The search for planets beyond our solar system

I'm here to tell you about
the real search for alien life.

Not little green humanoids
arriving in shiny UFOs,

although that would be nice.

But it's the search for planets

orbiting stars far away.

Every star in our sky is a sun.

And if our sun has planets --

Mercury, Venus, Earth, Mars, etc.

Surely those other stars should
have planets also

-- and they do.

And in the last two decades,

astronomers have found
thousands of exoplanets.

Our night sky is literally
teeming with exoplanets.

We know, statistically speaking,

that every star has at least one planet.

And in the search for planets,

and in the future, planets
that might be like earth,

we're able to help address

some of the most amazing
and mysterious questions

that have faced humankind for centuries.

Why are we here?

Why does our universe exist?

How did earth form and evolve?

How and why did life originate
and populate our planet?

The second question that
we often think about is:

Are we alone?

Is there life out there?

Who is out there?

You know, this question
has been around

for thousands of years,

since at least the time
of the Greek philosophers.

But, I'm here to tell you
just how close we're getting

to finding out the answer
to this question.

It's the first time in human history

that this really is within reach for us.

Now when I think about
the possibilities

for life out there,

I think of the fact that our sun

is but one of many stars.

This is a photograph of a real galaxy,

we think our milky way
looks like this galaxy.

It's a collection of bound stars.

But our milky way is one of
hundreds of billions of stars

and our galaxy is one of upwards
of hundreds of billions of galaxies.

Knowing that small planets
are very common,

you can just do the math.

And there are just so many stars
and so many planets out there,

that surely, there must be life
somewhere out there.

Well, the biologists get furious
with me for saying that,

because we have absolutely no evidence.

for life beyond earth, yet.

Well, if we were able to look
at our galaxy from the outside

and zoom in to where our sun is,

we see a real map of the stars.

And the highlighted stars are
those with known exoplanets.

This is really just
the tip of the iceberg.

Here, this animation is zooming in
onto our solar system.

And you'll see here the planets

as well as some spacecraft
that are also orbiting our sun.

Now if we can imagine going to
the west coast of North America,

and looking out at the night sky,

here's what we'd see on a spring night.

And you can see
the constellations overlaid

and again, so many stars with planets.

There's a special patch of the sky

where we have thousands of planets.

This is where the Kepler Space Telescope
focused for many years.

Let's zoom in and look at
one of the favorite exoplanets.

This star is called Kepler-186f.

It's a system of about five planets.

And by the way, most of these exoplanets,

we don't know too much about.

We know their size, and their orbit
and things like that.

But there's a very special planet
here called Kepler-186f,

this planet is in a zone that is not
too far from the star,

so that the temperature may be
just right for life.

Here, the artist conniption
is just zooming in

and showing you what that planet
might be like.

So, many people have this
romantic notion of astronomers

going to the telescope
on a lonely mountaintop

and looking at the spectacular night sky

through a big telescope.

But actually, we just work on
our computers like everyone else

and we get our data by email
or by loading from a database.

So instead of coming here
to tell you about

the somewhat tedious nature
of the data and data analysis

and the complex computer models we make,

I have a different way to try
to explain to you

some of the things that we're
thinking about exoplanets.

Here's a travel poster:

"Kepler-186f,

Where the grass is always redder
on the other side."

That's because Kepler-186f
orbits a red star,

and we're just speculating that
perhaps the plants there,

if there is vegetation that
does photosynthesis,

it has different pigments and looks red.

"Enjoy the gravity on HD 40307g, "

a super-earth.

This planet is more massive than earth

and has a higher surface gravity.

"Relax on Kepler-16b,

where your shadow always has company."

We know of a dozen planets
that orbit two stars,

and there's likely many more out there.

If we could visit one of those planets,

you literally would see two sunsets

and have two shadows.

So actually, science fiction
got some things right,

Tatooine from Star Wars.

And I have a couple of other
favorite exoplanets

to tell you about.

This one is Kepler-10b,

it's a hot, hot planet.

It orbits over 50 times
closer to its star

than the earth does to our sun.

And actually, it's so hot

we can't visit any of these planets,
but if we could,

we would melt long before
we got there.

We think the surface is
hot enough to melt rock

and has liquid lava lakes.

We use 1214b.

This planet, we know the mass
and the size

and it has a fairly low density.

it's somewhat warm.

We actually don't know really
anything about this planet.

One possibility is that
it's a water world,

like a scaled-up version of one
of Jupiter's icy moons

that might be 50 percent water by mass.

