The Tau Zero Foundation is pleased to announce that planet hunter extraordinaire Geoffrey Marcy is now affiliated with the organization. As a Tau zero practitioner, Dr. Marcy will serve as a major point of contact on exoplanet issues, bringing with him the most storied portfolio in the planet-hunting business. Working closely with Paul Butler and Debra Fischer, Dr. Marcy (University of California at Berkeley) has discovered more extrasolar planets than anyone else, including 70 out of the first 100 to be found. His team’s findings include the first multiple-planet system, the first Saturn mass planets, and the first Neptune-mass planet. His awards are numerous: Shaw Prize in 2005, Discovery Magazine‘s Space Scientist of the Year in 2003, the NASA Medal for Exceptional Scientific Achievement, the Carl Sagan Award, the Beatrice Tinsley Prize, and the Henry Draper Medal from the National Academy of Sciences.
A warm welcome, Geoff!
Centauri Dreams readers will recall our coverage of the Next 40 Years of Exoplanets workshop at the Massachusetts Institute of Technology, where Geoff took up Sara Seager’s challenge to be provocative by taking on the powers that be at NASA, JPL and his own exoplanet community on behalf of Terrestrial Planet Finder and the lamented Space Interferometry Mission. He closed that session by making the case for a robotic mission to Alpha Centauri, a project that could in his judgment revitalize NASA and space agencies worldwide. Let me quote him on this:
“I’d like to make an appeal to President Obama. I think he should stand up and make the following announcement: That before the century is out we will launch a probe to Alpha Centauri, the triple star system, and return pictures of its planets, comets and asteroids, as soon as possible, even if it takes a few hundred years or a thousand years to get there. [Going to Alpha Centauri] would engage the K-12 children, it would engage every sector of our society… It would jolt NASA back to life, if we’re really lucky. And of course any such mission should be an international one involving Japan, China, India, Europe…”
Marcy went on to note that such a mission would bring not only scientific progress but the diplomatic coherence required as the world worked together toward this momentous common goal. In some ways, the call reminded me of Daniel Goldin’s days as NASA administrator, when just as the Pathfinder spacecraft was nearing Mars, he told reporters that building a robotic probe that could reach another star would become a NASA priority. Back then small steps were indeed taken. An Interstellar Probe Science and Technology Definition Team met at the Jet Propulsion Laboratory in early 1999 to consider the prospect, but budget realities and the daunting nature of the mission brought an early end to any organized effort within the agency.
Will Marcy’s call for an Alpha Centauri mission meet a better fate? We can hope so and continue to draw researchers together to work toward this end even as the exoplanet hunt continues. Marcy’s challenge at the MIT meeting was embedded within a discussion of the exoplanet field and its tools today, and it’s a good time to review the discussion (you can see Geoff’s talk by following this link to the MIT archives). The key to exoplanet research is getting the spectra needed to study these worlds, and Marcy said it was the nearby stars that offered the real, 40-year future of exoplanet research: “Habitable planets around the nearest stars, those within 25 light years, offer enormous advantages over those that orbit more distant stars.”
The advantages: Planets around nearby stars can be imaged, allowing spectroscopy. Proximity also allows us to measure the zodiacal dust around those stars, both to study the dust in its own right, but also to be able to subtract the dust signature to more clearly resolve an Earth-like planet. We can also measure the masses of planets around nearby stars through either Doppler or astrometric methods. “And frankly,” Marcy added, “the nearby stars are the ones reachable by next generation propulsion systems. So I think spectroscopy of the habitable planets around the nearest stars is really the forty year future.” Thus the need for instrumentation to be able to image and take spectra of Earth-sized planets at reasonable distances from their stars.
Marcy was candid about his anger with the recent decadal survey and NASA response. For the 2010 decadal survey, New Worlds, New Horizons in Astronomy and Astrophysics, was remarkable for what it didn’t include. The Terrestrial Planet Finder mission was not mentioned at all as a priority. The reasons are many but Marcy blames NASA headquarters, scientists at the Jet Propulsion Laboratory, and people within the exoplanet community including himself for not having made a strong enough case to ensure its survival. He calls Terrestrial Planet Finder ‘our human genome project,’ noting that “The different gene sequencing TPF sub-projects cancelled each other out. Coronagraphs killed the interferometers which killed the occulters and SIM was left squashed. The squabbling cost the field ten years, and TPF is officially zeroed out.”
