Secrets of the Universe (2022–…): Season 1, Episode 5 - Hunting for Earth's Twin - full transcript
Secrets of the Universe -
Hunting for Earths Twin
We are in one of the greatest periods
of discovery in humanity's history.
Finding out more about the universe than ever before.
At a faster rate than ever before.
And of these discoveries,
perhaps the most fascinating of all,
is that there are other planets, other worlds,
orbiting other stars far away.
Exoplanets.
Today we take for granted that there are exoplanets
around other stars.
And yet only a few decades ago, we had not seen one.
Finding the first done in 1995,
I think nobody believed us.
It was too big.
Nobody thought
this was even a thing worth studying.
Back then, it was considered ridiculous
to search for exoplanets.
And it was definitely a taboo subject.
But what they found never ceases to amaze.
Nature didn't obey the laws that we had set for ourselves.
And that was exciting.
Everything is exotic outside the solar system.
The types of exoplanets that exist out there,
it's really, I think,
as far as your imagination can we reach.
These are real places we can point to
and say, "Yeah, this is a planet
"that'll rain diamonds or sulfuric acid."
But this quest has a very human face.
In my heart, I wanna go out there
and find the planet with oceans and continents
and breathable air.
A planet that just like Earth.
Humans have always been
fascinated by the heavens.
And wondered, what is our place within them?
Since the stars rotate over our heads every night,
it was only too easy to assume we were right in the middle
of this never ending spectacle.
We used to think that the Earth
was the center of the universe,
that the planets and the stars all revolved around Earth.
Then in the 16 century,
Polish polymath and Catholic canon,
Nicolaus Copernicus upset the status quo.
He figured that the apparent motion
of the stars in the night sky
was more likely due to the Earth moving, not the stars,
which he believed were fixed in the heavens.
Copernicus came along and had a new theory
that the planets, including Earth, revolved around the Sun.
And that was considered heretical.
Suddenly humankind is no longer center stage
and there is worse to come.
Turned out that not even the Sun
is in the center of everything.
The Sun is one out of a few hundred billion stars
orbiting the center of the Milky Way,
which itself is just one galaxy
out of probably a few hundred billions out there.
Over the centuries,
increasingly powerful telescopes
revealed that the cosmos
is both teaming with countless stars yet so vast
that it is mostly empty space.
If you shrink the Sun down to the size of a grain of salt,
the Earth would be about two inches away from the salt grain
and be almost microscopic,
it'd be the size of a particle of smoke, for instance.
And then one can ask, "Well, where do I put
"the next salt grain, the next closest star?"
That star, that next salt grain
would be seven and a half miles away.
So we are just dust grain floating out there.
But still it might be that we are
the only very interesting dust grain out there.
I don't think so though.
The thing of course that really drives all this is,
is there life elsewhere in the universe?
This is the fundamental question
that we have in astronomy, are we alone?
The sheer number of stars suggests
that worlds like our own must exist elsewhere in the cosmos.
But at the end of the 20 century,
there is no evidence that exoplanets exist at all.
And most astronomers believe that theorizing
about exoplanets and their potential habitability
is a pointless exercise.
They're just too small and far away to be observed.
In the early 1980s, we knew in our hearts philosophically
that exoplanets must exist.
But in astronomy evidence is king, it counts for everything.
And until you see one, there's always a niggling doubt.
Exoplanets, it seems
are an itch that can never be scratched.
Four, three, two, go for engine start, one.
But in 1983, a new kind of telescope
is about to challenge those assumptions.
The infrared astronomical satellite or IRAS,
exploits new technology, sensitive to light
beyond the range of human vision.
It's detecting wavelengths where you're seeing heat
as opposed to what the laypeople
will call light, visible light.
All objects in the universe
emit some level of infrared radiation.
And although it's invisible,
we can sometimes feel it as heat.
We're used to the idea that with an infrared camera,
we can see people at night while it's pitch black,
because things that are warm
show up by their infrared radiation.
IRAS applies the same principle
to its survey of the entire sky.
Point about infrared radiation is,
it gets to places that visible light can't.
It can penetrate a cloud of dust around a star.
The space between stars
is filled with bands of gas and dust
that absorb and scatter visible light
and block our view of the stars behind them.
But the longer wavelengths of infrared radiation
pass much more freely.
So previously hidden stars that emit
both visible and infrared light
are suddenly revealed by the IRAS detector.
Now I was working at that point on infrared technology
for big telescopes on the ground.
So we knew a lot about what IRAS was doing.
And in some ways that technology was really crude.
You just let the sky flow over the telescope,
and then when a bright object comes up, you go bing,
and you just map the sky bit by bit, as you drift over it.
There were thousands, millions of new objects.
It was a revolution.
Around six months into the survey,
IRAS detects a bizarre infrared signature
from the star, Beta Pictoris, 63 light years from Earth.
Beta Pictoris had all this extra infrared radiation
that was unexpected.
It wasn't part of the normal thermal spectrum,
if I can put it that way.
It's not coming from the star itself.
So where is this infrared radiation coming from?
It was a real puzzle.
We had no idea what it was,
and that began a big detective story in itself.
News of the Beta Pictoris anomaly
reaches a remote observatory and Chile,
where two NASA astronomers
decide to pause their survey of our solar system
and investigate.
We think perhaps this is a material
which is being illuminated by the star,
heating up and generating this excess infrared signature.
It was a tantalizing piece of evidence
that maybe there's something out there
that we should be looking for.
The telescope itself, it's on the end of a ridge,
almost like the prow of a ship
where the landscape falls away on three sides.
It's rather beautiful.
But it's also very, very dark
and very, very clear skies.
In spring of 1984,
the astronomers turned their optical telescope
towards the Milky Way.
Beta Pictoris was a star like any other star in the sky.
So one of thousands and thousands of stars to look at.
But when they tried to see
what could be causing the infrared access around the star,
there's a problem.
At the telescope, you really couldn't see anything.
And that's because the central star,
there is hundreds of millions of times brighter material
around that star.
Richard's only option
is to try and blot out the light of the star
by making a tiny Sun shield
that astronomers called a coronagraph.
A coronagraph is basically a way
of putting your thumb over the star
and being able to look at material around the star.
Coronagraphs are usually
precision engineered instruments,
but Richard will need to improvise his artificial eclipse
using supplies from the stationary cupboard.
We use these rub-on fonts.
We'd use the period, a half a millimeter in diameter,
and you needed to suspend that.
And at the very, very center of the cross,
we would fix this tiny period, and that would be our mask.
And suddenly, low and behold,
when we looked at Beta Pictoris with a chronograph, wow.
This extended disc showed up in the images.
A flattened disc of material surrounding the star.
What they saw looked like sort of two spikes
sticking out on either side.
They saw dust now, not emitting in the infrared,
but reflecting Sunlight from the star in the center.
This was called a debris disc.
What they have found
is an expansive disc of material, like the rings of Saturn,
but on a vastly larger scale.
It's really the fallout of the planet formation process.
Dust created from collisions between objects
like asteroids and rocky bodies.
You were seeing the first evidence of extra solar planets.
It was incredibly exciting, I mean,
this was the first evidence of the birthplace of planets
around other stars.
Richard Terrile's groundbreaking image
of the Beta Pictoris debris disc
creates a buzz of anticipation in the astronomy underground.
Could exoplanets be within our grasp?
It really opened people's eyes.
Maybe we're ready for prime time in terms of exoplanets.
But spotting an exoplanet
is very different from photographing a debris disc
bigger than our solar system.
And at decade later, exoplanets
are still strictly a French interest.
In the '90s, we had no exoplanets,
nobody has found anything.
I mean, the field did not exist at all.
When 26-year-old Didier Queloz
begins his PhD in astrophysics,
he sticks to more mainstream areas.
