World’s Largest Telescope Sees First Light Today
Lots of people are reporting today that the Great Canary Telescope (GCT), the world’s largest optical telescope, begins taking data today.
This telescope has a 10.4 meter (34.12 feet) diameter segmented mirror. While that by itself is pretty cool, the best part is that each segment can be rapidly moved via tiny actuators controlled by a computer which will changed the shape of the mirror’s surface.
Making small, rapid changes to the mirror will cancel out distortions of the image caused by the atmosphere once the photons are reflected off of the surface. The result is an image almost as clear as one taken from a telescope in space where the atmosphere is not a factor.
Changing the mirror in this way is known as adaptive optics, or AO, and is revolutionizing the usefulness of ground-based telescopes. Now we can get an image from the ground as good as can be taken in space, and at a fraction of the cost.
This is important because launching anything in space is expensive, and maintaining it is even more so. Keeping telescopes on the ground where we can get at them easy is very important for keeping costs down and doing research.
Another thing going for this telescope is its location. They built this thing on La Palma in the Canary Islands, just off the coast of Spain and Africa.
This location is one of the best in the world for telescopes, particularly infrared telescopes because the air above the islands is relatively free of water vapor. It’s very dry there and that’s a crucial component to looking at things in the infrared and near-infrared.
Looking in the infrared is hard to do from most places on Earth because water vapor in the atmosphere absorbs those wavelengths. In order to see anything in that part of the spectrum, we need to either get above the atmosphere or go to very dry places where there is little water vapor in the air.
La Palma and Mauna Kea are among the dryest places on Earth, and because they are islands, they also enjoy very stable and clear air. This is why these places are like Boardwalk and Park Place for astronomers. Everyone wants to build a telescope there.
I’ve heard it said many times that the future of astronomy is in the infrared, there is much to be learned by looking in this region. For example, the atmospheres of planets can be characterized properly, and the magnetic field of the Sun can be inferred by looking at the Zeeman effect of polarized light in this region.
Lots of groundbreaking astronomy will occur in the infrared, and I know that this telescope and many others at La Palma and Mauna Kea will do it. Space telescopes are just too expensive and, unless we use liquid mirrors, won’t be anywhere near as big.
This telescope’s going to be used for just about everything fun in astronomy. If you’re gonna spend 130m Euro (180m dollars) on something, then you’d damn well better play with it, right?
They are gonna look at distant galaxies (maybe make a new Ultra Deep Field?), study star formation, and of course, look for more Earth-like planets.
I wanna work there, where’s the human resources department?
Technorati Tags: adaptive optics, great canary telescope, infrared astronomy, telescopes
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2 opinions for World’s Largest Telescope Sees First Light Today
Brian
Jul 25, 2007 at 4:27 am
The article gives the impression that La Palma is a dry island. Fortunately for the 80,000 people that live on the island this is not correct. La Palma is actually a very green and fertile island with plenty of water for the inhabitants and their farms, banana, orange and avocado plantations etc etc.
It is the Observatory that is at a dry point on the island. At 2400 meters above sea level it is above cloud level almost all of the year. It does rain up there occassionally and there is snow for a few days each year but the air is beautifully clear and dry with little air or light polution.
Brian
http://www.islalapalma.com
Tony
Jul 25, 2007 at 9:43 am
Hi Brian,
Yes I guess it does give that impression. When I say ‘dry’ I am referring to the amount of water vapor in the atmosphere over the site of the telescope, not the climate.
Mauna Kea is also a very ‘dry’ spot and an excellent place to do infrared astronomy, but no one would try to argue that Hawai’i is not a lush and green island with lots of rainfall. The observatories there are situated high enough that is is above the clouds most of the time, like the observatory in La Palma.
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