The search for planets beyond our solar system
-
0:01 - 0:04I'm here to tell you
about the real search for alien life. -
0:05 - 0:08Not little green humanoids
arriving in shiny UFOs, -
0:08 - 0:10although that would be nice.
-
0:10 - 0:13But it's the search for planets
orbiting stars far away. -
0:14 - 0:16Every star in our sky is a sun.
-
0:16 - 0:17And if our sun has planets --
-
0:17 - 0:20Mercury, Venus, Earth, Mars, etc.,
-
0:20 - 0:22surely those other stars
should have planets also, -
0:22 - 0:23and they do.
-
0:23 - 0:25And in the last two decades,
-
0:25 - 0:28astronomers have found
thousands of exoplanets. -
0:29 - 0:31Our night sky is literally
teeming with exoplanets. -
0:31 - 0:33We know, statistically speaking,
-
0:33 - 0:35that every star has at least one planet.
-
0:36 - 0:38And in the search for planets,
-
0:38 - 0:41and in the future,
planets that might be like Earth, -
0:41 - 0:42we're able to help address
-
0:42 - 0:45some of the most amazing
and mysterious questions -
0:45 - 0:48that have faced humankind for centuries.
-
0:48 - 0:49Why are we here?
-
0:49 - 0:51Why does our universe exist?
-
0:51 - 0:54How did Earth form and evolve?
-
0:54 - 0:57How and why did life originate
and populate our planet? -
0:58 - 1:01The second question
that we often think about is: -
1:01 - 1:02Are we alone?
-
1:03 - 1:04Is there life out there?
-
1:05 - 1:07Who is out there?
-
1:08 - 1:11You know, this question has been around
for thousands of years, -
1:11 - 1:13since at least the time
of the Greek philosophers. -
1:13 - 1:16But I'm here to tell you
just how close we're getting -
1:16 - 1:19to finding out the answer
to this question. -
1:19 - 1:23It's the first time in human history
that this really is within reach for us. -
1:23 - 1:26Now when I think about the possibilities
for life out there, -
1:26 - 1:30I think of the fact that our sun
is but one of many stars. -
1:31 - 1:33This is a photograph of a real galaxy,
-
1:33 - 1:35we think our Milky Way
looks like this galaxy. -
1:35 - 1:37It's a collection of bound stars.
-
1:37 - 1:41But our [sun] is one
of hundreds of billions of stars -
1:41 - 1:46and our galaxy is one of upwards
of hundreds of billions of galaxies. -
1:47 - 1:49Knowing that small planets
are very common, -
1:49 - 1:51you can just do the math.
-
1:51 - 1:55And there are just so many stars
and so many planets out there, -
1:55 - 1:58that surely, there must be life
somewhere out there. -
1:59 - 2:02Well, the biologists get furious
with me for saying that, -
2:03 - 2:06because we have absolutely no evidence
for life beyond Earth yet. -
2:07 - 2:12Well, if we were able to look
at our galaxy from the outside -
2:12 - 2:14and zoom in to where our sun is,
-
2:14 - 2:16we see a real map of the stars.
-
2:16 - 2:19And the highlighted stars
are those with known exoplanets. -
2:20 - 2:22This is really just
the tip of the iceberg. -
2:23 - 2:26Here, this animation is zooming in
onto our solar system. -
2:27 - 2:28And you'll see here the planets
-
2:28 - 2:31as well as some spacecraft
that are also orbiting our sun. -
2:33 - 2:36Now if we can imagine going
to the West Coast of North America, -
2:36 - 2:38and looking out at the night sky,
-
2:39 - 2:41here's what we'd see on a spring night.
-
2:41 - 2:43And you can see
the constellations overlaid -
2:43 - 2:45and again, so many stars with planets.
-
2:45 - 2:49There's a special patch of the sky
where we have thousands of planets. -
2:49 - 2:53This is where the Kepler Space Telescope
focused for many years. -
2:54 - 2:58Let's zoom in and look
at one of the favorite exoplanets. -
2:59 - 3:02This star is called Kepler-186f.
