Looking For Earth-Like Exoplanets 73
Discover Magazine is running a story detailing the search for planets like Earth orbiting other stars. While we've been able to locate a few "super earths" so far, none of them really compare in size or the potential for habitability with our own world. Fortunately, advances in data analysis and new space-based telescopes — such as Kepler, the James Webb Space Telescope, and the already-launched CoRoT (PDF) — have some astronomers predicting we'll find such an exoplanet by 2010, and a habitable one by 2012. Earth-based telescopes are also in the hunt, though the article notes, "even if a habitable Earth-like world is found first from the ground, it will most likely take a space observatory to search for the chemical signals that tell us what we really want to know: Is anything living out there? If the planet is one that can be observed transiting, it just might be possible to provide a hint of an answer in the next few years."
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You mean Amarantin?
You mean American?
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Wow... An article about planets that isn't... (Score:5, Insightful)
Obsessed with the fact we haven't observed something we can't yet detect... This must be some sort of mis-post.
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This just seems like old news to me... I remember reading a post about 3 or 4 months ago about us finding "earth like" planets but outside the bounds of what we understand can substantiate life. Maybe it was on new scientist, but I swear I've seen almost the same tag line on a slashdot article.
This just reads like Discovery documentary - a lot of "meaningful"* questions, no real substance.
*by meaningful I mean trying to come across as meaningful, but either rhetorical or just plain obvious.
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There definitely needs to be some refinement of what qualifies as "earth like". I would consider Mars to be a the extreme outer edge of "earth like". Some of the more extreme bacteria and lichen from earth might be able to survive, maybe. I wonder what the parameters for "earth like" should be. Maybe: 0.4G to 1.4G gravity range, a temperature range between 180K and 335K, atmospheric pressure of 1kPa to 110k
Re:Wow... An article about planets that isn't... (Score:4, Funny)
Why such a low upper limit on gravity? Lichen don't care what they weigh.
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There are people who weigh 300 pounds and they function. I'm sure I could learn to function at that weight too.
Re:Wow... An article about planets that isn't... (Score:4, Interesting)
... I wonder what the parameters for "earth like" should be....
Do you mean by that the conditions necessary to develop intelligent life, such as the SETI project is looking for? Assuming that the laws of physics are the same everywhere in the universe, the molecular binding energies for living things would dictate the temperature range. For practical purposes this would mean the temperature range in which water remains liquid at least some of the time. This would require a stable orbit around a star the output of which does not fluctuate too much. Orbital mechanics show that such a star must not have a neighbor closer than about 3.8 ly. By that specification alone, about one half of all stars in the universe are disqualified from having such a planet because they are too close to each other.
Really big stars are also disqualified because their output varies too much in order for intelligent life to develop or exist. If a star is too small, a potential planet must be placed too close in order to get enough heat. Any such close in planets all are unlikely to freely rotate, thereby having one side always facing the star. That would mean the dark side would get extremely cold. Assuming there was a viable atmosphere, it would circulate violently between the day and night side.
Living processes involve large complex molecular structures which only the element carbon allows. Therefore, any physical life must be based on the chemistry involving carbon. Of course, there may be nonphysical life, but that is not what we are talking about here.
[citation needed] (Score:1)
Life can be based off of any atom with a valence higher than 2.
References, please. Silicon, valence 4, same as Carbon is a natural possibility, but I've never read anything seriously suggesting another base element.
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Still, why is it assumed that life has to develop on a planet by current definitions? We're looking at Enceladus as a possible habitable body in our own solar system, and all the gas giant planets have satellites aplenty. Why should another solar system have "naked" gas giants? I think it is more reasonable to assume that gas giants gather satellites, and that some of them will be fairly large.
Also, we have a situation here that we have yet to find elsewhere -- the stability of a "double planet" system. W
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> Still, why is it assumed that life has to develop on a planet by current definitions?
I don't believe it is so assumed, but planets are easier to find than satellites of gas giants.
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....why is it assumed that life has to develop on a planet by current definitions...
