The Search for a New Earth

Planet Earth, humanity's safe haven for over 200,000 years.

But some now believe that time is coming to an end.

Among them is the world's most famous scientist.

I am Stephen Hawking.

I am convinced that humans need to leave Earth

and make a new home on another planet.

To stay risks annihilation.

In the last 70 years,

the global population has tripled from 2.5 to 7.5 billion,

and our space and resources here are limited.

Professor Hawking believes we may have to find a backup plan.

We can and must use our curiosity

and intelligence to look at the stars.

We must start now.

For humans to survive,

I believe we must have the preparations in place within

100 years.

I'm Danielle George.

I studied astrophysics, and I'm now a Professor of Engineering.

And I'm Christophe Galfard. I'm a science writer and physicist.

I spent over six years working alongside Stephen Hawking.

We want to explore whether the human race can rise to Professor Hawking's

challenge. Could we really ever find a planet and set up a new home for

humanity? And if so, can we do it in such a short time?

To find out, we'll be travelling the globe,

meeting the scientists already working on this epic challenge.

Whoa!

Discovering that, behind closed doors, people are making amazing

advances in space technology.

And answering the big questions.

Wow! So, do you think that planet is

the best candidate we have if we want to colonise another world?

The answer would be yes at this moment in time.

How will we travel the vast distances,

and what will it take to make a new planet our home?

OK, James, so we arrive on a planet with no atmosphere.

How are you going to keep me alive?

You might think this sounds like science fiction...

..but think again.

Professor Hawking has good reasons for believing that humans might soon

have to leave the Earth.

As well as overpopulation,

there are countless other threats to the continued survival of our

species on this planet.

It could be an asteroid hitting the Earth.

It could be a new virus, climate change, nuclear war,

Artificial Intelligence gone rogue.

Earth's history is strewn with species

and civilisations that have gone extinct.

Professor Hawking believes that, if humanity is to avoid the same fate,

scientists face a huge challenge.

Is it really feasible to create a new human colony in just 100 years?

The first question to ask is obvious.

Is there another planet for us to go to?

The place to find out is here,

at Paranal Observatory in the middle of Chile's Atacama desert.

I've been given a rare chance to see one of the world's most powerful

telescopes in action.

When I was a child,

the only planets we knew about were the ones in our own solar system,

but none of these are suitable for humans to live on.

Now, though, we're discovering that

those aren't the only planets out there.

Here at Paranal,

astronomers search for new worlds outside our Solar System,

across the Milky Way.

This is European Southern Observatory's aptly named

"Very Large Telescope", the VLT,

and I can't deny, it's pretty massive.

And this is where some of the world's top planet-hunters hang out.

As our own star dips down over the horizon,

these incredible instruments come to life.

The VLT is in high demand, with researchers from around the world.

Tonight, Arthur Vigan and Raphael Galache are the planet hunters.

They're trying to determine if their current target star has a planet

orbiting it.

It looks like something is happening, so I'm going to go and

find out.

So now you can see there is a star here.

Oh, great. What we will want to do is to subtract all this light,

which is light from the star that we're not really interested in.

What we're interested in is the light of a faint planet that

would be around.

Planets orbiting other stars are known as exoplanets.

So far, astronomers have discovered over 3,000.

And tonight, Arthur and Raphael may add to the tally.

I'm not sure. I'm not convinced. So you think this is it?

I think this is it. Yeah, it's possible, it's possible.

So, the team here, optimist, pessimist, is it? LAUGHTER

I hope it's a planet.

We will have to re-observe that star in a few months from now,

and if it's still moving with the star, then it means it's a planet.

So if it turns out to be an exoplanet, do you guys get to name it?

Yeah. Yeah. It will be after the name of the star.

Excellent. And we know which star it is?

Yeah, we know, but we cannot tell you. Oh, OK. LAUGHTER

I mean, until it's confirmed and it's published,

everything is a secret.

So is there a general consensus amongst planet hunters,

how many potential exoplanets there could be?

We're really starting to think that planets are ubiquitous in the

universe. Really? And they're really everywhere.

