When you think of space, apart from the massive inky blackness and emptiness, you also think
of other planets.
As we are currently all still stuck here on earth, there are so many great and unanswered
questions that we could ask, and one of the most burning ones is the question of whether
there is life on other planets, and if indeed there are other planets with similar conditions
to Earth.
The Alpha Centauri system is the closest to our own, being just four light years away,
and could even have an earth-style planet in orbit around the stars, so let’s take
a look and ask, how would an Earth-like planet look in Alpha Centauri?
Alpha-Cen-Earth As we know, the closest stars to our own sun
are the three stars of the Alpha Centauri system.
As they are just four light years away, we have come to know quite a bit about this system.
The nearest of the three stars is a red dwarf called Proxima, which has two known planets.
However, the other sunlike stars in the system, Alpha Centauri A and B respectively, have
no known planets.
But that doesn’t mean they’re not out there!
As a matter of fact, astronomers have made a pretty big leap lately, imagining a yet-to-be
discovered world that could well exist in our neighbouring system.
By using a new computer model, all information that is known about Alpha Centauri can be
run and extrapolated, generating a set of characteristics of a possible world that could
be in orbit around A or B.
The hypothetical planet is called Alpha-Cen-Earth, but it could be much more than a hypothesis.
A recent study by researchers at ETH Zurich in Switzerland was published in The Astrophysical
Journal and explains their findings in detail.
Alpha Centauri A and B are an interesting pair, both orbiting each other closely, while
Proxima orbits them much further away.
They lie an average of twenty-three astronomical units apart, which is just a bit more than
the distance between our sun and Uranus, and that means that the conditions could be right
for a planet just like ours.
A Hypothetical World At the moment, it’s hard to say anything
completely concrete, because the planet is still only hypothetical, but the hypothesis
is based on everything we know about the two stars Alpha Centauri A and B, which is quite
a lot.
Astronomers have then been able to project that a rocky planet, much like earth, could
exist, as well as what it might look like and how it could have been formed.
The ETH astrophysicist Haiyang Wang led the team researching this hypothetical planet,
and the team calculated the composition of such a world in what’s known as the ‘habitable
zone’ of Alpha A and B.
This would be the region of the star system where conditions are suitable for water to
exist in liquid form.
It is interesting, because the two stars orbit one another so closely.
Using what we know about the chemical compositions of Alpha Centauri, scientists have extrapolated
the composition of a rocky planet in such a habitable zone and found that it made sense
because both stars as well as any actual currently unknown planets would have formed from one
primordial cloud of dust and gas.
This means that expected elements in such a hypothetical world would be rock-forming
elements like iron, silicon, and magnesium, as well as volatiles such as carbon, hydrogen
and oxygen.
A Habitable Planet With elements like these making up such a
world, it is easy to start forming your own ideas about what kind of world it is, but
of course, this is still just conjecture, and the study does not definitively say what
it would be like to live on a planet in Alpha Centauri, because it cannot, of course.
Still, it’s quite an impressive model and it gives us a lot of ideas about what might
be out there.
The burning question that’s probably forming in your mind then is the big one, ‘is there
life out there besides ours on Earth?’
Well, that’s highly likely, statistically speaking, as the universe is vast beyond any
and all knowledge and human experience, and if you increase the range wide enough, the
chances of finding anything dramatically increase.
As for Alpha Centauri, if there is truly a rocky planet there, then it would likely be
extremely similar to our own Sol three, or Earth, in terms of geochemistry.
The researchers who conducted the study also said that their model showed how this world
would most likely have a mantle that is enriched in carbon-bearing sorts of minerals like graphite
and diamond and would be riddled with silicates.
That would be an efficient mantle when it comes to storing water, in much the same way
as the mantle on this planet does.
Our Planetary Brother As you should probably expect, Alpha-Cen-Earth
would be a brother of sorts to our own planet, but it would absolutely not be a perfect twin.
For starters, the geography would be vastly different, but beyond that, from a scientific
perspective, its location would provide different results.
It would possibly have a fairly larger iron core, far lower geological activity and no
plate tectonics to speak of.
However, if has been said that the planet’s early atmosphere would likely resemble the
Earth’s early atmosphere.
This means that it should absolutely have an abundance of carbon dioxide, as well as
methane and good old H 2 O. That all sounds so far so good, right?
Well, there’s a bit more that goes into a planet being able to sustain life.
A part of the study says that “[…] the primitive mantle of this model planet is […] considerably
more reduced (by two orders of magnitude) than that of Earth.
[It] is also modeled to be relatively enriched in graphite or diamond (this should hold even
if some portion of native carbon species has been segregated into the core.
[…] together, these factors preferentially impose a stagnant-lid-tectonic regime.”
That means that we don’t know yet how a planet with no tectonic activity might be
able to sustain life, when we also suppose that plate tectonics were an important player
in the habitability of Earth.
There’s another factor too, and that is that Alpha Centauri is about one point five
to two billion years older than our own solar system!
That means, while we’re speculating about there being life on this ‘new’ planet,
the reality is that such a planet would be much, much, older than Earth, giving life
far more time to evolve, barring some kind of planetary cataclysm.
Right Time, Right Place The study is unlike many other studies, in
that it focuses largely on the volatile elements on the hypothetical planet.
Rocky planets like ours tend to share the chemical make ups of the host stars.
That means that yes, we can tell the refractory elements, like rock and metal, could be suitable,
but the volatile elements are the ones that decide if someone can go and live there.
But the fact this study has happened now is a happy piece of luck, as now is a wonderful
time to begin searching for this kind of planet in Alpha Centauri.
At the moment you see, and from now until 2035, the two stars, A and B, will be far
enough apart from each other in their binary orbit that we will have a much easier time
detecting planets that are orbiting them.
This means that we are in the lucky position of having the right equipment, the right technological
ability, the right knowledge and the right timing for the next thirteen years or so,
to see if we can find any planets like our own.
That’s an incredibly amazing thing to be able to do, and the next few years will give
us our best opportunity to confirm the presence of planets (or of course, the lack of any).
Of course, in the meantime, keep in mind that astronomers have already found over five thousand
exoplanets (meaning worlds outside our own solar system), all orbiting far off distant
stars.
This is one of the reasons that we are looking at Alpha Centauri, because it is so close
by and since we have already found the existence of worlds further out, conventional logic
would presuppose the existence of worlds much closer that we have just missed or overlooked.
The bottom line is that as we continue to explore all these places, it becomes more
and more likely that we will eventually encounter a world like our own, with the right combination
of elements, the right proximity to and from a star and the right terrestrial circumstances
to support life.
But will that life be similar to ours or a variation?
Could there even be another human race out there somewhere, asking all the same questions
that we are?
This study helps us a lot towards figuring out that answer.
But what do you think?
Comment down below.
And for more space tales, like this video and subscribe to Space Infinity!