges, valleys.

He saw for the first time

geographical terrain on
another astronomical object.

(narrator)
This means our Earth is not unique in the cosmos.

These patches that
you see are mountains.

The moon isn't smooth,
it's like the Earth.

But this is just the beginning.

Next, Galileo turns
his telescope on Jupiter,

one of the wandering stars.

He sees it as no one
has ever seen it before.

This is an exact
computer reconstruction

of what Jupiter looked like
through Galileo's telescope.

Calibrated
on Galileo's actual lenses,

itho
what a challenge he faced.

A replica of his telescope

reveals how hard it is
to get a still image.

Well, when I actually got
Jupiter in the telescope,

it was really difficult to focus
because the lens quality is

not very good compared to the
lenses that we would get today.

(narrator)
To the naked eye, Jupiter looks like a bright star,

a spot of light.

Seen through
Galileo's telescope,

all other stars
remain as spots of light.

But Jupiter suddenly appears
as a much larger round disk.

This blurry, shaky view
of Jupiter is a revelation.

Galileo comes to an
extraordinary conclusion.

Jupiter must be
a sphere, another world,

a planet,
as we understand it today

and around it
are even more surprises

(Geoff Marcy)
Picture yourself, you've just glued a little piece of glass

on the front of a long tube,
and to your utter surprise,

you see 2 or 3 or maybe
even 4 stars next to Jupiter,

like little ducklings
following a duck.

(narrator)
Night after night,

Galileo notes the changing
position of these new stars.

(Geoff)
Imagine your surprise!

Why should stars
be following Jupiter?

And of course, Galileo
learned only after

a week or 2 of watching
those little ducklings

following their mother

that those, in fact, were
moons orbiting Jupiter.

(narrator)
Galileo knows he has something spectacular on his hands.

He publishes his findings

in a book called
"The Starry Messenger."

(Albert Van Helden)
It is the most expl*sive scientific book ever written.

Its impact was immediate.

Galileo became a
superstar overnight.

(narrator)
But the biggest revelation is yet to come.

Galileo is recording something

that will change our view
of the universe forever.

He observes the planet
Venus changing shape and size

over a period of months.

As Galileo watches, Venus
transforms week after week

from a large crescent
to a small, round disk.

Then, shadows creep again
across the planet

returning it
to a large crescent.

To Galileo, the pattern of
shadows he sees on Venus

can only mean one thing:

Venus is going around the sun.

But the belief at the time

was that everything
circled the Earth.

Earth is no longer
the center of the cosmos.

And so it's said to us

wow, we're not at the center
of the universe anymore.

These very simple observations

literally rocked the foundations
of the world.

No longer is the Earth
the center of the universe.

The sun is the
center of the universe,

despite what our
ordinary senses tell us.

(narrator)
But these discoveries

famously bring Galileo
into direct conflict

with the Roman Catholic Church.

The church taught that God

placed mankind on Earth

at the very center of creation.

Defending a
sun-centered universe,

Galileo was actually challenging
the authority of the Church.

He was contradicting
what was considered

as the legitimate
interpretation of the Bible,

and the Church
couldn't tolerate this.

(narrator)
But what Galileo saw

is the solar system
we understand today.

The discoveries
that Galileo made,

they changed the world forever;

the world of science,

the relationship between
science and religion,

and the universe forever.

(narrator) This is
the universe

Galileo helps
reveal, planets

and their moons
orbiting the sun.

Telescopes today now reveal
this solar system in detail

that Galileo
could only dream of;

explosions on the
surface of the sun

the power of a
billion megatons of TNT...

features in the great
red spot on Jupiter,

a vast stormy vortex large
enough to swallow 3 Earths.

On Jupiter's moon Io,
we can watch volcanoes

spew ash and gas
high into space;

on mars a canyon 5 times
deeper than the Grand Canyon...

and a volcano
3 times higher than Everest.

On the surface of Venus

beneath roiling clouds
of sulfuric acid

mountains rise from
the rocky surface...

and circling the sun

at the very perimeters
of our solar system,

dwarf planets
made of rock and ice.