-
3:03 - 3:05It's a system of about five planets.
-
3:05 - 3:09And by the way, most of these exoplanets,
we don't know too much about. -
3:09 - 3:12We know their size, and their orbit
and things like that. -
3:12 - 3:16But there's a very special planet
here called Kepler-186f. -
3:16 - 3:20This planet is in a zone
that is not too far from the star, -
3:20 - 3:23so that the temperature
may be just right for life. -
3:23 - 3:26Here, the artist's conception
is just zooming in -
3:26 - 3:28and showing you what that planet
might be like. -
3:31 - 3:37So, many people have this
romantic notion of astronomers -
3:37 - 3:40going to the telescope
on a lonely mountaintop -
3:40 - 3:44and looking at the spectacular night sky
through a big telescope. -
3:44 - 3:47But actually, we just work
on our computers like everyone else, -
3:47 - 3:51and we get our data by email
or downloading from a database. -
3:51 - 3:54So instead of coming here to tell you
-
3:54 - 3:57about the somewhat tedious nature
of the data and data analysis -
3:57 - 3:59and the complex computer models we make,
-
3:59 - 4:01I have a different way
to try to explain to you -
4:01 - 4:04some of the things
that we're thinking about exoplanets. -
4:04 - 4:05Here's a travel poster:
-
4:05 - 4:07"Kepler-186f:
-
4:07 - 4:10Where the grass is always redder
on the other side." -
4:10 - 4:14That's because Kepler-186f
orbits a red star, -
4:14 - 4:16and we're just speculating
that perhaps the plants there, -
4:17 - 4:19if there is vegetation
that does photosynthesis, -
4:19 - 4:21it has different pigments and looks red.
-
4:22 - 4:26"Enjoy the gravity on HD 40307g,
-
4:27 - 4:28a Super-Earth."
-
4:28 - 4:30This planet is more massive than Earth
-
4:30 - 4:32and has a higher surface gravity.
-
4:32 - 4:35"Relax on Kepler-16b,
-
4:35 - 4:37where your shadow always has company."
-
4:37 - 4:39(Laughter)
-
4:39 - 4:43We know of a dozen planets
that orbit two stars, -
4:43 - 4:45and there's likely many more out there.
-
4:46 - 4:47If we could visit one of those planets,
-
4:47 - 4:49you literally would see two sunsets
-
4:49 - 4:51and have two shadows.
-
4:51 - 4:54So actually, science fiction
got some things right. -
4:54 - 4:55Tatooine from Star Wars.
-
4:56 - 4:58And I have a couple of other
favorite exoplanets -
4:58 - 5:00to tell you about.
-
5:00 - 5:01This one is Kepler-10b,
-
5:01 - 5:03it's a hot, hot planet.
-
5:04 - 5:07It orbits over 50 times closer to its star
-
5:07 - 5:09than our Earth does to our sun.
-
5:09 - 5:10And actually, it's so hot,
-
5:10 - 5:13we can't visit any
of these planets, but if we could, -
5:13 - 5:15we would melt long before we got there.
-
5:15 - 5:17We think the surface
is hot enough to melt rock -
5:17 - 5:19and has liquid lava lakes.
-
5:19 - 5:21Gliese 1214b.
-
5:21 - 5:23This planet, we know the mass and the size
-
5:23 - 5:25and it has a fairly low density.
-
5:25 - 5:26It's somewhat warm.
-
5:26 - 5:29We actually don't know
really anything about this planet, -
5:29 - 5:31but one possibility
is that it's a water world, -
5:31 - 5:35like a scaled-up version
of one of Jupiter's icy moons -
5:35 - 5:37that might be 50 percent water by mass.
-
5:37 - 5:40And in this case, it would have
a thick steam atmosphere -
5:40 - 5:42overlaying an ocean,
-
5:42 - 5:44not of liquid water,
-
5:44 - 5:47but of an exotic form
of water, a superfluid -- -
5:47 - 5:49not quite a gas, not quite a liquid.
-
5:49 - 5:50And under that wouldn't be rock,
-
5:50 - 5:52but a form of high-pressure ice,
-
5:52 - 5:53like ice IX.
