# Alpha Centauri has a planet



## James Coote (Oct 17, 2012)

http://www.bbc.co.uk/news/science-environment-19959531

It's earth sized, but is in such a close orbit to it's star, Alpha Centauri B, that it goes round every 3 days.

However, often systems with such planets have other similar planets further out where it isn't stupidly hot


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## Bowler1 (Oct 17, 2012)

http://www.bbc.co.uk/news/science-environment-19950923
http://www.bbc.co.uk/news/science-environment-19008908

What they're finding out there these days is getting exciting. Check these two links links, James, I love the first one.


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## James Coote (Oct 17, 2012)

I signed up to galaxy zoo when they first started. Been doing planethunters.org on and off for a year or two now


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## Metryq (Oct 18, 2012)

Bowler1 said:


> What they're finding out there these days is getting exciting.



Science by press release. All of this is pure speculation based on an incredibly tiny data set of _one_ planet (us) with life on it. Similarly, the "Goldilocks" habitable zone is a hypothesis repeated frequently enough that many accept it as "fact." 

Discovering a _mass_ orbiting a star at a given distance may be interesting, but hardly exciting, and certainly way too early to be declaring it "an Earth-like planet."

(On top of everything else, not all spectral shifts are due to the Doppler effect—another staple assumption in astronomy.)


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## James Coote (Oct 19, 2012)

I think 'Earth-like' is generally used in this context by scientists to mean 'of a similar mass and composition' to Earth, and that it is just the general public assuming anything more.

Scientists know this, but you can't really blame them for getting excited at the work they really enjoy and trying to enthuse others about it too at a time when interest in science seems to be declining amongst the wider population

Technology is improving such that maybe in 20 or 50 years time we will be able to directly observe some of these planets. It'd help if we had a good idea of the ones we might be interested in actually studying when that time arrives. Plus observing other solar systems in their entirety, rather than just their stars, allows us to test hypotheses about solar system formation on other solar systems, not just our own.


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## Metryq (Oct 19, 2012)

James Coote said:


> I think 'Earth-like' is generally used in this context by scientists to mean 'of a similar mass and *composition*'



Composition? Astronomers don't even know that much, yet Rigil Kentaurus is right next door. 

http://seagerexoplanets.mit.edu/research.htm

"While the detection of true Earth twins is some time off, we are busy trying to understand *hot* Jupiter and *hot* Neptune atmospheres observed by primary and secondary eclipses for transiting exoplanets."

"Exoplanet researchers have realized that there are fatal limitations to uncovering the interior composition of an exoplanet because *only the mass and radius can be measured*—no other information about the interior."

Astronomers have also been wrong about comets, which were thought to be "dirty snowballs," yet several probes have shown comet nuclei to be dry and rocky. Whispers of water found in the coma and tail were determined to be material sputtered from the surface combined with the solar "wind." 

Yet comets are close-up, by comparison.

Scientists and science journalists can be more accurate in their language. Granted, there are many who believe hover boards and lightsabers are real, but scientists don't need to feed into that with statements so watered down that they are gross exaggerations.


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## Harpo (Jan 10, 2013)

> *COLONISING ALPHA CENTAURI*
> 
> The most ambitious manned space journey envisaged by scientists would be to Alpha Centauri, a star system 4.3 light years away from our solar system, that may be able to sustain life.
> 
> ...


 
http://uk.news.yahoo.com/the-mars-c...her-new-plans-to-explore-space-163043691.html


In my opinion, if it would take 100,000 years to get there, isn't it better to wait a few extra centuries for faster spacecraft to be invented?  Maybe waiting ten thousand years would result in a journey lasting only fifty thousand years, resulting in arrival at Alpha Centauri 40 millenia sooner.


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## Starbeast (Jan 10, 2013)

Why go so far away to Alpha Centauri to live on a planet?

Why not a habitable world in our own galaxy? Earth can't be the only place where life exists in the entire Milky Way.


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## mosaix (Jan 10, 2013)

Starbeast said:


> Why go so far away to Alpha Centauri to live on a planet?
> 
> Why not a habitable world in our own galaxy? Earth can't be the only place where life exists in the entire Milky Way.



Alpha Centauri is in our own galaxy, Starbeast. It's about 4.4 light years from the Sun, just a little further from the star closest to us, Proxima Centauri at about 4.2 light years.


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## Metryq (Jan 10, 2013)

Maybe Starbeast has been watching some LOST IN SPACE reruns. Irwin Allen productions always had trouble with complex scientific terms, like Solar system and galaxy. 

Or perhaps he's been watching SPACE BATTLESHIP YAMATO and confused Alpha Centauri with Iskandar (in the Large Magellanic Cloud).


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## Starbeast (Jan 10, 2013)

mosaix said:


> Alpha Centauri is in our own galaxy, Starbeast. It's about 4.4 light years from the Sun, just a little further from the star closest to us, Proxima Centauri at about 4.2 light years.


 
I was thinking of the Andromeda Galaxy  Oopsie!

A mind is a terrible thing, when you're fighting a cold with medication. When the warning on the bottle says: "Do not operate heavy machinery", does that include automobiles?


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## Ursa major (Jan 10, 2013)

Starbeast said:


> When the warning on the bottle says: "Do not operate heavy machinery", does that include automobiles?


If you were trying to sue them for _their_ medication causing _your_ car accident, then yes.


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## Harpo (Jan 11, 2013)

and does that include Generation Ships heading for Alpha Centauri?