But one planet remains
an enduring mystery

for even the most
advanced telescopes...

Saturn and its enigmatic rings.

Galileo was the first to see

that this planet
was different from the rest.

For him, the strange features
he observed looked like ears.

He presumed they were moons.

Later astronomers saw them

as a vast flat ring
encircling the planet.

Then, one man discovered
that this ring was, in fact,

made up of several
concentric rings.

That man was astronomer
Giovanni Cassini.

Now, a mission named
after him is investigating

why Saturn has rings at all
and what they're made of--

NASA's Cassini Mission.

(man) 3...2...1

and liftoff
of the Cassini Spacecraft

on a billion-mile trek
to Saturn.

(narrator)
In the nose cone of this rocket

is the space probe, Cassini.

Ahead is a 2-billion-mile
journey to the planet Saturn.

Onboard the probe are
sophisticated telescopes.

They will investigate
Saturn's mysterious rings

by traveling
as close to them as possible.

(man)
Good, solid rocket booster separation.

Heading of 1-5-2.

(narrator)
As Cassini heads for Saturn,

the furthest planet
in Galileo's solar system,

it uses the massive
gravitational pull of Jupiter

as a boost
to slingshot it out

millions of miles
towards its destination.

In the world of telescopes,
Cassini has some of

the fastest moving telescopes
in the solar system,

going by Jupiter at something
like 70,000 miles per hour.

(narrator)
Even at such tremendous speeds the journey still takes 7 years.

But finally Cassini
approaches Saturn,

934 million miles from Earth.

It dives
through Saturn's outer rings

to enter orbit
around the planet.

These are some of the images
Cassini takes of the rings.

They may look solid,
but they are made up

of billions of chunks
of ice and rock,

ranging in size
from a grain of sand

to the size of a house,

and they are spread over
hundreds of thousands of miles.

But where is all
this stuff coming from?

Cassini's telescopes reveal
that the inner rings

are made up of material

blasted off the surfaces
of Saturn's moons by meteorites.

But the furthest visible ring
from Saturn is still a mystery.

This image
taken by Cassini

shows that unlike
the innermost rings,

the outermost ring is a ghostly
mist of microscopic particles.

Astronomers suspect that
the icy moon Enceladus

could be where the mist is
coming from,

but until now, no one has
been able to work out how.

Then, Cassini's
telescopes see something

never observed before,

vast plumes of vapor
streaming from fissures

in the surface of Enceladus.

These plumes go up
hundreds of kilometers.

That's pretty exciting to find
erupting out of an icy moon.

(narrator)
Could these plumes be the source of the outer ring?

To find out,

Cassini's telescopes do
something extraordinary.

They fly through the plumes

and "taste" the vapor
with onboard detectors.

That's a spectacular thing to be
able to do,

to be able to tap the interior
of an icy satellite.

(narrator)
Back at mission control,

astronomers analyze the data
streaming in.

The vapor
pouring out of Enceladus

is made up of ice,
salt, and ammonia.

It is exactly the same
material as the outer ring.

It can only mean one thing.

Enceladus' plumes are the source
of the misty ring.

This is a major discovery.

Cassini's spaceborne telescopes
are solving

the mystery of Saturn's rings

that has plagued astronomers
for centuries.

Telescopes today are
journeying deeper into space

and searching further
to discover secrets

that Galileo could
never have imagined.

But to capture
pristine images like these,

telescopes had to undergo
a dramatic evolution.

Back in the 1650's, the
first step in this evolution

was going to great lengths--
quite literally.

Telescopes became very long--
15, 20 feet.

(narrator)
The problem with early telescopes was fuzzy images.

The reason?
The shape of the lens.

As NASA astrophysicist
Kim Weaver demonstrates,

when a strongly-curved lens

bends or refracts
beams of light,

the light doesn't all
come to a single point.

First of all, the different
beams of light don't line up,

and so the image that
you get with this lens

would be really fuzzy.

Also, some of the light
has its colors split out,

and that distorts the image.

(narrator)
The only way to minimize the blurriness

and the rainbow colors

is to use thinner lenses
with a shallower curve.