But we still need space-borne interferometry, and an overwhelming case remains for the interferometric version of Terrestrial Planet Finder (TPF-I). Marcy says that free flying interferometers are the only plausible future for astrophysics, but competing designs were alternately funded and encouraged and then dropped, leaving proponents of each at war. I won’t go into all the specifics but send you instead to Marcy’s talk. Suffice it to say that all the presentations are worth hearing (the complete archive page is here), but Geoff’s call for an Alpha Centauri mission was what brought him into contact with the Tau Zero Foundation, and we’re honored by the chance to work with him in the future as studies of nearby stars including Alpha Centauri intensify.
I do not think we’re going to send a ship to alpha centauri if it takes longer than 50 years.
you do not want to wait for a probe to send back its information if it takes longer than 100 years.
And what if we do not find a habitable planet within 25 light years? What are we going to do then?
“I’d like to make an appeal to President Obama. I think he should stand up and make the following announcement: That before the century is out we will launch a probe to Alpha Centauri, the triple star system, and return pictures of its planets, comets and asteroids, as soon as possible, even if it takes a few hundred years or a thousand years to get there. [Going to Alpha Centauri] would engage the K-12 children, it would engage every sector of our society… It would jolt NASA back to life, if we’re really lucky. And of course any such mission should be an international one involving Japan, China, India, Europe…”
A politician can say anything he/she likes, but there is no way such a mission can be sustained in a political system with short term goals. The US could be a shadow of its former self within a century. Just as heartbreaking would be to spend the resources to launch a probe, only to fail to keep monitoring it’s signals.
Any probe we could send will likely suffer from having cheaper, faster successors, so we might not have impetus to launch even the slow probes.
I cannot imagine anything as wasteful in resources as this proposed mission, unless there is fundamental new physics that would allow a relatively cheap, rapid flight. And if that occurred, why be limited to alpha Centauri, rather than a more distant planet that imaging showed as being most earth like?
But let’s suppose we did send such a mission, it arrives within a century and shows a beautiful earth like world? Then what? What could we do with this information? Would it propel funding and launch of more probes, a manned mission? Or would it remain an inaccessible jewel in sky, apparently forever out of human reach?
But what if we could send a colony mission? Then what? Then very little. No trade, no economic growth, at best a lot of data on different lifeforms and possibly new biology.
Aren’t we a lot better off if we develop solar colonies that will allow growing the solar economy, until such time as sending fleets of starships becomes economically viable if desired?
I respect that Marcy is willing to stand up and make a call for such a mission. It reveals him as a visionary. I wish we had more respect for visionaries in our society these days. Perhaps if we’d listen to a few of them, and rearrange our priorities, we could again step up and accomplish great things.
Geoff Marcy is the perfect person to ask – “what are the limits to imaging?”. If instead of a probe, we build some hypothetical imaging system that could be pointed at a range of target stars, what level of resolution could we get given technology limits? Does gravitational lensing make a big impact? Could we get images comparable to those from pre-/early C20th telescopes of the planets?
The advantage of such a system is that one system could collect data on numerous targets and deliver it soon after deployment, rather than waiting for the duration of the flight with possible damage or loss in transit, or failure on arrival.
If we imagine BIG, what is within the realms of the possible?
Alex, if you want to think big, I can point you to Webster Cash’s work on occulters. At one point he was talking about the maximum possible image we might be capable of getting through such a device. When I talked to him in 2004, he envisioned this as a maximum high-end system (though be aware that TPF has had all kinds of technologies suggested for it, and this is just one, and it remains as controversial as could be). Anyway, from my Centauri Dreams book:
Disclaimer: Cash’s ideas have changed dramatically since he told me about this plan, and have now gone back to a more conventional kind of occulter — before, he was thinking about what was essentially an enormous pin-hole camera system. The book describes the idea, but the point is, it’s no longer in play to my knowledge. Still, the idea of a huge, massively interferometric system pulling in close images, while a matter for many technology generations down the road, does hold undeniable interest. Do keep in mind this is a Webster Cash idea, not Geoff Marcy’s. I don’t know what his take on this would be, but I’ll see if I can get a comment.
