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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
insignificant 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 four point two
three light years away while the Alpha
Centauri stars are four point three two
and four point three seven 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 Suns and it's radius is
around 15% of our Suns 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 means
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 planets rotation there are two
models that seem most probable Proxima
Centauri B may rotate in 3 to 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
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 together 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
thanks for watching guys subscribe to my
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as always feel free to email me
professor Dave explains at gmail.com
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