My supervisor, Michel Mayor, had a name on binary stars.
That was the business he was in.
Astronomers have been studying binary stars for decades.
That's when two stars orbit each other.
Binary stars are locked
in a complex gravitational dance
that Queloz is tasked with unraveling.
He never imagines that his student project
will kickstart the era of exoplanets.
My PhD actually was to design a new equipment
that we called a spectrograph.
Precise enough to detect tiny change
into the speed of the star.
Subtle speed changes of a large star
can reveal the presence of a much smaller companion star
because the gravitational pull of the companion
as it orbits, makes the main star appear to wobble slightly.
The size of the wobble reflects the size
of the companion star.
And if there is no companion,
then there will be no wobble in the star's position at all.
To be able to detect the smallest stars,
Queloz lanes to measure speed changes
of just 50 meters per second, or 110 miles per hour,
no mean feet and a cosmos and constant,
violent relative motion.
Everything is fast into space.
Like, I mean, the motion of the Earth on its orbit,
it's about 100,000 kilometer per hour.
So your have to fight with all this massive change of speed.
And you're trying to see a tiny, tiny bit.
It is as if you want to measure the speed of a snail
on the wing of a jet.
I'm not sure the snail will survive on the wing,
but that's about.
Queloz' spectrograph
explores the latest advances in computers and fiber optics
and its performance is a surprise, even to him.
I had a goal to reach 50 meter per second,
but I completely overshoot the goal,
I did much better than the goal.
We ended up with 15.
We talking about a tiny motion, which is essentially
the speed of a running man.
Queloz realizes that this unexpected extra sensitivity
to changes speed, means that his spectrograph
could now detect objects much smaller than stars.
With this kind of accuracy,
then you open a complete new window, which is the planet.
But like all aspiring astronomers,
Queloz knows that exoplanet hunting is seen
as a disreputable occupation at best.
Back then it was considered ridiculous
to search for exoplanets.
To study them at all, would've been laughable.
And it was definitely a taboo subject.
Making the wrong decision,
could spell career suicide for the young astrophysicist.
And I remember really Michel telling me,
"Look Didier you're not going to find any planet,
"is that okay with you?"
And I say yes, of course, because it's so cool for me
to demonstrate that the machine had the capability
to detect a planet.
In September, 1994,
Didier Queloz begins his search for exoplanets,
high in the mountains of Provence in France.
Meanwhile, his PhD supervisor, goes on vacation to Hawaii,
confident he will not be disturbed.
Queloz has a list of 142 stars
chosen because of their similarity to our own Sun.
And one of these stars was 51 Peg.
51 Pegasi is in the constellation of Pegasus
located 48 light years from Earth.
Queloz is looking for signs that the star
is wobbling slightly due to the tiny gravitational pull
of an unseen exo planet, as it orbits the star.
You take the light from the star and you spread it.
You do a rainbow, what's called the spectra.
Now, when you move the speed of the star,
you going to change the locations of each of this line.
In a way they become reddish or bluish.
And it's very tiny motions,
and you're trying to measure that,
to build up a single point of data,
which is the radial velocity.
The tug of an exoplanet
would cause changes in the star's speed
comparable to that of an Olympic runner.
But immediately 51 Pegasi makes Queloz question is methods.
I really kind of panicked when I got the first data,
because I think there is a bug in my software.
The problem is that the measurements
seem too good to be true.
The data were telling me a story
that was pointing to a planet,
while I want that star to behave normally.
And I'm trying to debunk the data
and go back to the software,
until I think to myself, I try all I could,
so it must be real.
It must be a planet, it must be a planet.
It's unbelievable, it's unbelievable.
And then I send this fax to Michel,
"I think I'll find a planet."
This is a half Jupiter mass
with the four and a half day periods.
And that was what came up out of the data.
I said to Michel, the distance of the orbiting body
is 20 times closer to the distance
between the Earth and the Sun.
So the planet's very hot.
After checking and rechecking the data,
in October, 1995, the first exoplanet
around a Sun-like star is announced.
Well, we went live with that.
And I think nobody believed us.
I remember this time
because I was in graduate school at the time.
And it was just wow, like so, so crazy.
And the reason this was so crazy
is our Jupiter takes years to go around the Sun.
But this planet orbits its star in a few days.
Not only did we definitely not have gas giants,
so close to our own Sun,
we didn't think planets could even form there.
How do you get a planet like that, so close to its star?
The accepted theory of planet formation
has gas giants forming only in the cold outer reaches
of planetary systems.
Assuming this new found signal was a planet,
it would have to have broken all rules.
The planet would've had to form somewhere else,
far out from the star.
And it would've had to migrate,
would've interact with the gas
or with other planets in the system and move inwards.
That means that big planet came orbiting in
destroyed all the small planets in its path.
That shouldn't happen.
That meant our solar system was quite different
from what they were finding.
And that was a tough pill to swallow for us,
for many people.
The community was absolutely convinced
a planet, like Jupiter, can only be there.
So you have to imagine that you are coming up
with the first planet ever on orbiting a star,
which is already a world premier,
but the planet to come up with,
it's not at all the one you expect.
I mean, it was impossible to swallow, it was too big.
But resistance is futile
when Queloz' breakthrough technique
leads to the discovery of a handful more,
close-orbiting gas giants.
In the following months, his achievement is undeniable
and hot Jupiters become a new category of planetary body.
Finding 51 Peg, in 1995, we kicked the door open.
At that time, I was very proud
to demonstrate the machine would do it,
I mean, eventually.
Well I was very far to realize
it eventually turned out to be only six months.
Really this what happened.
That moment in the mid '90s was when everything changed.
Nature, didn't obey the laws
that we had set for ourselves.
And that was exciting.
51 Pegasi b really tilted over our perspective
of the solar system as just one possible realization
of what can actually happen.
But 51 Pegasi b, also triggers
a more basic instinct.
The main reaction that we had from the public
and from the media, was to ask right away,
"Is that life on that planet?"
The idea of life is so profoundly
connected into the society,
then as soon as there is a little bit of a hint,
then you start to ignite the fire.
Inspired by 51 Pegasi,
another young astrophysicist decides to tackle
the formidable challenge
of searching for life on exoplanets.
I just love imagining
that there's some kind of life out there.
In my heart, I wanna go out there and find the planet
that's just like Earth,
with oceans and continents and breathable air,
a planet around a Sun-like star.
Sara focuses on the idea
that the atmospheres of exoplanets
could contain clues to biological processes.
The search for life by way of gases in an atmosphere,
this idea has been around for nearly a century.
Our atmosphere here on Earth has oxygen,
which fills our atmosphere to 20% by volume,
is only here because of plants and photosynthetic bacteria.
And without those who continuously replenish oxygen,
our Earth's atmosphere would have no oxygen.
The idea that an exoplanet atmosphere
might carry the fingerprints of any life, is attractive.
But putting that theory into practice
has a major stumbling block.
Well, that time we didn't know
if we could detect exoplanet atmospheres.
The astronomy community wanted to know why are we bothering?
We can barely detect the planets,
why are we studying the atmospheres?
A breakthrough comes in 1999
when a hot Jupiter is detected,
as it crosses the face of its star.
The method involves
measuring the dip in intensity of starlight as it transits.
And suggests an intriguing possibility,
could the atmosphere of a transiting planet
leave its mark on that starlight?
My prediction was that gases in the planet atmosphere,
or their signature, gets imprinted on the starlight.
The molecules in the atmosphere
should absorb certain wavelengths of starlight
as it passes through, leaving telltale gaps in the spectrum.
And by comparing the star when it's by itself
to when the planet's in front of the star
then we can then pick out what gases
are in the planet atmosphere.