I mean, we discovered the first exoplanets about 25 years ago.

And now we're finding more and more,

almost on average you find a few planets each day.

A few new planets each day.

Each day? Wow. So I should probably get out your way, then.

That was a hint. Yeah. Thanks, Raphael. Good luck, guys. LAUGHTER

See you later. See you.

The researchers at Paranal think there could be billions of potential

planets in the galaxy for a new colony.

But our criteria have to be pretty demanding.

Humans are very fragile creatures.

We've evolved in Earth's very specific habitat.

Stray too far from this and we're in trouble.

Out here in the Atacama Desert, it can get pretty hostile.

It is one of the driest, saltiest deserts on Earth.

But compared to pretty much any other places we might land on one

day, this is positively idyllic.

So, a potential new planet has to pass some stringent tests.

First, we need to find a planet that's rocky and about the same size

and density as the Earth.

It needs to be at the right temperature,

not too hot, not too cold.

Just right.

That's because, for us to survive on a planet,

we need water, and that water should be liquid, and on its surface.

Too far or too close to its star, and water will be ice or steam.

Only in a narrow orbit will conditions be just right -

what we call "the Goldilocks zone".

For our sun, a yellow dwarf star,

the Goldilocks zone stretches from roughly the orbit of Venus

to the orbit of Mars.

Earth sits neatly right in the middle.

But even if we find our perfect Goldilocks planet around another

star, there is one more tough criterion.

We have to be able to reach it.

Most of the things we can see in the night sky are a very,

very long way away.

Space is so enormous that using miles to measure it

doesn't really work.

Each light-year, a better way to measure it,

is around 6 million million miles.

Even the brightest stars in the sky are unbelievably distant.

Over here

is the Orion constellation.

And this is Betelgeuse, one of the biggest stars we know.

It is nearly 500 light-years away.

It might seem hopeless to explore those stars and their planets.

But luckily, not all the stars are quite so far away.

Now, over there is Proxima Centauri.

After the sun, that star is the closest to the Earth.

Our stellar next-door neighbour lies just 4.2 light-years away.

In cosmic terms, that is a tiny distance.

For human travel, it's still a long way,

but seems much more realistic than most others.

A planet around Proxima Centauri might just be reachable.

But looking with the Very Large Telescope, we can't see one.

Some planets are hidden from even the most powerful telescopes by the

brightness of their stars.

To look for a planet around Proxima Centauri,

we'll need a different method.

Swingball. Indeed. May the best man win. LAUGHTER

Oh! Well, you've trained, obviously.

Yeah, well, we had this when I was a kid, in my back yard.

Astronomer James Jenkins uses a less traditional method to look for exoplanets.

So tell me, what does the swingball got to do with

finding planets?

Well, if we consider that the ball is a planet, and the post there

represents our star in the centre,

we can see that the planet orbits the star, and not only that,

the planet exerts a gravitational force, it pulls the star.

And we can see with this analogy of the post that there's a wobble,

a movement of the star,

and that's what we search for when we look for planets.

All right.

James and his team used the telescopes in Chile to observe the

Proxima Centauri star for 60 nights in a row.

Each night, they measured the backward and forward movements of the star,

looking for the telltale sign of a wobble.

Back inside Paranal Observatory's astronomers' residence -

and yes, that is the hotel from James Bond, Quantum Of Solace -

James shows me what they found as the results came in.

Each night, as this data was coming in and we were putting those points

on this plot, we started to see this kind of oscillation, and this wobble

of the star, that we can see here, told us, "Hey...

"the indications we found before were correct."

That there is probably something out there?

There is probably a planet.

Each night we were seeing this confirmation, and after three weeks,

we knew pretty much for certain, Proxima b exists.

So do you think that planet is pretty much the best candidate we

have if we want to colonise another world?

I would have to say, the answer would be yes,

at this moment in time.

Just the distance between the sun and Proxima Centauri,

the fact that it's the nearest star to our sun and it has this planet

that could be Earth-like.

If, in the future, that we can build craft that can travel between the

stars, I think that Proxima b would be basically the first