-
5:55 - 5:57So out of all these planets out there,
-
5:57 - 6:00and the variety
is just simply astonishing, -
6:00 - 6:05we mostly want to find the planets
that are Goldilocks planets, we call them. -
6:05 - 6:07Not too big, not too small,
-
6:07 - 6:09not too hot, not too cold --
-
6:09 - 6:10but just right for life.
-
6:11 - 6:13But to do that,
we'd have to be able to look -
6:13 - 6:14at the planet's atmosphere,
-
6:14 - 6:17because the atmosphere
acts like a blanket trapping heat -- -
6:17 - 6:18the greenhouse effect.
-
6:18 - 6:21We have to be able to assess
the greenhouse gases -
6:21 - 6:22on other planets.
-
6:23 - 6:25Well, science fiction
got some things wrong. -
6:26 - 6:27The Star Trek Enterprise
-
6:27 - 6:31had to travel vast distances
at incredible speeds -
6:31 - 6:33to orbit other planets
-
6:33 - 6:37so that First Officer Spock
could analyze the atmosphere -
6:37 - 6:39to see if the planet was habitable
-
6:39 - 6:40or if there were lifeforms there.
-
6:41 - 6:43Well, we don't need
to travel at warp speeds -
6:43 - 6:45to see other planet atmospheres,
-
6:45 - 6:48although I don't want to dissuade
any budding engineers -
6:48 - 6:50from figuring out how to do that.
-
6:50 - 6:52We actually can and do study
planet atmospheres -
6:52 - 6:54from here, from Earth orbit.
-
6:54 - 6:57This is a picture, a photograph
of the Hubble Space Telescope -
6:57 - 7:00taken by the shuttle Atlantis
as it was departing -
7:00 - 7:02after the last
human space flight to Hubble. -
7:02 - 7:04They installed a new camera, actually,
-
7:04 - 7:06that we use for exoplanet atmospheres.
-
7:06 - 7:11And so far, we've been able to study
dozens of exoplanet atmospheres, -
7:11 - 7:13about six of them in great detail.
-
7:14 - 7:16But those are not
small planets like Earth. -
7:16 - 7:18They're big, hot planets
that are easy to see. -
7:18 - 7:19We're not ready,
-
7:19 - 7:24we don't have the right technology yet
to study small exoplanets. -
7:24 - 7:25But nevertheless,
-
7:25 - 7:29I wanted to try to explain to you
how we study exoplanet atmospheres. -
7:30 - 7:32I want you to imagine,
for a moment, a rainbow. -
7:33 - 7:35And if we could look
at this rainbow closely, -
7:35 - 7:38we would see that some
dark lines are missing. -
7:39 - 7:41And here's our sun,
-
7:41 - 7:42the white light of our sun split up,
-
7:42 - 7:45not by raindrops, but by a spectrograph.
-
7:45 - 7:47And you can see
all these dark, vertical lines. -
7:47 - 7:49Some are very narrow, some are wide,
-
7:49 - 7:50some are shaded at the edges.
-
7:50 - 7:54And this is actually how astronomers
have studied objects in the heavens, -
7:54 - 7:56literally, for over a century.
-
7:56 - 7:58So here, each different atom and molecule
-
7:58 - 8:00has a special set of lines,
-
8:00 - 8:01a fingerprint, if you will.
-
8:01 - 8:04And that's how we study
exoplanet atmospheres. -
8:04 - 8:06And I'll just never forget
when I started working -
8:06 - 8:08on exoplanet atmospheres 20 years ago,
-
8:08 - 8:09how many people told me,
-
8:09 - 8:11"This will never happen.
-
8:11 - 8:13We'll never be able to study them.
Why are you bothering?" -
8:13 - 8:17And that's why I'm pleased to tell you
about all the atmospheres studied now, -
8:17 - 8:19and this is really a field of its own.