It's not as straightforward as it sounds
because the signal of the atmosphere is tiny.
Think of the atmosphere like the skin of an onion
and that whole onion in front of a giant, glowing backdrop.
After years working on her theory,
Sara finally proves the skeptics wrong in 2001,
when the element sodium is detected
in the clouds of a gas giant, 159 light years from Earth.
Using my prediction, and it was the first time ever
that an exoplanet atmosphere
had been observed and identified.
And that was just a wow moment.
Sodium is quickly followed
by other elements and molecules, including water,
suggesting a tantalizing possibility,
could a hot Jupiter host living organisms?
All life as we know it needs liquid water.
But the hot Jupiters, they're way too hot for water clouds.
So close to its star,
that means its surface temperature
is probably above a thousand degrees Celsius.
So there is water in hot Jupiter atmospheres,
but it's just way too hot for liquid water.
Which means there's no chance
that there is life in the first place.
Hot Jupiters are both exotic and deadly.
But are they typical of all exoplanets?
In the early 2000s, we definitely had a skewed view
of planets and planetary systems.
We could only find big planets,
big planets close to the star.
Gas giants like 51 Pegasi b were found
because of their gravitational influence on their star,
a method that works best for spotting, very large exoplanets
in very tight orbits,
and misses any small, rocky Earth-like worlds,
if they exist at all.
Hot Jupiters, they're interesting.
But if you're saying,
"I want to know about life and a galaxy."
It is not the information you seek.
The search for exoplanets
capable of sustaining life will need a different approach.
T-minus 10, nine, eight, seven,
six, five, four, three.
My God.
I can't believe it.
In 2009, the Kepler space telescope
launches from Cape Canaveral.
Kepler was just a little, little, tiny mission
that pokes its nose into the galaxy and says,
"What's out there?"
The Kepler mission is a sky survey
dedicated to finding Earth-like exoplanets
around Sun-like stars
and is the brainchild of NASA scientist, Bill Borucki.
We want to go into space.
We wanna explore the stars.
Finding the extent of intelligence in any universe.
The only way you can do that is to prove ahead of time
that most stars have planets.
If there are no planets out there,
there's no life out there.
Borucki's plan is to detect small exoplanets
as they transit their star,
not individually, but on an incredible scale.
The mission concept was to have a wide field of view,
to observe many, many stars.
A hundred thousand stars at one time.
The technological challenge
was to be able to detect minute changes.
And by minute, I mean one part in a hundred thousand dip
in the light of a star as the planet crossed in front of it.
And can it do that all the way across
that field of a hundred thousand stars?
Bill first pitched his scheme to NASA
in the 1980s, when technology had little chance
of meeting the challenge.
When Bill Borucki first proposed this crazy technique
of looking for transits,
I think it wasn't really taken seriously.
In 1983, I used to walk into NASA headquarters
telling them they had to fund this mission.
And they would hide in their office,
they would hide under their desks
'cause I would harangue them.
I have to say that Bill Borucki
was one of the most tenacious
and dedicated scientists I've come across.
If you're in the space game,
you've gotta be prepared for the long haul.
But NASA was never gonna invest four or $500 million
in a mission unless they knew for sure that this would work.
The discovery of 51 Pegasi b in 1995,
encourages NASA to take a chance with Bill's mission.
Up to this point, people had speculated
that there were planets around other stars,
but no one had any empirical proof.
The fact that there was a detection
added scientific credibility.
25 years after Bill conceived his mission,
Kepler's search for Earth-like exoplanet is ready to begin.
Far above the Earth's atmosphere,
the telescope will enjoy a clear view of the Milky Way
that ground-based astronomers can only dream of.
Ambitious or foolhardy,
nothing like it has been tried before.
But finally, we look at the stars
and there are 10s of billions of stars shining.
It's beautiful.
And within a few hours, the data shows
that one of the stars that we know has a planet,
shows a transit.
The exoplanet
is an incredible 750 light years from Earth.
And Kepler passes its first test.
And that told us this instrument's working.
And we were so delighted.
Just ecstatic.
Finding an exoplanet you already know about
is one thing,
but Bill's sky survey is a huge gamble.
Transit technique only works
when that planet is rotating in exactly the same plane
that you're looking at.
You're basically eliminating 99% of the stars.
But even so there were so many stars with planets
that the transit technique
was just finding dozens and dozens.
All it does is take picture, after picture, after picture,
every six seconds, the same field of view, the same stars.
It's designed to be the most boring mission
that has ever built.
At the core of the Kepler mission
is Bill's desire to find Earth-like planets
in the habitable zone of their star.
Also known as the Goldilocks Zone,
this is the region that is neither too hot nor too cold
for liquid water.
Where life, as we know it, can thrive.
The mission was tuned very, very carefully,
Earth-like planets in the habitable zone,
where water could exist on the surface.
Kepler needs to observe three or four transits
to confirm an exoplanet detection,
so needs to last three or four years
to catch Earth-like orbits.
The whole thing was so fundamental and groundbreaking
because Bill's not just detecting planets,
but then finding the subset of planets
that were in the habitable zone,
where life might have appeared.
In the lobbies of our main administrative building,
we had a chart which had indicators,
which would show you how many exoplanets were discovered,
how many exoplanets were discovered in the habitable zone.
These numbers would grow and grow and grow,
and we'd suddenly discover
that we didn't have enough digits
to encompass all the planets that were being discovered.
We're here today to announce new discoveries
from NASA's Kepler mission.
After four years staring into the Milky Way,
Bill Borucki is ready to reveal his top picks
from the hundreds of planets discovered so far.
Today of like to announce, we have found two planets,
that in a habitable zone of another star,
and they are the best candidates found to date.
They may have the possibility of water as well.
More than 1200 light years away,
the most Earth-like of the two is called Kepler-62f
and Borucki's data suggests it could be a water world
completely covered by a vast ocean.
The reason that we call it, perhaps a water world,
is because given its mass and radius, it could in fact
harbor a huge envelope of water on the surface.
All sorts of life could exist in that ocean.
Could you have all sorts of little creatures
and fish to eat them,
and fish that don't want to be eaten,
so they learn to fly out of the ocean,
like our flying fish do?
Kepler-62f was certainly a high point.
We were delighted to find that.
And so were our sponsors at NASA headquarters
who paid for this.
But behind the scenes,
the Kepler mission faces a crisis.
The telescope's ability to stare at the same patch of sky
depends on four gyroscopic stabilizers
called reaction wheels.
That guidance system was so good,
the image of the same star sent a same pixel,
month after a month.
But in 2013, two of the reaction wheels fail.
That meant we could no longer point
at that area of the sky.
Telescope still worked, but we couldn't point there anymore.
Really, really a tense, tense period.
I thought the mission was done for.
I thought, well, got a good run,
got a lot of good data, but it's done for.
But Borucki is not done yet.
Perhaps the mission can be salvaged.
The team sent out an all-points bulletin,
you know, "Help, help, help" to the aerospace community.
All objects in space feel a slight push
from the light of the Sun,
a phenomenon called solar pressure.
Bill learns that this might be the solution to the problem.
The engineers have pointed out,
"You know, we've got two wheels
"and we've got the Sun shining, pushing on the spacecraft.
"We'll arrange it so the Sun acts like one of the wheels."
Each square meter of a satellite like Kepler
feels solar pressure equivalent to the weight
of a grain of salt on Earth.
The engineers hope that this tiny force will be enough
to stabilize the drifting telescope.
Clever idea, the way you use the very pressure
of the radiation from the Sun
as a countervailing force and thereby maintain stability
and extend the life of the mission,
to collect even more data.
The ingenious fix is a success,
but stabilizes the telescope
for much shorter periods than before,
with consequences for the mission.