Two things :
1) Why proposing a mission to Alpha Centauri *before* any planets are discovered ? Unless he knows something together with Debra Fisher we don’t know. And even if he does, people that remember my previous posts will remember my preference for a FOCAL type of mission (using the sun
gravitational lens).
2) I used to lament the loss of TPF too. However, I then found Da Vinci, a much simpler mission that, for $1.2 B promises to detect and measure spectra of Earths at 10 parsec :
http://exep.jpl.nasa.gov/files/exep/DAViNCI_ASMCS_Report-external-2011-04-07.pdf
I believe this to be a lot cheaper than TPF. And there are also similar other missions : I remember a whole report listing 4-5 similar ones.
Well, nice to have bold visions but it really is silly to talk Alpha Centauri when even a mundane mission to Moon seems like a herculean task in the current state of things (let alone a Mars one).
Let’s focus on what’s at hand and that’s our immediate space neighborhood with consecutive stops at: first – Moon, second – Mars, third – the asteroid belt, fourth – Jupiter’s and Saturn’s moons, fifth – the rest of the solar system. And it’s not governments or their state monopolies like NASA that are gonna take us there but the economy and private businesses looking for a profit.
We worry if we find any planets in the habitable zones of Alpha Centauri stars, yet we keep some sitting in Sol’s habitable zone still mostly unexplored. If it’s not silly in a bit I don’t know what is.
The Moon?
Heck, they are afraid to go to Hubble!
I think the most interesting/inspirational aspect of an interstellar mission is that if we can do it, then we’ll have made something that’s totally inaccessible to us — the stars — now accessible. How great is that?
If we merely settle for incremental space exploration (Moon… Mars… asteroids… Jupiter… etc.) then we’ll surely never get there.
The question is: How many times do we have to go back to the Moon, before we can allow ourselves to think bigger? The answer is: We can do both.
DAViNCI is a very credible mission design, I hope it gets funded. Even the scaled down 71cm mirrors version would be better than nothing.
Amen to Geoff Marcy. His focus is the right one, but first we need to find a habitable planet or Moon around Alpha Centauri or perhaps something as far out as ~12 LY’s. This is where Enzo’s very important post on DAViNCI comes in. Even if DAViNCI turns out to be $2 Billion as an initial “Detailed Surveyor” it would make sense. SIM would have been nice to have if we had gotten it by 2015, but DAViNCI is far better and we can easily have it by 2020 if it was properly funded. TPF or perhaps ATLAST is also very important, but either of these is going to take substantially longer and cost far more so TPF/ATLAST is probably more about 2030 then 2020. That said, it would be nice if there was something that could be added to DAViNCI that would allow a detailed survey of everything out to ~60 LY’s.
Barring some radical new physics I suspect that for at least the next ~500 years or so ~60 LY’s out from Sol/Terra will be Humanity’s likely “radius of potential influence” in terms of probes or Human travel. This is assuming that we have probes or ships capable of going ~.7C. If we are slower the the radius shrinks even more. In essence, we need to spend far more time on “whats real” even from a theoretical point of view while still having vision. Even if we find a perfect new Earth that is ~100 LY’s away so what since we are not going to get there anytime soon. Therefore, we might as well focus on locations that we could theoretically get to over the next couple of Centuries if we find anything of interest. This starts with Alpha Centauri and goes out to about 60 LY’s from Sol/Terra. Beyond that we are in “when pigs fly” land.
“And it’s not governments or their state monopolies like NASA that are gonna take us there but the economy and private businesses looking for a profit.”
