Great picture at APOD

Why are these people shooting a powerful laser into the center of our Galaxy?

Phil Plait explains:

The laser shoots up into the sky and excites atoms in the upper atmosphere, causing them to glow. That makes an artificial and very bright star in the sky! The telescope can then use that star to track the distortions in the atmosphere and compensate for them, allowing the images it makes to be incredibly clear and sharp.

With the laser, modern computers, and adaptive optics astronomers have solved a problem with Earth-based optical telescopes that goes back to Galileo.

Note that this is a technique for visible light observations. Space-based observatories are needed for the parts of the electromagnetic spectrum that are blocked by the Earth’s atmosphere.