Possible Habitable Planet Just 12 Light Years Away 420
sciencehabit writes "Astronomers have discovered what may be five planets orbiting Tau Ceti, the closest single star beyond our solar system whose temperature and luminosity nearly match the sun's. If the planets are there, one of them is about the right distance from the star to sport mild temperatures, oceans of liquid water, and even life (paper)."
Lets start seeding the galaxy with life (Score:4, Interesting)
Re:"JUST" 12 light years? LOL. (Score:5, Interesting)
These are some big IFs (Score:5, Interesting)
Even if the planets are inside the habitable zone, they would need to be the correct consistencies... Venus and Mars are in the zone here, but neither has life or is natively habitable. Yes, we're attempting to discover if Mars may have HAD life, but as far as we can obviously tell, it has none now...
So it's fun and interesting to search these types of star systems and planets--and I think it's absolutely worthwhile to focus a SETI program on them to try to determine if there are any stray signals we can pick up--but otherwise this really is not much more than dreaming and guessing.
Assuming SETI finds no signals, but we do believe there a couple of planets into the habitable zone, then I think it would make some sense to attempt a probe mission there... but it could be a while before we're at the technology level we'd need...
I think our current speed record in space is about 150,000mph ... which is ~1/5000th the speed of light. So while 12 years seems do-able from a speed of light point of view, there is no (present) method to send a probe there in a reasonable amount of time... I'd say reasonable would be a ~36 years to get there, plus another 12 years for the return signal... so roughly 50 years from launch to first data... meaning it would likely be a two, maybe three, generation program from a NASA engineer point of view.
We'd need something capable of:
a) Traveling at least 1/3rd the speed of light (roughly a quarter billion miles per hour)
b) A power source capable of lasting at least ~40 years or more with enough juice available near end of life to complete its mission
c) Capable of complete autonomy in 100% unknown situation
d) Possibly requiring the ability to actively correct its course en route, and maybe even detect and avoid collisions
Re:"JUST" 12 light years? LOL. (Score:5, Interesting)
Keep in mind that Voyager, apart from some gravitational assists [wikipedia.org], wasn't ever really made to "go fast". Even now, there are ways to send things moving much quicker such as the Ion Thruster [wikipedia.org] which although not NEARLY as powerful as a chemical rocket, is amazingly more efficient. The Weight to Thrust ratio is fantastic and could well be utilized to provide constant thrust for a long time. Once you exit the earth's gravity well, something like an Ion Thruster could over a number of years accelerate a craft to a much higher speed.
Re:It goes the other way, too (Score:5, Interesting)
If that planet were inhabited by a technological civilization, we should have been detecting their twelve-year-old radio transmissions, faint as they might be.
Re:Gravity? (Score:2, Interesting)
Correct me if I'm wrong, but doesn't that mean that the gravitational pull on surface dwellers would be four times that of Earth?
Not necessarily. You forget that both mass and distance play a role in gravitational attraction. Therefore, given a larger radius, it could in fact have a comparable or identical gravitational attraction on the surface, though the exact numbers vary depending upon the density and distribution of material in the various layers of the planet. Assuming identical density distribution, it would require a radius twice that of Earth to have identical gravity on the surface. At the same time, the rotation speed of the planet plays a not insignificant role in the perceived gravitational attraction, as the rotation would constantly be throwing surface dwellers outward with a small force, negating gravity's inward pull.
Re:These are some big IFs (Score:4, Interesting)
An Earth-like planet orbiting Tau Ceti could be examined telescopically in fair detail. If it's confirmed, it would be a great target for one of the extrasolar planetary imaging telescopes people are starting to design. It might even be possible, with refinement of current techniques, to get a rough spectrum from it with current telescopes.
Re:Tau Ceti is 2 X as old as our sun (Score:5, Interesting)
Just like Venus (Score:4, Interesting)
Re:It goes the other way, too (Score:3, Interesting)
It turns out that stars are pretty powerful radio transmitters, and the edge of a stellar system has considerable additional noise. And then there's the cube-square law. Even if they were deliberately transmitting directly at us 12 years ago, it's unlikely we could make out the signal from the noise.