I know some people really believe this, but I do not. It is historically not true. The belief that private enterprise is the be-all and end-all has always been propagated by those who believe the pursuit of a “Buck” must be the motivating force behind everything and everyone – and it isn’t.
It will NEVER be the force behind deep space exploration until reliable transportation and colonies and the mineral wealth to MAKE a profit has been developed. Companies want profits NOW, for the next quaterly report… they’re not worrying about a report to be filed 500 years from now, NOR will their investors be interested in that.
The whole concept of companies flying SPACESHIPS for profit is just plain silly. Heck, I see private companies having problems flying AIRPLANES for profit, and some think they can do better with spacecraft?
Deep space exploration, and colonization MUST be government backed – and multinational at that – or it will NEVER be done. Countries like China-authoritarian, growing wealthly and powerful – MIGHT have a chance because they do not have to put up with the special interest , “Gotta make a buck now” mentality that infests our government like a plague.
The “Bottom Line” is the END of deep space exploration, not the beginning.
Blue Indy, I do not believe that any of the problems you mention are inherent in private enterprise itself, but rather all, save one, to do with legislation constructing the limited liability company. These problems are deep but must be addressed some time and I say the sooner they are the better off we will all be.
Of your list of problems, that of the poor financial performance of the airline industry is the only one outside this area, and a very strange one it is indeed. One clue to the symptoms that produce it is the number of African countries that put a higher priority in subsidizing their own carriers than feeding their poor. Another is the number of brilliant entrepreneurs who mysteriously loose all judgment and risk all on this industry, only to fail. It is as if the thought of humans in flight generates irrational exuberance – but I have not seen compelling evidence that this effect extends to spaceflight.
As for you advocacy of multinational efforts v national ones I cannot help think of the value of the large hadron collider and international space station. What a pity that they are both overshadowed, one by better and more cost efficient American and Russian forerunners, the other by the half built superconducting supercollider. Neither can unambiguously show the superiority of international cooperation, so it is very worrying that these are seen as the best examples that we have for such cooperation being beneficial.
I agree with Blue Indy. Furthermore, it’s good to have visionaries to lay the “path to the stars”, like setting targets and founding institutes of research, but we have to be aware of the fact that humans have to be FAR more present in the inner solar system to prove concepts if nothing else. Psychological impact of deep space missions using “slow” transport on human crews has yet to be assessed, and that’s just one of the big challenges. It’s obvious that we have to push on multiple fronts at once and the commitment of all the countries and the planet as a whole has to be much, much greater. Just the building and operating of ISS in LEO is straining the planet it seems to the maximum it can do now; when we start talking of prolonged presence just at Mars it starts to look unrealistic with current state of the affairs, let alone something else.
Blue Indy, your choice of China as a country — authoritarian and powerful — which might succeed in deep-space exploration and colonisation is indeed ironic. It was precisely China which might have succeeded in government-backed global exploration and colonisation in the 15th century, but which instead withdrew and left the field open to English, Dutch, Portuguese and Spanish commercial traders, pirates and colonisers — generally motivated by the pursuit of profit.
The resulting explosion of commercial growth and innovation is what makes it possible for us now to send spacecraft out into the Solar System.
Stephen
Oxford, UK
spectroscopy sounds right. The TPF is also right, expensive as it might be.
I am sure that the Centauri system appears appealing, but it doesn’t sound right.
I realize there are possible, stable orbits for planets.
But how likely is it, really?
Large gravitational objects, like an extra nearby star, perturb planetary orbits, toss potentially beautiful worlds out into frozen deep, black space to die.
There is just no way anyone should commit any real resources to actually going there without VERY strong, convincing science that suggests that there is something there to find.
If that happens, I am all for it. But if not, we have to just keep looking.
Why are we here? Because it is an entirely boring area with just about nothing else around to get in the way. Even at that we are fortunate that Jove has stayed nice and stable and not done us more harm than good.
It’s very heartening to hear that Tau Zero and Geoff Marcy are now working more closely together. His suggestion that President Obama announce an intention to launch an interstellar probe to Alpha Centauri “before the century is out” is an ambitious one, and I welcome it. This would effectively be a roadmap for 21st century space exploration. It would be inspiring to have a principal, overarching long-term goal, and visiting an earth-sized planet in the habitable zone around a nearby sun-like star is such a compelling and obvious objective it feels like human destiny.