You could find short period of planets,
giant plants with one or two orbits,
but it didn't allow us to continue the original mission
for finding Earths.
We needed more time.
And so we were not able to find
that possibly true Earth analog.
On October the 30th, 2018,
the Kepler space telescope runs out of fuel.
The mission accomplished its objective.
So, okay, it died, it did its job.
The Kepler discovers over 2,600 exoplanets
with several hundred in the habitable zone.
But the real surprise is the incredible diversity
of these worlds.
Kepler found so many new types of planets,
just wow, opened up our eyes.
The planetary systems weren't like ours at all.
They had at big planets were we had little planets.
Giant planets, bigger than Jupiter,
little tiny planets disintegrating.
Kepler really showed that there's an interstellar zoo
of planetary worlds.
The types of exoplanets that exist out there
it's really, as far as your imagination can reach.
At NASA's jet propulsion lab,
observational data from surveys like Kepler
is used to model the conditions
on some of the extraordinary worlds in the cosmic zoo.
It's really taking what data we have available to us,
and then using our imagination
to try and understand what their weather,
what their atmospheres might be like.
And really start to hammer down
on whether or not there's life out there.
The number crunching
has led to some astonishing conclusions
about the exoplanets in our backyard.
55 Cancri e, what's not imagination
is the fact that we can actually see the star by eye.
40 light years away, 55 Cancri e
is twice the size of Earth.
It's in a ridiculously close orbit around its star.
So surface temperatures might well be above 1,000 Calvin.
So when I think of 55 Cancri e, I just think of lava.
None of the solids on the surface are able to stay solid.
The lavas way too hard to remain liquid all the time.
So there will be some kind of silicate gas as well.
On the backside of the planet,
it might well be that the gaseous rock steam atmosphere
forms droplets, and actually rains out.
And what does it rain out?
Then of course rocks.
So that's a very weird atmospheric scenario.
Despite the apocalyptic conditions,
this could be the most precious exoplanet yet discovered.
If you look at the star that 55 Cancri e is orbiting,
is actually a lot more carbon-rich than that at the Sun.
So 55 Cancri e might be a carbon world.
What happens in a planetary system
where there's more carbon than oxygen,
there could be a layer or part of the planet
that has diamonds.
These are real places we can point to and say,
"Yeah, this indeed is a planet that'll rain,
"you know, diamonds, or has a surface of liquid lava."
These are the worlds that exist in our universe.
55 Cancri e is a nightmare world
where life must be impossible.
But in 2017 and equally bizarre,
but utterly different planetary system is discovered
at about the same distance from Earth.
TRAPPIST-1 is a system
comprised of seven closely-packed planets
that are all roughly Earth-sized,
orbiting what's called an M dwarf star.
The TRAPPIST-1 system is exciting
because it looks like our solar system.
It's got a whole bunch of planets
and maybe two or three of them are in a habitable zone.
And that's really exciting.
It's just, you know, this is the model
that we all had in our minds
of what could happen around all the stars.
The star itself is a much cooler, redder
and smaller star than the Sun.
And indeed the solar system around TRAPPIST
is tucked in closer to this star.
You get the same kind of temperatures you get from Earth.
This mini solar system
could even have liquid water oceans.
The orbital configuration indicates
the planets may have migrated
from further from their star, originally.
And so they've had the opportunity
to accumulate a lot of ice,
which then melted to form water.
So if it were possible to stand
or float on a TRAPPIST-1 planet,
then you would see the star is much closer,
but it's also dimer and redder than our own Sun.
You wouldn't just have a moon in the sky,
but instead you'd be seeing the neighboring planets.
Everything that we would see was our human eye
would be red.
Plants with green leaves,
they would appear black to our eye.
I mean, everything is exotic.
M Dwarf stars, like TRAPPIST-1 are so dim
that from Earth they're to the naked eye,
but they're the most common type of star in the galaxy,
outnumbering Sun-like stars 10 to one.
This is the majority of stars out there.
And the majority of stars
might have these little mini solar systems
with habitable, like planets.
TRAPPIST-1 offers
a recognizable template for life.
But could recent observations of our nearest star,
Proxima Centauri, suggest we already have neighbors.
Proxima Centauri b, I think,
has captured a lot of people's imagination
because it's one of the closest systems we can investigate.
It's only four light years away.
It's in the habitable zone.
So as heated by the star,
it should be the right temperature for life.
Sounds positive, but then things get weird.
We think that it is tightly locked to its star,
like the moon is locked to the Earth.
That means one hemisphere is facing the star permanently.
So could a world
split between permanent day and eternal night,
ever support life?
We think any water on Proxima Centauri b
would probably end up on the night side and frozen.
But ice that's forming on the night side
could start to creep towards the day side,
and it would start to melt.
There is a region, a rim or a ring
around the planet that we refer to as The Terminator,
The Terminator zone, the transition zone
between bright and dark,
where the conditions might be just very favorable
for life to have formed.
These organisms would have to deal
with the perils of being so close to their star.
A particularly volatile red dwarf.
Though the smallest and dimmest kind of star,
at less than 5 billion years old,
Proxima Centauri is very young for a red dwarf
and is prone to violent outbursts.
When a red dwarf is young, it emits a lot more radiation,
including stellar flares.
So the planet's also going to be blasted with radiation.
Proxima Centauri b may be getting flared every week,
but the flare probably wouldn't kill life.
You know, there's always the dark side of the planet.
There's always the oceans, if there are oceans.
So I'm not too worried about life itself,
not being able to survive.
It just will create a very tricky landscape.
The violent stellar activity
could also create a spectacular light show
for those brave enough to venture out.
It could be that there's periodically
a transfer of high energy particles
from the star to the planet,
creating an Aurora that might be ever present.
So could Proxima Centauri b,
be a home from home?
Well, Proxima Centauri b is the closest world,
other than our solar system.
So one of the first places that humankind will explore,
if we go interstellar will be Proxima Centauri b.
In Proxima Centauri b we could discover
that Earth really does have a twin,
just not an identical twin.
Progress in exoplanet research is staggering,
but everything we know has been discovered
in a single generation.
We take for granted that there are exoplanets
orbiting around other stars.
And yet only a few decades ago, we had not seen one.
Less than 40 years after Richard Terrile
photographed the fuzzy debris disc around Beta Pictoris,
this astonishing footage of an exoplanet
actually orbiting the star was released.
We've come from these crude images in a coronagraph
to actually seeing an exoplanet orbiting that star.
It's very, very exciting to see that progression,
see that evolution of our knowledge.
Beta Pictoris b, it's actually called a super Jupiter
because it's more massive than Jupiter.
We've also been able to measure
the rotation rate of the planet.
This might actually resemble Jupiter,
in that it should have a lot of bands and vortices
that rotate in the atmosphere.
We were the first to see it.
And now it's to this interstellar zoo.
It's a great thing to have on your resume.
Every advance in technology
has added new detail to the exoplanet story,
but are we any closer to answering the big question?
Are we at the cusp of finding life today?
I would say no,
but we have a roadmap.
We know what we are looking for.
And we are developing the technology
to look for those traces
that we think could be evidence of life.
We look at the missions that are being planned,
that are such huge telescopes,
that we can see the atmospheres of planets.
What's in that atmosphere?
Is there some signs of life?
Maybe even see the planets?
Well, we see the ingredients for life everywhere,
but most of the universe is, I would say,
hostile towards life.
But I don't know, I don't feel the need to speculate.
The great thing about astronomy
is it won't be long before we have better answers.
And that all of our speculations and dreams,
we can see which one of those are real.
The universe is far more exciting than it was 40 years ago
when our imaginations didn't comprehend
the different environments that we have.
But I think the future is also gonna be very, very exciting.
