The Alpha Centauri System - YouTube

Since the dawn of the space age, in the middle of the 20th century, we’ve sent unmanned

probes all over the solar system, which have given us some incredible images of the planets

and moons that are part of our system.

There are plans to send humans to Mars, and the Galilean moons of Jupiter shouldn’t

be too long after that.

But as exciting as it will be to colonize our system, beyond Mars there are only a handful

of moons that are even remotely fit for such an endeavor.

Our search for habitable worlds will inevitably lead us outside of our own system.

This poses a tremendous challenge, because as far away as the other planets and moons

in this system are, this distance is utterly insignifcant compared to the vast distances

to other stars.

We will certainly need to innovate new methods of propulsion in order to get there in a reasonable

amount of time.

But we will achieve this, and when we do, where will we go first?

The most logical destination once we achieve the capacity for interstellar travel will

be the closest star to our own sun.

So which star is this?

If we look to Centaurus, a constellation in the southern sky, we will find this closest star.

Or technically, not the single closest, but rather, three stars that are extremely close

together, which as a whole, represent the system that is closest to our sun.

This triple star system is called the Alpha Centauri System.

The closest of these stars is called Proxima Centauri, named as such because of its proximity,

and this star is almost certainly gravitationally bound to the other two, which are called Alpha

Centauri A and Alpha Centauri B, which together form a binary system.

So how far away are these nearest neighbors?

They are farther than you think.

The fastest probe we have ever built would take over 50,000 years to get there.

Even light, traveling at the universal speed limit, would take more than four years to

get there.

Proxima Centauri is 4.23 light years away, while the Alpha Centauri stars are 4.32 and

4.37 light years away.

But if we can invent new methods of propulsion, like fusion, or solar sails, or some other

incredible new technology, it’s possible that we could get there within a human lifetime.

So what will we find when we get there?

Well we would reach Proxima Centauri first.

This is a dim red dwarf star, so it’s very tiny and cool, as far as stars go.

Its mass is only 12% of our sun’s, and its radius is around 15% of our sun’s.

It has one planet that we call Proxima Centauri b, which is therefore the closest exoplanet

to us, or the closest planet outside of our solar system.

It is roughly earth-sized, and has an orbital period of around 11 Earth days.

Its orbital radius is around 0.05 astronomical units, or 5% of Earth’s orbital radius.

Even though it is so close, because the star is so much smaller and cooler than ours, Proxima

Centauri b actually sits in the habitable zone of its star, which mean it could harbor

liquid water.

Based on density calculations, it seems likely that it has a rocky surface, potentially with

features that would be familiar to us, making it even more reasonable that this will be

the first planet we set foot on outside of our solar system.

The surface temperature depends on the rate of the planet’s rotation.

There are two models that seem most probable.

Proxima Centauri b may rotate in 3:2 resonance with its star, which would allow for a relatively

smooth distribution of heat from the star as the planet rotates.

But the planet may also be tidally locked, exhibiting synchronous rotation, meaning that

the same side always faces its star, like the way the same side of the moon always faces

the Earth.

This would make one side very bright and hot and the other side very dark and cold.

The habitability of the planet will depend greatly on which of these turns out to be correct.

The atmosphere will also be a factor, and this will depend on the strength of the planet’s

magnetic field.

The weaker the magnetic field is, the more likely it is that activity from its star will

have stripped away the atmosphere.

The stronger the magnetic field is, the more likely it is to have retained an atmosphere,

despite stellar activity.

We will continue to learn more about this planet in the coming decades.

There is also some evidence of another planet, named Proxima Centauri c, that may orbit at

1.5 astronomical units, which is extremely far from its star relative to the orbit of

Proxima Centauri b.

However, more data will have to be gathered to verify its existence.

Beyond this, there are two dust belts around the star, one at around 1 to 4 astronomical

units, and another at around 30.

Together, these planets, one confirmed and one unconfirmed, and some accompanying features,

make this quite an interesting system.

If we were to continue from here, it wouldn’t be too long before we reach Alpha Centauri

A and B. As we said, these make up a binary star system, which means two stars that are

quite close together, orbiting around their center of mass, in this particular case once

every 80 Earth years.

Their orbit is elliptical so the distance between them changes throughout the orbit,

but on average they are about as far apart as our sun and its outermost planets.

They are both very sun-like, almost the same as our sun in mass and size.

It is possible that either of these stars has one or more planets, and it is even possible

that there could be a planet orbiting the binary system as a whole.

We do think it is highly likely that such a planet exists, but there is not yet sufficient

evidence to conclude this.

We will continue to study this system from here on Earth, as there is more data to gather,

and hopefully later in this century, we can send an unmanned probe in that direction,

if we can figure out how to get it going fast enough to make it worth our while.

Perhaps if we can make it all the way there and get some more information, we can shed

some light on the habitability of the planet or planets in this system.

Could we ever colonize Proxima Centauri b?

It is difficult to say.

Because it is very close to Proxima Centauri, which is a flare star, so it is subjected

to intense stellar wind, which means plumes of high-energy particles emitted by Proxima

Centauri barrage the surface, with 2,000 times greater intensity than our sun sends to us

here on Earth.

This would make it difficult to live there, at least without protective habitats, and

it also makes it pretty unlikely that we would find any existing life when we get there,

as the radiation would kill any microscopic life we can conceive of.

But we certainly don’t know for sure, and we won’t know for sure until we set foot

there ourselves.

Hopefully we will unravel the secrets of the Alpha Centauri system one day, and perhaps

there are even people that are already alive that will personally set foot on these worlds.