If you follow astronomical technology at all, you know that telescopes are getting bigger. The largest mirrors in use now are between 8 and 10 metres in diameter, and three telescopes in the 30- to 40-metre range are either being planned or under construction.
But making a mirror bigger doesn't solve the main problem terrestrial astronomers face, namely the distortions caused by the Earth's atmosphere. You can solve this by putting your telescope in space (the Hubble Space Telescope), but we can't currently orbit really big mirrors.
Astronomers, ever inventive, have found a way around that, by bending the mirrors of their telescopes or their instruments in real time to compensate for the distortion. They shoot lasers into the atmosphere to create a guide star and use that and fast, sophisticated computer programs to figure out how to deform the mirror to reverse the atmospheric distortion.
One of the best explanations of how this works that I've found, is this Twitter thread on the People of Space account.
In order to take full advantage of the fact that large mirrors can resolve finer details we must therefore find a way to counteract atmospheric turbulence. We can do this with a technique called adaptive optics. That's like the best prescription glasses you could wish for :-)
This is the gist of it: by taking 1000s of images per second of a star we can measure how it’s deformed at any instant. We then make the light of that star bounce off a small deformable mirror whose shape changes very rapidly to precisely counteract these distortions.
The thread is also well illustrated, worth looking at just for the pictures.
Looks like a Star Wars battle station, doesn't it?
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