
Exoplanet found right next door in Alpha Centauri - iProject
http://arstechnica.com/science/2012/10/exoplanet-found-right-next-door-in-alpha-centauri/
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sounds
Now that we know how to detect exoplanets by their effect on the star's
wavelength, what are the implications to the Drake equation? [1]

Originally, we estimated that habitable planets were very rare. Then we
discovered exoplanets, and soon after, habitable exoplanets.

Drake also started by looking for radio signs of intelligent life. Now we
humans use frequency-hopping burst digital transmissions and the power level
is much lower, so detecting another planet by its radio signature seems a lot
less likely.

Since earth has been habitable for at least 3 billion years [2], what is the
probability that intelligent life (in our galaxy) is aware of this planet and
wants to look at it? My back-of-napkin estimate is that we are out on a limb
of the galaxy and therefore very visible.

[1] <http://en.wikipedia.org/wiki/Drake_equation>

[2] <http://en.wikipedia.org/wiki/History_of_Earth>

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stephengillie
What kind of periodic wobble would our Sol produce from our very-many body
solar system? Would it be easy to decipher, or easier to catalog as background
noise?

Maybe we'll start seeing advances in telescopic technologies and analyses in
the years to come -- to pick up on more complex periodic motion of the more
complex solar systems.

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InclinedPlane
If a clone of our Solar System were out in space our chances of detecting it
would be extremely low.

In order to detect Venus or Earth it would require around a 1 in 100 chance
alignment of the orbital plane relative to the observer to be detectable via
the transit method. Jupiter would be detectable through radial velocity
techniques but it would take a minimum of 12 years to confirm a single orbit
and more likely it would take at least 2 orbits for a proper confirmation. And
even so it would be a coin flip on whether the orbital plane was aligned
properly to be detectable at all.

With the increased sensitivity of the new instrumentation used to detect the
Alpha Centauri B planet things are improved slightly but still the chances of
detecting an Earth-clone via radial velocity aren't that great.

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uvdiv
Where are you getting your chances from? Is there some theoretical limit on
the sensitivity of the radial velocity technique, independent of current
technology?

(edit): This spectrometer is supposed to be capable of detecting an earth-
clone, starting around 2016:

<http://en.wikipedia.org/wiki/ESPRESSO>

This graph shows its predicted sensitivity (green line for a sun-like star),
compared to exoplanets previously detected by the same method (gray circles),
and solar system planets for reference:

[http://espresso.astro.up.pt/images/content/science/image012....](http://espresso.astro.up.pt/images/content/science/image012.png)

<http://espresso.astro.up.pt/science.php?show=chapter3>

~~~
InclinedPlane
You can get a rough estimate of the chances of being able to observe a planet
via the transit method by dividing a star's diameter by half of the orbital
diameter of the planet (for Earth it's something like a 1:300 chance).

For radial velocity the signal detected is proportional to the sine of the
orbital inclination. The detectability of Jupiter depends highly on which
instruments are being used for observation. My "coin flip" estimate was just a
SWAG. If you make use of the best radial velocity detection systems today
which have a sensitivity of around 1 m/s and compare that against the maximum
13 m/s radial velocity that Jupiter imparts on the Sun then you end up with
much higher chances of detection (80+%) assuming a random relative orbital
inclination, but that assumes there aren't any other sources of noise
involved.

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luke_s
From a technical point of view I know that there are two teams searching for
exoplanets around Alpha Centauri [1]. Hopefully this means that the other team
will be able to provide evidence that correlates this find.

From a human point of view, I'm in the southern hemisphere and we will have
clear skies. Alpha Centauri is still high above the horizon at this time of
year. Tonight, I'm going to take my two kids outside and point out Alpha
Centauri to them. I'll be able to tell them about it. Tell them, that now we
know, part of what’s there. Tell them, that there is likely other worlds.
Worlds more like ours orbiting that tiny, almost insignificant spark of light.

[1] <http://www.centauri-dreams.org/?p=22603>

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tejaswiy
I actually find it very scary that the nearest planet not in the solar system
is 4.3 Light years away!

If FTL / Close to light speeds are impossible in this universe, we're just
left with generation ships [1]. It seems that there is a very good chance that
we'd be stuck on this rock called the earth forever. Really need to take
better care of it.

[1] and generation ships are highly impractical (see
[http://www.antipope.org/charlie/blog-
static/2009/11/designin...](http://www.antipope.org/charlie/blog-
static/2009/11/designing_society_for_posterit.html) )

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zenon
Forever is a long time.

Alpha Centauri feels far away because our lifetimes are so ridiculously short,
and we're so unfathomably economically poor, compared to the age of and
resources available in the universe. These limitations don't have to apply to
whatever our descendants will be a few centuries or millenia from now.

To them, a trip to Alpha Centauri might be a weekend lark.

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arbuge
Sorry. Irrespective of your lifetime or economic resources, a weekend lark
would violate the laws of physics.

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zenon
It's metaphor. If your life span is indefinite, a journey lasting a few
hundred years is nothing.

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qwertzlcoatl
I understand basic physics and statistics but when I think of the fact that
they teased out a 0.5 m/s signal on something 40 trillion kilometers away, it
might as well be magic.

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robryan
I remember reading a long article (which I can't find right now) about those
searching for planets around this system for many years. Great to hear that
progress has been made.

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_kst_
The article doesn't actually say which of the three stars of the Alpha
Centauri system this planet is orbiting, though it implies that it's orbiting
Alpha Centauri B.

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lelf
α Cen B:
[http://www.eso.org/public/archives/releases/sciencepapers/es...](http://www.eso.org/public/archives/releases/sciencepapers/eso1241/eso1241a.pdf)

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chairsofter
So, the real question is Vekta or Helghan?

~~~
stephengillie
The Romulans took them both out as they left Vulcan.

Or maybe it was the Narn as they attacked Centaur who destroyed them...

