(stimulating orchestral music)
Today, the advent of cutting-edge
observational instruments is shedding light
on amazing facts about life and the universe.
In this first of two episodes,
we'll explore an alien planet that is filled with life.
Where is that planet?
Far beyond our solar system.
A location that astronomers
previously paid little attention to.
Near the kind of star that is most common
in the universe: a red dwarf.
Planets revolving around such stars
may be the best candidates for hosting alien life.
In particular, to try to find small planets
transiting small red dwarf stars,
planets that might of the kind to host life.
On this planet,
what is natural on Earth does not apply.
Strange trees grow on the land, drenched with red light.
Half the planet is in perpetual light ...
the other half locked in an endless, icy darkness.
But planets like this are still likely to host life.
And life on these worlds has had much more time
to develop than on Earth.
There may be lifeforms that have evolved far beyond us.
(creature growling)
If there are intelligent beings over there,
it's a great perk to be living on such a planet.
(rocket rumbling)
To further the search for planets hosting life,
NASA launched a new space telescope and began observations.
Among these myriad stars,
are any of them home to extraterrestrials?
In this episode, we'll explore an alien planet
overflowing with life.
(mysterious string music)
In late 2017, the world's scientific community
was excited by the discovery
of a mysterious object in space.
The UFO whipped across the night sky at a furious speed.
It was dubbed Oumuamua, a Hawaiian word
meaning "first messenger from afar."
Observations showed that it was about 400 meters in length,
with the long, narrow dimensions of a cigar.
No asteroid of this shape had ever been observed before.
What in the world was this strange object?
Astronomers throughout the world
tried to determine the nature of Oumuamua.
One of these scientists was Abraham Loeb
of Harvard University.
The properties of Oumuamua are very different
from the properties of asteroids and comets.
Asteroids and comets that come close to Earth
move in orbits that lie within the solar system.
But Oumuamua was different.
Using its speed to calculate its flight path
revealed that it came from outside the solar system.
This was the first time that humanity
had encountered a visitor from interstellar space.
Moreover, as Oumuamua approached the sun,
it experienced a mysterious acceleration.
In the case of a comet, the extra push
comes from the evaporation of ice on the surface of the rock
that creates out-gassing that is pushing on the rock
and giving it an extra acceleration.
But in the case of Oumuamua,
we didn't detect any gases around the object.
And, moreover, we didn't see
any cometary tail of dust behind it.
Oumuamua did not produce a comet's gas trail.
So, how did it accelerate?
After making his calculations,
Loeb reached a rather incredible hypothesis.
And so, the questions is whether it could be artificial
and some other civilization was using light sails
to produce spacecrafts that are floating in space
for some purpose, and this is one of them.
While most astronomers believe
it is a natural body, Loeb argued that it was
an artificial object made by aliens, or could be.
And its mysterious acceleration can be explained
by imagining a space yacht powered by the light of the sun.
There is a reason Loeb made his hypothesis.
Astronomy has recently opened up new frontiers
in the search for life in the universe.
Over the past decade or so, there was a revolution
in our understanding of the abundance of planets.
We now know that almost every star
has a planet like the Earth.
These frontiers lie
far beyond our solar system.
The stars that shine in our night sky
burn and emit light of their own, just as our sun does.
We now know that planets orbit these stars.
These are called exoplanets, and astronomical observation
is increasingly finding evidence of their existence.
If there are planets around each and every star we see,
there could be a trillion planets in our galaxy,
the Milky Way.
Life in some form is thought to exist
on an untold number of these worlds.
Most astronomers now believe
that extraterrestrial life does exist.
My basic premise is modest.
Out of modesty, I believe that we
are not unique and not special.
And so, if you roll the dice billions of times
in the Milky Way galaxy, surely there's a good chance
that what we see here on Earth will be reproduced.
From the time we humans first entered space,
we've been searching for extraterrestrial life.
We've explored numerous planets
and moons in our solar system
but have yet to find any trace of life.
But extraterrestrial life must exist somewhere.
Some 40 years ago, a young girl
became entranced by that dream.
From the first time her father took her star gazing,
Sara Seager would never forget the sight of the stars
in the heavens, away from the city lights.