Because the light comes to a
focus further from the lens,

refracting telescopes get longer

and get greater magnification.

17th-century astronomers
make ever thinner lenses

and space them further apart.

By about 1660,
telescopes

have magnified
50 or 100 times,

and those lengths
increased

and increased
and increased.

(narrator)
This is the first space race.

On the quest
to see ever further,

telescopes reach
absurd proportions,

up to 150 feet in length,

half the length
of a football field.

These unwieldy telescopes
are better,

but astronomers want
to see even more detail,

and these telescopes

don't eliminate
the rainbow colors altogether.

Then, one of science's
greatest minds

sets out to solve the problem,

Isaac Newton.

He takes a look at light itself.

Newton found that white light

was, in fact, composed

of all these different colors,

the colors of the rainbow.

(narrator)
As white light passes through a glass prism,

it bends, or refracts,

breaking up into the colors
of the rainbow.

This was the root of
the astronomers' problems.

Now, a lens is a kind
of a prism, if you like.

Once the light hits the lens
and passes through it,

it's broken up into its colors.

So Newton says well,

we'll abandon refracting
telescopes completely.

There's no future in this,
just forget them.

I'm going to design a telescope
which has

mirrors as the primary
components instead of lenses.

(narrator)
Newton will use mirrors in his new telescope.

He believes he can do this
because when mirrors are curved,

they bring light to a focus
just like a lens.

I'm using this lens right now

to focus the light
from the sun behind me,

and if I hold it just right
to a point on the card--

Oh my goodness,
it's catching on fire!

That was smoking!

(narrator)
Next up: the curved mirror.

And you can see
as I bring it closer

to the focal point
of the mirror,

it actually begins to
burn the paper again.

(narrator)
But there's one critical difference

between a mirror and a lens.

The light bounces off
the mirror's surface,

it doesn't pass through it,
so there are no rainbow colors.

Newton creates a tiny
telescope only 6 inches long.

He makes a curved mirror
only 1-1/2 inches across

and inserts it into
the base of the tube.

Light from the heavens
passes down the tube,

reflects off the curved mirror,

then reflects off
a second flat mirror,

and is focused by an eyepiece.

This small reflecting
telescope works just as well

as a 4-foot telescope
that uses lenses.

Isaac Newton,
in creating the first reflector,

eradicates rainbow colors,

a problem that has
plagued telescopes

since the time of Galileo.

Today, telescopes
stare out from observatories

across the world and in space.

They are expanding
our view of the cosmos,

capturing light that has been
traveling across our universe

for billions of years.

The clarity is so exceptional

that these real images continue
to amaze and inspire us.

All these telescopes
rely on large mirrors

with the perfect shape.

Making them is a feat

of precision engineering.

Deep below the football field
of the University of Arizona

is a hi-tech mirror lab
where glass blocks are melted

in giant furnaces at over
2000 degrees Fahrenheit,

the temperature
of volcanic lava.

The hot liquid is spun into
super-smooth curved dishes.

The 20-ton disks of
cooled glass are then ground

to within fractions of a human
hair to make the precise shape.

It is only when a thin
film of aluminum is applied,

only 100 nanometers thick,

that the glass dishes
become mirrors

like those of the large
binocular telescope in Arizona.

At 28 feet wide,

these mirrors
are 64,000 times the size

of Isaac Newton's first mirror,

and they can
collect light from stars

billions of light-years away.

In Isaac Newton's day,

making large mirrors
exactly the right shape

is far too difficult.

It will be
a century after Newton

before a new pioneer

picks up his revolutionary
design and transforms it.

That man is musician and amateur
astronomer William Herschel.

Herschel has great ambitions.

He wants to use a larger
version of Newton's reflector

to see further into
space than anyone before.

Herschel is a musician,
he's not an astronomer.

He's a clarinet player, he's
an impresario, he's a composer.

But his real passion
isn't music, it's astronomy.

(narrator)
Herschel wants to look anew at the night sky.

He wants to look beyond
the planets to the stars.

And to see the
very faintest stars,

invisible to other telescopes
of the day,

Herschel needs big mirrors.

