Very Large Telescope

The Very Large Telescope is in Chile, in South America. It sits on top of a mountain in a desert.

It is not just one telescope. There are four giant ones and four smaller ones!

The Very Large Telescope stands on top of Cerro Paranal, a mountain 2,635 meters high in the Atacama Desert of northern Chile. It is run by ESO, the European Southern Observatory.

It is made of four Unit Telescopes, each with a main mirror 8.2 meters across, and four smaller Auxiliary Telescopes, with mirrors 1.8 meters across, that can be moved from place to place.

ESO describes the VLT as a flagship facility for European ground-based astronomy and one of the world's most advanced optical telescopes. It consists of four Unit Telescopes with main mirrors 8.2 meters in diameter and four movable Auxiliary Telescopes 1.8 meters in diameter, on Cerro Paranal at 2,635 meters in the Atacama Desert.

ESO calls Paranal one of the very best astronomical observing sites in the world. On extremely clear days, it says, the 6,739-meter volcano Llullaillaco can be seen from there, 190 kilometers away on the border with Argentina.

The telescopes can join together and work like one super telescope. Then they can see tiny details far out in space.

Scientists used it to take a picture of a planet going around another star!

The telescopes can work together as one giant instrument called an interferometer. Joined up, they pick out much finer details than any one of them could alone. The big telescopes are usually used one at a time, so the four smaller movable telescopes let the interferometer work every night.

The VLT took the first picture of a planet outside our solar system, and it has tracked stars moving around the huge black hole at the center of our galaxy, the Milky Way.

Combined, the telescopes form the VLT Interferometer (VLTI), which lets astronomers resolve much finer details than the Unit or Auxiliary Telescopes alone; the longest baseline between Unit Telescopes is 130 meters, and with the Auxiliary Telescopes 140 meters. Because the Unit Telescopes are mostly used individually, the four dedicated Auxiliary Telescopes let the VLTI operate every night.

ESO lists notable firsts: the first image of a planet outside the solar system, tracking individual stars moving around the supermassive black hole at the center of the Milky Way, and observing the afterglow of the farthest known gamma-ray burst. With adaptive optics, ESO says, the VLT can make out details smaller than a DVD on the International Space Station, seen from the ground.

In this photo, four big boxy buildings stand in a row on the flat mountain top. Far away, you can see the sea and soft clouds!

This aerial photo was released by ESO in October 2015. The four tall, boxy buildings of the Unit Telescopes stand in a row on the flat mountain top, with their doors open. Small round white domes of the movable telescopes sit on the paved platform in front.

Beyond the brown desert hills lies a layer of clouds, and the Pacific Ocean stretches to the horizon under a glowing orange sky.

The photograph (released October 2015, ESO/G. Hüdepohl) is an aerial view of the Paranal platform: the four Unit Telescope enclosures in a row, the white domes of Auxiliary Telescopes on the paved platform, and further buildings, with the desert ranges, a cloud layer and the Pacific horizon beyond. ESO's caption notes that the VLT Survey Telescope is also in the view.

ESO's own description of the image calls the Paranal mountain top home to the world's most advanced ground-based facility for astronomy.