(gentle orchestral music)
She wondered, "Somewhere among those stars
"there must be someone like me
"gazing at the glittering sky."
Carrying this thought with her, Seager became an astronomer.
She now leads a major project
that hopes to find a yet undiscovered planet
teeming with life.
Why are we here?
Why does our universe exist?
How did Earth form and evolve?
How and why did life originate and populate our planet?
The second question that we often think about
is are we alone?
Is there life out there?
I'm here to tell you just how close we're getting
to finding out the answer to this question.
It's the first time in human history
that this really is within reach for us.
This space telescope, TESS,
is assisting Seager's search for life in the universe.
And I can guarantee that, in the next generation
of space telescopes, and the second generation,
we will have the capability to find
and identify other Earths.
And so, I envision that our descendants
hundreds of years from now will embark
on an interstellar journey to other worlds,
and they will look back at all of us
as the generation who first found the Earth-like worlds.
Thank you.
(audience applauding)
Seager spent 20 years
working to realize her vision.
She wanted to build a space telescope
to search for other Earths outside the solar system.
(soft orchestral music)
As a graduate student, Seager studied physics.
During that time, a major discovery
helped to determine the course of her life.
In 1995, news broke of a momentous event.
Far outside the solar system,
in the direction of the constellation Pegasus,
a planet was discovered revolving around a star.
(stirring orchestral music)
At that time, no one expected that planets
beyond the solar system could be detected,
so this was an astonishing development.
The discovery was later recognized with a Nobel Prize.
Moreover, the planet was revolving around a star
about the same size as our sun.
This discovery spurred astronomers around the world
to search for planets outside the solar system.
To date, more than 4,000 such exoplanets
have been identified.
However, most of these planets are too close
to the star they orbit, and so are scorching hot.
They are not planets with water, like Earth.
In other words, they cannot sustain life.
But then came a new discovery that thrilled Sara Seager.
It was early in 2017.
Planets were found that could support life,
in a place where no one expected them.
Well, with this discovery, we've made a giant,
accelerated leap forward in the search for habitable worlds
and life on other worlds, potentially speaking.
40 light years from the Earth,
in the direction of the constellation Aquarius,
there is a small, read star known as TRAPPIST-1.
Seven planets were found the be orbiting the star.
(intriguing percussive music)
Surprisingly, three of them are cool enough to contain water
and maybe even oceans.
One of the reasons astronomers are so excited about it
is it's a veritable laboratory for studying planets
orbiting very cool, very small, very dim red stars
that are so incredibly different form our sun.
TRAPPIST-1 is a small, red dwarf,
a type known as an M dwarf.
It is very different from our own sun,
which burns at a fierce 10,000 degrees fahrenheit.
Typical red dwarfs are much smaller than the sun,
with surface temperatures about 2,000 degrees cooler.
Three habitable planets exist there,
in part because the star is so cool.
Whether liquid water can exist on a planet
depends on its distance from the star.
If it's too close, water will evaporate as a gas.
If it's too far away, it will freeze into a solid.
(ice creaking)
Only at the right distance will water remain as a liquid.
Because a red dwarf is cooler,
at a distance where our sun would scorch a planet,
liquid water can still exist.
Until recently, astronomers believed that life
could only exist on planets that orbited stars
similar to the sun.
As a result, they didn't even make observations
of red dwarfs, considered too small and dark.
People hated M dwarf stars.
But that's the evolution of the field.
Initially, it's like it has to be
just like Earth, just like our sun.
But that's very hard to do, and so now,
that's like in my talk when I was asking
how do we find another Earth?
We're taking this shortcut,
like a shortcut to just get there.
But of all the stars in the night sky,
only a minority resemble the sun.
On the other hand, red dwarfs make up
most of the stars in the Milky Way.
There are hundreds of billions of them.
(dramatic orchestral music)
If a space telescope targeted these stars for observation,
it should find large numbers of habitable planets.
How many could support life?
Seager made an estimate based on current theory.
She took the number of observable stars
and calculated the probability of an exoplanet
being in the habitable zone around each star,
as well as other factors.
Her result was ...
