Destination: Alpha Centauri

[Jetfire]

Alpha Centauri (α Centauri, α Cen; also known as Rigil Kentaurus, Rigil Kent, or Toliman) is the name for the brightest naked-eye (apparent) star in the southern constellation of Centaurus, which is the closest apparent star to the sun, and the name for the multi-star system that composes that apparent star. To the unaided eye this multi-star system appears as a single star, whose total visual magnitude would identify it as the third brightest star in the night sky. The visible part of Alpha Centauri is actually a binary star system, the individual stars being designated Alpha Centauri A (α Cen A) and Alpha Centauri B (α Cen B), or, collectively, Alpha Centauri AB (α Cen AB). They are 1.34 parsecs or 4.37 light years away from our Sun.[9] However, a third star called Proxima Centauri, or Proxima, or α Cen C, which is not visible to the naked eye, is likely to be a gravitational companion of this binary system. The whole (potential) trinary star system may also be called Alpha Centauri or α Cen AB-C. Proxima Centauri is the closest known star at 4.24 light years away from the Sun, and it is 0.21 light years away from α Cen AB.

Would an unmanned mission happen this century? Or would one happen only if evidence of a planet in the "Earthzone" is discovered around one of the 3 stars?

What is the most realistic means of travel with technology currently available or in development?

[edit]

How long would a communication from Alpha Centauri to get back to earth?

 

[SilentP]

Well to answer the easiest part of the question (time lag in communication), it would take anywhere between 4.24 to 4.45 years for a communication from there to reach us, based on the number of light years from Sol to Proxima Centauri* (the 4.24 figure) or Alpha Centauri AB** quoted in the Wikipedia article for them.

As for the unmanned mission itself, it's a lot less controversial to send an unmanned probe to a system than a manned mission, so there'd be less resistance to such a project, and could be done with existing technology today, the only problem being the quality of the data being sent back (do we still get data being beamed back from the Pioneer and Voyager probes?).

I could imagine that if an 'Earthzone' planet was detected, there'd definitely be a rush to send something there to check it out up close, and an unmanned probe would be the first choice for such a mission.

*Proxima Centauri aka Alpha Centauri C, the smallest of the stars in the system.

**The two primary stars in Alpha Centauri system.

 

[Jetfire]

It says that Proxima Centauri would be the 1st destination...but wouldn't Alpha Centauri -A- be a more likely destination because it is more like our Sun?

I forgot about the communication thing.

[edit]

Unless they send a massive probe that splits into 3 to explore each system...

 

[SilentP]

Hmmm, I guess a 3-part probe could be a possibility, though it depends if the observations and investigations that astronomers wish to make on each individual star have to be made over a very long time period and can't be done by a single probe orbiting the one star.

If that isn't the case, a probe could do a flyby of Proxima Centauri on it's way to Alpha Centauri A (perhaps it might even be required for a slingshot move) and gain data that way.

If planets are detected around each of the stars, I could definitely imagine that a 3 part probe could be a possibility. Hell, a small fleet of probes might be sent, since I can aimgine that you'd want the best probes possible to observe each element of the Alpha Centauri system.

 

[Christopher]

Here's a blog that's heavily devoted to the subject of Alpha Centauri, the search for planets there, and the prospects for missions there (along with other subjects that grow out of that):

http://www.centauri-dreams.org/

Pretty much every question raised in this thread is covered there.

And we'll probably know within the next year or two whether there are planets in the Alpha Centauri system. There are several active searches underway.

 

[Lindley]

You'd have to use gravity slingshots to do any kind of course change or deceleration. That's going to be a potential problem; I doubt we have good enough positional resolution on the system to really plot out a gravity-assisted course from this distance. Thus any probe may be limited to a simple flyby.

 

[Christopher]

You'd have to use gravity slingshots to do any kind of course change or deceleration.

No, you wouldn't. A solar or magnetic sail is a much more effective way to maneuver and decelerate. An unmanned sail probe could be beam-accelerated to high relativistic velocity in a short amount of time and could then gradually decelerate as it approached Alpha Centauri -- a lightsail by the light pressure from the target star, a magsail by thrusting against the star's magnetic field.

 

[SilentP]

I apologise is that Centauri Dreams website has already covered this (I'm unfamiliar with how to use that site in terms of looking for specific topics) but has signal degradation of long range craft been tackled as a topic/problem?

 

[RobertVA]

It's going to take a VERY long time for any sort of probe to travel that far. It might be a while before we could build a probe that could remain functional after that long a period in the deep chill of interstellar space.

Then there's the matter of building a probe with a radio transmitter powerful enough it could be detected at that distance. Most of the probes to the outer planets have been powered by small nuclear reactors, but still have transmission power comparable to the bulb in a typical household refrigerator. An interstellar probe would need a bigger reactor, with a much larger quantity of toxic radioactive fuel, to power a bigger transmitter and keep the remainder of the probe warm enough to function. There would be concerns about how such a large quantity of nuclear fuel could be launched into space without risking a disaster if the launch vehicle(s) failed.

