Alpha Centauri

[steve01]

Could a solar filter of sorts be used to tone down the glare on this pic so it could be possible to see the actual stars?<br />http://antwrp.gsfc.nasa.gov/apod/ap030323.html<br />

 

[steve01]

Have you seen any good pics of the system, if so any links??<br />thx

 

[thalion]

There is some good info (and a few pics) here:<br /><br />http://www.solstation.com/stars/alp-cent3.htm

 

[mooware]

I think also that Alpha A & B, are the only stars within 10 light years of us that might have the possibility of life. (no one is saying intelligent here).. The stars are similar in age and size and energy output to our sun, there is a metalicity content which may breed a couple or three rocky/wet planets, as well as A and B being far enough apart to harbor a stable orbit within the goldilocks zone.<br /><br />Well, let's say maybe a better chance there than the rest of our neighbors within 10 ly<br /><br /><br />

 

[jcdenton]

Imagine how different their sky would look from ours with the different variations of both suns. Sometimes you would have one large sun in the sky, at other times a smaller one, sometimes both, other times none at all. Difficult schedule to adapt to (from what we're used to). <div class="Discussion_UserSignature"> </div>

 

[mooware]

I believe most of the stars within 10 ly from us are red dwarves.. One one have to be very close to a red dwarf to have liquid water. Then of course, the radiation from the star might sterilize everything on the planet.. Especially if the it's a flare star.<br /><br />

 

[thalion]

It would indeed be a spectacular sight--from either star, the other would shine hundreds of times brighter than the Full Moon; long, dark nights would be pretty scarce. <br /><br />Our own Sun would be a bright star between Cassiopeia and Perseus. <img src="/images/icons/wink.gif" />

 

[redracer02]

So, with current rocket technology, how long would it take to get there? Lets say we used nuclear.

 

[heyscottie]

If Voyager 1, which is currently the fastest moving craft we have, was heading directly at Alpha Centauri, then going at its current speed of 3.623 au/yr, it would take about 76000 years to cover the 4.23 light year distance.

 

[nacnud]

Have a look at Project Daedalus [wikipedia.org] for a possible interstellar craft. Although outside our current capabilities, it is a design that could be built eventually.<br /><br /><font color="yellow"><b><br />Project Daedalus </b>was a study conducted between 1973 and 1978 by the British Interplanetary Society to design a plausible interstellar unmanned spacecraft. A dozen scientists and engineers led by Alan Bond worked on the project.<br /><br />The design criteria were that the spacecraft had to use current or near-future technology and had to be able to reach its destination within a human lifetime (a flight time of 50 years was alotted). The target chosen was Barnard's Star, 5.9 light years away, which at the time was believed to posses at least one planet (the evidence on which this belief was based has since been discredited). The design was required to be flexible enough that it could be sent to any of a number of other target stars, however.<br /><br />The design was not intended to enter orbit around the target star but would pass through the system making observations at around 12% of the speed of light.<font color="yellow"><br /></font></font>

 

[silylene old]

If there were a (moonless) water-planet in the habitable zone around alpha centauri, how big would the tides be due to the attraction of beta centauri over the planetary orbital period, and as the two stars orbited each other? How much would the solar irradiance vary as the two stars orbited each other? I can envision a rather complicated plot (especially if the planet was tilted on its axis). Is it likely that the planet's rotation become gravitationally locked?<br /><br />And if there were a (moonless) water-planet in the habitable zone around beta centauri, same questions as above, what would it be like? <div class="Discussion_UserSignature"> <div class="Discussion_UserSignature" align="center"><em><font color="#0000ff">- - - - - - - - - - - - - - - - - - - - - -</font></em> </div><div class="Discussion_UserSignature" align="center"><font color="#0000ff"><em>I really, really, really miss the "first unread post" function.</em></font> </div> </div>

 

[thalion]

Tidal forces vary with the cube of the distance, and neither star in the AC system gets closer than 11 AUs to the other; tides from the other star would be probably be almost immeasurably small. The irradiance would probably contribute to some slight warming over what could be produced by one star alone, but not disastrously so. The ultimate limiting factor in where a planet could orbit around either star is the zone where gravitational perturbations could remove a planet from orbit, somewhere around 3 AUs from each star. Finally, an orbiting planet would not become tidally-locked unless it were orbiting very closely around either star.

