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

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Not little green humanoids
arriving in shiny UFOs,

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although that would be nice.

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But it's the search for planets

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orbiting stars far away.

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Every star in our sky is a sun.

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And if our sun has planets --

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Mercury, Venus, Earth, Mars, etc.

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Surely those other stars should
have planets also

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-- and they do.

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And in the last two decades,

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astronomers have found
thousands of exoplanets.

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Our night sky is literally
teeming with exoplanets.

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We know, statistically speaking,

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that every star has at least one planet.

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And in the search for planets,

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

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we're able to help address


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some of the most amazing
and mysterious questions

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that have faced humankind for centuries.

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Why are we here?

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Why does our universe exist?

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How did earth form and evolve?

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How and why did life originate
and populate our planet?

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The second question that
we often think about is:

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Are we alone?

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Is there life out there?

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Who is out there?

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You know, this question
has been around

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for thousands of years,

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since at least the time
of the Greek philosophers.

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

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to finding out the answer
to this question.

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It's the first time in human history

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that this really is within reach for us.

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Now when I think about
the possibilities

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for life out there,

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I think of the fact that our sun

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is but one of many stars.

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This is a photograph of a real galaxy,

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we think our milky way 
looks like this galaxy.

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It's a collection of bound stars.

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

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

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Knowing that small planets 
are very common,

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you can just do the math.

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

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that surely, there must be life
somewhere out there.

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

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because we have absolutely no evidence.


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for life beyond earth, yet.

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

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and zoom in to where our sun is,

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we see a real map of the stars.

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And the highlighted stars are
those with known exoplanets.

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This is really just
the tip of the iceberg.

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

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And you'll see here the planets


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

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

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and looking out at the night sky,


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

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And you can see
the constellations overlaid

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and again, so many stars with planets.

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There's a special patch of the sky

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where we have thousands of planets.

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

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

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This star is called Kepler-186f.

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It's a system of about five planets.

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And by the way, most of these exoplanets,

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we don't know too much about.

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

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

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

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so that the temperature may be 
just right for life.

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Here, the artist conniption
is just zooming in

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and showing you what that planet
might be like.

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So, many people have this
romantic notion of astronomers

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going to the telescope
on a lonely mountaintop

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and looking at the spectacular night sky

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through a big telescope.

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

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

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So instead of coming here 
to tell you about

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the somewhat tedious nature 
of the data and data analysis

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and the complex computer models we make,

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I have a different way to try to explain
to you

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

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Here's a travel poster:

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"Kepler-186f,

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

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

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

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if there is vegetation that 
does photosynthesis,

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it has different pigments and looks red.

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Enjoy the gravity on HD 40307g,

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a super-earth.

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This planet is more massive than earth

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and has a higher surface gravity.

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Relax on Kepler-16b,

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where your shadow always has company.

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We know of a dozen planets
that orbit two stars,

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and there's likely many more out there.

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If we could visit one of those planets,

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you literally would see two sunsets

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and have two shadows.

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So actually, science fiction 
got some things right,

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Tatooine from Star Wars.

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And I have a couple of other 
favorite exoplanets

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to tell you about.

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This one is Kepler-10b,

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it's a hot, hot planet.

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It orbits over 50 times closer
to its star

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than the earth does to our sun.

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And actually, it's so hot

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we can't visit any of these planets,

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but if we could,

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we would melt long before
we got there.

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We think the surface is hot enough
to melt rock

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and has liquid lava lakes.

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We use 1214b,

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this planet,

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we know the mass and the size

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and it has a fairly low density,

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it's somewhat warm.

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

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One possibility is that 
it's a water world,

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

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that might be 50 percent water by mass.

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In this case, it would have
a thick steam atmosphere

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overlaying an ocean,

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not of liquid water,

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but of an exotic form of water,

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a superfluid --

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not quite a gas, not quite a liquid.

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Under that wouldn't be rock,

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but a form of high pressure ice, 
like (word)

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So out of all these planets out there,

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and the variety is 
just simply astonishing,

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we mostly want to find the planets

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that are Goldie Locks planets,
we call them,

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not too big, not too small

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not too hot, not too cold --

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just right for life.

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

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at the planet's atmosphere

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because the atmosphere acts
like a blanket

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trapping heat --

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the greenhouse effect.

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We have to be able to asses
the greenhouse gasses

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on other planets.

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Well, science fiction got
some things wrong.

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The Star Trek Enterprise had to travel
vast distances

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at incredible speeds 
to orbit other planets

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so that First officer Spok 
could further analyze

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the atmosphere and see
if the planet

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was habitable or if 
there were lifeforms there.

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

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to see other planets' atmospheres,

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although I don't want to dissuade 
any budding engineers

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from figuring out how to do that.