7.5
let's round that up to eight.
Okay, let's call it 7.5, but we don't have half planets,
so we'll call that eight.
So we could have eight.
So, although initially I feel discouraged
that the numbers are so small,
it's actually wonderful that we have any chance at all
to make the first efforts to try
to find signs of life out there.
So I am encouraged by the numbers.
I try to make it so it's not zero.
(soft orchestral music)
A space telescope could be used
to find habitable planets.
Seager believed that was the best path
to finding extraterrestrial life in the universe.
This was the origin of the TESS space telescope mission.
The standard search for planets
has been carried out by telescopes
exploring limited areas of the sky, one zone at a time.
But TESS will be different.
It will search the universe in all directions,
rotating its four cameras to tile images of outer space.
It's an unprecedented approach
to the search for habitable planets.
Despite its revolutionary promise,
TESS was almost aborted due to lack of funding.
But Seager would not give up.
She traveled throughout the United States, giving lectures
and arguing that the project was indispensable.
Her passion bore fruit, and private sector organizations
agreed to donate funds.
The mission moved ahead.
In 2013, TESS was officially recognized
as part of NASA's mission.
More than 10 years passed since the initial research began.
April 18, 2018.
A special day had arrived for Sara Seager,
the launch of the TESS telescope.
It's a whole mix of emotions,
just excitement and nervousness
and just hoping everything goes well.
Seager and her family
came to the Kennedy Space Center, eager to witness
a major step in the realization of her dream.
Three, two,
one, zero. (rocket rumbling)
Liftoff.
SpaceX Falcon 9 carrying TESS, a planet-hunting spacecraft
that will search for new worlds beyond our solar system.
(crowd applauding)
Fantastic launch.
It was the perfect launch.
It went up into the sky.
Beautiful.
Yeah, it was pretty cool.
I mean, it's nothing like we've ever seen before.
Yeah, it was really cool.
Definitely better than playing Fortnite at home.
(rocket rumbling)
The launch was flawless.
TESS headed toward an orbit in outer space.
(dynamic orchestral music)
Far darker than any spot on Earth,
the position is ideal for observing
the faint light of red dwarfs.
The search for habitable planets is on.
The dream space telescope
is about to begin its observations.
(intriguing orchestral music)
July 2018.
The time has come for the first pictures
from the TESS space telescope to reach Seager and her team.
In this image, taken with four cameras,
of an area near the south celestial pole,
there are 2.8 million red dwarf stars.
I was amazed.
I was just ...
It's just incredible how many stars TESS sees,
and also it's really beautiful
and just this really wonderful snapshot
of a huge swathe of the sky.
So, I was amazed that we could see so much of it
in such great detail all at once.
When I saw this image for the first time,
I was just happy.
It's incredibly beautiful,
more beautiful than you could imagine.
And it shows you some detector effects
when there's a very bright star,
but on the whole it's just absolutely stunning.
So, honestly, our real goal
is to just find the best targets,
the best potentially habitable planets.
How can planets be found
among these endless stars?
Planets do not emit light themselves,
but when one passes in front of a burning star,
the star's light is partially blocked.
Observing this tiny drop in emitted light
reveals the presence of a planet.
(intriguing instrumental music)
This drop-off in light is called a transit.
The orbital cycle of a planet can be calculated
from the interval between transits.
To that end, TESS will continue to take photographs
of the same areas of the sky again and again.
(soft electronic music)
Eight months after the launch.
In this meeting, the team tried to identify
possible planets from the images sent by TESS.
This is an image taken by the space telescope.
What did the team think?
I would be suspicious
of the secondary eclipse.
Looking at the ...
Oh, 'cause there's like a little bump here?
Yeah.
One transit.
Let's get a closer look.
There were 170,000 red dwarf stars
in this image.
When they were analyzed, one of the stars
showed a fluctuation in emitted light.
It's the red dwarf LHS 3844,
49 light years from Earth.
I really like this.
All right, so this is actually a really exciting one.
That's a good catch, yeah.
Good candidate.
All right.
When the data on the starlight
was examined more closely,
the level fluctuated only at certain times.
This phenomenon occurred regularly, at 11-hour intervals.