You know, this first step was finding planets,
the next step is finding life.
Hunting for Earths Twin
We are in one of the greatest periods
of discovery in humanity's history.
Finding out more about the universe than ever before.
At a faster rate than ever before.
And of these discoveries,
perhaps the most fascinating of all,
is that there are other planets, other worlds,
orbiting other stars far away.
Exoplanets.
Today we take for granted that there are exoplanets
around other stars.
And yet only a few decades ago, we had not seen one.
Finding the first done in 1995,
I think nobody believed us.
It was too big.
Nobody thought
this was even a thing worth studying.
Back then, it was considered ridiculous
to search for exoplanets.
And it was definitely a taboo subject.
But what they found never ceases to amaze.
Nature didn't obey the laws that we had set for ourselves.
And that was exciting.
Everything is exotic outside the solar system.
The types of exoplanets that exist out there,
it's really, I think,
as far as your imagination can we reach.
These are real places we can point to
and say, "Yeah, this is a planet
"that'll rain diamonds or sulfuric acid."
But this quest has a very human face.
In my heart, I wanna go out there
and find the planet with oceans and continents
and breathable air.
A planet that just like Earth.
Humans have always been
fascinated by the heavens.
And wondered, what is our place within them?
Since the stars rotate over our heads every night,
it was only too easy to assume we were right in the middle
of this never ending spectacle.
We used to think that the Earth
was the center of the universe,
that the planets and the stars all revolved around Earth.
Then in the 16 century,
Polish polymath and Catholic canon,
Nicolaus Copernicus upset the status quo.
He figured that the apparent motion
of the stars in the night sky
was more likely due to the Earth moving, not the stars,
which he believed were fixed in the heavens.
Copernicus came along and had a new theory
that the planets, including Earth, revolved around the Sun.
And that was considered heretical.
Suddenly humankind is no longer center stage
and there is worse to come.
Turned out that not even the Sun
is in the center of everything.
The Sun is one out of a few hundred billion stars
orbiting the center of the Milky Way,
which itself is just one galaxy
out of probably a few hundred billions out there.
Over the centuries,
increasingly powerful telescopes
revealed that the cosmos
is both teaming with countless stars yet so vast
that it is mostly empty space.
If you shrink the Sun down to the size of a grain of salt,
the Earth would be about two inches away from the salt grain
and be almost microscopic,
it'd be the size of a particle of smoke, for instance.
And then one can ask, "Well, where do I put
"the next salt grain, the next closest star?"
That star, that next salt grain
would be seven and a half miles away.
So we are just dust grain floating out there.
But still it might be that we are
the only very interesting dust grain out there.
I don't think so though.
The thing of course that really drives all this is,
is there life elsewhere in the universe?
This is the fundamental question
that we have in astronomy, are we alone?
The sheer number of stars suggests
that worlds like our own must exist elsewhere in the cosmos.
But at the end of the 20 century,
there is no evidence that exoplanets exist at all.
And most astronomers believe that theorizing
about exoplanets and their potential habitability
is a pointless exercise.
They're just too small and far away to be observed.
In the early 1980s, we knew in our hearts philosophically
that exoplanets must exist.
But in astronomy evidence is king, it counts for everything.
And until you see one, there's always a niggling doubt.
Exoplanets, it seems
are an itch that can never be scratched.
Four, three, two, go for engine start, one.
But in 1983, a new kind of telescope
is about to challenge those assumptions.
The infrared astronomical satellite or IRAS,
exploits new technology, sensitive to light
beyond the range of human vision.
It's detecting wavelengths where you're seeing heat
as opposed to what the laypeople
will call light, visible light.
All objects in the universe
emit some level of infrared radiation.
And although it's invisible,
we can sometimes feel it as heat.
We're used to the idea that with an infrared camera,
we can see people at night while it's pitch black,
because things that are warm
show up by their infrared radiation.
IRAS applies the same principle
to its survey of the entire sky.
Point about infrared radiation is,
it gets to places that visible light can't.
It can penetrate a cloud of dust around a star.
The space between stars
is filled with bands of gas and dust
that absorb and scatter visible light
and block our view of the stars behind them.
But the longer wavelengths of infrared radiation
pass much more freely.
So previously hidden stars that emit
both visible and infrared light
are suddenly revealed by the IRAS detector.
Now I was working at that point on infrared technology
for big telescopes on the ground.
So we knew a lot about what IRAS was doing.
And in some ways that technology was really crude.
You just let the sky flow over the telescope,
and then when a bright object comes up, you go bing,
and you just map the sky bit by bit, as you drift over it.
There were thousands, millions of new objects.
It was a revolution.
Around six months into the survey,
IRAS detects a bizarre infrared signature
from the star, Beta Pictoris, 63 light years from Earth.
Beta Pictoris had all this extra infrared radiation
that was unexpected.
It wasn't part of the normal thermal spectrum,
if I can put it that way.
It's not coming from the star itself.
So where is this infrared radiation coming from?
It was a real puzzle.
We had no idea what it was,
and that began a big detective story in itself.
News of the Beta Pictoris anomaly
reaches a remote observatory and Chile,
where two NASA astronomers
decide to pause their survey of our solar system
and investigate.
We think perhaps this is a material
which is being illuminated by the star,
heating up and generating this excess infrared signature.
It was a tantalizing piece of evidence
that maybe there's something out there
that we should be looking for.
The telescope itself, it's on the end of a ridge,
almost like the prow of a ship
where the landscape falls away on three sides.
It's rather beautiful.
But it's also very, very dark
and very, very clear skies.
In spring of 1984,
the astronomers turned their optical telescope
towards the Milky Way.
Beta Pictoris was a star like any other star in the sky.
So one of thousands and thousands of stars to look at.
But when they tried to see
what could be causing the infrared access around the star,
there's a problem.
At the telescope, you really couldn't see anything.
And that's because the central star,
there is hundreds of millions of times brighter material
around that star.
Richard's only option
is to try and blot out the light of the star
by making a tiny Sun shield
that astronomers called a coronagraph.
A coronagraph is basically a way
of putting your thumb over the star
and being able to look at material around the star.
Coronagraphs are usually
precision engineered instruments,
but Richard will need to improvise his artificial eclipse
using supplies from the stationary cupboard.
We use these rub-on fonts.
We'd use the period, a half a millimeter in diameter,
and you needed to suspend that.
And at the very, very center of the cross,
we would fix this tiny period, and that would be our mask.
And suddenly, low and behold,
when we looked at Beta Pictoris with a chronograph, wow.
This extended disc showed up in the images.
A flattened disc of material surrounding the star.
What they saw looked like sort of two spikes
sticking out on either side.
They saw dust now, not emitting in the infrared,
but reflecting Sunlight from the star in the center.
This was called a debris disc.
What they have found
is an expansive disc of material, like the rings of Saturn,
but on a vastly larger scale.
It's really the fallout of the planet formation process.
Dust created from collisions between objects
like asteroids and rocky bodies.
You were seeing the first evidence of extra solar planets.
It was incredibly exciting, I mean,
this was the first evidence of the birthplace of planets
around other stars.
Richard Terrile's groundbreaking image
of the Beta Pictoris debris disc
creates a buzz of anticipation in the astronomy underground.
Could exoplanets be within our grasp?
It really opened people's eyes.
Maybe we're ready for prime time in terms of exoplanets.
But spotting an exoplanet
is very different from photographing a debris disc
bigger than our solar system.
And at decade later, exoplanets
are still strictly a French interest.
In the '90s, we had no exoplanets,
nobody has found anything.
I mean, the field did not exist at all.
When 26-year-old Didier Queloz
begins his PhD in astrophysics,
he sticks to more mainstream areas.