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We actually can and do study
planet atmospheres

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from here, from earth orbit.

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This is a picture, a photograph

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of the Hubble Space Telescope

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taken by the shuttle Atlantis
as it was departing

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after the last human space 
flight to Hubble.

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They installed a new camera, actually,

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that we use for exoplanet atmospheres.

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

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about six of them in great detail.

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But those are not small planets like earth.

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They're big, hot planets

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that are easy to see.

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We're not ready,

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we don't have the right technology yet

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to study small exoplanets.

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But nevertheless,

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I wanted to try to explain to you

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how we study exoplanet atmospheres.

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

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And if we could look 
at this rainbow closely,

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we would see that some
dark lines are missing.

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And here's our sun,

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the white light of our sun split up,

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not by raindrops, but by a spectrograph.

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And you can see all these dark, vertical lines.

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Some are narrow, some are wide,

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some are shaded at the edges.

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And this is how astronomers have studied
objects in the heavens

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literally, for over a century.

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So here, each different atom and molecule

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has a special set of lines,

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a fingerprint, if you will.

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And that's how we study
exoplanet atmospheres.

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

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on exoplanet atmospheres
20 years ago,

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how many people told me,

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"This will never happen,

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we'll never be able to study them.

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Why are you bothering?"

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

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all the atmospheres studied now,

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and this is really a whole field
of its own.

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So when it comes to other planets,
other earths,

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in the future when we can observe them,

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what kind of gasses would be looking for?

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

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to 20 percent by volume.

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That's a lot of oxygen.

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But without plants 
and photosynthetic life,

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there would be no oxygen,
virtually no oxygen

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in our atmosphere.

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So oxygen is here because of life

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and our goal then is to look for gasses

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in other planet atmospheres,

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gasses that don't belong,

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that we might be able to attribute to life.

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But which molecules should 
we search for?

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I actually told you how diverse
exoplanets are,

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we expect that to continue in the future

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when we find other earths.

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

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I have a theory about this.

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It reminds me that nearly everyday,

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I receive an email --

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email or emails--

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from someone with a crazy theory
about physics, gravity

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or cosmology or some such.

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

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Well, I have my own crazy theory.

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But, who does the MIT professor go to?

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Well I emailed a Nobel Laureate 
in physiology and medicine

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

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So I brought my two biochemistry frirnds

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

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And that theory was that life produces
all small molecules,

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so many molecules.

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Like, everything I could think of,

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but not being a chemist.

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Think about it:

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carbon dioxide, carbon monoxide,

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molecular hydrogen, molecular nitrogen,

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methane, methal choloride (?) --

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so many gasses,

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they also exist for other reasons,

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but just life even produces ozone.

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So we go to talk to him about this,

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and immediately, he shot down
the theory.

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He found an example that didn't exist.

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So, we went back to the drawing board

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and we actually think we have
found something

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very interesting in another field.

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But back to exoplanets,

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

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literally thousands of gasses.

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

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on which types of exoplanets,

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which gasses could be attributed to life.

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And so when it comes time

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that we find gasses on exoplanet
atmospheres,

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

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by intelligent aliens or by trees,

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or earth(?) swamp,

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or even just by simple, single celled 
microbial life.

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And so working on the models

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and thinking about biochemistry

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it's all well and good.

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But a really big challenge ahead of us

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is how.

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How are we going to find these planets?

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They're actually many ways to find planets,

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several different ways.

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But the one that I'm most focused on

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is how can we open a gateway

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so that in the future,

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we can find hundreds of earths.

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We have a real shot
at finding signs of life.

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

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in this very special phase
of a concept

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we call the star shade.

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And the star shade is very
specially shaped screen

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and the goal is to fly that star shade

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so it blocks out the light of a star

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so that a telescope can see 
the planets directly.

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Here, you can see myself 
and two team members

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holding up one small part of the star shade.

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It's shaped like a giant flower,

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and this is one of the prototype petals.

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

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with the petals unfurling
from the stowed position.

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The central trust would expand,

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with the petals snapping into place.

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Now, this has to be made very precisely,

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literally, the petals to microns

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and they have to deploy to millimeters.

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And this hole structure would have to fly

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tens of thousands of kilometers
away from the telescope,

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it's about tens of meters in diameter.

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

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

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It has to be a very special shape

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because of the physics of defraction.

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Now this is a really project 
that we worked on,

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literally, you would not believe how hard.

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

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here's a real photograph
of a second generation

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star shade deployment 
test bed in the lab.

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And in this case,

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I just want you to know,

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that that central trust
has heritage left over

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from large radio deployables in space.

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So after all of that hard work

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where we try to think of all 
the crazy gasses

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that might be out there,

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we build the very
complicated space telescopes,

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what are we going to find?