They had discovered a planet
on an 11-hour orbit around the red dwarf.
(dramatic orchestral music)
On this day, the team analyzed
a total of 40 planet candidates.
And TESS's observations have only just begun.
These particular planets are not gonna be habitable.
However, these are a faint set of stars.
They're relatively faint.
And so, it will be really not as easy,
kind of challenging to find a habitable planet around them.
We're definitely on track to finding habitable planets.
It's really just a matter of time.
(ethereal music)
TESS is continuing its efforts
to search for planets that orbit red dwarf stars.
But research increasingly indicates that these alien worlds
contain entirely different environments than Earth.
Because these planets around the tiny star,
they're so close to the star, the year of someone
on that planet would just be literally a few days.
And just incredible to think how all the things
we've talked about about red dwarf stars
are even more extreme with these planets.
It's a very extreme place.
The surface temperature
on red dwarfs is relatively low.
As a result, planets must be quite close to the star
for water to remain in its liquid state.
Because these planets are so close,
they are strongly influenced
by the gravitational forces of the star.
This causes the planet's orientation to the star
to be fixed, a phenomenon known as tidal locking.
A tidally locked planet always faces the star
from the same side.
Thus, it's divided in two.
Light falls on one hemisphere, which is always day,
while the other hemisphere is always night.
Perpetual day and perpetual night.
Is it possible for such an unusual world to host life?
(upbeat percussive music)
NASA scientist Tony Del Genio believes that life
does exist on these tidally locked planets.
But for some reason, he first took us into a pizzeria.
(fire crackling)
Here you go.
Thank you.
Enjoy, bon appetit.
We used to think that tidally locked planets
were something like pizzas:
hot on one side, with lots of good stuff ...
but not much going on on the other side of the planet.
But now we know that tidally locked planets
are much more dynamic.
What is this world like,
if it's more dynamic that the simple dichotomy
of the top and bottom of a pizza?
(spirited orchestral music)
Del Genio uses computer simulations
to study the climate on a tidally locked planet.
His simulation shows that large amounts of heat
are transferred from the day side to the night side,
a dynamic circulation of the atmosphere.
So, every planet with an atmosphere,
the atmosphere, the main job of the atmosphere on any planet
is to move warm air to cold places
and cold air to warm places.
That's what weather does.
A tidally locked planet is not cleanly divided
into worlds of blazing heat and frigid cold.
A planet bathed in the red light of a red dwarf star.
Let's take a look at the circulation
of water and atmosphere that takes place here.
On the day side, where light shines endlessly,
at its center, where the light falls most intensely,
a super giant cumulonimbus cloud forms.
(rain pouring)
Rain falls like a waterfall suspended in the air.
But before that rain reaches the surface,
it's vaporized by the heat.
That water vapor carries heat across the entire planet.
(delicate piano music)
And that warm air goes up
and then starts drifting over the poles,
over to the night side, and then over to the dawn
and dusk sides of the planet, and over to the night side.
On the night side,
where frigid temperatures are expected,
the warm air carries heat that raises the temperature
in places above -20 degrees celsius.
That's -4 degrees fahrenheit.
And there is one area on a planet like this
where lifeforms would be most likely to thrive.
This is the border between the day side and the night side:
the twilight zone.
It is believed that a superb climate takes form here.
Average temperature range from zero to 20 degrees celsius,
or 32 to 68 degrees fahrenheit.
The area is bathed in the perpetual red glow of twilight.
Its sun never moves from its position in the sky.
At times, rain falls,
bringing its blessings to living things.
This environment that could be agreeable to life
covers as much as 20% of the planet.
(gentle orchestral music)
The net result of all of that
is that a larger fraction of the planet
could be habitable than what we initially imagined.
I'm absolutely certain that there is life
elsewhere in the universe.
Life almost certainly exists
on such tidally locked planets.
But what form does that life take?
We paid a visit to David Aguilar,
who studies extraterrestrial life.
(uncanny instrumental music)
He has participated in space missions
such as the New Horizons probe sent to Pluto and beyond.
Based on the latest scientific thinking,
he is exploring what extraterrestrial life might be like.
