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Looking For Earth-Like Exoplanets
Posted by
Soulskill
on Sat Oct 11, 2008 09:39 AM
from the dust-motes-orbiting-a-yottawatt-light-bulb dept.
from the dust-motes-orbiting-a-yottawatt-light-bulb dept.
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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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.
Re: (Score:3, Insightful)
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.
Re: (Score:3, Interesting)
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.
Parent
Re: (Score:3, Interesting)
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.
Parent
Re: (Score:2)
Super Earths??? (Score:4, Funny)
The future is 2012 (Score:3, Funny)
Re: (Score:3, Funny)
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
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
Re: (Score:2)
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
Re: (Score:2)
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.
Parent
Re: (Score:2)
> 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
Re: (Score:2)
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.
Re: (Score:2)
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.
Re: (Score:3, Interesting)
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
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
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.
Re: (Score:2)
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!
Parent
Re: (Score:2)
> ...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.