It does not really matter what you call the environment where life may exist or develop. It could be a spaceship such as Hollywood's death Star. The point is, that the environmental requirements for physical life are quite narrow. Even a single cell is far more complicated than a large city. On the atomic and molecular level, the process of life is extremely complicated and intricate. More complex systems generally have stri
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ALL humans are INCURABLY religious? That's a big claim. For a start I know of at least one human who's been cured of the religious delusions inserted into his head in childhood. So that disposes of your "all" claim, and your incurable claim simultaneously.
But more realistically, surely most humans have been and will be cured of their religious delusions in the few seconds between their heart stopping and their brain succ
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....For a start I know of at least one human who's been cured of the religious delusions....
I assume you are mean yourself here? Well I got news for you! Everybody, even atheists have a world view, life philosophy if you will. You BELIEVE far more things than you KNOW.
(...will be cured of their religious delusions in the few seconds between their heart stopping and their brain succumbing to hypoxia...)
That shows your faith right there! You don't KNOW that this is so, but simply BELIEVE that as part of your
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I agree that stability of energy output (on a moderate timescale - thousands of years or longer) is a desirable. But really big stars have a more serious limitation - duration.
The evidence from fossils is that it took between a half billion and a billion years for the first lifeforms to evolve on Earth ; developing intelligent life took another several billions, though that might co
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Take some time (Score:1, Informative)
To travel to such a planet will take a ship of multiple generations. We haven't even remotely touched the Oort cloud with the 30 years (quite fast) traveling Voyager 1. ... take your time. People just don't grasp how far this really is.
So
Super Earths??? (Score:4, Funny)
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Super Earths last all summer long.
The future is 2012 (Score:3, Funny)
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Yes. It will be like a whole new world.
The psychological limit of awesomeness, really (Score:3, Insightful)
Well, it seems to me that it's just a matter of perspective. We don't really see absolute values, we see deltas, and the baseline is the present.
Think of, say, dollars. Just saying "in year X you'll earn Y dollars a month" is only saying anything as a comparison. Whether it's in absolute dollar values, or "how much can I buy with it", the comparison only says much compared to your current lot in life. A 1960 standard of living would be luxury for someone from 1912 (think even just having antibiotics for a c
Re:But... (Score:4, Funny)
Increase the rotational speed of the planet so much that the centripetal force counteracts gravity. Then, with giant nets, catch the oil as it floats up from the surface. Then, pump it through a hose and squirt it back to a giant funnel sitting outside earth. I mean, our only other alternative is NON-fossil based fuels, and that's just CRAZY!
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Chance of choosing a suitable star system (Score:2)
If we observe a random star sustem which seems like it could have earthlike planets, it seems to me that observing a transition is unlikely.
Suppose that earth was the only planet revolving around the sun; the chance of observing a transition from some large distance is approximately:
(diameter of sun / diameter of earth) 109
(2 au / diameter of earth) 73686 earth diameters.
The chance of the orbit being oriented correctly seems to be 0.00147986287 [google.com].
I suppose you could increase the chances by choosing larger
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Ah, dammit. Did'nt read the article properly...
It seems they will be observing up to 12 000 systems at once:
Those scientists think of everything. Still, they say that one in a hundred will be orientated properly, but accor
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The looking at one star part. Fortunately there are LOTS of stars to look at.
High resolution images possible in near future? (Score:2)
It will be nice when we find an oxygen planet but still we will only know it as a small blue dot I expect. Anybody have ideas for what kind of telescope could actually take detailed pictures - perhaps enough to even see cities - of exoplanets?
Say 50 light years. I wonder is it possible to run an interferometer across spacecraft far apart in the solar system? The separation is I suppose a matter of trigonometry and optics. Then the question of what do we need to do it and when?
Re:High resolution images possible in near future? (Score:5, Interesting)
It's harder than that. I assume by "see" you mean two-dimensional visible or near-visible light images. To produce images like that you have to be able to move each telescope in your interferometer (or have lots of them), in two dimensions. The big radio interferometers put the radio telescopes on train tracks. Some proposals for space interferometers put one on each end of a tether, spin them, then winch them closer and farther apart to trace out a spiral.
The other problem with crazy long baseline interferometry is that you need to transmit the received signal (including phase) between the individual elements. For radio that's not too bad because you can actually detect and record the phase, for low enough frequencies. For optical it's much harder.
