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Galaxy Guy
2005-Mar-14, 12:11 AM
What progress has been made in the attempt to find terrestrial planets orbitting Alpha Centauri A and B of the binary system? It has been proven that stable orbits within the circumstellar habitable zone (CHZ) of both stars are possible, and I have heard from a forgotton source sometime ago that hubble was scheduled to search the binary system. If terrestrial planets are discovered, and if more advanced future telescope projects like the NASA funded terrestrial planet finder mission (TPF) identifies chemical markers of atmospheric gasses hospitable to earth-like life, then will the demand for an interstellar mission capture the attention of major space agency organizations? What mode of propulsion would be the most feasible to transport a space probe to the mystery planet in, say, the lifetime of a researcher (around 50 years)? I would appreciate any thoughts. Thank you.

Theoretical modes of propulsion from off the top of my head: lightsail, antimatter annihilation, nuclear fusion/fission

eburacum45
2005-Mar-14, 04:07 AM
No planets have been detected around Alpha Centauri A or B yet. There may be no substantial planets there at all; close binary stars like these might perturb their planetary systems out of existence.
The first missions to nearby stars will probably be flybys by lightsail;
otherwise the Daedalus design (basically a modified Orion) looks promising.

There are a number of good concepts in these links;
http://scientium.com/diagon_alley/commenta...hip/rockets.htm (http://scientium.com/diagon_alley/commentary/bowden_essays/startrip/starship/rockets.htm)
http://scientium.com/diagon_alley/commenta...rship/sails.htm (http://scientium.com/diagon_alley/commentary/bowden_essays/startrip/starship/sails.htm)

I would recommend the beamed particle concepts, and the antimatter Ram- augmented rocket; a further refinement of the ram concept is the seeded ram, which involves a pathway seeded with pellets by a particle beam accelerator, which the ram collects and uses for fuel and propellant.

By golly, by hook or by crook we will get there.

piersdad
2005-Mar-14, 09:03 AM
i read that to get there the space ship would need a 1 G acceleration for 30 years and a corresponding 1 G deceleration for another 30 years to reach alpha centauri

Planetwatcher
2005-Mar-16, 07:08 AM
Alpha Centauri has been and is the continued subject of near constant observation.

A number of years ago was an internet article about a possible planet passing in from of Alpha Centauri seen by the Hubble, but it was never confirmed.
The last speculation I heard of possible planets was propounding that the third, but closest star, a red dwarf, was a little more likely then the other two for planets, and even then they would be quite likely very small.

Barnard's Star, the 2nd closest a lone red dwarf, is also the subject of much study.
It was rumored to have two possible planets, but again, unconfirmed.

When exo-planets were still in the first couple years of being discovered, there was early data that the 4th closest star Lalande 21185 may have a planet. But there has been nothing conclusive since.

The closest star known to have any planets is Epsilon Eridani. It is the 9th closest star system 10 1/2 Light Years distant. An orange K class star, and interesting enough is the star of the Vulcun homeworld in the Star Trek Saga.

antoniseb
2005-Mar-16, 08:19 AM
Originally posted by nicolii@Mar 14 2005, 12:11 AM
if more advanced future telescope projects like the NASA funded terrestrial planet finder mission (TPF) identifies chemical markers of atmospheric gasses hospitable to earth-like life, then will the demand for an interstellar mission capture the attention of major space agency organizations?
Yes, if such things are found, it will certainly capture the attention of the world. I suspect that the first big budget thing that would result from such a discovery would be the creation of a very large scale space optical interferometry system for better imaging of this place. This would be hugely expensive, but very cheap compared to actually sending even a one gram payload to it.

As other people have indicated bove, I do not think we will find terrestrial sized planets in the Alpha Centauri system, as I suspect that the protoplanetary disks of the two stars would have been pretty disrupted by the companion star.

In several thousand years, Barnard's Star will be the closest one to the sun. Perhaps we should consider that as our first stellar destination. The earlier claims that it had planets have been disproved, but these would have been huge planets. It could potentially have some Pluto sized companions.

