Photo of the day: The planet of the Extremely Large Telescope

At first glance, the photo below can be confusing. It may seem that this is a frame from the movie “Star Wars” and in front of us is the desert planet Tatooine and the spaceship “Millennium Falcon” taking off. But in fact, we see our Earth and the foundation of the tower, which will house the main cosmic eye of humanity — ESO’s Extremely Large Telescope (ELT).

The construction site of the ESO’s Extremely Large Telescope (ELT). Image in a spherical projection. Source: G. Hüdepohl (

The foundation of the ELT began in 2018 at the top of the Chilean Cerro Armazones mountain. When completed, the telescope will become the largest terrestrial astronomical instrument on Earth, conducting research in the optical range. Its central component is a giant rotating dome with a height of 80 m and a mass of 6,100 tons. The diameter of the dome room will be 88 m, which is comparable to the area of a football field.

The unique spherical photo of the ELT construction site was taken in January 2022 in a stereographic projection, so that the panoramic image is projected onto the plane. In the full-rotation image, it is already possible to distinguish the first outlines of a spherical dome, which will contain a huge 39-meter main mirror M1. It will consist of 798 hexagonal segments and be controlled in real time by a system of high-precision sensors that ensure constant perfect optical alignment.

Another mirror, M4, will deform at a frequency of up to 1000 times per second, compensating for the influence of atmospheric turbulence. This technique, called adaptive optics, will allow ELT to obtain incredibly clear and detailed images of celestial bodies. It is expected that the new observatory will be able to directly photograph exoplanets, study their atmospheres, observe the birth of new planetary systems, and also help measure the acceleration of the expansion of the Universe.

The photo also shows how isolated the ELT installation site is from light pollution, which is usually caused by nearby cities. The site on the top of Cerro Armazones lies at an altitude of 3000 m above sea level, there are more than 320 cloudless nights a year. This is one of the best places on the planet for observing the starry sky.

According to