Plus you have the problem that interferometers have great resolution but poor light gathering capability. They can't see things that aren't bright.
A back of the envelope calculation (which might be wrong) shows that a 50 km city at 50 light years would be about 2 x 10^-5 miliarcseconds. To get that kind of resolving power in the middle of the visible spectrum you'd need a telescope about 6000 kilometres across. That's not too insane. You might be able to pull it off with an array of a hundred or so reasonably sized space telescopes all orbiting around a L point somewhere. If you could collect enough light, and distinguish between the city light, the non-city planetary light and the star, of course.
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> It's harder than that. I assume by "see" you mean two-dimensional visible or
> near-visible light images. To produce images like that you have to be able to move each
> telescope in your interferometer (or have lots of them), in two dimensions.
You can produce useful "images" that are not free of ambiguity, though. For example, you might be able to show that features in a certain size range (i.e., continents or clouds) exist without being able to produce pictures of them.
> The other problem with
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Certainly, but the original poster wanted images of cities. 1D lines, though very useful, don't really catch the attention of people who want to see something like this [nasa.gov].
Ditto with radio images. Extremely useful, but probably not what the poster was hoping for.
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If you make a pixel 1000 km, which gives you about eight across the disk of an Earth size planet, you get a resolution of about 0.0004 mas, needing an aperture of about 300 km. With a nice desert you could potentially do that on the surface, although you might still want to build a space interferometer instead.
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A back of the envelope calculation (which might be wrong) shows that a 50 km city at 50 light years would be about 2 x 10^-5 miliarcseconds. To get that kind of resolving power in the middle of the visible spectrum you'd need a telescope about 6000 kilometres across. That's not too insane.
Even with a telescope that's big enough and perfect enough to not be limited by diffraction or aberration, would there be so few photons that the required integration time would mean that it'd only be able to image detail on slowly-rotating planets?
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It depends on how much light collecting area you have. That is the problem with interferometers, all right - they can have the resolving capability of a gigantic telescope, but they don't have the light collecting capability.
Still, you should be able to build some monstrous mirrors in space. The biggest problem with building gigantic telescopes on Earth is that gravity tries to warp them, so bigger mirrors have to be much stronger. If your 6000 km interferometer was composed of 100 m space telescopes, yo
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On the other hand, if you can figure out the rotation time of the planet, you can image it for as long as you want, taking breaks while the face you're interested in is facing away.
Ah, good point. You'd just have to take (exo-)daily samples.
Does either the inter-stellar atmosphere or gravity waves eventually impose resolution limits?
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Probably. Over 50 light years unless you happen to pick a really bad direction you're probably okay trying to image a planet. I don't think gravity waves would be a problem. Unless you really took things to extremes.
Incidentally, optical interferometry gives you some immunity to blurring from the Earth's atmosphere too.
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OK, thanks.
It looks like we could therefore use SETI to spread through the galaxy at near c:
If there's no suitable civilisation to leap through you'd have to shoot massive numbers of self-constructing nanotech AI particles in the desired direction, hoping that some impact solid bodies.
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There's a novel, actually a series I think. Unfortunately I can't remember the title. But one day our civilization finds an alien artifact floating out at the gravitational focus of the sun. That's where the sun's gravity focuses light rays, like a giant lens. When we go out to find out what this thing is, it turns out it's a transporter. It dematerializes you and transmits you (and the speed of light, using the sun as a giant lens, to another star where you're rematerialized. Some aliens seeded these
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Thanks, I wasn't familiar with such solar focus points. It looks like they're about 14 times farther from the Sun than Pluto. That's one tough sentinel.
In terms of our present understanding of Physics, such a transporter's more in the fantasy realm. AI envoys are more realistic.
Because there is likely to be such a small gap between a civilisation able to receive radio signals from space, and one able to run a properly described AI sim, one wouldn't have to transmit any info about how to construct a si
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Whoops, that'd be c/2, unless the computer blueprint and the scientist binary were transmitted at the same time.
I'm trying to think of protocols that would assure the aliens that we did not have an evil intent, and to prevent empowering aliens who had evil intent.