Nyrath
2005-Mar-16, 03:42 PM
Originally posted by Planetwatcher@Mar 16 2005, 07:08 AM
The closest star known to have any planets is Epsilon Eridani. It is the 9th closest star system 10 1/2 Light Years distant. An orange K class star, and interesting enough is the star of the Vulcun homeworld in the Star Trek Saga.
Though there is an argument to be made that Vulcan is around 40 Eridani.
http://www.projectrho.com/vulsun.htm

John L
2005-Mar-16, 11:29 PM
I'd recommend a fusion jet. Collect a huge amount of hydrogen from Jupiter and store it in giant ring tanks surrounding the fusion reactor and crew compartments. Use the heat of fusion of some of the hydrogen to heat and accelerate the rest of the hydrogen as a propellant. As the ship uses up the hydrogen from a ring storage tank it is jetisoned. You should be able to reach 0.1C, which will get you 5 lightyears in 50 years.

eburacum45
2005-Mar-17, 12:29 AM
Originally posted by Nyrath@Mar 16 2005, 03:42 PM
...Vulcan is around 40 Eridani.
http://www.projectrho.com/vulsun.htm

Vulcan is generally thought of as being around Keid (40 Eridani); it is there in the Celestia Star Trek add-on pack (just a little further from the sun than Ander's Sandberg's Twilight (http://www.orionsarm.com/worlds/Twilight.html))(which is of course in a different universe altogether)

eburacum45
2005-Mar-17, 01:00 AM
Originally posted by piersdad@Mar 14 2005, 09:03 AM
i read that to get there the space ship would need a 1 G acceleration for 30 years and a corresponding 1 G deceleration for another 30 years to reach alpha centauri
No; that would be ridiculously over the top.
Take a look at this site;
http://math.ucr.edu/home/baez/physics/Rela.../SR/rocket.html (http://math.ucr.edu/home/baez/physics/Relativity/SR/rocket.html)
To get to Alpha Centauri, you accelerate at 1 gee for 1.8 years (ship time), then 1.8 years (ship time) decelerating at 1 gee will get you there.

The time that passes for an observer on Earth during your trip would be significantly longer than 3.6 years, because of time dilation.

Guest
2005-Mar-17, 10:26 AM
Originally posted by Planetwatcher@Mar 16 2005, 07:08 AM
Alpha Centauri has been and is the continued subject of near constant observation.

A number of years ago was an internet article about a possible planet passing in from of Alpha Centauri seen by the Hubble, but it was never confirmed.
The last speculation I heard of possible planets was propounding that the third, but closest star, a red dwarf, was a little more likely then the other two for planets, and even then they would be quite likely very small.

Barnard's Star, the 2nd closest a lone red dwarf, is also the subject of much study.
It was rumored to have two possible planets, but again, unconfirmed.

When exo-planets were still in the first couple years of being discovered, there was early data that the 4th closest star Lalande 21185 may have a planet. But there has been nothing conclusive since.

The closest star known to have any planets is Epsilon Eridani. It is the 9th closest star system 10 1/2 Light Years distant. An orange K class star, and interesting enough is the star of the Vulcun homeworld in the Star Trek Saga.
References?

How can they see planets around stars hundreds of light years away, but not around one 4 light years away?

One thing I hate about astronomy is the sheer contradictions & lack of answers - the "illogic" hiding behind a veneer of "logic".

antoniseb
2005-Mar-17, 11:06 AM
Originally posted by Guest@Mar 17 2005, 10:26 AM
How can they see planets around stars hundreds of light years away, but not around one 4 light years away?
They haven't seen them so much as detected them, and the ones they've detected are VERY massive, and very close to their star.

If we observe planets as maasive (or more) than Jupiter around a star a hundred lightyears away, how far away could we observe a planet one ten thousandth the mass of Jupiter using the same techniques?

Alpha Centauri probably has:
- some small rocky inner planetoids somewhere around the size of Ceres or Vesta
- Asteroids
- something like the Kuiper belt outside the orbit of Alpha Centauri B
- Something like the Oort cloud

Observing these directly will take some instrumentation we don't have yet.

Nereid
2005-Mar-17, 01:14 PM
One thing I hate about astronomy is the sheer contradictions & lack of answers - the "illogic" hiding behind a veneer of "logic".
I'm curious - could I trouble you to spend an hour or so and write down what you see as the three (or five) most contradictory things in astronomy? You may be voicing a common perception, and I'd like to understand where it comes from (so I can do something about addressing it).

Kind Regards
Nereid

skipperjohn
2005-Mar-17, 04:39 PM
How can they see planets around stars hundreds of light years away, but not around one 4 light years away?


They haven't seen them so much as detected them, and the ones they've detected are VERY massive, and very close to their star.

I believe detection usually involves either a planet passing in front of the star to obscure it's light, or for very massive planets, perturbing the position of the star as they orbit.

