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TED2014

Jeremy Kasdin: The flower-shaped starshade that might help us detect Earth-like planets

March 19, 2014

Astronomers believe that every star in the galaxy has a planet, one fifth of which might harbor life. Only we haven't seen any of them -- yet. Jeremy Kasdin and his team are looking to change that with the design and engineering of an extraordinary piece of equipment: a flower petal-shaped "starshade" positioned 50,000 km from a telescope to enable imaging of planets about distant stars. It is, he says, the "coolest possible science."

Jeremy Kasdin - Planet finder
Using innovative orbiting instruments, aerospace engineer Jeremy Kasdin hunts for the universe’s most elusive objects — potentially habitable worlds. Full bio

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The universe is teeming with planets.
00:12
I want us, in the next decade,
00:15
to build a space telescope that'll be able to image
00:17
an Earth about another star
00:20
and figure out whether it can harbor life.
00:22
My colleagues at the NASA
Jet Propulsion Laboratory
00:25
at Princeton and I are working on technology
00:27
that will be able to do just that in the coming years.
00:30
Astronomers now believe that every star
00:33
in the galaxy has a planet,
00:35
and they speculate that up to one fifth of them
00:37
have an Earth-like planet
00:39
that might be able to harbor life,
00:40
but we haven't seen any of them.
00:42
We've only detected them indirectly.
00:44
This is NASA's famous picture of the pale blue dot.
00:47
It was taken by the Voyager spacecraft in 1990,
00:50
when they turned it around as
it was exiting the solar system
00:53
to take a picture of the Earth
00:55
from six billion kilometers away.
00:57
I want to take that
00:59
of an Earth-like planet about another star.
01:01
Why haven't we done that? Why is that hard?
01:04
Well to see, let's imagine we take
01:06
the Hubble Space Telescope
01:07
and we turn it around and we move it out
01:09
to the orbit of Mars.
01:11
We'll see something like that,
01:13
a slightly blurry picture of the Earth,
01:14
because we're a fairly small telescope
01:16
out at the orbit of Mars.
01:18
Now let's move ten times further away.
01:20
Here we are at the orbit of Uranus.
01:22
It's gotten smaller, it's got less detail, less resolve.
01:24
We can still see the little moon,
01:26
but let's go ten times further away again.
01:28
Here we are at the edge of the solar system,
01:30
out at the Kuiper Belt.
01:32
Now it's not resolved at all.
01:33
It's that pale blue dot of Carl Sagan's.
01:35
But let's move yet again ten times further away.
01:37
Here we are out at the Oort Cloud,
01:40
outside the solar system,
01:41
and we're starting to see the sun
01:43
move into the field of view
01:44
and get into where the planet is.
01:46
One more time, ten times further away.
01:47
Now we're at Alpha Centauri,
01:49
our nearest neighbor star,
01:51
and the planet is gone.
01:52
All we're seeing is the big beaming image of the star
01:54
that's ten billion times brighter than the planet,
01:56
which should be in that little red circle.
01:59
That's what we want to see. That's why it's hard.
02:01
The light from the star is diffracting.
02:03
It's scattering inside the telescope,
02:05
creating that very bright image
02:07
that washes out the planet.
02:09
So to see the planet,
02:10
we have to do something about all of that light.
02:12
We have to get rid of it.
02:14
I have a lot of colleagues working on
02:15
really amazing technologies to do that,
02:17
but I want to tell you about one today
02:19
that I think is the coolest,
02:20
and probably the most likely to get us an Earth
02:22
in the next decade.
02:24
It was first suggested by Lyman Spitzer,
02:26
the father of the space telescope, in 1962,
02:28
and he took his inspiration from an eclipse.
02:31
You've all seen that. That's a solar eclipse.
02:33
The moon has moved in front of the sun.
02:35
It blocks out most of the light
02:37
so we can see that dim corona around it.
02:39
It would be the same thing if I put my thumb up
02:41
and blocked that spotlight
that's getting right in my eye,
02:43
I can see you in the back row.
02:46
Well, what's going on?
02:48
Well the moon
02:49
is casting a shadow down on the Earth.
02:51
We put a telescope or a camera in that shadow,
02:53
we look back at the sun,
02:56
and most of the light's been removed
02:58
and we can see that dim, fine structure
03:00
in the corona.
03:02
Spitzer's suggestion was we do this in space.
03:03
We build a big screen, we fly it in space,
03:06
we put it up in front of the star,
03:08
we block out most of the light,
03:11
we fly a space telescope in
that shadow that's created,
03:12
and boom, we get to see planets.