-
8:19 - 8:22So when it comes to
other planets, other Earths, -
8:22 - 8:24in the future when we can observe them,
-
8:24 - 8:26what kind of gases
would we be looking for? -
8:26 - 8:29Well, you know, our own Earth
has oxygen in the atmosphere -
8:29 - 8:31to 20 percent by volume.
-
8:31 - 8:33That's a lot of oxygen.
-
8:33 - 8:36But without plants
and photosynthetic life, -
8:36 - 8:38there would be no oxygen,
-
8:38 - 8:40virtually no oxygen in our atmosphere.
-
8:40 - 8:42So oxygen is here because of life.
-
8:42 - 8:46And our goal then is to look for gases
in other planet atmospheres, -
8:46 - 8:48gases that don't belong,
-
8:48 - 8:51that we might be able
to attribute to life. -
8:51 - 8:53But which molecules should we search for?
-
8:53 - 8:55I actually told you
how diverse exoplanets are. -
8:55 - 8:57We expect that to continue in the future
-
8:57 - 8:59when we find other Earths.
-
8:59 - 9:01And that's one of the main things
I'm working on now, -
9:01 - 9:03I have a theory about this.
-
9:03 - 9:05It reminds me that nearly every day,
-
9:05 - 9:08I receive an email or emails
-
9:08 - 9:11from someone with a crazy theory
about physics of gravity -
9:11 - 9:13or cosmology or some such.
-
9:13 - 9:17So, please don't email me
one of your crazy theories. -
9:17 - 9:18(Laughter)
-
9:18 - 9:20Well, I had my own crazy theory.
-
9:20 - 9:22But, who does the MIT professor go to?
-
9:23 - 9:27Well, I emailed a Nobel Laureate
in Physiology or Medicine -
9:27 - 9:29and he said, "Sure, come and talk to me."
-
9:29 - 9:31So I brought my two biochemistry friends
-
9:31 - 9:33and we went to talk to him
about our crazy theory. -
9:33 - 9:37And that theory was that life
produces all small molecules, -
9:37 - 9:38so many molecules.
-
9:38 - 9:41Like, everything I could think of,
but not being a chemist. -
9:41 - 9:43Think about it:
-
9:43 - 9:45carbon dioxide, carbon monoxide,
-
9:45 - 9:47molecular hydrogen, molecular nitrogen,
-
9:47 - 9:48methane, methyl chloride --
-
9:48 - 9:49so many gases.
-
9:49 - 9:51They also exist for other reasons,
-
9:51 - 9:53but just life even produces ozone.
-
9:53 - 9:55So we go to talk to him about this,
-
9:55 - 9:57and immediately, he shot down the theory.
-
9:57 - 9:59He found an example that didn't exist.
-
10:00 - 10:02So, we went back to the drawing board
-
10:02 - 10:05and we think we have found something
very interesting in another field. -
10:05 - 10:07But back to exoplanets,
-
10:07 - 10:10the point is that life produces
so many different types of gases, -
10:10 - 10:12literally thousands of gases.
-
10:12 - 10:15And so what we're doing now
is just trying to figure out -
10:15 - 10:16on which types of exoplanets,
-
10:16 - 10:20which gases could be attributed to life.
-
10:22 - 10:24And so when it comes time
when we find gases -
10:24 - 10:26in exoplanet atmospheres
-
10:26 - 10:28that we won't know
if they're being produced -
10:28 - 10:31by intelligent aliens or by trees,
-
10:31 - 10:32or a swamp,
-
10:32 - 10:35or even just by simple,
single-celled microbial life. -
10:36 - 10:37So working on the models
-
10:37 - 10:39and thinking about biochemistry,
-
10:39 - 10:40it's all well and good.
-
10:40 - 10:43But a really big challenge
ahead of us is: how? -
10:43 - 10:45How are we going to find these planets?
-
10:45 - 10:47There are actually many ways
to find planets, -
10:47 - 10:49several different ways.
-
10:49 - 10:53But the one that I'm most focused on
is how can we open a gateway -
10:53 - 10:54so that in the future,
-
10:54 - 10:56we can find hundreds of Earths.
