Towards Milky Ways Centre
On 6 August 2010, the ESO Photo Ambassador Yuri Beletsky
took this photograph of the Astronomical Observatory Paranal
in Chile, where a group of astronomers were observing the center of the Milky Way using one of the four optical telescopes (called " Yepun ") of the Very Large Telescope
The laser beam of Yepun
crosses the southern sky and creates an artificial star at an altitude of 90 km , the height of the Earth's mesosphere . This Laser Guide Star (LGS ) is part of the VLT adaptive optical system and is used as a reference to correct the blur effect of the atmosphere on images.
The color of the laser is precisely calibrated to energize a layer of sodium atoms found in one of the upper layers of the atmosphere - one can recognize the familiar color of the street lamps , which use sodium lamps. It is thought that this layer of sodium atoms is a residue left by meteorites entered the Earth's atmosphere.
When excited by light emitted by the laser, the atoms begin to glow, forming a small bright spot that can be used as artificial star of reference by adaptive optics. Using this technique, atronomers can get more precise observation. For example, when you look at the center of the Milky Way, researchers can better monitor the galactic center, where a supermassive black hole, surrounded at a short distance from the orbiting stars, swallows gas and dust .
Taken by a panoramic lens, this photo covers the sky at about 180°. Source
: http://commons.wikimedia.org/wiki/File:Laser_Towards_Milky_Ways_Centre.jpg #Milky_way #space
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