 

[Jetfire]

Here's a blog that's heavily devoted to the subject of Alpha Centauri, the search for planets there, and the prospects for missions there (along with other subjects that grow out of that):

http://www.centauri-dreams.org/

Pretty much every question raised in this thread is covered there.

And we'll probably know within the next year or two whether there are planets in the Alpha Centauri system. There are several active searches underway.

Thanks! When i get some time I will give it a look.

 

[Christopher]

It's going to take a VERY long time for any sort of probe to travel that far.

Not necessarily. Microsail probes -- sails a few centimeters across carrying microchip sensor payloads -- could be accelerated to relativistic speeds fairly easily. You send a few thousand of those on their way, it takes them 5-6 years to arrive, and in-system they network to collect and broadcast data.

It might be a while before we could build a probe that could remain functional after that long a period in the deep chill of interstellar space.

The Voyager probes are still sending back data after more than 30 years in space. Cold isn't an issue for probes like that, because they have radiothermal generators, nuclear material whose decay provides them with heat and power. Remember, vacuum is an insulator, so the "chill of space" is a myth. If you're not generating heat and aren't in bright sunlight, then yes, you would gradually radiate away all your heat, though far more slowly than you would in an atmosphere or in water, say. But if you have an onboard heat source, you have to worry about overheating, not freezing.

Of course, microsail probes would lose heat quite rapidly, but hey, ever heard of superconductors? A lot of technology thrives in ultracold conditions.

Then there's the matter of building a probe with a radio transmitter powerful enough it could be detected at that distance.

This is one of the topics that's addressed on Centauri Dreams. The best option is to use the Sun's gravitational focus. The Sun functions as a gravity lens whose focal point is about 550 AU out -- quite a distance, but if we can make it to Alpha Centauri, we can surely make it there. By positioning an antenna at that distance (or beyond) in the opposite direction from Alpha Centauri, we could use the Sun as a powerful magnifying lens to amplify light or radio signals from Alp Cen and pick up the transmissions from the probes.

Alternatively, you could send assembler probes programmed to build a transmitter -- and possibly more and bigger probes -- out of local materials upon arrival.

 

[sojourner]

There would be concerns about how such a large quantity of nuclear fuel could be launched into space without risking a disaster if the launch vehicle(s) failed.

If you have the capabilities to build an interstellar probe this would most likely be a non-issue at that point.

 

[JarodRussell]

There would be concerns about how such a large quantity of nuclear fuel could be launched into space without risking a disaster if the launch vehicle(s) failed.

If you have the capabilities to build an interstellar probe this would most likely be a non-issue at that point.

I don't think the logic is too sound.

 

[sojourner]

Nuclear fuel can be made safe from launch accidents today. In fact, fuel rods that have not been used in a reactor are not all that radioactive and can be handled by hand with no ill effects. So, getting the fuel in space is not a problem. Just don't fire it up until out of the atmosphere.

 

[Trekker4747]

If there aren't 10-foot-tall blue elfin hottie hippies living there I'll be very upset.

 

[Christopher]

If there are 10-foot-tall blue elfin hottie hippies living there I'll be very upset.

The thing about Avatar is that it was scientifically obsolete before it came out, because astronomical observations have effectively ruled out the possibility of gas giant planets in the Alpha Centauri system. If there are exoplanets there, they would have to be below 3 Earth masses to have avoided detection.

Although that's hardly the only thing about Avatar that's scientifically implausible.

 

[Trekker4747]

If there are 10-foot-tall blue elfin hottie hippies living there I'll be very upset.

The thing about Avatar is that it was scientifically obsolete before it came out, because astronomical observations have effectively ruled out the possibility of gas giant planets in the Alpha Centauri system. If there are exoplanets there, they would have to be below 3 Earth masses to have avoided detection.

Although that's hardly the only thing about Avatar that's scientifically implausible.

Why do you have to ruin it for me?

Just let me keep thinking there's floating waterfall sections of earth in the sky. LET ME HAVE MY DREAMS!

 

[Jetfire]

How the hell can mountains and waterfalls float? I haven't seen AVATAR and don't want to...but still.

I think we need to seen a probe to Alpha Centauri soon...within 10-20 years hopefully.

 

[RobertVA]

In the film the planet had powerful magnetic anomalies and the mountains were made of a room temperature superconductor called unobtainium (yes they really called it that!).

They didn't explain how the water supply was so plentiful for the waterfalls.

 

[Trekker4747]

In the film the planet had powerful magnetic anomalies and the mountains were made of a room temperature superconductor called unobtainium (yes they really called it that!).

They didn't explain how the water supply was so plentiful for the waterfalls.

Rain and lakes?