Increased investment in exoplanet research, lowering the cost of space access through private innovation, and building space infrastructure are logical early steps to fulfilling that objective. Commercial enterprise must play an important role.
But I can’t imagine that Obama would make such an announcement in the current political and economical climate. Although visionary, to many the idea seems quixotic. It’s an easy opening for criticism by opponents, and without funding, it will seem more like a whimsical gesture than a real Apollo-style programme, so it could lose on both sides when it comes to public perception.
Marcy’s proposal also seems a little early, because we still have no confirmation of exoplanets at Alpha Centauri, let alone “earthlike” ones in a habitable zone, and I think it is obvious that to get enthusiastic public support for an interstellar mission, we must first have identified the best possible Earth twin candidate around a nearby star, and preferably have compelling images of it.
There is a difference between making a provocative suggestion and making a commitment. Suggestions incur little cost yet can spur wiser thinking. Recall that all the successful rocketry pioneers were inspired by the science fiction of their day [Emme 1982] – where fiction is admittedly unreal. But those suggestions, be they fiction or high goals, set our minds to think beyond the next paycheck – to create opportunities that others can’t fathom.
Thereafter, how those aspirations intersect with reality depends on what we discover to be real and where we chose to make our commitments. And regarding costs, these things are relative. It is difficult to gauge is the cost of NOT attempting grand things. Where would our society be today if the scale of effort behind Apollo continued past 1966? Would we have colonies on Mars that could ensure humanity’s survival regardless of the habitability of the Earth? What about all the billions in the bailout? If those funds had been invested ahead of time into research to improve the human condition (I mean science and technology, not just welfare), would we have even needed the bailout?
While such things are not absolutely predictable, my personal belief is that we have more to gain by attempting grand goals than by waxing pedantic. And the value is NOT so much on whether we achieve those goals, but by what WE LEARN IN THE PROCESS -lessons that would otherwise be unknown. Progress is not made by conceding defeat.
Ad astra, incrementis… and where those steps ARE the value generators.
– Marc
Gotta luv Marcy taking on NASA and the deeply totally flawed decadal survey. These guys brought us the wasteful Gravity Probe B which spent billion$ telling us what we already knew to greater precision and brought us LISA which even as LISA 2.0 has discovered…nothing. NASA and these programs are simply jobs programs for PhDs.
How an agressive exoplanets initiative could be left out of the next 10 plus years plans is unconscionable.
That said, I can think of many, many more productive efforts over the next decades than some way way fiture probe to Alpha C. Imaging is where it’s at in productivity, results and cost/return until maybe just maybe late 21st century when and if exotic propulsion schemes become more viable.
Oh Marc ! You have said what I have been syaing! The Bailout is ongoing and it is TRILLIONS funneled through the fed the Congress was a diversionary tactic to look away from the fed just printing trillions
IF THE FED CAN PRINT TRILLIONS for sham financial companies why Cant we go to Neptune/ Why cant we replace fossil fuels? WHT CANT WE START PROJECT ICARUS . The JOBS created would be stunning -the stimulus unbelievable!We need TRILLIONS to get us out of this mire and not trillions to scam financial companies.
WE NEED TO BUILD SOMETHING SOMETHING GREAT
THERE IS NOTHING GREATER THAN A STARSHIP!
Sorry for the all the caps and ! but I want to express how Marcs spot on comments really got me going
Ho hum, van Vogt beat you to it decades ago, in his story “Far Centaurus”. A bunch of rich guys were just so determined to get to AC, that they slept for 100 yr at a stretch in their own slowship at 0.01c. But, every so often, propulsion advanced, so by the time they were like 50 years out from Earth, people had already gotten there by faster ships still STL, and then finally FTL ships. So finally they got there… and it was already full for centuries.
So better to wait till we know what we’re doing. That sure isn’t the case right now. And there’s no way Obama would have the sense to even think about such a thing.