If the star is not rotating in a plane whereby its planets could obscure the light we see, and if no massive planets perturb it's position, then it would be very difficult to detect planets around another star (unless they were exceeedingly bright - perhaps very large planets covered with a very reflective surface - maybe ice, and relatively close by).

scorpio711
2005-Mar-17, 10:08 PM
Guest,
re. your very "straightforward" opinions:
1) here are references of the (found) planet around epsilon eridani, and of the lack of success re. Lalande 21185
http://www.obspm.fr/encycl/eps-Eri.html
http://www.obspm.fr/encycl/Lalande21185.html

2) re. how they can detect (and not "see") extrasolar planets can also be found on http://www.obspm.fr/encycl/encycl.html or on one of the links included into this site.

3) they can detect "far" planets (well very few beyond 100 light years actually !!!! ) because the detected planets are big enough AND are close enough to their star. They can find also similar size/distance planets few l.y. away from us !!!! The fact that none has been found means that either the close stars don't have planets, or that they have planets but too small or too far from their star to be detected.
Instruments and methods available to us at present allow only to detect massive planets not too far from their star. Only exception is pulsars, due to extreme sensitivity of their rotation, small gravitational influences can be detected much more easily, thus earth-sized planets can be detected (reference http://www.obspm.fr/encycl/1257+12.html).

I do not personnally see any contradiction nor lack of answer in all this.

Scorpio

piersdad
2005-Mar-18, 03:14 AM
To get to Alpha Centauri, you accelerate at 1 gee for 1.8 years (ship time), then 1.8 years (ship time) decelerating at 1 gee will get you there.

Thanks for that update in calculations eburacum45

some of my reading can be 30 years out of date
the site you quoted has some high powered calculations in it that seem pretty accurate according to present knowledge

Matthew
2005-Mar-18, 05:58 AM
Originally posted by John L@Mar 17 2005, 10:29 AM
I'd recommend a fusion jet. Collect a huge amount of hydrogen from Jupiter and store it in giant ring tanks surrounding the fusion reactor and crew compartments. Use the heat of fusion of some of the hydrogen to heat and accelerate the rest of the hydrogen as a propellant. As the ship uses up the hydrogen from a ring storage tank it is jetisoned. You should be able to reach 0.1C, which will get you 5 lightyears in 50 years.
Pulling such amounts of hydrogen from Jupiter would take a lot of force. But then if you already had a fusion drive....

Dave Mitsky
2005-Mar-18, 07:05 AM
Originally posted by Guest+Mar 17 2005, 10:26 AM--></div><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (Guest @ Mar 17 2005, 10:26 AM)</td></tr><tr><td id='QUOTE'> <!--QuoteBegin-Planetwatcher@Mar 16 2005, 07:08 AM
Alpha Centauri has been and is the continued subject of near constant observation.

A number of years ago was an internet article about a possible planet passing in from of Alpha Centauri seen by the Hubble, but it was never confirmed.
The last speculation I heard of possible planets was propounding that the third, but closest star, a red dwarf, was a little more likely then the other two for planets, and even then they would be quite likely very small.

Barnard&#39;s Star, the 2nd closest a lone red dwarf, is also the subject of much study.
It was rumored to have two possible planets, but again, unconfirmed.

When exo-planets were still in the first couple years of being discovered, there was early data that the 4th closest star Lalande 21185 may have a planet. But there has been nothing conclusive since.

The closest star known to have any planets is Epsilon Eridani. It is the 9th closest star system 10 1/2 Light Years distant. An orange K class star, and interesting enough is the star of the Vulcun homeworld in the Star Trek Saga.
References?

How can they see planets around stars hundreds of light years away, but not around one 4 light years away?

One thing I hate about astronomy is the sheer contradictions & lack of answers - the "illogic" hiding behind a veneer of "logic". [/b][/quote]
It may be that the "illogic" can be attributed merely to your lack of knowledge as the answers to your query were supplied easily enough.

Dave Mitsky

ASEI
2005-Mar-18, 03:42 PM
I&#39;m still hoping that there is some way to get that fusion magnetic ramjet idea to work. It would be a whole lot better than lugging a few hundred million tons of liquid hydrogen around. It would be a pain to accelerate that mass at a reasonable thrust rate and a reasonable Isp.

Maybe you could reduce the amount of fuel necessary for an interstellar trip by using magnetic braking of some sort. You could generate drag by reacting against the interstellar, and stellar medium as you barrel towards the target system.

Guest
2005-Mar-18, 07:12 PM
Originally posted by Dave Mitsky@Mar 18 2005, 07:05 AM
It may be that the "illogic" can be attributed merely to your lack of knowledge as the answers to your query were supplied easily enough.


Hmm, so you believe cosmology addresses all logical concerns? Or, as an astronomer, you don&#39;t waste your time with philosophy?