03:15
Well that would look something like this.
03:17
So there's that big screen,
03:20
and there's no planets,
03:21
because unfortunately it doesn't
actually work very well,
03:22
because the light waves of the light and waves
03:25
diffracts around that screen
03:28
the same way it did in the telescope.
03:29
It's like water bending around a rock in a stream,
03:31
and all that light just destroys the shadow.
03:34
It's a terrible shadow. And we can't see planets.
03:36
But Spitzer actually knew the answer.
03:39
If we can feather the edges, soften those edges
03:40
so we can control diffraction,
03:43
well then we can see a planet,
03:45
and in the last 10 years or so we've come up
03:46
with optimal solutions for doing that.
03:48
It looks something like that.
03:50
We call that our flower petal starshade.
03:54
If we make the edges of those petals exactly right,
03:56
if we control their shape,
03:59
we can control diffraction,
04:01
and now we have a great shadow.
04:02
It's about 10 billion times dimmer than it was before,
04:04
and we can see the planets beam out just like that.
04:06
That, of course, has to be bigger than my thumb.
04:10
That starshade is about
04:12
the size of half a football field
04:13
and it has to fly 50,000 kilometers
away from the telescope
04:15
that has to be held right in its shadow,
04:18
and then we can see those planets.
04:20
This sounds formidable,
04:22
but brilliant engineers, colleagues of mine at JPL,
04:24
came up with a fabulous design for how to do that
04:27
and it looks like this.
04:29
It starts wrapped around a hub.
04:31
It separates from the telescope.
04:32
The petals unfurl, they open up,
04:34
the telescope turns around.
04:37
Then you'll see it flip and fly out
04:38
that 50,000 kilometers away from the telescope.
04:40
It's going to move in front of the star
04:44
just like that, creates a wonderful shadow.
04:46
Boom, we get planets orbiting about it.
04:49
(Applause)
04:53
Thank you.
04:55
That's not science fiction.
04:57
We've been working on this
for the last five or six years.
04:59
Last summer, we did a really cool test
05:02
out in California at Northrop Grumman.
05:04
So those are four petals.
05:07
This is a sub-scale star shade.
05:08
It's about half the size of the one you just saw.
05:10
You'll see the petals unfurl.
05:13
Those four petals were built by four undergraduates
05:14
doing a summer internship at JPL.
05:16
Now you're seeing it deploy.
05:19
Those petals have to rotate into place.
05:20
The base of those petals
05:22
has to go to the same place every time
05:23
to within a tenth of a millimeter.
05:25
We ran this test 16 times,
05:27
and 16 times it went into the exact same place
05:29
to a tenth of a millimeter.
05:32
This has to be done very precisely,
05:33
but if we can do this, if we can build this technology,
05:35
if we can get it into space,
05:37
you might see something like this.
05:39
That's a picture of one our nearest neighbor stars
05:41
taken with the Hubble Space Telescope.
05:43
If we can take a similar space telescope,
05:46
slightly larger,
05:48
put it out there,
05:49
fly an occulter in front of it,
05:51
what we might see is something like that --
05:52
that's a family portrait of our
solar system -- but not ours.
05:54
We're hoping it'll be someone else's solar system
05:57
as seen through an occulter,
06:00
through a starshade like that.
06:01
You can see Jupiter, you can see Saturn,
06:02
Uranus, Neptune, and right there in the center,
06:04
next to the residual light
06:07
is that pale blue dot. That's Earth.
06:08
We want to see that, see if there's water,
06:10
oxygen, ozone,
06:13
the things that might tell us that it could harbor life.
06:14
I think this is the coolest possible science.
06:17
That's why I got into doing this,
06:19
because I think that will change the world.
06:21
That will change everything when we see that.
06:23
Thank you.
06:25
(Applause)
06:27

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Jeremy Kasdin - Planet finder
Using innovative orbiting instruments, aerospace engineer Jeremy Kasdin hunts for the universe’s most elusive objects — potentially habitable worlds.

Why you should listen
At Princeton’s High Contrast Imaging Laboratory, Jeremy Kasdin is collaborating on a revolutionary space-based observatory that will unveil previously unseen (and possibly Earth-like) planets in other solar systems.

One of the observatory’s startling innovations is the starshade, an orbiting "occulter" that blocks light from distant stars that ordinarily outshine their dim planets, making a clear view impossible. When paired with a space telescope, the starshade adds a new and powerful instrument to NASA’s cosmic detection toolkit.
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