He builds telescopes that
are bigger than other people's

because he realizes that
the wider his aperture,

the more light he can collect,

the further he
can see into space.

(narrator)
Making large, curved mirrors though,

is still a major technical
challenge in Herschel's day.

Glass mirrors have
not yet been invented.

Mirrors are still made of metal.

So working in his basement,

Herschel casts disks
of a metal called speculum,

a special mixture
of molten tin and copper.

These will become his mirrors.

We don't know what the neighbors
thought of this mad fiddler

burning the entire road down.

(narrator)
Casting the metal disks is just the first step.

To become mirrors,
the cooled flat disks

need a shiny, curved surface.

Herschel painstakingly grinds
and polishes the metal disks

by hand into the precise
shape needed to form an image.

(Jim Bennett)
This is the reflecting mirror,

the most precious component
in the telescope, made in metal

by William Herschel himself,
made by hand.

He was like
a craftsman making something

which required
manual skill

as well as
intellectual effort.

(narrator)
This telescope, over 200 years ago,

makes a revolutionary discovery.

...or perhaps
a comet.

(narrator)
In 1781, Herschel peers night after night into the heavens,

at his side,
his sister Caroline.

She records all
their observations

and will become a
prominent astronomer herself.

Her observations were critical.

(David Devorkin)
She was one of his true secret weapons.

(narrator)
Then on March 13, Herschel sees an object through his telescope

that they have
never recorded before,

a very faint star
that seems to move

against the backdrop
of the other stars.

This wandering star is
a brand-new planet, Uranus.

The planets
had been identified

since the dawn
of written astronomy.

And then suddenly,
you have this clarinet player

with homemade telescopes
in his back garden,

and he discovers another one.

The thing is
utterly astonishing!

(narrator) Uranus,
with its own set of rings,

is the size of 63 Earths.

But no one has
identified it before

because it is barely
visible with the naked eye.

1900 million miles
from the sun,

it is twice as far
from the sun as Saturn,

until then,
the furthest known planet.

Overnight, Herschel doubles
the size of the solar system.

The discovery sparks
a frenzied hunt for planets.

It is a quest that the world's
most sophisticated telescopes

continue to this day.

The sun is setting
on Mauna Kea, Hawaii.

The giant dome of
the Keck Observatory opens.

Its 33-foot-wide mirror
turns towards the heavens.

Geoff Marcy is one of the
world's foremost planet hunters.

He is using
the Keck telescope

to hunt for planets
in solar systems beyond our own.

Well, when you look
up into the night sky,

you see all the thousands
of twinkling lights.

Those are stars like our sun.

(narrator)
Planet hunters like Marcy think that many of these stars

could have their
very own planets.

But finding them
is another question.

Your mission as a
planet hunter is to find

that needle in a haystack.

(narrator)
Telescopes only made a breakthrough

as recently as 1995.

They recorded a perfectly
ordinary star wobbling minutely.

There was some
gravitational pull on the star,

evidence of a planet
they couldn't see

orbiting around it...

Exoplanet: 51 Pegasi b.

The discovery
of the first planet

around a normal star,
around 51 Pegasi,

was an extremely profound moment
for humanity.

We now know as a species

that there are
other worlds out there.

(narrator)
Since then, teams of astronomers across the world

have found evidence for
more than 400 other exoplanets.

But most of the planets
discovered so far

are gas giants
the size of Jupiter,

orbiting far too close to
their suns to support life.

And a planet
that can support life

is what the planet hunters
are really after.

(Geoff Marcy)
What we'd love to know is

whether there are other Earths,
habitable worlds, out there,

whether they are
lukewarm with liquid water,

having the vibrancy, the
conditions suitable for life

and perhaps even
intelligent life.

(narrator)
Looking for small rocky planets like Earth

is a whole new ball game.

Cue a brand-new NASA

space telescope called Kepler.

(man) And liftoff of the
Delta 2 rocket with Kepler,

on a search for planets
in some way like our own.

(narrator) Kepler's
3-year mission

is to find planets

the size of our Earth
orbiting other stars.