Astronomical facts need to be painted into a "frame". I don&#39;t think we have that "frame" at all. To arrive at that "big picture", we must resort to things such as "superstrings" and "sparticles" and "parallel universes" and "higher dimensions" etc etc blah blah blah. That goes outside the scope of "logical deduction". And yet astronomical science is based upon this foundation.

Hence my comment that science is inherently "illogical". It most certainly is the result of "lack of knowledge". Can anybody enlighten me?

Too much faith in science...and other realms of thinking as well.

piersdad
2005-Mar-18, 07:28 PM
Hence my comment that science is inherently "illogical". It most certainly is the result of "lack of knowledge". Can anybody enlighten me?

We are like a inteligent microbe in a puddle of murky water we can see and sense what is around us but cant comprehend what its like out there.

So to try to undestand we have to make up some sort of vision that will enable us to focus on some sort of experiments that will prove some way or the other the vision and as each experiment it completed the vision changes.

so we make up all sorts of names like quarks and gluons etc and set out some sort of experiment that will prove or disprove it. then work on from there.

Science is a mixture of lateral thinking 1% dreaming 1% and hard precise repeatable experiments 99%

Guest
2005-Mar-18, 07:36 PM
Originally posted by piersdad@Mar 18 2005, 07:28 PM
We are like a inteligent microbe in a puddle of murky water we can see and sense what is around us but cant comprehend what its like out there.

So to try to undestand we have to make up some sort of vision that will enable us to focus on some sort of experiments that will prove some way or the other the vision and as each experiment it completed the vision changes.

so we make up all sorts of names like quarks and gluons etc and set out some sort of experiment that will prove or disprove it. then work on from there.

Science is a mixture of lateral thinking 1% dreaming 1% and hard precise repeatable experiments 99%
I totally agree (except your ratios add up to 101% :P )... So why the conservative insistence on things that are obviously assumptions? Why not, instead, "We/I don&#39;t know". I hear too much "No, you are mistaken", or, "You lack knowledge", or, "This is the way things are (in a cosmic sense)".

This is not SCIENCE as I was taught at high school. Science was taught to me as a set of assumptions created around empirical data. Why so many people treat it as gospel? Very dangerous, I believe.

piersdad
2005-Mar-18, 07:44 PM
(except your ratios add up to 101%

Yes well im not good at maths

Keeping the mind open
Saying im sorry i was wrong there or you have a point

is the way ahead

Guest
2005-Mar-18, 07:45 PM
I&#39;ll buy you a beer&#33; :lol:

Nereid
2005-Mar-18, 10:58 PM
Astronomical facts need to be painted into a "frame".
Other than that of physics (a.k.a. physical theory), why?

I don&#39;t think we have that "frame" at all. To arrive at that "big picture", we must resort to things such as "superstrings" and "sparticles" and "parallel universes" and "higher dimensions" etc etc blah blah blah.
If you mean there is no good &#39;theory of everything&#39; yet, then yes; but why is it necessary for you to have a &#39;frame&#39;?

That goes outside the scope of "logical deduction".
Really? Why? Are you saying that things which physicists are working on such as M-Theory, LQG, and supersymmetry are illogical? or not consistent with good observational results?

And yet astronomical science is based upon this foundation.
Indeed; what then is the basis of your disdain?

vet
2005-Mar-19, 01:45 AM
none of us may live to see it, not on earth---but time is not understood, nor &#39;initial conditions&#39;. i feel it safe to predict humanity&#39;s children to achieve the building of &#39;eternal energy, negative entropy&#39; environments for This universe---it is the only Ethical outcome---call it Heaven---the far future of now---but in the meantime, i see no restraints on even individuals, participating in the &#39;multiverse&#39;. in physics it&#39;s often been said, even of the universe---there is a free lunch---

Planetwatcher
2005-Mar-19, 09:05 AM
Astronomical facts need to be painted into a "frame". I don&#39;t think we have that "frame" at all. To arrive at that "big picture", we must resort to things such as "superstrings" and "sparticles" and "parallel universes" and "higher dimensions" etc etc blah blah blah. That goes outside the scope of "logical deduction". And yet astronomical science is based upon this foundation.

Detecting exo-planets has nothing to do with superstrings, higher dimensions, or any of that other kind of stuff. It is all very scientific, and athough I don&#39;t understand all the nuanuces, the basic principle is a very simple scientific application. It has to do with the dopler effect. Our instruments can detect the star&#39;s wobble as the planet pulls on it from different parts of it&#39;s orbit. Now it&#39;s not a big wobble, but it doesn&#39;t have to be. Just enough to shift the light spectrium a little bit of an already known star.

As for planets actually passing infront of the star, that has happened too. although not often, but our telescopes can detect that as well.