the largest telescope in the world is a little closer to the stars

The Extremely Large Telescope (ELT), the most powerful optical instrument ever built and which will dramatically increase astronomers’ observation capacity, is slowly emerging from the ground in northern Chile, one of the best places to see the stars.

This new “eye on the sky”, which will be added from 2027 to the powerful observation instruments already in use in the Atacama Desert, will make it possible to multiply by 5,000 the current observation capacity and point to a look at hitherto unknown places to answer questions that are still open about the origin of the universe.

“There are certain scientific questions that we would like to answer, and these questions lead to the need for technology to help us answer them,” Chilean astronomer Luis Chavarria, of the European Southern Observatory (ESO), told AFP, finances the construction of the ELT.

“Astronomy is always working on the edge of technology, on the edge of detection, on the edge of everything these wonderful instruments can deliver,” he says.

Current observational instruments, such as the Very Large Telescope (VLT) – the most powerful instrument currently in operation – and ALMA, the largest radio telescope in the world, both located in northern Chile, are able to answer the questions that scientists asked themselves. three decades ago.

But the boundaries of knowledge have been pushed back, forcing the construction of even more efficient instruments, such as the ELT, which will be installed at an altitude of more than 3,000 meters on the hill of the Armazones, about twenty kilometers from the VLT. , owned by ESO in the middle of the desert.

ELT, whose construction began in 2017, will consist of a primary mirror of 39 meters in diameter, consisting of 798 small hexagonal mirrors. It will be housed in a huge hemispherical dome 85 meters in diameter that will culminate 74 meters above the ground. Two rounded doors will open sideways to allow observations at night.

“It’s a huge technological feat to be able to have the precision levels needed to be able to use these telescopes to the maximum (…), something that pushes the barriers of technology back,” says Luis Chavarria enthusiastically.

– “Image 15 times sharper” –

The construction cost of the huge set of 2,800 tonnes is estimated at 1.3 billion euros.

The “major construction work” phase is currently 40% complete, with the construction of the surrounding wall supporting the dome, which will support the mirror panel.

“ELT is the development of VLT (…) It is clear that it is a completely different scale than anything that has been done before, so it has very different (technological) requirements,” hence the time required for the work, Guido Veccia, site manager, tells AFP.

Above all, the current optical telescopes with a diameter of 8 to 10 meters have made it possible for scientists to discover exoplanets, these planets in orbit around other stars, where the search for traces of life is concentrated.

But to deepen their knowledge, more accurate and therefore larger observational instruments are needed that are capable of collecting a greater amount of light.

With a diameter of 39 meters, the ELT will “collect 15 times more light than optical telescopes in operation today and will provide images 15 times sharper than the Hubble Space Telescope”, according to ESO, the Intergovernmental Organization for Astronomy in Europe. funded annually by 198 million euros by 16 European Member States.

“This is a project for the future that will enable us to reach other distances in the universe,” said Susy Solis, geologist and technical assistant for the construction of the ELT.

The climatic characteristics of the Atacama Desert and its dry weather, which allow observations in a clear sky a very high proportion (90%) of the nights of the year, make it a particularly favorable place for astronomical observations.

One of its ultimate goals, according to ESO, would be to have images “of rocky exoplanets to characterize their atmospheres and directly measure the acceleration of the expansion of the universe”.

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