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 uur 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 one but 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 ones 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 some 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
on 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 180-6F.
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 180-6F,
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 a 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
is 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 (word)
So out of all these planets out there,
and the variety is
just simply astonishing,
we mostly want to find the planets
that are Goldie Locks planets,
we call them,
not too big, not too small
not too hot, not too cold --
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 further analyze
the atmosphere and 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 planets' 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 image, 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 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, gravity
or cosmology or some such.
Please don't email me
one of your crazy theories.
Well, I have 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 frirnds
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
that 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 star shade.
And the star shade is very
specially shaped screen
and the goal is to fly that star shade
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 star shade.
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 percussion
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
star shade deployment
test bed in the lab.
And in this case,
I just want 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,
we build the very
complicated space telescopes,
what are we going to find?
Well, in the best case,
we will find an image
of another eco-earth.
Here's earth as a pale blue dot.
This is actually a real photograph
of earth
taken by the Voyager I 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 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 what
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 speicla kind of planet
called transient exoplanets,
and that will be our first shot
at studying small plants
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.
It's our job to make sure that
what the other peson is saying
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)