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Thank you *very* much for your hard work and excellent replies. Though of course visible light at even higher resolution than the Earth by night pic of the day, I wouldn't disparage radio or other spectra especially if they provide higher resolution.
Unfortunately I do not have enough technical background to understand interferometers well yet. If you can indeed store the phase information (interference pattern?) of each telescope for combining in what I think is called a nulling interferometer at a later po
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For interferometry you need two or more observations made at the same time, from different locations. You then arrange for those signals to interfere. Basically, optical interference is a Fourier transform, so you can then read off the Fourier coefficients by examining the interference pattern. You need to move your observing stations (or have more than two) in order to measure more than one Fourier coefficient. Once you've got enough, you can inverse Fourier transform to get your image.
With radio astr
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A telescope at the Sun's gravity focus.
http://www.centauri-dreams.org/?p=785 [centauri-dreams.org]
(the comments contain some interesting information as well.
The resolving power is a bit of slippery subject, because gravity microlensing doesn't work quite like a regular refractive lens. According the the comments, you can basically see anything, no matter how far away (subject to caveats when you start getting insanely far away) as if it were in close orbit around the sun. So the resolution you can obtain really depends on what
Any later and it would be hopeless (Score:1, Redundant)
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> ...support a significant enough portion of the human population to allow for a decent
> level of diversity in reproduction...
Eggs and sperm can be frozen and revived. AI works.
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> ...support a significant enough portion of the human population to allow for a decent
> level of diversity in reproduction...
Eggs and sperm can be frozen and revived. AI works.
Who exactly is going to revive the eggs&sperm? Even if the AI does it, you can't exactly just fertilize a bunch of eggs and hope for the best.
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AI-> Artificial Insemination, not Artificial Intelligence. As to who is to revive it, the colonists. I just wanted to point out that the effective gene pool of a colony can be much larger than that provided by the colonists on the ship.
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But *I* want to live!
And Holly, the lovable, senile, bald AI exists?
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...If the laws of Biology are any indication...
Underlying the laws of biology are the laws of physics. In this case, specifically the electronic binding energies of atoms to each other. To have PHYSICAL life forms, requires complex molecular structures, such as proteins. One of the definitions of "life" is the ability to reproduce. This implies some way to record and pass on the structural and functional capabilities, such as DNA. We have evidence that the elements that exist here on Earth are also present
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With the exception of the various extremophiles, which may be the closest remaining organisms to the last common ancestor. They're active up to the 60s, higher for some.
Wow pretty good article; are transits best method? (Score:2)
Yes, I know that implies I read TFA. But it was pretty good, I thought it concisely explained that they'll be using transits to look for these exo-planets then hopefully use the Webb space telescope to get an idea of the planet's atmosphere by looking at the spectrum in the infra-red. (That's where Webb is designed to be most sensitive and that's where the star "only" outshines any orbiting earth-like planet by say 10,000:1).
My question is: So does that mean that transit detection has won out over looking
Re:Wow pretty good article; are transits best meth (Score:2)
...You know of course that IF they find a whole bunch of earthlike planets...
That is a big IF. Over half of all known stars can never have an earth-like planet for the simple reason that half of all stars are too close to each other. To have a planet with a temperature range suitable for life, its orbit has to be very regular. Another star too close prevents such stable orbits. Other parameters such as the right elements in the proper proportions must also be right, as must be the rotation rate and gravity
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Why would they stop using one technique when a different technique is developed which attacks a different question from a different perspective with different constraints to the original technique?
More techniques will be developed for detecting and studying planets in orbit around other stars. But the current techniques will continue to be used until there is nothing more that can be wrung out of them. W
one more eye (Score:2)
..but we need to be like an insect with thousands of eyes, spaced far enough apart. These should be far enough from earth to be able to use interferometry or even triangulation to add data and knowledge about a particular object. It is only with such a system of such sensitivity, precision, and accuracy that we will have the confidence needed to send probes and manned craft beyond this solar system.
We are the bad guys in the sci-fi B movies (Score:1)
You know all of those movies about aliens from outer space that come to inhabit earth because they have burned out the resources on their own planets?
Yeah, well, we're the aliens.
I'm sure we'll feel justified in displacing whatever inferior species we find out there.