Suns have a lot of light noise too, so we probably wouldn't see a laser transmitter either, unless it were from the very edge of the system.
What we might see if we were looking for it would be the ion emissions of decelerating incoming craft using ion engines, or the thermal signatures of interstellar craft using nuclear thermal propulsion. But by then it might be too late. Or esoteric energy uses like fusion. Or signatures of H-bombs near the periphery of the stellar system.
At 15 degrees Right Ascension, Tau Ceti is a little far off the solar system plane for an exploratory trip just now. Maybe in 50 years.
Re:It goes the other way, too (Score:5, Interesting)
Don't feel too badly, you were on the right track. IIRC clear back in the 1970s it was determined that at TV frequencies the Earth was the brightest (known) object in the galaxy.
Re:It goes the other way, too (Score:5, Interesting)
"On a small scale" is an understatement. We have virtually sent no signals at all. To any system past Alpha Centauri we would be dead silent on a radio scan of our system 99.9999999999999999999999999999% of the time. Are you wondering why we haven't made any effort to send signals? Fear. Even many radio astronomers themselves are frightened of attracting the attention of more advanced civilizations that may be listening. If we are too afraid to do it other civilizations may be as well. So we all listen but never speak. Everyone will stay very quiet out of ignorance and fear. Hence Fermi's Paradox and The Great Silence.
Re:"JUST" 12 light years? LOL. (Score:4, Interesting)
By "it" in my last sentence, I meant Voyager I. You can get to the stars faster if you spend more delta V doing so.
An interesting tidbit is that 1 year at 1 g thrust gets you to just about the speed of light. After 1 year at one g, you don't really go much faster (from the standpoint of someone left behind) but, boy does the relativistic time dilation kick in. Factoring in time dilation, you can get to almost anywhere in a fairly reasonably subjective time (i.e., the relativistic proper time for the traveler), assuming you can accelerate and deaccelerate continuously at 1 g. , Thrusting at 1 g also has the comfort advantage that we are totally used to it.
Of course, if you go very far, humans, or even the Earth, may not be there when you get back. And, how to achieve a constant 1 g thrust has to left as an exercise for the reader...
Re:"JUST" 12 light years? LOL. (Score:2, Interesting)
let's just make a bunch of incredibly fast scientific probes, say 0.3 c
We should to this for no other reason than to see if it's even possible to detect and evade objects. A little interstellar gas and dust pinging you with that kind of energy might just degrade the outer skin. We can handle that. Anything over a certain size will just explode the craft. IIRC, a paint fleck hit the space shuttle and made a scary pit in the cockpit window one time. That was considerably less than 0.3c. If a frozen bacterium hit your head at 0.3c, I bet it would explode.
Re:It goes the other way, too (Score:3, Interesting)
It turns out that stars are pretty powerful radio transmitters, and the edge of a stellar system has considerable additional noise.
So what?
And then there's the cube-square law.
Don't you mean inverse square law?
Even if they were deliberately transmitting directly at us 12 years ago, it's unlikely we could make out the signal from the noise.
While noise (snr) is certainly a problem in any long range communication, if transmitting at the proper frequencies (ie. 1-10 Ghz; 34-37 Ghz; 75-80 Ghz) it isn't a major one.
The problems are more along the lines of:
1. It seems unlikely that any system within 50 ly of us would contain a planet with not just life, but intelligent life. Biogenesis has been compared to a tornado in a junkyard constructing a car. We really have no idea how to even do it ourselves. So it really may be quite rare. And even where there is life, intelligent life of the giant parabolic dish building variety is certainly not a given. Consider how many species there are on our planet brimming with life from pole to pole and only a single species seems to be intelligent enough to build computers and spacecraft and giant radio telescopes. If intelligence is such a good survival strategy why have more species not taken advantage of it? Even with all those stars out there intelligent life of the radio telescope building kind may be far more rare than those of us who enjoy science fiction may like to believe. The majority of life on earth is still simple microbial life.
