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The search for planets beyond our solar system

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    I'm here to tell you about
    the real search
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    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 uur 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
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    is 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 one but 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 ones 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 some planets
    as well as some spacecraft
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    that are also orbiting our sun.
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    Now if we can imagine
    going to the west coast
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    of North America and looking out
    on 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 180-6F.
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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 180-6F,
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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 a 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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    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
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    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,
Title:
The search for planets beyond our solar system
Speaker:
Sara Seager
Description:

more » « less
Video Language:
English
Team:
closed TED
Project:
TEDTalks
Duration:
16:14

English subtitles

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