My supervisor, Michel Mayor, had a name on binary stars.
That was the business he was in.
Astronomers have been studying binary stars for decades.
That's when two stars orbit each other.
Binary stars are locked
in a complex gravitational dance
that Queloz is tasked with unraveling.
He never imagines that his student project
will kickstart the era of exoplanets.
My PhD actually was to design a new equipment
that we called a spectrograph.
Precise enough to detect tiny change
into the speed of the star.
Subtle speed changes of a large star
can reveal the presence of a much smaller companion star
because the gravitational pull of the companion
as it orbits, makes the main star appear to wobble slightly.
The size of the wobble reflects the size
of the companion star.
And if there is no companion,
then there will be no wobble in the star's position at all.
To be able to detect the smallest stars,
Queloz lanes to measure speed changes
of just 50 meters per second, or 110 miles per hour,
no mean feet and a cosmos and constant,
violent relative motion.
Everything is fast into space.
Like, I mean, the motion of the Earth on its orbit,
it's about 100,000 kilometer per hour.
So your have to fight with all this massive change of speed.
And you're trying to see a tiny, tiny bit.
It is as if you want to measure the speed of a snail
on the wing of a jet.
I'm not sure the snail will survive on the wing,
but that's about.
Queloz' spectrograph
explores the latest advances in computers and fiber optics
and its performance is a surprise, even to him.
I had a goal to reach 50 meter per second,
but I completely overshoot the goal,
I did much better than the goal.
We ended up with 15.
We talking about a tiny motion, which is essentially
the speed of a running man.
Queloz realizes that this unexpected extra sensitivity
to changes speed, means that his spectrograph
could now detect objects much smaller than stars.
With this kind of accuracy,
then you open a complete new window, which is the planet.
But like all aspiring astronomers,
Queloz knows that exoplanet hunting is seen
as a disreputable occupation at best.
Back then it was considered ridiculous
to search for exoplanets.
To study them at all, would've been laughable.
And it was definitely a taboo subject.
Making the wrong decision,
could spell career suicide for the young astrophysicist.
And I remember really Michel telling me,
"Look Didier you're not going to find any planet,
"is that okay with you?"
And I say yes, of course, because it's so cool for me
to demonstrate that the machine had the capability
to detect a planet.
In September, 1994,
Didier Queloz begins his search for exoplanets,
high in the mountains of Provence in France.
Meanwhile, his PhD supervisor, goes on vacation to Hawaii,
confident he will not be disturbed.
Queloz has a list of 142 stars
chosen because of their similarity to our own Sun.
And one of these stars was 51 Peg.
51 Pegasi is in the constellation of Pegasus
located 48 light years from Earth.
Queloz is looking for signs that the star
is wobbling slightly due to the tiny gravitational pull
of an unseen exo planet, as it orbits the star.
You take the light from the star and you spread it.
You do a rainbow, what's called the spectra.
Now, when you move the speed of the star,
you going to change the locations of each of this line.
In a way they become reddish or bluish.
And it's very tiny motions,
and you're trying to measure that,
to build up a single point of data,
which is the radial velocity.
The tug of an exoplanet
would cause changes in the star's speed
comparable to that of an Olympic runner.
But immediately 51 Pegasi makes Queloz question is methods.
I really kind of panicked when I got the first data,
because I think there is a bug in my software.
The problem is that the measurements
seem too good to be true.
The data were telling me a story
that was pointing to a planet,
while I want that star to behave normally.
And I'm trying to debunk the data
and go back to the software,
until I think to myself, I try all I could,
so it must be real.
It must be a planet, it must be a planet.
It's unbelievable, it's unbelievable.
And then I send this fax to Michel,
"I think I'll find a planet."
This is a half Jupiter mass
with the four and a half day periods.
And that was what came up out of the data.
I said to Michel, the distance of the orbiting body
is 20 times closer to the distance
between the Earth and the Sun.
So the planet's very hot.
After checking and rechecking the data,
in October, 1995, the first exoplanet
around a Sun-like star is announced.
Well, we went live with that.
And I think nobody believed us.
I remember this time
because I was in graduate school at the time.
And it was just wow, like so, so crazy.
And the reason this was so crazy
is our Jupiter takes years to go around the Sun.
But this planet orbits its star in a few days.
Not only did we definitely not have gas giants,
so close to our own Sun,
we didn't think planets could even form there.
How do you get a planet like that, so close to its star?
The accepted theory of planet formation
has gas giants forming only in the cold outer reaches
of planetary systems.
Assuming this new found signal was a planet,
it would have to have broken all rules.
The planet would've had to form somewhere else,
far out from the star.
And it would've had to migrate,
would've interact with the gas
or with other planets in the system and move inwards.
That means that big planet came orbiting in
destroyed all the small planets in its path.
That shouldn't happen.
That meant our solar system was quite different
from what they were finding.
And that was a tough pill to swallow for us,
for many people.
The community was absolutely convinced
a planet, like Jupiter, can only be there.
So you have to imagine that you are coming up
with the first planet ever on orbiting a star,
which is already a world premier,
but the planet to come up with,
it's not at all the one you expect.
I mean, it was impossible to swallow, it was too big.
But resistance is futile
when Queloz' breakthrough technique
leads to the discovery of a handful more,
close-orbiting gas giants.
In the following months, his achievement is undeniable
and hot Jupiters become a new category of planetary body.
Finding 51 Peg, in 1995, we kicked the door open.
At that time, I was very proud
to demonstrate the machine would do it,
I mean, eventually.
Well I was very far to realize
it eventually turned out to be only six months.
Really this what happened.
That moment in the mid '90s was when everything changed.
Nature, didn't obey the laws
that we had set for ourselves.
And that was exciting.
51 Pegasi b really tilted over our perspective
of the solar system as just one possible realization
of what can actually happen.
But 51 Pegasi b, also triggers
a more basic instinct.
The main reaction that we had from the public
and from the media, was to ask right away,
"Is that life on that planet?"
The idea of life is so profoundly
connected into the society,
then as soon as there is a little bit of a hint,
then you start to ignite the fire.
Inspired by 51 Pegasi,
another young astrophysicist decides to tackle
the formidable challenge
of searching for life on exoplanets.
I just love imagining
that there's some kind of life out there.
In my heart, I wanna go out there and find the planet
that's just like Earth,
with oceans and continents and breathable air,
a planet around a Sun-like star.
Sara focuses on the idea
that the atmospheres of exoplanets
could contain clues to biological processes.
The search for life by way of gases in an atmosphere,
this idea has been around for nearly a century.
Our atmosphere here on Earth has oxygen,
which fills our atmosphere to 20% by volume,
is only here because of plants and photosynthetic bacteria.
And without those who continuously replenish oxygen,
our Earth's atmosphere would have no oxygen.
The idea that an exoplanet atmosphere
might carry the fingerprints of any life, is attractive.
But putting that theory into practice
has a major stumbling block.
Well, that time we didn't know
if we could detect exoplanet atmospheres.
The astronomy community wanted to know why are we bothering?
We can barely detect the planets,
why are we studying the atmospheres?
A breakthrough comes in 1999
when a hot Jupiter is detected,
as it crosses the face of its star.
The method involves
measuring the dip in intensity of starlight as it transits.
And suggests an intriguing possibility,
could the atmosphere of a transiting planet
leave its mark on that starlight?
My prediction was that gases in the planet atmosphere,
or their signature, gets imprinted on the starlight.
The molecules in the atmosphere
should absorb certain wavelengths of starlight
as it passes through, leaving telltale gaps in the spectrum.
And by comparing the star when it's by itself
to when the planet's in front of the star
then we can then pick out what gases
are in the planet atmosphere.
It's not as straightforward as it sounds
because the signal of the atmosphere is tiny.