We live in an exciting age when almost all of the major solar system bodies have been visited by robotic space probes albeit in varying amounts (e.g. Mars has received more attention than Mercury) or will soon be visited. The New Horizon’s mission, wow, I can hardly believe it, is just a few years from Pluto/Charon and will, assuming its continued success, complete the initial reconnaissance of the solar system. Our solar system is a huge, diverse, and resource rich place. Of course, significant technological development will have to occur before we can access those resources. But once we start exploring and then settling the solar system, will we ever need any more space than it has to offer? If the answer to this question is “no”, then perhaps interplanetary travel is all that will be needed to ensure the survival of our species. Thus, interstellar travel may be done for other reasons, but I suspect it will not be NECESSARY for our survival as a species.
Now, in no way am I saying that we should give up on the goal of interstellar travel! I am just questioning the necessity of it. I am not questioning the necessity of interplanetary spaceflight and settlement: if humanity does not start expanding into space, then we will go extinct on Earth– this is a certainty. I fully support the goal of interstellar spaceflight because of the intellectual challenge it presents and the exploratory treasure trove of worlds that await us amongst the stars.
In addition to Dr. Marcy’s probe to Alpha Centauri proposal to President Obama, I have another proposal that should be given as much weight. The proposal is that a certain amount of money should be allocated to a program called the Spaceflight as a Means of Human Species Survival Program. In essence, a certain amount of money should be invested in a specific streamlined program whose goal is nothing other than development of technologies whose existence will enable settlement of the solar system. Its justification is in its very title. It will be hard to counter the need for the existence of such a program because by doing so you would be questioning the need for the only real way to ensure humans do not go the way of the dinosaurs.
We don’t really need a grandiose 100 year plan for a single mission that will never happen. What we need is a continuous stream of Voyagers, one every year or more. Each faster, more powerful, and longer-lived than the ones before it. Before long, we will have created a large, ever-expanding network of eyes and ears that will explore the solar system, use ultra-long-baseline interferometry and perhaps the sun’s gravitational focus to image exoplanets in great detail. Eventually even reach them physically.
Ad astra incrementis, indeed.
The need for the detection and (spectroscopic) characterization of Alpha Centauri (terrestrial) planets prior to any mission is such an obvious matter that I think this is the simple reason why Marcy did not explicitly mention it.
But yes, first things first, an aggressive program toward an interstellar mission must always start with an aggressive (terrestrial) planet detection and analysis program.
And it does not look like that in any way at all.
Remarkably nobody sofar in this thread mentions the possibility of private non-corporate funding, i.e. rich philanthropists like Gates, Buffett, etc.
Maybe a private fund could be set up to finance un- or underfunded (expensive) scientific programs with great potential but no direct financial returns, such as TPF like interferometers, solar gravitational telescope, anti-gravity and other breakthrough research, non-conventional nuclear fusion research (like Polywell, Focus), etc.
When it comes to the role of private enterprise in space exploration I do not see such a stark contradiction like some others (or or), but rather several possible combinations: now already a company like Spacex is exploring the possibilities to go to Mars the cheap way (more or less Zubrin style), possibly using nuclear propulsion (VASIMR like) and I can imagine governments hiring/subcontracting such companies or entering joint-ventures.
With regard to distance (henk, Kenneth Harmon): I can imagine that a terraformable or primordial, but uninhabited, terrestrial planet near Alpha Centauri constitutes a more appealing target for an interstellar mission than a true garden planet much farther (12, 20, 30, … ly) away, but this will also depend on available (breakthrough) technologies.
@Alex Tolley: the incentive for interstellar travel and colonization will most likely never become commercial in any foreseeable future. Rather scientific discovery and study, and human survival.
Much as I’ve applauded Marcy for having the guts to call out NASA (and his colleagues) over the the cancellation of “TPF” (the orginal concept was dead as soon as Webster Cash started publishing about his external occulter idea), a call for a mission to Alpha Centauri is not one, but several, bridges too far.
