Big telescopes feature some of the finest and most precise mirrors in the world. So when one gets dirty, what happens?
What is it?
The European Southern Observatory (ESO) operates some of the most powerful telescopes in the world. Established in 1962 by 16 countries across the globe, the ESO is a hub for astronomers looking to uncover the mysteries of our universe.
The observatory hosts four extremely powerful telescopes, which are used to survey the farthest corners of our galaxy, studying a variety of space structures and phenomena, from black holes to stars to asteroids.
Where is it?
While ESO's headquarters are in Garching, Germany, its four telescopes all sit in the Atacama Desert in Chile (hence the "Southern" part of ESO name). This photo was taken at the La Silla Observatory in Chile.
Why is it amazing?
ESO hosts four different telescopes in Chile: the Very Large Telescope (VLT), the Atacama Large Millimeter/submillimeter Array (ALMA), the Extremely Large Telescope (ELT, which is currently being built), and La Silla, the subject of this photo.
While all four facilities focus on solving the mysteries of space, La Silla is centered specifically on finding exoplanets. Its two telescopes, the 11.5-foot (3.5 meters) New Technology Telescope (NTT) and the 11.8-foot (3.6 m) telescope both use ultraprecise mirrors to bounce images back from space for analysis.
In this photo, staff at La Silla work to clean the 11.8-foot telescope's primary mirror. As the mirror was made with fused silica, it takes a delicate process to restore it to a clean, ultraprecise state. Staff have to chemically strip the mirror's old aluminum coating before rinsing it with demineralized water.
The mirror then goes into a special vacuum chamber, where aluminum is deposited in a new layer thinner than the width of a human hair. If the aluminum layer were too thick or uneven, the mirror would lose its precision and with it, data from space.
Want to learn more?
You can read more about ESO's many telescopes and their work looking at exoplanets and other structures within our universe.
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