Think of the atmosphere like the skin of an onion
and that whole onion in front of a giant, glowing backdrop.
After years working on her theory,
Sara finally proves the skeptics wrong in 2001,
when the element sodium is detected
in the clouds of a gas giant, 159 light years from Earth.
Using my prediction, and it was the first time ever
that an exoplanet atmosphere
had been observed and identified.
And that was just a wow moment.
Sodium is quickly followed
by other elements and molecules, including water,
suggesting a tantalizing possibility,
could a hot Jupiter host living organisms?
All life as we know it needs liquid water.
But the hot Jupiters, they're way too hot for water clouds.
So close to its star,
that means its surface temperature
is probably above a thousand degrees Celsius.
So there is water in hot Jupiter atmospheres,
but it's just way too hot for liquid water.
Which means there's no chance
that there is life in the first place.
Hot Jupiters are both exotic and deadly.
But are they typical of all exoplanets?
In the early 2000s, we definitely had a skewed view
of planets and planetary systems.
We could only find big planets,
big planets close to the star.
Gas giants like 51 Pegasi b were found
because of their gravitational influence on their star,
a method that works best for spotting, very large exoplanets
in very tight orbits,
and misses any small, rocky Earth-like worlds,
if they exist at all.
Hot Jupiters, they're interesting.
But if you're saying,
"I want to know about life and a galaxy."
It is not the information you seek.
The search for exoplanets
capable of sustaining life will need a different approach.
T-minus 10, nine, eight, seven,
six, five, four, three.
My God.
I can't believe it.
In 2009, the Kepler space telescope
launches from Cape Canaveral.
Kepler was just a little, little, tiny mission
that pokes its nose into the galaxy and says,
"What's out there?"
The Kepler mission is a sky survey
dedicated to finding Earth-like exoplanets
around Sun-like stars
and is the brainchild of NASA scientist, Bill Borucki.
We want to go into space.
We wanna explore the stars.
Finding the extent of intelligence in any universe.
The only way you can do that is to prove ahead of time
that most stars have planets.
If there are no planets out there,
there's no life out there.
Borucki's plan is to detect small exoplanets
as they transit their star,
not individually, but on an incredible scale.
The mission concept was to have a wide field of view,
to observe many, many stars.
A hundred thousand stars at one time.
The technological challenge
was to be able to detect minute changes.
And by minute, I mean one part in a hundred thousand dip
in the light of a star as the planet crossed in front of it.
And can it do that all the way across
that field of a hundred thousand stars?
Bill first pitched his scheme to NASA
in the 1980s, when technology had little chance
of meeting the challenge.
When Bill Borucki first proposed this crazy technique
of looking for transits,
I think it wasn't really taken seriously.
In 1983, I used to walk into NASA headquarters
telling them they had to fund this mission.
And they would hide in their office,
they would hide under their desks
'cause I would harangue them.
I have to say that Bill Borucki
was one of the most tenacious
and dedicated scientists I've come across.
If you're in the space game,
you've gotta be prepared for the long haul.
But NASA was never gonna invest four or $500 million
in a mission unless they knew for sure that this would work.
The discovery of 51 Pegasi b in 1995,
encourages NASA to take a chance with Bill's mission.
Up to this point, people had speculated
that there were planets around other stars,
but no one had any empirical proof.
The fact that there was a detection
added scientific credibility.
25 years after Bill conceived his mission,
Kepler's search for Earth-like exoplanet is ready to begin.
Far above the Earth's atmosphere,
the telescope will enjoy a clear view of the Milky Way
that ground-based astronomers can only dream of.
Ambitious or foolhardy,
nothing like it has been tried before.
But finally, we look at the stars
and there are 10s of billions of stars shining.
It's beautiful.
And within a few hours, the data shows
that one of the stars that we know has a planet,
shows a transit.
The exoplanet
is an incredible 750 light years from Earth.
And Kepler passes its first test.
And that told us this instrument's working.
And we were so delighted.
Just ecstatic.
Finding an exoplanet you already know about
is one thing,
but Bill's sky survey is a huge gamble.
Transit technique only works
when that planet is rotating in exactly the same plane
that you're looking at.
You're basically eliminating 99% of the stars.
But even so there were so many stars with planets
that the transit technique
was just finding dozens and dozens.
All it does is take picture, after picture, after picture,
every six seconds, the same field of view, the same stars.
It's designed to be the most boring mission
that has ever built.
At the core of the Kepler mission
is Bill's desire to find Earth-like planets
in the habitable zone of their star.
Also known as the Goldilocks Zone,
this is the region that is neither too hot nor too cold
for liquid water.
Where life, as we know it, can thrive.
The mission was tuned very, very carefully,
Earth-like planets in the habitable zone,
where water could exist on the surface.
Kepler needs to observe three or four transits
to confirm an exoplanet detection,
so needs to last three or four years
to catch Earth-like orbits.
The whole thing was so fundamental and groundbreaking
because Bill's not just detecting planets,
but then finding the subset of planets
that were in the habitable zone,
where life might have appeared.
In the lobbies of our main administrative building,
we had a chart which had indicators,
which would show you how many exoplanets were discovered,
how many exoplanets were discovered in the habitable zone.
These numbers would grow and grow and grow,
and we'd suddenly discover
that we didn't have enough digits
to encompass all the planets that were being discovered.
We're here today to announce new discoveries
from NASA's Kepler mission.
After four years staring into the Milky Way,
Bill Borucki is ready to reveal his top picks
from the hundreds of planets discovered so far.
Today of like to announce, we have found two planets,
that in a habitable zone of another star,
and they are the best candidates found to date.
They may have the possibility of water as well.
More than 1200 light years away,
the most Earth-like of the two is called Kepler-62f
and Borucki's data suggests it could be a water world
completely covered by a vast ocean.
The reason that we call it, perhaps a water world,
is because given its mass and radius, it could in fact
harbor a huge envelope of water on the surface.
All sorts of life could exist in that ocean.
Could you have all sorts of little creatures
and fish to eat them,
and fish that don't want to be eaten,
so they learn to fly out of the ocean,
like our flying fish do?
Kepler-62f was certainly a high point.
We were delighted to find that.
And so were our sponsors at NASA headquarters
who paid for this.
But behind the scenes,
the Kepler mission faces a crisis.
The telescope's ability to stare at the same patch of sky
depends on four gyroscopic stabilizers
called reaction wheels.
That guidance system was so good,
the image of the same star sent a same pixel,
month after a month.
But in 2013, two of the reaction wheels fail.
That meant we could no longer point
at that area of the sky.
Telescope still worked, but we couldn't point there anymore.
Really, really a tense, tense period.
I thought the mission was done for.
I thought, well, got a good run,
got a lot of good data, but it's done for.
But Borucki is not done yet.
Perhaps the mission can be salvaged.
The team sent out an all-points bulletin,
you know, "Help, help, help" to the aerospace community.
All objects in space feel a slight push
from the light of the Sun,
a phenomenon called solar pressure.
Bill learns that this might be the solution to the problem.
The engineers have pointed out,
"You know, we've got two wheels
"and we've got the Sun shining, pushing on the spacecraft.
"We'll arrange it so the Sun acts like one of the wheels."
Each square meter of a satellite like Kepler
feels solar pressure equivalent to the weight
of a grain of salt on Earth.
The engineers hope that this tiny force will be enough
to stabilize the drifting telescope.
Clever idea, the way you use the very pressure
of the radiation from the Sun
as a countervailing force and thereby maintain stability
and extend the life of the mission,
to collect even more data.
The ingenious fix is a success,
but stabilizes the telescope
for much shorter periods than before,
with consequences for the mission.