The best any president might do (and Obama is the perfect choice as he’s very pro-science) is to call for NASA to pick one TPF concept and get busy building it. A good start would be an external occulter to be used with the JWST, which could be built for right around what the Kepler mission costs.
I just read that detailed construction plans for the European E-ELT, to be the largest telescope in the world with about 40 m primary mirror diameter, have just been approved.
However, I wonder whether direct imaging and spectroscopic analysis of earthlike exoplanets would be possible such an instrument or that a space-based interferometer will still be needed for that purpose.
The idea of an unmanned probe to the Alpha Centauri system is a brilliant long term vision. While many find difficulty in the funding for such a mission, and others the prioritization of other more desirable projects currently pending, or proposed, I feel there is something being overlooked in this discussion. As mentioned in several of the prior posts, how can we expect to plan and fund a mission to another STAR if we can’t even get out of the solar system? Or more specifically, agree on where to go and how. We can’t even get back to the moon. While the image of sending a probe to another star is both inspiring and thought inducing, there are places here in the solar system that we need to go in the interim, such as Europa or Triton (et al …) that would fill our knowledge canisters for decades to come. My chief thought is the technological barrier. Even if we were to develop light sail technology (or something similar) that could get us there in mere decades, by the time we get it funded, built, launched, and monitored, by the time it got there and found something (if anything), we would probably have better technology that could have seen the same thing from earth. Let alone if we could even get it there in mere decades – otherwise, it would take more like tens of- to hundreds of thousands of years to get there; by which time we most assuridly would have surpassed the technology already invested in the probe. Sure, we could LEARN form building such a probe, possibly even the new technology we would need to get there faster (say ~0.1 – 0.3C), such technology could be used on mere concrete exploration closer to home. Think of how fast we could get to the outer solar system at even 0.1C!! That opens up the realm of manned exploration of some of the places we are sorely dying to get to! (Titan, Europa, Callisto, Triton, even Pluto) This is why I love these discussions. It gets people debating all the pros and cons and devising new ideas of how to do it and how to get there. The big downfall – making it happen. While I eagerly watch and listen to all the developments in light of the Kepler, HARPS and other missions searching for exoplanets, until we are sure that they are there (and I am) and where they are, we probably should find out about our own back yard before climbing the fence into the neighbors yard unless we are sure there is something over there we want. Keep up the great work, Geoff!! You are an inspiration for my generation and many more to come!! (My 7 y/o son wants to be an astronaut)
Richard Black – Aurora, CO
Oscillations in the Habitable Zone around Alpha Centauri B
Authors: Duncan Forgan
(Submitted on 6 Feb 2012)
Abstract: The Alpha Centauri AB system is an attractive one for radial velocity observations to detect potential exoplanets. The high metallicity of both Alpha Centauri A and B suggest that they could have possessed circumstellar discs capable of forming planets.
As the closest star system to the Sun, with well over a century of accurate astrometric measurements (and Alpha Centauri B exhibiting low chromospheric activity) high precision surveys of Alpha Centauri B’s potential exoplanetary system are possible with relatively cheap instrumentation.
Authors studying habitability in this system typically adopt habitable zones (HZs) based on global radiative balance models that neglect the radiative perturbations of Alpha Centauri A.
We investigate the habitability of planets around Alpha Centauri B using 1D latitudinal energy balance models (LEBMs), which fully incorporate the presence of Alpha Centauri A as a means of astronomically forcing terrestrial planet climates.
We find that the extent of the HZ is relatively unchanged by the presence of Alpha Centauri A, but there are variations in fractional habitability for planets orbiting at the boundaries of the zone due to Alpha Centauri A, even in the case of zero eccentricity. Temperature oscillations of a few K can be observed at all planetary orbits, the strength of which varies with the planet’s ocean fraction and obliquity.
Comments: 10 pages, 9 figures, accepted for publication in MNRAS
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:1202.1265v1 [astro-ph.EP]
Submission history
From: Duncan Forgan Dr [view email]
[v1] Mon, 6 Feb 2012 20:27:04 GMT (124kb)
http://arxiv.org/abs/1202.1265