We thought Earths like we live on
would be the most common planet out there for life,
and we were wrong.
So, maybe our little Earth is an oddity.
And the most common planets for life
will never see a sunset, a sunrise.
(bright piano music)
Aguilar has been considering the lifeforms
that might live in the twilight zones
of planets that orbit red dwarf stars.
To that end, he traveled to MIT.
It's me again. -: Hello.
Hi, David. Hi, Sara.
How are you?
Come on in.
It's been a while since the early days.
He came to see Sara Seager,
as one of the leaders of the TESS space telescope project.
(Sara chatting)
What types of life does she imagine we'll find there?
Hot, cold.
I'm always thinking we're gonna find something
right around in here
that may be adapted to go into the cold,
maybe adapted to venture into here.
You know, these M dwarf stars, they are kind of faint.
And through a very thick atmosphere,
there might not be too much light.
So what if you had creatures, lifeforms,
like birds with giant wings,
that the wings themselves could carry out photosynthesis?
(intriguing instrumental music)
Seager believes some planets
might have denser atmospheres than Earth
and high air pressure.
And so if you had that dense air over water,
there could be life that can transfer from water to air,
just like we have amphibians that go from water
and they can live on land,
there could be fish that truly fly.
(intriguing instrumental music)
Under their small red suns,
tidally locked planets.
What kind of life might inhabit the twilight zone?
Aguilar tries to give shape to the lifeforms
that might be suited to the environment on these planets.
This is a red dwarf, one of the most numerous
and common stars in the universe.
Let's go take a look at the spectacles
that unfold on this living planet.
Riding the air currents that flow
from the day side into the night side,
a world wrapped in perpetual darkness
unfolds into the distance.
The temperature is -10 degrees celsius,
or 14 degrees fahrenheit.
(uncanny instrumental music)
(ground rumbling)
Something is swelling.
And now, it begins to float.
(creature whistling)
It's one of the creatures that inhabit this planet.
They feed on microorganisms that ride the wind
and live by taking advantage
of the circulation of the atmosphere.
They're heading toward the border between the night side
and the day side, the twilight zone.
These large creatures can glide in the sky
because hydrogen gas is produced
when they digest their food.
Stored in their bodies,
it allows them to float like balloons.
When they expel the gas, they move at will
into the perpetual red glow of the twilight zone.
Let's descend for a look around.
This is an oasis with the water that is essential for life.
Strange plants grow in profusion.
Much of the light from the red dwarf is infrared,
so photosynthesis is different from what occurs on Earth.
The red sun never shifts its position in the sky.
As a result, all of the vegetation
faces in the same direction.
We feel comfort when we see beautiful green
and fields of green, and forests, and valleys.
Those would be there, too, but they would be
beautiful black forests in magenta fields.
It would look very odd to us.
This creature lives on land and in the water.
(gentle piano music)
Because the atmosphere is dense,
it has evolved to move freely between land and water.
(creature chirping)
On this planet, where the atmosphere circulates
in a dynamic fashion, the twilight zone
has the most stable environment,
a paradise for living beings.
(creature growling)
But this creature's wingspread is three meters.
Its exoskeleton is hard and thick,
covering its body like armor.
It evolved into this shape in order to capture its pray.
(creature roars)
(creatures chirping)
(splashing)
Perhaps the intense struggle to survive
serves as a spur to develop intelligence.
We reach out and we realize that we're quite special,
and this planet is very special,
but there's going to be more mystery out there.
There's going to be worlds that will just dazzle us,
amaze us, and they're just waiting for us to find them.
One feature in particular
promotes the evolution of life here.
The lifespan of a red dwarf star
is much longer than our sun,
which burns out 10 billion years after its formation.
As a result, life on this planet
is able to evolve over a longer period of time
than it took us to develop intelligent life on Earth.
M dwarfs are unique because they can live
a very long time.
They can live for billions or tens of billions of years.
And so that gives life longer to evolve.
Now, at this very moment,
scientists are continuing their efforts
to find extraterrestrial life.
The TESS space telescope continues its search
for planets outside our solar system.
It sends new images form its observations
to Earth at a steady pace.
