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Two Telescopes Linked To Find Planets
glinden writes: "Two telescopes at the Kech Observatory have been optically linked to form the Keck Interferometer. The resolving power of this combined telescope will apparently be sufficient to see earth-sized planets around nearby stars." quoll contributes a link to NASA's own version of the story, too.
You're right. There is no realistic prospect of interferometry with Gemini using any current technique. The point of building the two telescopes identical was to cut down on design costs, to allow exhchange of instruments and so on.
It is interesting to speculate on how one might do real long baseline optical interferometry, by
analogy with the techniques used in radio astronomy. Essentially you would need to record the phase of the incoming light at (point in the image of) each telescope as well as its intensity. This phase calculation would need to be stable over the duration of the recording, requiring something like a laser whose phase didn't drift by more than a few femtoseconds per hour -- a clock accurate to 1 part in 10^18 or so. This will give a rather large (petabytes/second/pixel) dataset.
Once you have done that you need to track the relative movement of the two telescopes to within a fraction of a wavelength, which will require allowing for the Earth's rotation, tidal distortion, thermal expansion and contraction of the rock, special and general relativistic effects from the Earth's rotation and gravity and probably much more. A better approach might be to observe a known source near the target star and try and calibrate from that. Using three or more telescopes also helps.
Then it just comes down to a comparatively well-understood, if enormous, computing task, to combine the datasets from all the telescopes and synthesise an image.
COAST has five in it's array. It's first images were made in 1995.
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Moderator's essentials
Thats not a moon. Its a space station.
Disclaimer: I know they can't detect Death Star sized objects with this. That is, not until its too late!
Some university in Britain did this a few years ago with an array of telescopes in a hexagon shape I seem to remember. They proved that this technology could take better piccies than Hubble. Beyond that . . . memory fading . . . can't . . . remember . . . any more.
Actually, the velocity probably wouldn't be a problem. Just use an Orion. Then you could also put sufficient armor on it and carry plenty of supplies. Orion type ships don't have much problem with mass-ratio.
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-- Have you ever imagined a world with no hypothetical situations?
Just a tibit of correction. The VLT is not in New Mexico. You're thinking of the VLA - the very large array, run by the National Radio Astronomy Observatory. The VLT is in Chile and run by the European Space Organization.
The VLT is an optical telescope, and they are designed to do optical interferometry with 4 telescopes, but I'm not sure that this has been done yet. The VLA is an radio telescope, and interferotetry has been done with radio waves for decades. Essentially, the difficulty goes with the length of the wavelenght. I.e. the longer the wavelength, the more room for error you have when you stack the signals. That's why its possible to stack nearly 30 signals at the VLA, but we're only doing 2 or 4 in the optical.
This is really quite an achievement. And no, you don't 'listen' to the radio telescopes like Ms. Foster did in Cotact...
Also, Gemini is a joint project among *many* countries, spearheaded by the group here in the US. I'm not even sure ESO is a part of it. The members are Chile, US, Australia, Brazil, Canada, UK, and Argentina. Please check your facts before you do this sort of ting.
By the way, the OWL is a concept telescope which has yet to be developed and probably won't be for a decade or two. You are right, however, in your general ideas, but bear in mind that even what they are doing at Keck is very difficult, and it will be years before Gemini starts operating as an interferometer (and even so, I'm not sure if it's equipped to do it yet). Right now, Gemini is just starting individual science observations.
It really is an exciting time to be doing astronomy, professional or otherwise.
I've thought of this before, but I didn't think they would do it on Earth. I was thinking that they should launch another Hubble and do it. In space you could easily move the telescopes closer together or further apart.
Of course, this increases the resolving power but it does nothing for light-gathering capability.
The problem is lenses. They simply have to be too big. What could we put in space that would act like a really big lens? The only way I know of to focus light without passing it directly through a lens or bouncing it off a mirror is with gravity.
It simply isn't practical for us to built a gravity telescope.
Is there anything else that will bend light? If we could create a large "light bending field" in space, we could get a lens the size of a planet. We would just have to be careful that we didn't put the Earth in the focus. Then again, maybe the Ant People from Andromeda are already planning to do that to us.
For all intensive purposes, "whom" is no longer a word. That begs the question, "who cares"?
I'm suprised that this sort of thing isn't better done in orbit, where at least gravity and temparature are on your side. You could imagine slipping a few big mirrors up to the lagrange points, and focussing them on hubble or something for the inferomtery.
Just a thought.
But the next leap forward is going to be European... ESO (European Southern Observatory) are constructing two identical telescopes in Chile and Hawaii (project Gemini.) How's that for a long baseline? ;p
And for bluesky "gee whizz" quotient, check out the Overwhelmingly Large Telescope (OWL)...
I've seen a chart somewhere (can't find a link - anyone?) charting aperture (light collecting capacity) of telescopes since Galileo. The Keck and other 10m class telescopes have moved the curve from a nice straight line to an exponetial curve - and that's not allowing for vastly increased computer power, active optics, and out-of-visible band stuff. Truly this is a fantastic time to be interested in astronomy, even (especially?) as an amateur. For a couple of thousand dollars you can do stuff in your yard that was the province of professionals only a few decades ago.