-
10:56 - 10:58We have a real shot
at finding signs of life. -
10:58 - 11:01And actually, I just finished
leading a two-year project -
11:01 - 11:03in this very special phase
-
11:03 - 11:06of a concept we call the starshade.
-
11:06 - 11:09And the starshade
is a very specially shaped screen -
11:09 - 11:11and the goal is to fly that starshade
-
11:11 - 11:14so it blocks out the light of a star
-
11:14 - 11:17so that the telescope
can see the planets directly. -
11:17 - 11:20Here, you can see myself
and two team members -
11:20 - 11:22holding up one small part
of the starshade. -
11:22 - 11:23It's shaped like a giant flower,
-
11:23 - 11:26and this is one of the prototype petals.
-
11:27 - 11:31The concept is that a starshade
and telescope could launch together, -
11:31 - 11:34with the petals unfurling
from the stowed position. -
11:35 - 11:37The central truss would expand,
-
11:37 - 11:40with the petals snapping into place.
-
11:40 - 11:42Now, this has to be made very precisely,
-
11:42 - 11:44literally, the petals to microns
-
11:44 - 11:47and they have to deploy to millimeters.
-
11:47 - 11:49And this whole structure would have to fly
-
11:49 - 11:52tens of thousands of kilometers
away from the telescope. -
11:52 - 11:54It's about tens of meters in diameter.
-
11:55 - 12:00And the goal is to block out
the starlight to incredible precision -
12:00 - 12:02so that we'd be able to see
the planets directly. -
12:03 - 12:06And it has to be a very special shape,
-
12:06 - 12:07because of the physics of defraction.
-
12:07 - 12:10Now this is a real project
that we worked on, -
12:10 - 12:12literally, you would not believe how hard.
-
12:12 - 12:15Just so you believe
it's not just in movie format, -
12:15 - 12:17here's a real photograph
-
12:17 - 12:22of a second-generation
starshade deployment test bed in the lab. -
12:22 - 12:24And in this case,
I just wanted you to know -
12:24 - 12:26that that central truss
has heritage left over -
12:26 - 12:28from large radio deployables in space.
-
12:29 - 12:31So after all of that hard work
-
12:31 - 12:35where we try to think of all the crazy
gases that might be out there, -
12:35 - 12:38and we build the very
complicated space telescopes -
12:38 - 12:39that might be out there,
-
12:39 - 12:40what are we going to find?
-
12:41 - 12:42Well, in the best case,
-
12:43 - 12:45we will find an image
of another exo-Earth. -
12:46 - 12:49Here is Earth as a pale blue dot.
-
12:49 - 12:51And this is actually
a real photograph of Earth -
12:51 - 12:53taken by the Voyager 1 spacecraft,
-
12:53 - 12:55four billion miles away.
-
12:55 - 12:58And that red light is just scattered light
in the camera optics. -
12:59 - 13:02But what's so awesome to consider
-
13:02 - 13:05is that if there are intelligent aliens
-
13:05 - 13:09orbiting on a planet
around a star near to us -
13:09 - 13:11and they build complicated
space telescopes -
13:11 - 13:13of the kind that we're trying to build,
-
13:13 - 13:15all they'll see is this pale blue dot,
-
13:15 - 13:17a pinprick of light.
-
13:17 - 13:21And so sometimes, when I pause to think
-
13:21 - 13:25about my professional struggle
and huge ambition, -
13:25 - 13:27it's hard to think about that
-
13:27 - 13:29in contrast to the vastness
of the universe. -
13:30 - 13:34But nonetheless, I am devoting
the rest of my life -
13:34 - 13:36to finding another Earth.
-
13:36 - 13:39And I can guarantee
-
13:39 - 13:41that in the next generation
of space telescopes, -
13:41 - 13:42and the second generation,
-
13:43 - 13:48we will have the capability
to find and identity other Earths. -
13:48 - 13:51And the capability
to split up the starlight -
13:51 - 13:52so that we can look for gases
-
13:52 - 13:56and assess the greenhouse gases
in the atmosphere, -
13:56 - 13:57estimate the surface temperature,
-
13:57 - 13:59and look for signs of life.