(man)
The vehicle is now going supersonic.

I think Kepler is going to
go down in the history books

as one of the
greatest telescopes ever

in the history of humanity.

(narrator)
Kepler's mission is to collect light

from a field of 100,000
stars inside our Milky Way,

looking for clues
to other worlds.

As the dust cover falls away, it
begins measuring the starlight.

All that happens
is you watch the star,

and Earth happens to
orbit in front of the star.

It blocks a tiny fraction
of the starlight on its way.

And when it blocks that light,
the star dims a tiny amount.

(narrator)
Kepler has already discovered several new exoplanets.

It hasn't found an
Earth-like planet yet,

but astronomers believe
it is only a matter of time.

I believe in the next few years,
we will have

the first detections
of Earth-like planets,

places that you might
indeed want to call home.

(narrator)
Though Kepler is looking at 100,000 stars,

this is only
a tiny patch of the sky.

There are hundreds of billions
more stars out there to search.

The hunt for exoplanets
requires that we look at

hundreds of thousands of stars.

(narrator) So planet hunter
David Charbonneau

uses more down-to-earth
technology.

(David)
The revolution has been to use "humble" telescopes

to study the closest stars.

(narrator)
Using small robotic telescopes,

he scans 2000 stars that are far
less bright than our own sun.

This makes it easier
to spot a small planet

passing in front of it.

And he has
discovered a planet

only 2.7 times the size
of our Earth-- a super Earth.

Importantly, it appears
to be covered in water

and have an atmosphere.

At 400 degrees Fahrenheit,
it is still too hot to inhabit,

but it's a tantalizing
glimpse of what is out there.

If we can succeed in finding
habitable worlds, then

that would have implications
far beyond mere astronomy.

(narrator)
In a bid to find habitable planets,

the professional astronomers

are getting a little bit
of help on the side.

(David)
Amateur astronomers are central

to our understanding
of planets orbiting other stars.

The amateur astronomers
are stationed, of course,

all over the world,
they have telescopes,

which are certainly large
enough to conduct a survey.

(narrator)
Ron Bissinger is one such astronomer.

He is following in the
footsteps of William Herschel

and his discovery of Uranus.

(Ron)
When I come up here every night and open that thing up,

fire up the telescope,
fire up the computer,

I know the target star
I'm gonna look at,

everything is mine, that's
my world alone.

I may for that night be

the only human being looking
at that star.

(narrator)
He has a telescope advanced enough

to help out the professionals.

Professional observatories
cannot spend the time

staring at one star night
after night after night.

But we can.

(narrator)
He too waits for the telltale dimming of a star's light,

just one star at a time.

To find a world out there
no one's ever known of

or seen or detected before
from your own backyard,

a person who is not
a career scientist,

I don't know of any
other scientific endeavor

where somebody like me
or so many other amateurs

can do that kind of thing.

(narrator)
Bissinger's patience has paid off.

He has already discovered

several large exoplanets
of his own,

though all are too close
to their suns to support life.

Like all known exoplanets,

they orbit stars
within our galaxy.

We know today that this is
a vast collection of stars

in which our sun, Earth,
and solar system also reside.

But just over 200 years ago,

we didn't even know
we lived in a galaxy.

Discovering this
just by looking at the stars

would be a great challenge.

In 1781, William Herschel is

the man
who takes the challenge on.

To do it, he just needs
a bigger telescope.

He builds a
reflector 20 feet long.

With this he is able to see

more stars than
any other telescope on Earth.

And he observes one part of
the night sky in particular,

the strip of stars
we call the Milky Way.

This will be Herschel's key
to the shape of our galaxy.

On a clear night,

the Milky Way
is a majestic spectacle,

a brilliant band of
starlight arcing overhead.

To the ancients,
it looked like milk

had been poured across the sky,

and it's why the Greeks
first called it

the "galaxias kuklos,"
or milky circle.

It's from this
we get our word "galaxy."

It fascinates astronomers
to this day.

The Milky Way stretches

across the sky from horizon
to horizon.

It's like a big band that goes
all the way around us.

