Why do telescopes use laser guide stars?

On 26 April 2016 an event at ESO’s Paranal Observatory in Chile marked the brilliant first light for the four powerful lasers that form a crucial part of the adaptive optics systems on ESO’s Very Large Telescope. Attendees were treated to a spectacular display of cutting-edge laser technology against the majestic skies of Paranal. These are the most powerful laser guide stars ever used for astronomy and mark the first use of multiple laser guide stars at ESO. This spectacular image shows the four beams emerging from the new laser system on Unit Telescope 4 of the VLT.

Telescopes are powerful tools that allow us to observe distant objects in the universe with greater detail and clarity. One of the key components of a telescope is the primary mirror, which is used to collect and focus light from distant objects. However, the accuracy of the telescope’s observations can be affected by various factors, including atmospheric conditions and the movement of the earth.

To improve the accuracy of observations, telescopes use a technique called adaptive optics. This involves using a deformable mirror to correct for distortions in the incoming light caused by atmospheric turbulence. However, in order to correct for these distortions, the telescope needs to be able to measure them.

This is where laser guide stars come in. Laser guide stars are artificial stars created by shining a laser beam into the atmosphere. The laser beam ionizes the atoms in the atmosphere, creating a bright, artificial star that can be used as a reference point for the telescope’s adaptive optics system.

The laser guide star is used to measure the distortions in the incoming light caused by atmospheric turbulence. The telescope’s computer then uses this information to adjust the deformable mirror, correcting for these distortions and improving the accuracy of the telescope’s observations.

Laser guide stars are particularly useful for telescopes located at high altitudes, where the atmosphere is thin and the natural stars are faint. By creating a bright, artificial star at a specific location in the sky, the telescope can use the laser guide star to improve its accuracy even in these challenging conditions.

In conclusion, telescopes use laser guide stars to improve the accuracy of their observations by using them as reference points for their adaptive optics systems. These artificial stars allow the telescope to correct for distortions caused by atmospheric turbulence, resulting in clearer and more detailed images of distant objects in the universe.

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