 

[silylene old]

1/500'th is a LOT.<br /><br />Maybe my original question wasn't explicit enough.<br /><br />The Milkanovitch insolation cycles change the total solar insolation by only 0.15% - but the climatological effect gets magnified by the Earth's axial tilt and this amplifies the impact of small changes. The gravitational influence of Jupiter and Venus are what causes the cyclical changes in both the eccentricity of Earth's orbit, and the obliquity, giving the cycles.<br /><br />So I am wondering what would be the amplitude in the changes in insolation by a putative Earth-like planet orbiting alpha centauri, as caused by beta centauri, taking into account eccentricity and obliquity effects. The answer would require a lot of modeling. But I bet it is significant in the proposed planet's climatology. It isn't a simple answer. It would be a good interesting research paper, in fact.<br /><br />And if there was a "Jupiter" also ciricling alpha centauri, and its oribital eccentricity was being cyclically influenced by beta centauri, this would further perturb the cycles on the "alpha-earth".<br /><br />The reverse case of a planet orbiting beta centauri could also be consdiered.<br /><br />It's all interesting!<br /> <div class="Discussion_UserSignature"> <div class="Discussion_UserSignature" align="center"><em><font color="#0000ff">- - - - - - - - - - - - - - - - - - - - - -</font></em> </div><div class="Discussion_UserSignature" align="center"><font color="#0000ff"><em>I really, really, really miss the "first unread post" function.</em></font> </div> </div>

 

[jcdenton]

Maybe he meant Proxima Centauri? <div class="Discussion_UserSignature"> </div>

 

[redracer02]

Did anyone say how far apart A and B are from each other?

 

[mkofron]

<blockquote><font class="small">In reply to:</font><hr /><p>but not quite as far the distance between the sun and Uranus<p><hr /></p></p></blockquote><br /><br />So.. how far is the sun from Uranus? <br />

 

[jcdenton]

Uranus mean distance from the Sun (km) = 2,870,990,000<br /><br />Views of the Solar System <div class="Discussion_UserSignature"> </div>

 

[jcdenton]

Yes I know the details of the Alpha Centauri system. It's just that when silylene said the "reverse", I thought he was referring to Proxima Centauri (or Alpha Centauri C) since it orbits Alpha Centauri A and B from 0.24 light years away. <div class="Discussion_UserSignature"> </div>

 

[silylene old]

oops my error, sorry about that.<br /><br />I was talking about:<br />Alpha Centauri A (the G-type star similar to our sun) <br />Alpha Centauri B (the cooler K-type star) <br />which orbit one another.<br /><br />I don't care about beta centauri which is many light years away. <div class="Discussion_UserSignature"> <div class="Discussion_UserSignature" align="center"><em><font color="#0000ff">- - - - - - - - - - - - - - - - - - - - - -</font></em> </div><div class="Discussion_UserSignature" align="center"><font color="#0000ff"><em>I really, really, really miss the "first unread post" function.</em></font> </div> </div>

 

[jcdenton]

Alright, thanks for the clarification. <div class="Discussion_UserSignature"> </div>

 

[redracer02]

1 AU <img src="/images/icons/laugh.gif" /><br /><br />I hope when we get that next space telescope up there, Alpha Centauri will be the first system we look at.<br /><br />It sounds like it could have something there, if the dust formed in the right areas.

 

[jcdenton]

Well red dwarfs can have surface temperatures of up to 3500 K (in comparison to the Sun's 6000 K), so if that planet's orbit is 50-60% of Earth's orbit, its distance from Proxima Centauri can be roughly the distance between the Sun and a point in between Mercury and Venus to have a life-sustaining temperature. If that planet had a magnetic shield of similar magnitude of that of Earth, wouldn't it be enough to protect that world's inhabitants from a flare?<br /> <div class="Discussion_UserSignature"> </div>

 

[thalion]

^<br />The situation is a little worse than that.<br /><br />The brightest red dwarfs are not much more than a hundredth as bright as our Sun, so to get an amount of irradiation to support Earth-like temperatures a planet would have to orbit very close-in, much closer than Mercury's average distance. Typical orbital periods would be measured in days or weeks. For fainter red dwarfs, it only gets worse.<br /><br />Check out the following link for a typical red dwarf:<br /><br />http://www.solstation.com/stars/la21185.htm<br />

 

[steve01]

Good point!<br />They may not have even have well-developed "rays"-to help see dim, balck and white objects in their eyes(assuming they even have eyes)<br />I hate to get talking about extra-terrestrial beings outside of the SETI forum(terribly upsets stevehw) but, they could conceivably have an advanced solar-powered culture yet have no idea that the universe extends past Alpha Centauri A+B!!

 

[jcdenton]

You're right, I was forgetting about the low luminosity of red dwarves. <div class="Discussion_UserSignature"> </div>