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Well, in the best case,

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we will find an image 
of another eco-earth.

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Here's earth as a pale blue dot.

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This is actually a real photograph
of earth

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taken by the Voyager I spacecraft,

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four billion miles away.

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


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But what's so awesome to consider
is that

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if there are intelligent aliens
orbiting on a planet

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around a star near to us

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and they build complicated
space telescopes

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of a kind we're trying to build,

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all they'll see is this pale blue dot,

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a pinprick of light.

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And so sometimes when I pause
to think about

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my professional struggle
and huge ambition,

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it's hard to think about that
in contrast

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to the vastness of the universe.

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But nonetheless, I am devoting
the rest of my life

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to finding another earth.

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And I can guarantee that in 
the next generation

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of space telescopes,

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and the second generation,

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00:13:42,506 --> 00:13:46,885
we will have the capability to find
and identity other earths.

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And the capability to split up 
the starlight

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so that we can look for gasses

345
00:13:52,211 --> 00:13:55,981
and assess the greenhouse gasses
in the atmosphere,

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estimate the surface temperature,

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and look for signs of life.

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But there's more,

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in this case of searching
for other planets like earth,

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00:14:03,742 --> 00:14:07,413
we are making a new kind of map

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of the nearby stars and 
of the planets orbiting them,

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including stars that actually might be

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00:14:12,794 --> 00:14:15,225
inhabitable by humans.

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00:14:15,225 --> 00:14:17,670
And so I envision that our descendants,

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hundreds of years from now,

356
00:14:19,149 --> 00:14:21,513
will embark on an interstellar journey

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to other worlds.

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And they will look back at all of us

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

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Thank you.

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00:14:30,785 --> 00:14:37,794
(Applause)

362
00:14:37,794 --> 00:14:38,970
June Cohen: And I give you, 
for a question,

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00:14:38,970 --> 00:14:41,759
Rosetta Mission manager Fred Jansen.

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00:14:41,759 --> 00:14:43,434
Fred Jansen: You mentioned halfway through

365
00:14:43,434 --> 00:14:47,683
that the technology to actually look
at the spectrum

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00:14:47,683 --> 00:14:50,736
of an exoplanet-like earth
is not there yet.

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00:14:50,736 --> 00:14:52,360
When do you expect this will be there

368
00:14:52,360 --> 00:14:53,865
and what's needed?

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00:14:53,865 --> 00:14:55,620
Sara Seager: Well actually, 
what we expect is what


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we call our next-generation
Hubble telescope.

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And this is called the 
James Webb Space Telescope,

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and that will launch in 2018

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

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

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00:15:06,097 --> 00:15:07,857
called transient exoplanets,

376
00:15:07,857 --> 00:15:09,642
and that will be our first shot

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00:15:09,642 --> 00:15:11,423
at studying small plants 
for gasses that might indicate

378
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the planet is habitable.

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00:15:12,602 --> 00:15:18,210
JC: I'm going to ask you one
follow-up question, too, Sara,

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00:15:18,210 --> 00:15:19,431
as the generalist.

381
00:15:19,431 --> 00:15:22,657
So I am really struck by the notion
in your career

382
00:15:22,657 --> 00:15:24,216
of the opposition you faced,

383
00:15:24,216 --> 00:15:25,983
that when you began thinking about
exoplanets,

384
00:15:25,983 --> 00:15:28,422
there was extreme skepticism
in the scientific community

385
00:15:28,422 --> 00:15:29,226
that they existed,

386
00:15:29,226 --> 00:15:30,826
and you proved them wrong.

387
00:15:30,826 --> 00:15:33,143
What did it take to take that on?

388
00:15:33,143 --> 00:15:36,457
SS: Well, the thing is that
as scientists,

389
00:15:36,457 --> 00:15:37,219
we're supposed to be skeptical.

390
00:15:37,219 --> 00:15:39,520
It's our job to make sure that
what the other peson is saying

391
00:15:39,520 --> 00:15:41,164
makes sense or not.

392
00:15:41,164 --> 00:15:43,814
But being a scientist,

393
00:15:43,814 --> 00:15:46,518
I think you've seen it
from this session,

394
00:15:46,518 --> 00:15:48,611
it's like being an explorer.

395
00:15:48,611 --> 00:15:50,398
You have this immense curiosity,

396
00:15:50,398 --> 00:15:51,721
this stubbornness,

397
00:15:51,721 --> 00:15:54,127
this sort of resolute will
that you will go forward

398
00:15:54,127 --> 00:15:56,633
no matter what people say.

399
00:15:56,633 --> 00:15:57,764
JC: I love that. 
Thank you, Sara.

400
00:15:57,764 --> 00:16:02,039
(Applause)