… because I bet the Europeans have plans for a bigger one. A way bigger one.
They just released an announcement that they will fund a study to build a telescope that is so big that it has been informally dubbed the Extremely Large Telescope, or ELT:
European astronomy has received a tremendous boost with the decision from ESO’s governing body to proceed with detailed studies for the European Extremely Large Telescope. This study, with a budget of 57 million euro, will make it possible to start, in three years time, the construction of an optical/infrared telescope with a diameter around 40m that will revolutionise ground-based astronomy.
42 meters (the actual planned size) is pretty frakking big. That’s a mirror nearly 140 feet across!
To give you an idea of how ridiculously huge that is, here’s an artist’s conception of the observatory:
See those two dinky sticks and a longer dinky thing next to them in the lower left? Those are two people and a pickup truck (click the link to see some bigger images; they’re pretty nifty).
Like I said, frakking big.
The biggest optical telescope in the world is the Keck 10 meter in Hawaii (technically, it sees in infrared, and there are two of them). The ELT’s planned 42 meter mirror means it’ll have 18 times the surface area, so it can see object 18 times fainter in the same exposure as Keck. It’ll also have 4.2 times the resolution, meaning it will be able to separate out objects 1/4 the distance apart as Keck (so two stars that might be blurred together in a Keck image will be separated in the ELT image). It’s actually a bit more complicated than that, but you get the idea.
I don’t care how much it costs to build. Look at that thing! I hope they do it. That is just too cool.
December 11th, 2006 at 5:44 pm
Awesome:)! I was hoping one of these giant telescope concepts would get some funding. I hope they end up building it.
December 11th, 2006 at 5:51 pm
Will this thing have the resolution to see to the CMB wall? If I recall correctly this thing will have the resolution to pick up a few of the extra-solar planets. Way cool stuff for sure.
December 11th, 2006 at 5:58 pm
Ahhhhhhhhh………..the allure of big telescope mirrors! I know it well. Brings back memories of seeing the first casting of the 200″ Hale Telescope (Mt. Palomar) telescope mirror at the Corning Museum of Glass. Also brings back memories of visiting the University of Arizona’s Steward Observatory Mirror Lab. I was there right after they had made the first 8.4 meter mirror in 1997. And that was quite exciting and cutting edge then! So 42 meters is pretty awesome!
Phil, any idea who’s supposed to make the 42 meter mirror? The U of A? Corning Incorporated? Or perhaps someone else? That would be interesting to know.
Thanks!
Astrogirl
December 11th, 2006 at 6:04 pm
Wow. That thing is huge. HUGE! I’ve never seen a telescope, planned or unplanned, that can even come close to how freaking large this one is. It’s almost insane. The only thing that would make it cooler would be if they built it in space to replace Hubble. How ridiculous would that be?
December 11th, 2006 at 6:07 pm
I gotta couple spare .965″ eyepieces…if I brought ‘em along, ya think they’d let me try ‘em out?
December 11th, 2006 at 6:07 pm
Fantastic! If it’s built it will truly be an amazing feat and hopefully I’ll get to use it sometime in my career (I’m an astronomy student as we speak). But as to how it compares with my scope? Well scope my actually exists now and it fits in the back of my truck. Proof of its infinite superiority.
December 11th, 2006 at 6:17 pm
That picture, with the pickup for scale, reminds me a lot of the 1950s artist’s conception for the Naval Research Laboratory’s Big Ear. The Big Ear was to be a huge radio telescope, designed to listen to internal radio communications in the Soviet Union via moonbounce.
The Big Ear would have weighed as much as a WWII aircraft carrier, and would have been the largest land-based moving object ever made by humans. The shape of the dish was to be maintained by an optomechanical feedback system (no computers in the loop).
NRL actually started construction, but it proved to be an impossible task. The underground control room was turned over for use as government offices, and the special alloy structural parts were sold as scrap.
It will be interesting to see how this scope compares. The fact that this is an optical scope shows how much the technology has improved.
