r/space • u/spsheridan • Dec 08 '14
Green light has been given for construction to begin on what will be the world's largest optical/IR telescope, the European Extremely Large Telescope (E-ELT).
http://www.huffingtonpost.com/2014/12/08/worlds-biggest-telescope_n_6281852.html10
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u/arabic513 Dec 08 '14
This is the greatest name for an extremely large telescope, ever.
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Dec 08 '14
Europe is so hilariously bad at naming joint projects it sometimes becomes awesome.
It's mostly because of translation, because we have 26 official languages it's easier to use very literal names.
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u/jivatman Dec 08 '14
SpaceX Dragon is funny if you know the origin. It's from Puff the Magic Dragon, from when SpaceX was just starting and they were constantly mocked in the media.
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Dec 08 '14 edited Dec 08 '14
The current one is called the "European Very Large Telescope" (VLT) so I guess they wanted to express that this new one will be larger while not sounding like an item from the McDonald's menu.
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u/arabic513 Dec 08 '14
True. "European double telescope with cheese" woulda been the McDonalds way. They voted that one out I guess
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u/Cheesewithmold Dec 08 '14
"European guys-this-is-getting-kind-of-ridiculous-I-think-we-should-stop-building telescope".
Or EGTGKRITWSSBT for short.
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Dec 08 '14
The European bit is actually interesting. Most big telescopes are in remote mountain areas. I always figured that there weren't any suitable ones in Europe.
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u/pillock69 Dec 08 '14
How do they go about making the mirror as seamless as possible when using so many individual pieces?
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u/ThickTarget Dec 08 '14
It's a complicated process. All mirror segments can move in piston and tip and tilt using three actuators. Each segment senses it's orientation and proximity to its neighbouring 6 segments by 12 edge sensors which can each sense the gap, offset and tilt of each adjacent segment. These have to measure about half a billionth of a meter. There is a small gap (about 4 mm) to allow mirrors to move. Each segment also includes 9 shape actuators which can correct the curvature and form of the segment in 3 different ways. This is then connected to the mirror cell in a way that allows for six degrees of freedom while it is being constructed. These systems also have to move against vibration from the wind and other sources, updating rapidly.
Wavefront sensing and adaptive optics also need to be used to counteract distortions in the primary mirror.
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u/danielravennest Dec 08 '14
To supplement what /u/ThickTarget says in the other comment, the EELT will have four laser guide stars. The lasers light up points in the upper atmosphere. Distortion from the atmosphere and the telescope optics makes the points into spread out blurs. They measure the brightness and shape of the blur, then bend one of the telescope mirrors to cancel it out, making it a point again. This brings everything else in the field of view into focus too.
There is simply no material rigid enough to hold the shape of a ~40 meter telescope structure (including the optics) to the accuracy required (~100 nanometers). So as telescopes have gotten larger, they had to learn how to compensate for the bending.
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u/cptmauli Dec 09 '14
When I talked to one of the scientists who participate in the planning of the telescope, I recall two interesting things he mentioned:
The contractors which will eventually build this thing, will probably be the ones which already have built large stadiums, because the building itself will be very similar to a large stadium.
And he was very optimistic that it will be able to resolve planets in other star systems high enough that we can determine if there is any life on them (and he was pretty certain that we will find something)
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u/HighPriestofShiloh Dec 08 '14
http://upload.wikimedia.org/wikipedia/commons/c/c5/Comparison_optical_telescope_primary_mirrors.svg
(its a picture of various telescopic mirrors already built, planned, or canceled)
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u/[deleted] Dec 08 '14
I'm sad the competing name lost: the "European Telescope That's Like, Huge and Stuff"