As our loyal readers may recall, a few months ago we stopped by Lick Observatory to see some really big and impressive telescopes. These big machines are so powerful that they actually able to look back in time - truly amazing. This video shows the Keck Observatory on Hawaii in operation.
Of particular interest is the laser beams that you see coming out of the telescopes. Normally you think of a telescope gathering light, not creating it.. but modern telescopes actually shine lasers into the sky.
It wasn't that long ago astronomers thought that land based telescopes would never be as useful as space based ones because they have to look through the atmosphere. The air around us has a tendency to cause distortion as the turbulence of different temperatures and motions of air masses cause the light to refract or bend slightly. At very high magnification, these effects are exaggerated to the point that the images are often unusable. Some bright folks at Lawrence Livermore National Laboratory invented something called the laser guide star - the laser beams you see in the video. These super powerful lasers excite the sodium atoms in the upper levels of the atmosphere and create a bright spot at the very edge of our atmosphere. With some fancy computers and something called adaptive optics, they are able to observe the artificial star made with the laser and see how much it is affected by the atmosphere. They use this information to correct their images for whatever distortion the atmosphere may have created. Cool stuff.