In this case, it would have
a thick steam atmosphere

overlaying an ocean,

not of liquid water,

but of an exotic form of water,

a superfluid --

not quite a gas, not quite a liquid.

Under that wouldn't be rock,

but a form of high pressure ice,
like ice-nine.

So out of all these planets out there,

and the variety is
just simply astonishing,

we mostly want to find the planets

that are Goldielocks planets,
we call them,

not too big, not too small

not too hot, not too cold --

but just right for life.

But to do that, we'd have to
be able to look

at the planet's atmosphere

because the atmosphere acts
like a blanket

trapping heat --

the greenhouse effect.

We have to be able to asses
the greenhouse gasses

on other planets.

Well, science fiction got
some things wrong.

The Star Trek Enterprise
had to travel vast distances

at incredible speeds
to orbit other planets

so that First Officer Spok
could analyze

the atmosphere to see
if the planet was habitable

or if there were lifeforms there.

Well, we don't need
to travel at warp speeds

to see other planet atmospheres,

although I don't want to dissuade
any budding engineers

from figuring out how to do that.

We actually can and do study
planet atmospheres

from here, from earth orbit.

This is a picture, a photograph

of the Hubble Space Telescope

taken by the shuttle Atlantis
as it was departing

after the last human space
flight to Hubble.

They installed a new camera, actually,

that we use for exoplanet atmospheres.

And so far, we've been able to study
dozens of exoplanet atmospheres,

about six of them in great detail.

But those are not
small planets like earth.

They're big, hot planets
that are easy to see.

We're not ready,

we don't have the right technology yet

to study small exoplanets.

But nevertheless,

I wanted to try to explain to you

how we study exoplanet atmospheres.

I want you to imagine,
for a moment, a rainbow.

And if we could look
at this rainbow closely,

we would see that some
dark lines are missing.

And here's our sun,

the white light of our sun split up,

not by raindrops, but by a spectrograph.

And you can see
all these dark, vertical lines.

Some are narrow, some are wide,

some are shaded at the edges.

And this is how astronomers have studied
objects in the heavens,

literally, for over a century.

So here, each different atom and molecule

has a special set of lines,

a fingerprint, if you will.

And that's how we study
exoplanet atmospheres.

And, I'll just never forget
when I started working

on exoplanet atmospheres
20 years ago,

how many people told me,

"This will never happen,
we'll never be able to study them.

Why are you bothering?"

And so that's why I'm pleased
to tell you about

all the atmospheres studied now,

and this is really a whole field
of its own.

So when it comes to
other planets, other earths,

in the future when we can observe them,

what kind of gasses would be looking for?

Well, you know, our own earth
has oxygen in the atmosphere

to 20 percent by volume.

That's a lot of oxygen.

But without plants
and photosynthetic life,

there would be no oxygen,

virtually no oxygen in our atmosphere.

So oxygen is here because of life.

And our goal then is to look for gasses

in other planet atmospheres,

gasses that don't belong,

that we might be able
to attribute to life.

But which molecules should
we search for?

I actually told you how diverse
exoplanets are.

We expect that to continue in the future

when we find other earths.

And that's one of the main things
I'm working on now,

I have a theory about this.

It reminds me that nearly everyday,

I receive an email --

email or emails--

from someone with a crazy theory
about physics of gravity

or cosmology or some such.

Please don't email me
one of your crazy theories.

Well, I had my own crazy theory.

But, who does the MIT professor go to?

Well I emailed a Nobel Laureate
in physiology and medicine

and he said, "Sure, come and talk to me."

So I brought my two biochemistry friends

and we went to talk to him
about our crazy theory.

And that theory was that life produces
all small molecules,

so many molecules.

Like, everything I could think of,
but not being a chemist.

Think about it:

carbon dioxide, carbon monoxide,

molecular hydrogen, molecular nitrogen,

methane, methal choloride (?) --

so many gasses,

they also exist for other reasons,

but just life even produces ozone.

So we go to talk to him about this,

and immediately, he shot down the theory.

He found an example that didn't exist.

So, we went back to the drawing board

and we actually think we have
found something very interesting

in another field.

But back to exoplanets,

the point is that life produces
so many different types of gases,

literally thousands of gasses.

And so what we're doing now
is just trying to figure out

on which types of exoplanets,

which gasses could be attributed to life.