-
14:00 - 14:01But there's more.
-
14:01 - 14:05In this case of searching
for other planets like Earth, -
14:05 - 14:07we are making a new kind of map
-
14:07 - 14:10of the nearby stars
and of the planets orbiting them, -
14:10 - 14:14including stars that actually might be
inhabitable by humans. -
14:15 - 14:17And so I envision that our descendants,
-
14:17 - 14:19hundreds of years from now,
-
14:19 - 14:22will embark on an interstellar
journey to other worlds. -
14:23 - 14:26And they will look back at all of us
-
14:26 - 14:29as the generation who first found
the Earth-like worlds. -
14:30 - 14:31Thank you.
-
14:31 - 14:38(Applause)
-
14:38 - 14:40June Cohen: And I give you,
for a question, -
14:40 - 14:41Rosetta Mission Manager Fred Jansen.
-
14:42 - 14:44Fred Jansen: You mentioned halfway through
-
14:44 - 14:48that the technology
to actually look at the spectrum -
14:48 - 14:50of an exoplanet like Earth
is not there yet. -
14:50 - 14:52When do you expect this will be there,
-
14:52 - 14:54and what's needed?
-
14:54 - 14:58Actually, what we expect is what we call
our next-generation Hubble telescope. -
14:59 - 15:01And this is called the James Webb
Space Telescope, -
15:01 - 15:03and that will launch in 2018,
-
15:03 - 15:04and that's what we're going to do,
-
15:04 - 15:07we're going to look
at a special kind of planet -
15:07 - 15:08called transient exoplanets,
-
15:08 - 15:11and that will be our first shot
at studying small planets -
15:11 - 15:15for gases that might indicate
the planet is habitable. -
15:15 - 15:18JC: I'm going to ask you
one follow-up question, too, Sara, -
15:18 - 15:20as the generalist.
-
15:20 - 15:23So I am really struck
by the notion in your career -
15:23 - 15:24of the opposition you faced,
-
15:24 - 15:26that when you began thinking
about exoplanets, -
15:26 - 15:29there was extreme skepticism
in the scientific community -
15:29 - 15:30that they existed,
-
15:30 - 15:31and you proved them wrong.
-
15:31 - 15:33What did it take to take that on?
-
15:33 - 15:35SS: Well, the thing is that as scientists,
-
15:35 - 15:37we're supposed to be skeptical,
-
15:37 - 15:40because our job to make sure
that what the other person is saying -
15:40 - 15:42actually makes sense or not.
-
15:42 - 15:44But being a scientist,
-
15:44 - 15:47I think you've seen it from this session,
-
15:47 - 15:48it's like being an explorer.
-
15:48 - 15:50You have this immense curiosity,
-
15:50 - 15:52this stubbornness,
-
15:52 - 15:54this sort of resolute will
that you will go forward -
15:54 - 15:56no matter what other people say.
-
15:56 - 15:58JC: I love that. Thank you, Sara.
-
15:58 - 16:01(Applause)
- Title:
- The search for planets beyond our solar system
- Speaker:
- Sara Seager
- Description:
-
Every star we see in the sky has at least one planet orbiting it, says astronomer Sara Seager. So what do we know about these exoplanets, and how can we find out more? Seager introduces her favorite set of exoplanets and shows new technology that can help collect information about them — and even help us look for exoplanets with life.
- Video Language:
- English
- Team:
- closed TED
- Project:
- TEDTalks
- Duration:
- 16:14
Morton Bast edited English subtitles for The search for planets beyond our solar system | ||
Krystian Aparta edited English subtitles for The search for planets beyond our solar system | ||
Morton Bast edited English subtitles for The search for planets beyond our solar system | ||
Morton Bast approved English subtitles for The search for planets beyond our solar system | ||
Morton Bast edited English subtitles for The search for planets beyond our solar system | ||
Morton Bast edited English subtitles for The search for planets beyond our solar system | ||
Morton Bast edited English subtitles for The search for planets beyond our solar system | ||
Morton Bast edited English subtitles for The search for planets beyond our solar system |