So from here on Earth,

it's kind of like we're sitting
on the hub of a wheel,

and the Milky Way is a big tire
all the way around us.

(narrator)
Looking through his telescope,

Galileo was the first to
discover that the Milky Way

is made up of stars.

But no one knows it is a galaxy.

They don't even really
know what its shape is.

Finding this out now becomes
Herschel's obsession.

What is the actual
shape of the Milky Way?

We're in the middle
of it presumably.

What would it look
like from the outside?

(narrator)
He gazes tirelessly at the heavens night after night

mapping the positions of stars.

(Jim Bennett)
Herschel's nothing if not passionate.

He's a natural obsessive.

But good for him,

he does something extraordinary
with this obsession.

(narrator)
Herschel maps the distribution of all the stars he can see

in a great circle that
cuts through the Milky Way.

(Michael Hoskin) He introduced
into astronomy

the technique of star counts,

and just counting-- how many
stars can I see?

In one direction you see very
few stars,

in another direction you see
zillions of stars, and so

he plots this distribution

and comes up with
a view of the Milky Way.

(narrator)
The survey takes over a year of precise recording.

Herschel finally produces
a map called the grindstone,

because of its shape.

For the first time Herschel sees
that the Milky Way

is more than just
a strip of stars in the sky.

It is a vast disk of stars.

And Herschel believes
this is the whole cosmos.

When Herschel made his map
of the Milky Way Galaxy,

to him, he was making a map
of the entire universe.

(narrator)
The edges of this star disk

are the edges
of Herschel's universe.

Inside it lies our solar system,
our sun, and our Earth.

The amazing thing is
that over 200 years ago,

Herschel almost got it right.

The most powerful telescopes
on Earth and in space now

reveal that Earth and our solar
system lie in a spiral arm

in the suburbs of our galaxy,

dwarfed within a giant disk
of 200 billion stars

spinning together around
a bright central bulge

that hides
a supermassive black hole.

The Milky Way is so large

that it would
take 100,000 years

traveling
at the speed of light--

that's 670 million
miles per hour--

to cross from one
edge to the other.

♪
♪

Now, a new telescope
is about to see

what more it can find out
about our Milky Way...

The Herschel Space Observatory.

Bill Latter is a key member
of the Herschel team.

(Bill)
Herschel will map the entire Milky Way Galaxy

in terms of how stars
are formed, how stars die,

and how the galaxy
is put together.

(man, in French)
Sept, six, cinq...

(narrator)
After years of careful preparation,

the finely-tuned telescope
is about to launch.

(Bill Latter)
Launch is a violent thing.

There's no other
way to describe it.

We light
this candle, it shakes,

we throw the thing
out into space,

and we only can hope
that it all holds together.

One million miles above Earth,

the largest mirror
ever launched into space

is looking beyond visible light

to wavelengths
our eyes cannot even see--

the far infrared.

This means it can measure tiny
fluctuations in temperature

and see right
through clouds of dust

to give us the clearest
images of the Milky Way ever.

(Bill Latter)
The results were astonishing.

What we're able to see with
the Herschel Space Observatory

are right into the
cradles of newborn stars.

We see something very different
than we would with our eyes.

If we looked at the same
region in visible light,

it would be full of stars.

But here in the infrared,
we're seeing the dust and gas

that really make up the majority
of material in our galaxy,

and it's where stars form.

(narrator)
No other telescope is able see

the Milky Way in this detail.

Stars in these regions
of our Milky Way

were invisible
to William Herschel.

Yet over 200 years ago,

he can see more in the night
sky than anyone before him.

And as he maps the stars
through his telescope,

one great mystery remains,

thousands of strange objects
that astronomers can't explain.

They call them "nebulae,"

Latin for clouds.

There are fuzzy patches of light
that you can see in the sky.

They kind of look like
pieces of the Milky Way

that have been detached,
and a couple of them

you can actually just see
with the naked eye.

But through a telescope,
there are thousands of them,

and they have all kinds

of different patterns
and shapes and sizes.

They're quite beautiful
and quite mysterious.

One of my favorites
is the Andromeda Nebula,

which you can actually
see with the naked eye.

