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The Science Of Planet Detection
Black Dog writes: "It seems like we're hearing about the 'Extra-Solar Planet of the Week" lately. I thought it might be useful for everyone to bone up on planet detection techniques. Two of JPL's projects are at: The Terrestrial Planet Finder and techniques for planet detection."
[NASA] Yes, we have visual confirmation of another earthlike planet at a mere distance of 666 Million light years from Earth!
several months later:
[SETI] After focusing our efforts on that section of the sky, we've intercepted what appears to be a possible signal. We've began our analysis.
months pass...
[SETI] Our scientists have finally unveilled the meaning of the alien transmission. It appears that they are sending us this message, looped over and over again:
This was mainly, a monumental data processing achievement. They described it on a recent TV program as "like detecting a firefly sitting on the edge of a searchlight 10 miles away". As I understand it, they modeled the way that the reflected light would change with both orbital geometry and Doppler shift and used very sophisticated processing to extract a signal with those characteristics from the background time-resolved spectrum of the star.
One bonus of this work is that the planet's signal is much stronger in green light than in red or blue, giving an idea of its colour. The same approach might eventually allow for detection of the presence or absence of specific compounds on the planets surface.
The authors don't see this approach generalizing to find Earth-like planets. They are too dim, and their orbital velocities are low enough that the Doppler shift is lost in the shifts due to movement of gas on the Sun's surface. On the other hand, they thought that interferometric work in the medium IR stood a good chance. You would need a flottile of perhaps 4 8m space telescopes, with supercooled detectors and extremely accurate station-keeping (to with 1 micron over extended periods) but you could then use interference to cancel the image of the star almost completely, while preserving any light from the planet.
Do you notice the baseball that just landed in your lap first, or the kid at the end of the block that put it through your window? Okay then, that's why we detect particles first. God is, of course, the brat kid that broke your window in this analogy.
DARWIN from Europe, and Kepler another proposal from the US.
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The Internet is the Suppository of All Knowledge. You get it in the end.
Oh, I agree, there are some exciting ideas in space propulsion technology. However, I don't consider something to be "current technology" until somebody has gone out and built one and proven that it works.
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Most cutting-edge science has no immediate practical use. We will find uses for it in the future, assuming that we keep up with the cutting-edge science. We cannot predict what uses may come of it now, but you can rest assured that they will come in time.
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That in turn reminds me of a short SciFi story I read a while ago..
The gist of it was that Earth's first extra solar, manned mission gets shot into deep space, to land on a far away planet. Years later, they arrive, only to be met by (much younger) explorers from Earth, who had left Earth much more recently....
I think the SIM or Space Interferometry Mission has good goals in searching for new planets. But what new information is there to learn about Earth from these other planets. What are the pratical gains from this?
I think is great that they have discoved that a planet around some near by star creates a "wobble" that they can dected. But sences Space travle is far from getting anything to a distint planet in other Star System. Thus we can't go and see for ourselves if this planet even exists that we think we dedcited by "indirict means"
I'm not trying to belittle the scinces of this. Or deny that just having new information about the univerise is a gain in and of itself. But how can we benfit from this in pratical ways. AKA how does this make my box run faster? Or How can this help world hunger? That kind of thing.
Whereas most (extra-solar) planets have been detected by the gravitational pull on the neighboring star, the one last year was visually detected. This was done by noting a small, regular dimming of the star. So...basically, we had a stellar eclipse.
This is important because a earth-sized planet has almost zero gravitational effect on the sun, but, it does block light (however small the amount). Indeed, this might be a way of detecting smaller, more earth-like planets.
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"2nd Place is a fancy word for losing" --Bender (Futurama)
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Time is Nature's way of keeping everything from happening at once... the bitch.
That's funny, I misread 'planet detection' as 'planet destruction', and thought to myself "so NASA has a Death Star..."
Yes, but even if we do find "Earthlike" planets, and we manage to find our way to the stars, and actually find an advanced species, let's all face the fact that it is highly unlikely we will be welcome.
More likely we'll be treated as the interstellar equivalent of a first time AOL user and face some massive interplanetary LART for simply being what we are: A species who may conquer time and space, but can't make a toupee that doesn't get big laughs.