You could find short period of planets,
giant plants with one or two orbits,
but it didn't allow us to continue the original mission
for finding Earths.
We needed more time.
And so we were not able to find
that possibly true Earth analog.
On October the 30th, 2018,
the Kepler space telescope runs out of fuel.
The mission accomplished its objective.
So, okay, it died, it did its job.
The Kepler discovers over 2,600 exoplanets
with several hundred in the habitable zone.
But the real surprise is the incredible diversity
of these worlds.
Kepler found so many new types of planets,
just wow, opened up our eyes.
The planetary systems weren't like ours at all.
They had at big planets were we had little planets.
Giant planets, bigger than Jupiter,
little tiny planets disintegrating.
Kepler really showed that there's an interstellar zoo
of planetary worlds.
The types of exoplanets that exist out there
it's really, as far as your imagination can reach.
At NASA's jet propulsion lab,
observational data from surveys like Kepler
is used to model the conditions
on some of the extraordinary worlds in the cosmic zoo.
It's really taking what data we have available to us,
and then using our imagination
to try and understand what their weather,
what their atmospheres might be like.
And really start to hammer down
on whether or not there's life out there.
The number crunching
has led to some astonishing conclusions
about the exoplanets in our backyard.
55 Cancri e, what's not imagination
is the fact that we can actually see the star by eye.
40 light years away, 55 Cancri e
is twice the size of Earth.
It's in a ridiculously close orbit around its star.
So surface temperatures might well be above 1,000 Calvin.
So when I think of 55 Cancri e, I just think of lava.
None of the solids on the surface are able to stay solid.
The lavas way too hard to remain liquid all the time.
So there will be some kind of silicate gas as well.
On the backside of the planet,
it might well be that the gaseous rock steam atmosphere
forms droplets, and actually rains out.
And what does it rain out?
Then of course rocks.
So that's a very weird atmospheric scenario.
Despite the apocalyptic conditions,
this could be the most precious exoplanet yet discovered.
If you look at the star that 55 Cancri e is orbiting,
is actually a lot more carbon-rich than that at the Sun.
So 55 Cancri e might be a carbon world.
What happens in a planetary system
where there's more carbon than oxygen,
there could be a layer or part of the planet
that has diamonds.
These are real places we can point to and say,
"Yeah, this indeed is a planet that'll rain,
"you know, diamonds, or has a surface of liquid lava."
These are the worlds that exist in our universe.
55 Cancri e is a nightmare world
where life must be impossible.
But in 2017 and equally bizarre,
but utterly different planetary system is discovered
at about the same distance from Earth.
TRAPPIST-1 is a system
comprised of seven closely-packed planets
that are all roughly Earth-sized,
orbiting what's called an M dwarf star.
The TRAPPIST-1 system is exciting
because it looks like our solar system.
It's got a whole bunch of planets
and maybe two or three of them are in a habitable zone.
And that's really exciting.
It's just, you know, this is the model
that we all had in our minds
of what could happen around all the stars.
The star itself is a much cooler, redder
and smaller star than the Sun.
And indeed the solar system around TRAPPIST
is tucked in closer to this star.
You get the same kind of temperatures you get from Earth.
This mini solar system
could even have liquid water oceans.
The orbital configuration indicates
the planets may have migrated
from further from their star, originally.
And so they've had the opportunity
to accumulate a lot of ice,
which then melted to form water.
So if it were possible to stand
or float on a TRAPPIST-1 planet,
then you would see the star is much closer,
but it's also dimer and redder than our own Sun.
You wouldn't just have a moon in the sky,
but instead you'd be seeing the neighboring planets.
Everything that we would see was our human eye
would be red.
Plants with green leaves,
they would appear black to our eye.
I mean, everything is exotic.
M Dwarf stars, like TRAPPIST-1 are so dim
that from Earth they're to the naked eye,
but they're the most common type of star in the galaxy,
outnumbering Sun-like stars 10 to one.
This is the majority of stars out there.
And the majority of stars
might have these little mini solar systems
with habitable, like planets.
TRAPPIST-1 offers
a recognizable template for life.
But could recent observations of our nearest star,
Proxima Centauri, suggest we already have neighbors.
Proxima Centauri b, I think,
has captured a lot of people's imagination
because it's one of the closest systems we can investigate.
It's only four light years away.
It's in the habitable zone.
So as heated by the star,
it should be the right temperature for life.
Sounds positive, but then things get weird.
We think that it is tightly locked to its star,
like the moon is locked to the Earth.
That means one hemisphere is facing the star permanently.
So could a world
split between permanent day and eternal night,
ever support life?
We think any water on Proxima Centauri b
would probably end up on the night side and frozen.
But ice that's forming on the night side
could start to creep towards the day side,
and it would start to melt.
There is a region, a rim or a ring
around the planet that we refer to as The Terminator,
The Terminator zone, the transition zone
between bright and dark,
where the conditions might be just very favorable
for life to have formed.
These organisms would have to deal
with the perils of being so close to their star.
A particularly volatile red dwarf.
Though the smallest and dimmest kind of star,
at less than 5 billion years old,
Proxima Centauri is very young for a red dwarf
and is prone to violent outbursts.
When a red dwarf is young, it emits a lot more radiation,
including stellar flares.
So the planet's also going to be blasted with radiation.
Proxima Centauri b may be getting flared every week,
but the flare probably wouldn't kill life.
You know, there's always the dark side of the planet.
There's always the oceans, if there are oceans.
So I'm not too worried about life itself,
not being able to survive.
It just will create a very tricky landscape.
The violent stellar activity
could also create a spectacular light show
for those brave enough to venture out.
It could be that there's periodically
a transfer of high energy particles
from the star to the planet,
creating an Aurora that might be ever present.
So could Proxima Centauri b,
be a home from home?
Well, Proxima Centauri b is the closest world,
other than our solar system.
So one of the first places that humankind will explore,
if we go interstellar will be Proxima Centauri b.
In Proxima Centauri b we could discover
that Earth really does have a twin,
just not an identical twin.
Progress in exoplanet research is staggering,
but everything we know has been discovered
in a single generation.
We take for granted that there are exoplanets
orbiting around other stars.
And yet only a few decades ago, we had not seen one.
Less than 40 years after Richard Terrile
photographed the fuzzy debris disc around Beta Pictoris,
this astonishing footage of an exoplanet
actually orbiting the star was released.
We've come from these crude images in a coronagraph
to actually seeing an exoplanet orbiting that star.
It's very, very exciting to see that progression,
see that evolution of our knowledge.
Beta Pictoris b, it's actually called a super Jupiter
because it's more massive than Jupiter.
We've also been able to measure
the rotation rate of the planet.
This might actually resemble Jupiter,
in that it should have a lot of bands and vortices
that rotate in the atmosphere.
We were the first to see it.
And now it's to this interstellar zoo.
It's a great thing to have on your resume.
Every advance in technology
has added new detail to the exoplanet story,
but are we any closer to answering the big question?
Are we at the cusp of finding life today?
I would say no,
but we have a roadmap.
We know what we are looking for.
And we are developing the technology
to look for those traces
that we think could be evidence of life.
We look at the missions that are being planned,
that are such huge telescopes,
that we can see the atmospheres of planets.
What's in that atmosphere?
Is there some signs of life?
Maybe even see the planets?
Well, we see the ingredients for life everywhere,
but most of the universe is, I would say,
hostile towards life.
But I don't know, I don't feel the need to speculate.
The great thing about astronomy
is it won't be long before we have better answers.
And that all of our speculations and dreams,
we can see which one of those are real.
The universe is far more exciting than it was 40 years ago
when our imaginations didn't comprehend
the different environments that we have.
But I think the future is also gonna be very, very exciting.
You know, this first step was finding planets,
the next step is finding life.