And through a telescope...

if I can find it here...

it's really mysterious--
you just see this glowing light

that gets brighter and brighter
towards the middle.

It's like, what is that?

(narrator)
Herschel makes a catalogue

of these mysterious objects,

counting and classifying
over 2300 nebulae.

But even with his
giant telescopes

Herschel can't tell what
they are or where they are.

There were little smudges
that you could see

in the best telescopes
of the day.

Those smudges were thought to be
nebulae, clouds of gas.

But people began wondering how
far away those smudges were.

(narrator)
The mystery of the nebulae

will continue to perplex
astronomers for decades.

60 years later at
Birr Castle, Ireland,

the eccentric Lord Rosse

builds the largest telescope
in the world.

He wants to finally crack
the enigma of the nebulae.

6-story walls support
a tube 60 feet long,

and the mirror is
the height of a man.

(Jim Bennett) He's
a natural engineer.

And if you see the Great
Leviathan of Parsonstown,

as it's called, this great
6-foot aperture telescope,

it's a vast machine.

(narrator)
Lord Rosse points the telescope at the nebulae.

He sketches what he sees.

For the first time the fuzzy
clouds begin to come into focus.

Inside some of them
Rosse can see stars

and spiraling structures.

But there is a problem--

Rosse's telescope can
only move up and down,

and the mirror tarnishes easily.

The giant telescope
falls into disrepair.

It will take 80 years,

a great revolution
in technology,

and a telescope bigger
than Galileo ever imagined,

high on a mountain peak,

before the mystery
is finally solved.

♪
♪

This great telescope on
Mount Wilson, California,

will reveal that the spiral
nebulae first sketched by Rosse

are, in fact, separate
galaxies beyond our own.

The universe will
be blown wide open.

It completely revolutionized

our idea of the scale
of the universe.

No longer were we just confined
to the Milky Way.

(narrator)
Our galaxy, the Milky Way,

will no longer be the
only galaxy in the cosmos.

It will become just one

of hundreds of billions
of galaxies

spinning within
an inconceivably vast universe.

(Wendy Freedman)
The introduction of telescopes to astronomy

opened up an entirely
new window on the universe.

(narrator)
The race will continue to build bigger and bigger.

Our technology has reached
a point where we can build

gigantic
ground-based telescopes.

We can launch huge
space-based telescopes

and see the most distant
things in the universe.

(narrator)
The telescope is pushing forward the frontiers of our universe.

So what will colliding galaxies

billions of light-years away
tell us about our own Milky Way?

And right at the limits
of the cosmos,

what will the afterglow
of the big bang

tell us about
how our universe began?

Every time you try and explore
a new part of the universe,

we have these great discoveries
and these great surprises.

Most surprising of all,
telescopes will reveal

that right now, we can
only see 5% of the universe.

Only a few percent
of the total matter

and energy content
of the universe

consists of things
that we can see.

(narrator)
So what is the rest of the universe made of?

In many ways we're
at the beginning

of our quest of discovery.

We're learning about the
major part of the universe

we didn't even know existed
10 years ago.

(narrator)
Telescopes will point to an elusive and powerful force

that is shaping the
fate of our universe--

dark energy.

I think dark energy is

the most mysterious thing
we've ever discovered.

(narrator)
Telescopes are on the brink

of a new era of discovery
and exploration.

♪
♪

It's such an exciting future

to think about all of the
discoveries yet to come.

♪
♪

We are uncovering a universe

we are only just beginning
to understand,

as telescopes that are

bigger and more sophisticated
than ever

continue the
hunt for the edge of space.

♪
♪

Next time on "NOVA"...

For the next generation
of telescopes

a new quest begins--
Can we see the invisible?

10,000 galaxies
in that single spot.

(narrator)
Go back further in time.

We could actually
deduce things that happened

in the first trillionth
of a trillionth of a second.

(narrator)
Reveal mysterious forces shaping the cosmos.

Dark energy is one of the keys

to understanding
the fate of the universe.

(narrator) Watch
the next episode of...

(narrator) Watch
the next episode of...

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