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I appreciate it might take 200 hundred years - but that's not long in the grander scheme of things.
Do we have the technology that will get it that far and slow it down - and not break??? :)
(August 2231: "I can't believe they put NT on that probe ship - oh my fscking god!)
:wq
Does anyone think it's ironic that we're better at detecting new sub-atomic particles than new planets?
kwsNI
I'm not an apologist for NASA (heh -- you ought to hear some of the stories I can tell), but you ought to realize that there's plenty of science done without them (yes, even space and planetary science), and plenty of science interest independent of NASA on the part of the media.
If you want to bash 'em, do it on reasonable grounds; don't try to link it to something else entirely...
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Politics is about making compromises. Religion isn't. --Michael Horton
Popular Science has some recent articles discussing planet detection as well.
They cover the announcement of the two smallest extra-solar planets discovered to date (announced Wednesday) here.They also have an article that summarizes techniques for planet detection (including SIM and the TPF, among others) here. This article also offers some insights into the challenges of actually sending probes to these remote places, with some possible (and definitely futuristic) suggestions.
--The Colonel
There is a group at my university's physics department working on a design for a cool planet detecting satillite. It is called BOSS. Check it out, cool stuff.
A wealthy eccentric who marches to the beat of a different drum. But you may call me "Noodle Noggin."
Quando Omni Flunkus Moritati
Our basic problem is that we are getting fairly good at finding planets, but not terrestrial ones. Gas giants, no prob. But Earth-sized, we're not quite there yet.
Additionally, the ones we do find that might be earth-sized we find only because they are erratic in orbit or receive too much radiation (which is how we can find them).
We need to start sending out packages above or below the solar plane, with sufficient telemetry and telescope size (e.g. Hubble), and in greater number. And we need to start sending drone ships with basic measurement devices towards some of the more likely candidates, to extend the search range.
But we would rather spend the money on fueling up our SUVs and creating military forces to get fuel for those SUVs. For only $10 a year per capita, we could (the US or the EU) easily create enough detection equipment and the scientists to analyze it.
Will in Seattle
My old astronomy lab have a group working on optical interferometry, and have a working optical interferometry complete with four (or possibly now five) telescopes linked together. If you are interested in the details, there is a good introduction and more detailed information here. Now the interesting thing here is that it is very important to keep the telescopes at exactly the same distance apart or compensate in some way (here there are trolleys running up and down a long (30m) optical bench and the telescopes are concreted into the ground. The problems inherent in doing optical interferometry in space present many of the same problems examined in this project, plus the limitation that you can't just stick an optical bench on a satellite and hope to get it off the ground. On the other hand, ten years ago people were highly sceptical of getting optical interferometry working on anything more than a rudimentary basis and felt that map making was many years away, so maybe those problems can be solved too.
Cheers,
Toby Haynes
Anything I post is strictly my own thoughts and doesn't necessarily have anything to do with the opinions of IBM.
I took a good look at the proposed detector, which is essentially a directional spectroscopic satellite. It looks feasible enough, given enough time and enough satellites, if the initial assumption (that terrestrial planets are common) is correct. It won't produce quick results, I expect.
This is actually a very interesting line of investigation, and one that is highly popular in SF. Instead of the current approach of scanning stars for the results of gravitational perturbations (which I was surprised to see finding sub-Jovian planets), the TPF scans for light in specific emission spectrums - water, maybe oxygen and ozone, perhaps ammonia and methane, nitrogen... I'd assume this would mean using a time-based saturation filter to screen out everything from the star and all the stars behind it, loose ice and dust and complex non spectral light sources and reflectors.
If they're smart, they'll find a way to factor the red/blue shift of the target bodies into the filter, as well as shifting the spectrums. Given enough time, they could build up the period of the target body, and therefore determine its orbital radius...
Of course, that would entail finding the signatures in the first place. Unfortunately, the fact that a dimmer star might have a terrestrial planet very, very close could result in a very high periodic shift (relatively), which might cause problems if a very narrow wavelength filter were being used to stamp out undesirable light sources.
Lots of things for them to think about when building this... and all relying on getting a tremendous amount of ultra-sensitive electronics into orbit. Shame we don't have orbital industry yet.
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I see even classic Slashdot is now pretty much unusable on dial up anymore.