Night after night in the dry air of Chile's Atacama Desert, fine dust and pollutants settle on the aluminum coating of the mirrors belonging to the Very Large Telescope, part of the European Southern Observatory (ESO). This process degrades the mirrors' reflectivity and clarity over time, so technicians regularly recoat and polish them to ensure the best precision.
What is it?
Keeping a 25-ton (23 metric tons) mirror in perfect condition is a delicate process. For light cleaning, technicians sometimes spray frozen carbon monoxide across the surface to dislodge the dust. Eventually, however, the thin aluminum coating has to be replaced.
After the mirror is painstakingly removed from its mount, engineers check for particles and chemically strip away the old layer of aluminum before adding a shiny new layer just 80 nanometers thick, a thousand times thinner than a human hair.
Where is it?
This image was taken at the VLT basecamp at the foot of Cerro Paranal.
Why is it amazing?
The VLT has delivered some of the most detailed observations of our universe. From imaging exoplanets to probing the environments around supermassive black holes at the centers of galaxies, the VLT has pushed the limits of what ground-based telescopes can achieve.
Want to learn more?
You can read more about the Very Large Telescope and other telescopes in Chile.
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