2. The transmission has to either be aimed directly at us or be of orders of magnitude more power than at least we are capable of transmitting if only for economic reason. Either possibility seems rather unlikely.
3. No one really knows about us yet. We are just another star in a sky filled with them. If we embarked upon a major coming out party and transmitted signals for long periods to every star within, say, 100 ly then things might be different, but as it is there is no reason for anyone out there to point a dish in our direction except for causal surveys of nearby stars which might listen for only a few seconds each decade.
4. The aliens could be transmitting directly at us and we probably wouldn't hear them because they might be transmitting on one of the many frequencies that we are not listening on or which are attenuated by our oxygen-nitrogen atmosphere. Anything from 20-30 Ghz or above 100 Ghz is mostly blocked by our thick atmosphere. Very high frequencies tend to be more effecient at interstellar communication. Which is why setting up radio telescopes on the moon or mars would be rather nice.
Re:"JUST" 12 light years? LOL. (Score:5, Interesting)
You make me post this in every extrasolar planetary thread and it's really annoying.
Voyager 1 is nowhere near current technology. We have ion thrusters now. We have supercomputers now. Hell, your cellphone would have been a supercomputer to the guys who designed that thing. We have water on the moon, in near-earth asteroids, and a limitless supply in Ceres, and we didn't know that then. We have new methods of separating that water into hydrogen and oxygen on orbit efficiently, so it doesn't have to be hoisted out of our gravity well. We have far more understanding about long-term space missions and habitation. Plants grow in space! We didn't know that either. We have commercial rockets that can dock with the space station: an absurd sci-fi fantasy back then. We have robots who can do the work of gathering fuel without too much supervision. We have robots that could survive the kind of acceleration provided by a 1000 km railgun that it would take to put the robots there in a reasonable time, and a place in low-g to put that rail gun and robots to build it. And software to put on the robots that apparently can withstand a 24 year ping time.
In fact, recent learnings about the Voyager Anomaly point to an obvious way to propel interstellar spacecraft: Put a couple dozen 200 MW fission reactors behind some heat/radiation shields and point them in the opposite direction from where you want to go, and let them melt down. The heat provides thrust. At 745 W per HP, that's good for a few thousand horsepower of thrust. Since a Newton is a Horsepower-second, near enough, and the reactors run for many years, that's insane number of Newtons. We actually used to have a project that worked on this theory called Project Orion.
So, for example, get the robots to gather up some water and refine it into LH2/LO2. Slide some of that fuel down to LEO and pick up a commercial hydrox booster and lift it into high orbit and fill it. Repeat until you have seven of them. Now arrange them in a filled hexagon at L2 orbit just beyond the moon, and fill with hydrox. Strap your meltdown-driven spacecraft and habitat/humans/robotic exploration package on the nose, and at the most opportune time when your cislunar orbit is headed closest to the desired direction, light that shit off. Boost for 2.5 minutes at 6 g, and discard the 7 Saturn boosters. You're already several times past solar system escape velocity, and your course is assured. Then engage the thermal drive and melt down the reactors and continue to boost at something on the order of 40 billion Newtons per year as you head to the nearest star. Somebody do the math for me. I'm thinking 50 years.
"Oh, but the cost!" you might say. Well look. We don't need the work of all the people we have. It turns out that something like 1 in 4 Americans is all that's required to maintain our standard of living. According the US Bureau of Labor Statistics [bls.gov] we have 11 million underemployed people in the US, or $500B/year worth of people who could do be doing something interesting and useful who aren't. And that's just the US, and I think that number is understated 2x. Besides, we'd like to be rid of that nuclear fuel anyway.
I'm not even in the space field and I could figure out how to get people to Tau Ceti in under one human lifespan with resources like that, or robots sooner still. We could do it, right now, with the resources and science that we have. It would be a one-way trip, but we would not lack for volunteers or robots. From one economic point of view it wouldn't cost us one whit more than we're already paying, and instead of being unhappily idle the proletariat would be excitedly engaged in a worthy endeavour. You just have to sell it.
Just because your grandparents couldn't figure out how to do this don't assume that the current generation can't.