December 11th, 2006 at 6:27 pm
Can the Hubble still “see” better than this proposed ground based ELT? With so many telescopes working right now (earth and space based) I wonder what kind of discovery this yet-to-be built telescope will make that makes such a huge investment worthwhile. Yes, the manufacture of the mirror alone will involve superior fabrication techniques that may spin off into other scientific developments.
ELT reminds me of ELO: Electric Light Orchestra….
December 11th, 2006 at 6:50 pm
Now that’s a little tool I’d like to have in my backyard…. well, I’d need a new backyard first.
Soooo… what’s coming after Extremely large? Obnoxiously large?
December 11th, 2006 at 6:53 pm
Astrogirl Says: “Phil, any idea who’s supposed to make the 42 meter mirror? The U of A? Corning Incorporated? Or perhaps someone else?”
My thoughts exactly. Even more, how are they going to cast the blank uniformly enough, and then grind/polish it? How are they going to control horizon/zenith sag? How will they coat it? (and re-coat it periodically)
These are some of the reasons that Keck uses segmented mirrors. A few years ago “Astronomy” mag had a good article on large ’scopes and said that the idea of a single monolithic mirror is so 20th century (well, I’m paraphrasing), and that after Keck proved the technique, all future big scopes would use segmented mirrors.
- Jack
December 11th, 2006 at 6:56 pm
OK, I should have read the link before posting. I see that the design uses a huge number of segments (over 900!).
- Jack
December 11th, 2006 at 7:10 pm
I would love some time on that thing.
December 11th, 2006 at 7:24 pm
Ohh, pretty. I’d love a peak with that thing. Wonder how Jupiter or the Moon would look.
I hope this does get built. It would be a great tool in space science.
December 11th, 2006 at 7:37 pm
You know what they say about guys with big telescopes – they can show you a Big Bang!
Har, har. Hey, I just made it up, seriously.
December 11th, 2006 at 8:01 pm
“ELT reminds me of ELO: Electric Light Orchestra….”
Yes, dare I say it? Extremely Large Observ- no, I can’t, I just can’t!
December 11th, 2006 at 9:18 pm
My second thought (the first was the same inarticulate moan that most of the commentors made) was, why build such a thing inside the atmosphere? I really thought the day for optical telescopes down here had passed.
My third thought was, how will they keep it clean? I suppose there will be little robot polishers scampering all over it during daylight hours, but the image that lept to mind was of some poor Carol Burnett charwoman crawling across the mirror with a slop-bucket and rag, polishing, polishing, polishing…
December 11th, 2006 at 9:44 pm
Does anyone know if they make adaptive optical mirrors for small amatuer scopes?
December 11th, 2006 at 9:52 pm
Adaptive optics can make it so that the ’scope can have extremely good resolution, as good as Hubble’s. They already do that for the VLT, Keck, and other instruments. Do a search on adaptive optics on this blog or the main site for more.
December 11th, 2006 at 9:57 pm
I prefer OWLs to ELTs:
http://www.eso.org/projects/owl/
At least they’re still reserving the name for something truly Overwhelmingly Large!
December 11th, 2006 at 11:01 pm
Well, I’m glad that at least one person here (tacitus) knows about OWL. This 40m baby is a pretty scaled down version of OWL and is just going to be another ELT (that is a class of telescopes, not the name of a particular one…) as are the Giant Magellan, http://www.gmto.org/ and the Thirty Meter, http://www.tmt.org/
A couple of people here asked whether U of A or Corning would build the mirrors… I’m afraid I’ll have to rant slightly on that. It is a European telescope for crying out loud! This organization (The European Southern Observatory – ESO) built the VLT and VLTI http://www.hq.eso.org/outreach/ut1fl/ – the first multi (more than two)-telescope interferometer at visible wavelengths – okay, slightly infrared… Why would we have to come to the US and ask for help, when we have so much experience and expertice in cutting edge technologies and science, related to telescopes, as well as in general??? The US really isn’t the only place in the world with enough technological resources and know-how – And you don’t neccessarily find the best technology in the US. Please have a look at the world around you!
Thanks,
Regner Trampedach
P.S. Thanks Phil, for a great BLOG and a great web-site!
