How Do Lasers Work in Telescopes to Capture Images of the Universe?

[pvk21]

Well I was watching this documentary.there was reference to laser telescope.it use laser to get images of universe.I know the basic principle.it shoots out laser is space and get images from reflected light.but is that lasers really powerful enough to get images of objects which are far in the universe?

 

[Bandersnatch]

it shoots out laser is space and get images from reflected light.

I don't think that's what it is. You're probably thinking of this:
http://en.wikipedia.org/wiki/Laser_guide_star
Which uses a laser to help calibrate the optics.

You can't really use lasers like what you described, as it's impossible to maintain a tight, collimated beam over large distances, impossible to get a reflected beam that gets back to you without a dedicated mirror (like with the Lunar Ranging experiment), and most importantly, impossible to wait a number of years for your beam to get to the target, bounce back and hit the aperture of your telescope. All you have is a night.

 

[pvk21]

Ohh.its much complicated than i saw it in documentary.

 

[mfb]

You can't really use lasers like what you described, as it's impossible to maintain a tight, collimated beam over large distances, impossible to get a reflected beam that gets back to you without a dedicated mirror (like with the Lunar Ranging experiment), and most importantly, impossible to wait a number of years for your beam to get to the target, bounce back and hit the aperture of your telescope. All you have is a night.

A small but relevant fraction of the photons in lunar laser ranging comes from the lunar surface around the retroreflectors. Not with such a nice timing as the surface is not completely flat, but I guess it could be possible to do lunar ranging without retroreflectors today.

Apart from that special application: yeah, laser guide stars.