Artificial stars

We are familiar with the twinkling of stars in the night sky, but did you know that this effect is due to the Earth's atmosphere? 

This twinkling is something of a nuisance to astronomers, and so they have developed a technique called adaptive optics to counteract it. The orange lasers in this image come from Yepun — the fourth Unit Telescope of ESO's Very Large Telescope. They create artificial stars that measure the blurring effects caused by Earth's atmosphere, which are then corrected by the telescope.