(dramatic orchestral music)
The TESS team met one year after the telescope was launched.
Do you have other planets?
Yeah, there's one other one.
There's an interesting case, actually.
This is the other star that I've requested time on.
Oh, yeah, this is--
Okay.
So, this is an M dwarf.
This is a much cooler and fainter star.
Nice, very nice.
Yeah.
(upbeat electronic music)
The candidate star they found was L 98-59,
a red dwarf some 35 light years from Earth.
It is orbited by not one but three planets
the same size as Earth.
(dynamic brass music)
Today, TESS is capturing images of planets
heretofore unknown.
The exciting thing, I think, about that
is, even though we release them in chunks,
and so we release like 20 at a time and then 40 at at time,
if you divide it over the course of the year,
it's like we've been finding a planet a day almost.
A planet candidate.
Yeah, a planet candidate.
These are planet candidates
that TESS has identified.
(uplifting orchestral music)
The number of candidates has passed 1,000.
As you know, in exoplanets everything's incredible.
It's so diverse.
Planets are all sizes and masses and orbits.
And so, we try not to have preconceived notions.
We're just trying to go out there and see what's there,
and that's the sense of why it's like true exploration.
At the same time, another effort
to find direct evidence of extraterrestrial life has begun.
(dramatic instrumental music)
Through photosynthesis, plants create oxygen.
Animals emit carbon dioxide and methane gas.
(gas hissing)
Finding these substances in the atmosphere of exoplanets
would provide direct evidence of life.
(waves crashing)
This is the island of Tenerife in the Canary Islands.
Here, Japanese astronomer Norio Narita
uses a ground-based telescope
to more closely observe the planets TESS discovered.
This is the camera that Narita developed.
(impressive instrumental music)
When a planet crosses in front of a star,
light passes through the layer
of atmosphere around the planet.
By analyzing this minuscule amount of light,
the components of the atmosphere can be deduced.
The attempt to find the first hard evidence
of extraterrestrial life continues.
On the other side of the globe, in Chile,
in 2019, one of the world's largest instruments
for analyzing atmospheric gases went into operation.
David Ehrenreich declares that the day we capture evidence
of life in the universe is certain to come.
My dream is to find traces of life
in the atmosphere of another planet.
We should be open to find life
in completely different forms in completely different place.
The challenge of that is that,
how are we going to recognize that this is actually life?
Throughout the world,
a friendly competition is on
to be the first to discover evidence
of extraterrestrial life.
(mysterious music)
And what about that visitor from outside the solar system,
Oumuamua?
NASA clocked it at 196,000 miles per hour
as it sling-shotted past the sun on September 9, 2017.
Its rapid acceleration led some
to believe it was a spaceship.
Where did the strange object originate from?
A research team in Europe is working to solve that riddle.
The scientists have followed the trajectory
of Oumuamua's flight path.
They have identified a number of stars
in the direction of the constellation Cetus
as possible sources.
(rousing orchestral music)
And then there are some smaller, fainter objects
that are also more red, and for example this one,
and these are what we call red dwarfs.
They are smaller stars, older stars.
All of the points you see here
are stars that may have been the original system
where Oumuamua was formed.
Whether Oumuamua is a cigar-shaped asteroid
or a spaceship, what might its home planet look like?
(rousing operatic music)
Could it be this planet,
bathed in the light of a red dwarf star?
Is this an alien planet?
Somewhere in the vast expanse of space,
there may be a civilization far more advanced than ours,
gazing out at our plant.
(gentle guitar music)
Sara Seager continues to search for exoplanets
with with the TESS telescope.
On one of her days off,
she and her family went out stargazing.
The telescope looks quite small,
but it's a fantastic lens,
so things we'll see are incredibly sharp.
The young girl who was entranced
by the starry skies holds true to her vision.
But when I look at the night sky,
I look at the stars, and I wonder,
are there any planets around those stars?
And I wonder if there's any intelligent life
around the planets around those stars,
looking back at our sun and wondering the same thing.
(gentle piano music)
Pursuing planets with extraterrestrial life.
For Sara, her childhood dream lives on.
(gentle instrumental music)
(creature vocalizing)