December 11th, 2006 at 11:36 pm
→ John McKay: I think one problem with space-based telescopes is that it is that it is difficult to get them into orbit; the space shuttle can only carry a limited-sized payload and so the apertures can’t be that large. And of course they’re more difficult to maintain, service, and so on, so ground-based telescopes still complement them.
I was sure there was a recent article in Scientific American about this, but I can’t seem to find it. If anyone knows which issue it was, I’d be much obliged.
December 11th, 2006 at 11:59 pm
How does this compare to linked, interferometry-based telescopes?
I can’t remember the details, but I remember seeing a documentary about a group of telescopes, linked together, providing a much larger “virtual” aperture. I know they’ve been doing this since forever with radio-telescopes, but this plan was for optical ’scopes. At the time the documentary I saw was shot, only the first of the ’scopes was up, and already producing good results, but the astronomers were buzzing with excitement at the thought of having an aperture of ~100 meters once everything was in place.
Did this idea not pan out in practice? Because if it did, it would surely eclipse even this monster’s resolving power.
December 12th, 2006 at 1:07 am
We really need a fleet of space scopes positioned well away from the inner solar system in all directions. Make it far enough and you can make your scope primaries from WATER ICE, and there is plenty of water out there to be had (if you go far enough). Go further and make ‘em out of frozen gas.
Giant gradient index optics might be easier to manufacture in deep space as well- if the focal ratio is long and the primary aperture very large the gradient can be so gradual as to be almost imperceptible, and so easy to make. Its the small ones with small f ratios that are hard.
What has me bugged is whether in deep space low temperatures mean that impacts might propogate cracks through the optic, resulting in its destruction.
Personally though, it might be interesting to have myriad scopes out about where Sedna is and the foci accessible from earth.
Or we could use the money on projects that need doing now and can’t wait- like saving endangered languages and lifeforms. But heck, who needs apes and whales, or Yahgan…… Stars are just so pwetty….
Jess Tauber
December 12th, 2006 at 4:42 am
OK, I’m not an astronomer and I don’t get. Somebody please explain…
Why build a multi-zillion dollar, ground-based ’scope when a space-based scope can see better, farther, faster, etc.?
It seems to me that the same money could buy a smaller space scope that can do far more. Why when we can put these into space are we still building them on the ground?
I understand from an amateur point of view (it’s cool to look at space from your backyard) but in the science community it makes no sense to me.
Anyway, they’re doing it so there must be a good reason. What is it?
December 12th, 2006 at 4:54 am
Also not an astronomer, but I’m willing to take a guess: Ground-based telescopes, as stated above, can be made much bigger than space-based ones, and thus have a higher resolving power. They can “see smaller things”. Space-based ones are smaller, but get a clearer view (although modern optical techniques can now compensate for much of the atmospheric distortion.
Space-based ’scopes have some big advantages in non-visible chunks of the spectrum. No amount of optical compensation can fix the fact that some parts of the spectrum are totally absorbed by the atmosphere. And spce-based ’scopes can be kept much cooler, making them more sensitive to e.g. infra-red.
But orbital observatories are not cheaper than land ’scopes: Launching, maintaining and upgrading the little floating buggers gets quite pricey.
So there’s pros and cons to both approaches. It seems that astronomers are making the most of these different approaches by using each type where it’s stronger.
December 12th, 2006 at 5:55 am
Grand Lunar, do not look at the Moon through a 42-metre telescope: it could seriously damage your eyes. I once observed a full moon through a 10″ Dobsonian, and it actually hurt my (dark-adapted-but-not-for-long) eyes.
Have I got my maths wrong, or will this thing be able to resolve some of the junk left on the Moon from the Apollo programme?
December 12th, 2006 at 7:41 am
Nigel Depledge says, “Have I got my maths wrong, or will this thing be able to resolve some of the junk left on the Moon from the Apollo programme?” Sadly the answer is no. I wish we could. But it is an optical impossibility from the earth. We just can’t resolve it from here. One webite that does a decent job at explaining it visually is: http://www.pa.msu.edu/people/frenchj/moon/landingsite.html
I’m sure there are plenty more, but that was a quick find. That was one of those questions in college physics classes that we all wanted to learn about in covering optics and ray diagrams.