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If the good lord had meant me to live in Los Angeles
I'm not a genious in optics, but I don,t understand how 2 parallel telescopes see smaller objects than 1 telescope.
Light from an extrasolar planet has been detected, in a sense, by a group of astronomers. What they did was to use the fact that the reflected light from the planet is blue-shifted when the planet is moving towards us in its orbit and red-shifted when it's moving away. It also varies in brightness in a characteristic way depending on how much of the planet we can see.
Essentially the researchers used very sophisticated image processing software to detect this "signature" pattern of colour and brightness variations in the light of the star (before processing the signal was 20000 times fainter than the noise). They can't point to any one photon and say "this is reflected light from the planet" but they can say statistically that reflected light is almost certainly present in their data.
The Keck Interferometer will be able to detect planets farther from their parent stars, helping to pave the way for future interferometers in space that will look for Earth-like planets, NASA said.
Correct me if Im wrong (im sure you will all have no problem with this request) - but we are not going to be capable of imaging the actual planet body but instead be capable of detecting the influence of smaller planets on their stars...?
Imaging an actual planet is very different from detecting wobbles in Star orbits... where the former is surely the 'holy grail' our planet needs to motivate - and provide perspective to our opportunity in the universe - and work towards a real and noble goal of establishing a permanent, self-sustaining, Human presence other than Terra.
Not only is Mauna Kea not likely to ever erupt again (see the "hotspot" explanation posted elsewhere), but my understtanding is that the site offers some of the most uniformly best seeing available within the US borders, due to its elevation, the smooth air flow off of the ocean (minimizing "twinkle"), and the distinct absence of light pollution. Not only that, but its proximity to the equator offers views well into the southern celestial hemisphere, allowing observatories based there access at one time or another to nearly the entire sky.
Even if there was a real risk of the volcano erupting, I'd still be very tempted to stick a telescope or two up there....
-- WhiskeyJack
Does this remind anyone else of SMP? :)
On reading the title of this story, my first thought was that they just stuck the eyepiece of one into the lens of the other. Kinda like Bart did with the megaphones in that one episode. Was wondering why they didn't try this before when it hit me that it was probably a bit more complicated.
College hasn't healed a genetically predetermined boneheadedness, it seems. ^_^
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IANAPA (I am not a professional astronomer)
No, this instrument will not see Earth sized extrasolar planets. Read the article.
This has been thought of before, and not even this past century, but only recently (past 20 years) has the tech been there to actually DO this. The optics and the placement of them, esp in the delay line, has to be quite precise. We're dealing with fractions of wavelengths here.
Basically it works like this: You have two telescopes, and the two light beams are brought together accurately so that they create interference fringes (hence the name interferometer). The interference fringes tell you about the light at a specific spot in the sky, in a very narrow angle (well, a REALLY REALLY narrow angle). From this, maps can be made of spots on very active stars, etc. (None of this is seen directly). Effectively, what you get is the same resolution of a theoretical mirror that's the same diameter of your baseline. You just don't get the light grabbing ablity of that theoretical mirror.
Dim light is the bane of interferometry. In an ideal world with ideal funding, interferometers would be nuked in favor of full sized optics kilometers across, but who's going to foot the bill?
The longer the baseline, the narrower the angle you can see, hence more resolution. Keck is a good start, but the baseline is way too narrow for what people are speculating on this weblog. Maybe someday when someone finds the funding, we'll have a space based interferometer with big mirrors and a few thousand klicks in between for a baseline.
What next? Are they going to add a blue filter on one and a red filter on the other???
hmm... for fun I enjoy launching DDoS attacks against 127.87.42.5
I'm no professional, but...
Nothing we have can see extrasolar planets. The planets that have been detected thus far (AFAIK) have all been roughly the size of Jupiter or larger, and were detected indirectly by looking at the motion of the parent star. The gravitational pull between the star and its satellites causes the star to "wobble" from our perspective. That is, of course, only if the system's axis is mostly perpendicular to our viewpoint. If it's parallel, a doppler shift measurement can be used.
So while the Keck Interferometer may not provide an actual look at a planet, the increased clarity *should* allow us to detect the smaller wobbling caused by smaller orbiting masses (they estimate Earth-sized). At least, that's my interpretation of all of this.
Ok so this thing will help detect the presense of planets around suns. Here's a question:
How long do you think it will be before we can actually see big "high" quality pictures where you could make out features on the surface etc?
Is such a thing possible without actually visiting the system?
No, I did not read the f***ing article!
Abso-fucking-lutely!! :)
I couldn't agree with you more! Many of Terra's problems are because of lack of focus and 'in-fighting' - if the whole world suddenly woke up one day to a 'newscast' saying 'This is the image of another planet that has oxygen, water, and is capable of sustaining us' everything would change! Instantly! It would be like a visit from Aliens. If we could ever show people this - they would stop fighting about Coke-vs.-Pepsi and other 'in-bred-cockfighting' and start thinking for a moment; We can actually GOTO ANOTHER PLANET!
