Finding Life Beyond Earth Page #10

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with Earth-like qualities.

So much for theory.

The question is:

Do such planets actually exist?

Geoff Marcy is one astronomer

trying to directly answer

that question.

He's a planet hunter, scanning

the heavens for signs of planets

that may have already formed

around other stars

thousands of light years away

from our solar system.

It is actually quite a challenge

to find planets

around other stars,

and the reason is very simple--

planets don't shine.

Planets are essentially dark.

NARRATOR:

By using advanced telescopes,

dedicated planet hunters

like Geoff

have found ways to overcome

this challenge.

If you watch a star,

it ought to have the same

brightness all the time, 24/7.

But if there's a planet orbiting

that star,

when the planet crosses in front

of the star,

the planet will block a little

of the starlight

and you'll see the star dim,

a tiny amount,

every time the planet

crosses in front,

over and over in a repeated way.

And, marvelously, you can learn

the size of the planet,

because the bigger

the planet is,

the more light

from the star it blocks.

And so we learn an enormous

amount of information

about these planets

just by watching stars dim.

NARRATOR:

Not surprisingly, most of the

planets astronomers have found

this way are giant ones

that block a lot of star light.

By also observing

the gravitational pull

they have on their stars,

Geoff calculates that most

of these giant planets

are made of gas and are unlikely

to be habitable.

But the holy grail is to find

far smaller, rocky worlds,

like Earth, where the conditions

for life could exist.

MARCY:

The challenge of finding

Earth-sized planets is enormous.

When an Earth crosses

in front of a star,

it blocks only one one hundredth

of one percent

of the light from the star.

NARRATOR:

The Kepler space telescope

is designed to detect

this subtle dimming.

Its mission:
to focus on one

tiny spot of space

and scrutinize 1 50,000 stars

for signs of planets

the size of Earth.

Sensitive enough to detect

minute dips in a star's light,

Kepler is already producing

mountains of data,

and thousands of new planet

candidates are being discovered.

MARCY:

Kepler has now already

discovered

a few planets that have

a diameter and a mass

that indicates clearly

the planet is rocky.

And so we now have for the first

time in human history

definite planets out there

among the stars

that remind us of home.

NARRATOR:

These first rocky planets

are too close to their stars

to sustain life.

But the sheer number

of smaller planets being found

is transforming our view

of solar systems beyond our own.

MARCY:

We've learned that nature

makes some large planets,

the size of Jupiter and Saturn,

but nature makes even more

of the smaller planets

the size of Neptune,

and even more of the planets

the size of the Earth.

The number of planets

is sort of like

the rocks and pebbles

you see on a beach.

There are a few big boulders;

there are many more rocks;

and there are an uncountable

number of grains of sand

that represent the Earth-sized

planets we see in the cosmos.

NARRATOR:

Geoff believes

it's only a matter of time

before we find

a habitable planet.

I suspect that this scene we see

here is one that's reproduced

billions of times over

among the Earth-like planets,

the habitable planets,

in our Milky Way galaxy.

NARRATOR:

But even if we find a world

just the right size

and in just the right place,

with oceans of liquid water,

could we detect life from a

distance of trillions of miles?

The James Webb space telescope

may be able to do just that.

Due to go into orbit

later this decade,

this new telescope is three

times more powerful than Hubble.

It will be able to analyze

starlight

passing through the atmospheres

of the closest Earth-like

worlds,

looking for the telltale signs

of life itself.

I think the chances are very

good that if you find a planet

with oxygen, methane,

carbon dioxide, nitrogen,

like our own Earth,

there's probably plant life

on that planet

that is producing the oxygen.

NARRATOR:

As telescopes see farther

and spacecraft voyage closer

to distant worlds,

new discoveries are transforming

what we thought we knew

about our solar system

and our galaxy.

GREEN:

I am constantly awestruck

by the data that's coming in

our current fleet of missions.

Science fiction didn't tell us

in any way, shape or form

what we're finding out now.

SQUYRES:

Years from now, people are

gonna look back on this

as being the golden age of

exploration in the solar system.

You can only go someplace for

the first time once, right?

And we're doing that now.

NARRATOR:

Scientists are finding

organic molecules,

the raw ingredients

that life needs to take hold,

in our solar system and beyond.

GLAVIN:

I think we'd be naive to think

that this chemistry

and life here on earth

is the only place that it's

happening in the universe.

I mean the fact is that

we've got billions of galaxies,

you know, trillions

of star-forming environments

that probably have

the same chemistry going on.

NARRATOR:

The right conditions

that make a world habitable

could be more widespread

than ever imagined.

All of this leads us to think

that life should be an easy

start on another world.

NARRATOR:

And the same forces of nature

that forged life here

could be playing out elsewhere

in our galaxy.

A lovely exercise for everyone

to do

is to look up

into the night sky,

look at the twinkling lights

and realize that those stars

by and large all have planets.

And that's just our galaxy.

There are hundreds of billions

of galaxies out there

like our Milky Way,

and so the number of planets

in our universe

is a truly uncountable number.

NARRATOR:

So the race is now on

to see if life actually exists

beyond Earth.

Will life first be discovered

on a moon such as Enceladus?

Will it be found

by an advanced telescope?

Or will it be found at all?

Whatever the answer,

many believe this is a turning

point in history,

when we at last have the

technology and the know how

to find out if there is life

beyond Earth.

The exploration continues

on NOVA's website,

where you can watch any part

of this program again,

take a tour

of the solar system,

find out how we can detect

distant planets

where life might be possible,

and dig deeper into space and

flight with expert interviews,

interactives, video clips

and more.

Follow NOVA on Facebook and

Twitter, and find us online

at pbs.org.

Major funding for NOVA

is provided by:

And...

And the Corporation

for Public Broadcasting

and by PBS viewers like you.

Additional funding is provided

by Millicent Bell, through:

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