A laser optics system can produce a guide star anywhere in the night sky of the southern hemisphere, thanks to work by scientists at Cerro Paranal in Chile, home of ESO’s Very Large Telescope array. The star allows astronomers to apply adaptive optics systems to their telescopes effectively cancelling out atmospheric disturbances, better known as a star’s twinkle!
The guide star is formed by a spotlight of laser light focused on a point 90 km above the Earth’s surface that causes sodium atoms at this altitude to glow yellow-orange. Despite this star being some twenty times fainter than the faintest star visible with the naked eye, it is bright enough for the telescope’s adaptive optics to measure and correct for blurring effects caused by the atmosphere. The launch of this guide star was the culmination of five years of collaborative work by a team of scientists and engineers from European Southern Observatory and the Max Planck Institutes for Extraterrestrial Physics in Garching and for Astronomy in Heidelberg, Germany.
Laser star
Image sharpness in terrestrial telescopes is severely limited by atmospheric turbulence, which makes light from objects outside the Earth’s atmosphere, planets, comets, stars, galaxies, etc, twinkle. This drawback can be overcome by using adaptive optics that compensate for the distortion. However, in order to function, adaptive optics requires a nearby reference star that has to be relatively bright, thereby limiting the area of the sky that can be surveyed. The artificial star surmounts this limitation by providing astronomers with a reference that can be aimed anywhere in the night sky.
Laser star lab
Laser star kit
Further reading
European Southern Observatory
http://www.eso.org/public/
Max-Planck-Institut für extraterrestrische Physik
http://www.mpe-garching.mpg.de/
Max Plank Institute for Astronomy
http://www.mpia.de/Public/menu_q2e.php
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