And Nigel Depledge, you are right about the moon being too bright. The moon (and most of the planets too bright for astrophotography) are too bright through even a 10-20″ Dobsonian.
No matter what it costs, or how long it takes to build, I hope that they do build this wonderful telescope. Also hope we can get some on this order into orbit!
Astrogirl
December 12th, 2006 at 8:34 am
So when does work start on the FET?
(Frakking Enormous Telescope)
December 12th, 2006 at 9:05 am
I’m hoping that someone is thinking of how best to use the planned manned moon base for astronomy.
As for earth-based vs space-based ’scopes, I think that one of the biggest advantages to earth-based is that you can swap out the instrument packages easily. That can be something of a problem for the space-based scopes.
December 12th, 2006 at 9:58 am
Even if it proves too prohibitive it will be great to see what the engineers learn is possible.
and damn thatsa purdy telescope.
December 12th, 2006 at 10:11 am
The moon is certainly a prime location for a telescope, and I am sure astronomers are already planning what instruments they want carried up there as soon as the new moon base (sorry, outpost) has been constructed. And a polar base will allow instruments to be positioned in perpetual deep freeze (out of the sun) and out of sight of all that noisy radio interference from Earth.
Getting it all up there will be the hard part.
December 12th, 2006 at 11:19 am
Astrogirl, while that link is a great demonstration, it is the comparison for an 8″ mirror. That doesn’t particularly address the capabilities of a much larger scope (i.e. 40 m, 100 m, etc).
I recall some time back a new adaptive optic scope talking about imaging the moon to try out the adaptive optics. There was some possibility that it would see something and the best resolution.
December 12th, 2006 at 12:54 pm
It’s not going to be made of a single piece – it will be segmented (like the Kecks) with (according to the release) “906 hexagonal segments, each 1.45 m in size”.
Interferometers have high resolution, but relatively small collecting area. For an optical telescope, this would make them less useful if you just wanted to take spectra, for instance (which is what a lot of the large telescopes spend most of their time doing). They also tend to have problems with extended objects – they cannot see details larger than a certain size. If all that was wanted was resolution, then an optical interferometer might well do better than a single dish (they’re going to need some fancy AO to get anywhere near their diffraction limit – thus the five mirrors in the optical path), but if you want a huge light-bucket then a single dish is the thing to go for.
I still things “more than one hundred times more sensitive than the present-day largest optical telescopes, such as the 10-m Keck telescope” (the press release again) is pushing it somewhat though! It will have about 18 times the collecting area – where’s the other factor of 6 coming from?
It is interesting the way these things keep shrinking. OWL was 100-m, EURO-50 was 50-m, the E-ELT is now 42-m. One joke doing the rounds at the AAS in Calgary was that the acronym ‘TMT’ was chosen (for one of the US ELT projects) so that it could be scaled down from Thirty Meter Telescope to Twenty Meter Telescope without having to change the logo…
December 12th, 2006 at 2:05 pm
Irishman says, “Astrogirl, while that link is a great demonstration, it is the comparison for an 8″ mirror. That doesn’t particularly address the capabilities of a much larger scope (i.e. 40 m, 100 m, etc).”
So here you go: http://www.spacedaily.com/telescopes.html#17
The answer is that you would need a 200 meter mirror to see the flag and a 75 meter to even make out the lunar rover. It’s been awhile since I took Optics. Hope this link helps out.
Astrogirl
December 12th, 2006 at 2:30 pm
Darmok: the Scientific American, Vol. 294 Number 5, May 2006, has the article you’re remembering titled Giant Telescopes of the Future, by Roberto Gilmozzi.
December 12th, 2006 at 3:29 pm
Telescopes of Unusual Size? I don’t think they exist…
December 12th, 2006 at 9:54 pm
Adaptive optics are amazing. They have an active system on the Kecks which use a laser to generate an artificial guide stat. Well, since the telescopes are so large, the seeing can vary across the field of view. This problem will be more pronounced with larger telesopes.