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## Dr Bloodmoney (Jan 12, 2013)

Not entirely sure Starbeast should be operating a colouring book and some crayons at the moment to be honest. 

Someone with a physics degree or something can correct me please, but my understanding is that fuel isn't as much of an issue as it sounds. As the spacecraft gets further away from the sun's gravitational pull, there would be increasingly diminished loss of momentum. Once past the edge of the Oort Cloud (still nearly a light year away), there should be minimal gravitational forces acting upon the spacecraft. Newton's first law of motion states that if there is no net force acting upon an object then the object continues to travel in a straight line with constant velocity (with no atmospheric resistance or gravity slowing the object, no thrust is needed to maintain velocity).

Once the gravitational pull of the Centauri system takes effect, velocity should actually increase steadily. Obviously thrust would be needed to control any sort of orbit or landing.

So essentially there should be the fuel needed to exit the solar system, for course corrections along the journey and then for the final stages for orbit and landing. Still much more fuel than in any space flight ever planned before but not as much as it seems at first glance.


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## Gordian Knot (Jan 12, 2013)

I believe you are essentially correct. The issue in the scenario you stated is lack of speed. You would be essentially coasting the entire way, and it would take a verrrrrrrrrry long time to get there. More fuel would be a requisite to increase the vessel's speed to anything even semi-respectable. And the fuel requirement for that would indeed be enormous.


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## Harpo (Jan 12, 2013)

Which is one of the reasons for waiting another few centuries until we've invented much better spaceships, as I mentioned earlier.


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## Biskit (Jan 14, 2013)

The fuel issue is a complex one and there are a number of factors to consider, even for a simplistic analysis.  In no particular order,

1: The mass of fuel - the more fuel you carry, the more mass to be accelerated, so the more fuel you need... (and then you get into complex discussions on things like 'energy density' in your fuel system.)

2: From a practical point of view, you can only accelerate as fast as the contents of your ship can stand.   As current space and military operations show, humans can tolerate multiple g-forces for short periods, but unless someone shows reasonable tolerance above 1-g then that's going to be your limit.

2b: I can not recall where, but I am sure I came across info based on long-term work in the various orbital research labs that various folks have put up over the decades which indicate that people may not do too well in the long term in low gravity.  It may be that you need to maintain the 1-g for the bulk of the journey as a health factor, and that will bump up your fuel requirements.  I am sure that someone will suggest rotating/centrifugal accommodation - that's going to bring up issues of long-term reliability and maintenance of moving parts.

3: However fast you can accelerate, if you intend to do anything at the far end, you have to slow down again and that's going to take fuel and be subject to the same limitations in (2).  

4: Your fuel system needs to be reliable over long timescales and you want some reasonable assurance of that before you leave.    This is not a trivial issue - I have worked on long-term reliability of materials, trying to predict working life over a span of a decade or two, and the whole topic is fraught with problems.   So your fuel has to remain operational, all of the 'engine' mechanisms must remain operational (or repairable) over a long period and any spare matériel you carry needs a very long shelf life.
(4b: All the stuff about long-term viability applies to all the other parts of the ship.)

5: I'm sure there's other stuff I've forgotten - I wasn't a rocket-scientist.


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## Harpo (Jan 14, 2013)

http://www.extremetech.com/extreme/...will-eventually-power-interplanetary-missions



"Proving yet again that _Star Trek_ was scarily prescient, NASA has announced that its NEXT ion drive — NASA’s Evolutionary Xenon Thruster — has operated continually for over 43,000 hours (five years). This is an important development, as ion thrusters are pegged as one of the best ways to power long-term deep-space missions to other planets and solar systems. With a proven life time of at least five years, NEXT engines just made a very big step towards powering NASA’s next-gen spacecraft."


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## gully_foyle (Feb 1, 2013)

Harpo said:


> http://uk.news.yahoo.com/the-mars-c...her-new-plans-to-explore-space-163043691.html
> 
> 
> In my opinion, if it would take 100,000 years to get there, isn't it better to wait a few extra centuries for faster spacecraft to be invented?  Maybe waiting ten thousand years would result in a journey lasting only fifty thousand years, resulting in arrival at Alpha Centauri 40 millenia sooner.


I'm sure it was a premise for a SF story, that when such an expedition reached the planet they found the remnants of a civilisation and then realised it was a civilisation founded from Earth that left after them.


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## Metryq (Feb 1, 2013)

gully_foyle said:


> I'm sure it was a premise for a SF story



http://en.wikipedia.org/wiki/Alpha_Centauri_in_fiction



> *Far Centaurus* (1944), short story by A. E. van Vogt published in the collection Destination: Universe! (1952). A crew of Terran explorers who have been hibernating through a centuries-long voyage to Alpha Centauri discover on arrival that their technology has been radically superseded; humanity has arrived at the Alphan planet Pelham via superluminal travel long before them, and has long forgotten about them and their primitive mission (compare Comics: Guardians of the Galaxy below). The travelers must overcome their childlike naïveté to cope with the near Godlike human civilization that has evolved in their absence—a good example of the "quasimessianic ... transcendental omnipotence" with which van Vogt often furnishes his protagonists in order to generate a sense of wonder in his tales.


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## Brian G Turner (Jan 21, 2017)

Well, we know Proxima Centauri has an earth-sized planet and about Breakthrough Starshot: to Alpha Centauri in 20 years.

Now Breakthrough Starshot have stumped up the cash to do a dedicated search for planets within the Centauri system, using the Very Large Telescope Array in Chile: VLT to Search for Planets in Alpha Centauri System - Astrobiology Magazine


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