And so when it comes time
when we find gasses

on exoplanet atmospheres,

that we won't know if they're
being produced

by intelligent aliens or by trees,

or earth(?) swamp,

or even just by simple,
single-celled microbial life.

And so working on the models

and thinking about biochemistry

it's all well and good.

But a really big challenge
ahead of us is how.

How are we going to find these planets?

They're actually many
ways to find planets,

several different ways.

But the one that I'm most focused on

is how can we open a gateway

so that in the future,

we can find hundreds of earths.

We have a real shot
at finding signs of life.

And actually, I just finished
leading a two-year project

in this very special phase
of a concept

we call the Starshade.

And the Starshade is very
specially shaped screen

and the goal is to fly that Starshade

so it blocks out the light of a star

so that a telescope can see
the planets directly.

Here, you can see myself
and two team members

holding up one small part
of the Starshade.

It's shaped like a giant flower,

and this is one of the prototype petals.

The concept is that a star shade
and telescope launch together,

with the petals unfurling
from the stowed position.

The central trust(?) would expand,

with the petals snapping into place.

Now, this has to be made very precisely,

literally, the petals to microns

and they have to deploy to millimeters.

And this hole structure would have to fly

tens of thousands of kilometers

away from the telescope.

it's about tens of meters in diameter.

And the goal is to block out
the starlight to incredible precision

so that we'd be able to see
the planets directly.

It has to be a very special shape

because of the physics of defraction.

Now this is a really project
that we worked on,

literally, you would not believe how hard.

Just so you believe that it's
not just in movie format,

here's a real photograph
of a second generation

Starshade deployment
test bed in the lab.

And in this case,

I just wanted you to know,

that that central trust
has heritage left over

from large radio deployables in space.

So after all of that hard work

where we try to think of all
the crazy gasses

that might be out there,

and we build the very
complicated space telescopes

that might be out there,

what are we going to find?

Well, in the best case,

we will find an image
of another exo-earth.

Here's earth as a pale blue dot.

This is actually a real photograph
of earth

taken by the Voyager 1 spacecraft,

four billion miles away.

And that red light is just scattered light
in the camera optics.

But what's so awesome to consider is that

if there are intelligent aliens
orbiting on a planet

around a star near to us

and they build complicated
space telescopes

of a kind that we're trying to build,

all they'll see is this pale blue dot,

a pinprick of light.

And so sometimes when
I pause to think about

my professional struggle
and huge ambition,

it's hard to think about
that in contrast

to the vastness of the universe.

But nonetheless, I am devoting
the rest of my life

to finding another earth.

And I can guarantee that in
the next generation

of space telescopes,

and the second generation,

we will have the capability to find
and identity other earths.

And the capability
to split up the starlight

so that we can look for gasses

and assess the greenhouse gasses
in the atmosphere,

estimate the surface temperature,

and look for signs of life.

But there's more,

in this case of searching
for other planets like earth,

we are making a new kind of map

of the nearby stars and
of the planets orbiting them,

including stars that actually might be
inhabitable by humans.

And so I envision that our descendants,

hundreds of years from now,

will embark on an interstellar journey

to other worlds.

And they will look back at all of us

as the generation who first found
the earth-like worlds.

Thank you.

(Applause)

June Cohen: And I give you,
for a question,

Rosetta Mission manager Fred Jansen.

Fred Jansen: You mentioned halfway through

that the technology to actually
look at the spectrum

of an exoplanet-like earth
is not there yet.

When do you expect this will be there

and what's needed?

Sara Seager: Well actually,
what we expect is our next --

we call our next-generation
Hubble telescope.

And this is called the
James Webb Space Telescope,

and that will launch in 2018

and that's what we're going to do,

we're going to look at
a special kind of planet

called transient exoplanets,

and that will be our first shot
at studying small planets

for gasses that might indicate
the planet is habitable.

JC: I'm going to ask you one
follow-up question, too, Sara,

as the generalist.

So I am really struck by
the notion in your career

of the opposition you faced,

that when you began thinking about
exoplanets,

there was extreme skepticism
in the scientific community

that they existed,

and you proved them wrong.

What did it take to take that on?

SS: Well, the thing is that
as scientists,

we're supposed to be skeptical

because our job to make sure that
what the other person is saying

actually makes sense or not.

But being a scientist,

I think you've seen it
from this session,

it's like being an explorer.

You have this immense curiosity,

this stubbornness,

this sort of resolute will
that you will go forward

no matter what people say.

JC: I love that.
Thank you, Sara.

(Applause)