In order to solve it, they are going to outfit the the Kecks with FIVE lasers each so they can do corrections for atmospheric distortions at different parts of the field! Wonder what the system would be like on a 42 meter telescope?
December 12th, 2006 at 10:14 pm
One wonders about the effect of seismic processes on a scope this large. As Doug Welch (MACHO Project astronomer) mentioned on a podcast following the earthquakes on Mauna Loa: (paraphrasing) “The best observing tends to be on top of mountains, and these mountains get there by seismic activity…” If I remember correctly the largest scopes experienced accelerations of up to (possibly in excess of) 10Gs at the top. How would a scope 42m in size withstand these levels of force? I hope this scope does get built, it would provide truly amazing levels of resolution!
December 13th, 2006 at 7:06 am
There’s an terrific book on the 200″ mirror at the Hale observatory, and the planning / politics / mechanics that went into it. Obviously, this project would dwarf the Hale mirror, but the book is WONDERFUL!
“The Perfect Machine” by Ronald Florence, at some public libraries and, of course, available online.
Kevin
December 13th, 2006 at 12:19 pm
Yes KStebleton, “The Perfect Machine” is a fine book. It has a whole lot about how the 200″ mirror of the Mt. Palomar mirror was made. That telescope was the biggest that had ever been built at the time. To test the new designs that accomidated the enormous weight of the biggest telescope mirror ever created up to that point, a prototype was made. It was 1/10th the scale model of the size that Palomar was to be made. They had to test all the new engineering before the full-scale one was made.
Wonder how they’ll test the design of the 42 meter telescope? That will be interesting to see!
December 13th, 2006 at 12:51 pm
How does one define how large a telescope is these days? Do the two Kecks, or the four VLTs count as one, since they can work together despite being housed in separate observatory domes? Is it the size of any single mirror (or parabolic surface)?
I hear Keck and VLT routinely cited as the world’s largest telescopes. But are they? The Large Binocular Telescope in Arizona has two 8.4 meter mirrors on a single alt-azimuth mount. (That counts as one telescope in my book.) The mirrors themselves are the largest-diameter monolithic telescope mirrors ever made…and given the direction technology is going (Keck-style with multiple segments), they are likely to hold that record for a long time.
Phil, can you help…what is currently the definitive largest telescope in the world? (Yeah, I work for Steward Observatory/U of A…just a little bit of pride on the line here.) Whenever people ask me the question I always have to quantify it as I’ve done above. Is it not just a simple answer anymore?
December 13th, 2006 at 1:05 pm
Eric, that’s easy: Arecibo.
December 13th, 2006 at 3:43 pm
DOH!! You got me there.
However, that answer would suggest that telescope arrays, such as the VLA, do not count as one telescope. (Though I’m not sure if all the VLA dishes add up to more surface area than Arecibo.)
Now, for the electromagnetic spectrum-impaired (that would be me), what do you consider as the largest optical telescope in the world?
December 14th, 2006 at 5:39 pm
Dear All,
An amateur astronomer myself, I have the privilege of working at the VLT (you can guees by my website). There seems to be some confusion regarding the ELT and the OWL. The thing is that ESO dropped the idea of the OWL, and replaced it by the ELT. Preliminary studies resulted in: The OWL is sooooo expensive, that it may never be built before 2070, so we will concentrate on building something that we will see on our lifespan, so we make it smaller, and we rename it as the ELT, saving the OWL name for some telescope in the future. This does not come free anyway. They (ESO) are talking about shutting down the operations on La Silla, an ESO owned observatorie, one of the biggest in Chile in domes count:
http://www.ls.eso.org
Hope this helps. Cheers from Paranal (Home to the VLT)
Alex.
December 28th, 2006 at 6:13 am
“The biggest optical telescope in the world is the Keck 10 meter”
I was under the impression that SALT (Southern African Large Telescope) is currently the biggest optical telescope in the world, at least it has the largest single primary mirror:
http://en.wikipedia.org/wiki/List_of_largest_optical_reflecting_telescopes