I just hope that someone is able to produce an image of some planet - not a wobble - but an image.
Now, the question is: How do we actually send anything (ourselves even) millions of light years away???!?!! This is the non-trivial part of the problem.
There are other factors 'working against the journey' so to speak.
It would take emmense propulsion power to get a craft of any reasonable mass up to near light speeds.
Technically, near-light speeds are attainable with enough propulsion force.
But, there's a lot of crap out there. Rocks and Dust, perhaps, but at those kinds of speeds any stray bits of matter in the way might as well be a brick wall, because they're coming right through the hull of any vessle that hits them.
Supposing you point your craft into the right trajectory, you then have to spend a long period of time accelerating up to the speed. You're THEN going to have to fly at that speed for several years hoping you don't plow right into something like a large rock, or a gravel cloud, or a really slow UFO.
And ONCE you've now pulled off two impossible stunts, you have to go for a third by stopping, which is going to take up just as much power as getting yourself UP to this speed (and let's not even get into the troubles associated with the attitude control of a vessel trying to come down from almost-photonic speeds.)
Then of course you have the superficial problems of keeping those silly humanoid things onboard alive for the journey. Food. Water. Environmental control. Internet Access. It's a real pain.
"Everything you know is wrong. (And stupid.)"
"Everything you know is wrong. (And stupid.)"
Moderation Totals: Wrong=2, Stupid=3, Total=5.
Hawaii=Mountains with Volcanoes West Virginia=Mountains with no Volcanoes Do the math. Which one would you trust with a multi-million dollar telescope?
You stupid bastard, you don't have no arms left. It's just a flesh wound.
A couple of people have asked questions about detecting planets, so here goes...
There are three or four popular methods for looking for planets, and the differences are quite subtle (well, they were to me).
The first method is Doppler velocity detection - the planet and star both orbit about their mutual center of gravity, a point somewhere near the center of the star as the mass of the star >> mass of the planet. The light of the planet itself is not detected, but a spectrograph analyses the stellar light to measure the velocity of the star with respect to the Earth. This is due to the Doppler effect, i.e. the starlight is slightly blue-shifted for the star coming towards us, red-shifted if it's going away.
After subtracting off the eath and sun's velocities, and taking measurements over a few years, a periodic shift is seen in the star's velocity and this is attributed to the gravitational influence of a planet. To date, this is the method that has pulled out all the detections so far.
However, the reflex motion of the star is only about 10 meters/second, and the spectrograph can only detect signals typically bigger than 3 meters/second. Also, only large planets near to the star are easily detectable.
A second method is planet transit - if the orbital plane of the planet is edge-on to the our Solar system, then the planet can move between us and the star and the starlight will dim for a few hours as the planet crosses the sun's disk - the trouble with this method is that you only see planetary systems that are edge on as viewed from Earth. To dats, only one system has been discovered with this method, and even that one was suggested by a Doppler velocity search.
The third method is a variation on interferometry called 'nulling' interferometry, and relies on the wave nature of light. AFAIK, the Keck interferometer is quite a way off achieving this sort of performance, but the trick here is that the light from the two telescopes are combined in such a way that the starlight cancels out but the starlight reflected from the planet's atmosphere is not cancelled out.
One way of thinking of this is looking at a car's headlamp and a bicycle lamp next to each other, and then looking at them through a picket fence. By moving your head laterally you can get one fencepost to block the car headlamp, and get the bicycle lamp light to shine through one of the gaps. The separation of the two telescopes then determines the effective pitch of the fenceposts.
If this super-telescope will allow us to look at earth-sized planets, will it also allow us to gain more insight into those fifty or so planets that we have already discovered? It did not sound that likely from the NASA article, more that it would simply allow us to detect these same planets more directly. Other than simply gathering information, what are we gaining from this? It does not sound like we will be learning much other than possibly locating a few more planets that we know absolutely nothing about. Someone clue me in on what the benefit is with this, beyond simply being 'BIGGER! BETTER!'
The resolving power of this combined telescope will apparently be sufficient to see earth-sized planets
Whereas the article says:
The Keck Interferometer will be able to detect planets farther from their parent stars, helping to pave the way for future interferometers in space that will look for Earth-like planets, NASA said
To find Earths (at least directly) you have to go to space Don't expect this for another 10 years or so.
Space exploration has, to some extent, died off. We spend a lot of time heaving new shiny things into orbit, but we don't seriously talk about new colonies or settling other planets.
I wonder, if this telescope spotted an earth-sized planet, suitable for life, with an earth-like atmosphere, would space research undergo a rennisance? Would the idea that "we can go there!", with a very specific there in mind, a there you could point at in the heavens, somehow inspire the human race?
Maybe the state's highest function is to grind out insoluble problems. (Zelazny, Hall of Mirrors)
Hey, they found stars in my web browser? :-)
Sorry... just found it funny...
"Giving money and power to government is like giving whiskey and car keys to teenage boys" P. J. O'Rourke