"Twinkle, twinkle, little star" are words that make astronomers scowl. Twinkling happens because light headed earthward bends each time it passes through a layer of atmosphere with a different temperature than the one above. Just watch Sirius, the brightest star, as it flickers above the southwest horizon around midnight in early March (11 p.m. later in the month). It's pretty to look at but a nightmare for science: Dancing images look smeared through a telescope.
There are two solutions, and neither is easy. One is to place the instrument above the atmosphere, which is why there is a Hubble Space Telescope. The other is to use optical technology to unscramble the effects of turbulence. This approach has a huge advantage: It can coax sharper views from existing ground observatories.
