Chile: the world’s largest telescope is a little closer to the stars

Chile: the world's largest telescope is a little closer to the stars

At the construction site of the Extremely Large Telescope (ELT), on Mount Cerro Armazones, in the Atacama Desert, about 1,150 km north of Santiago, June 21, 2022 Martin BERNETTI

The Extremely Large Telescope (ELT), the most powerful optical instrument ever built that will dramatically increase astronomers’ observing capabilities, is slowly emerging from the ground in northern Chile, one of the best places for stargazing.

This new “eye in the sky”, which will be added from 2027 to the powerful observation instruments that are already in service in the Atacama Desert, will allow the current observation capacity to be multiplied by 5,000, and point the view hitherto unknown places to answer still open questions about the origins of the Universe.

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

“Astronomy always works at the edge of technology, at the edge of detection, at the edge of everything these wonderful instruments can provide,” he says.

Current observation instruments, such as the Very Large Telescope (VLT) -the most powerful instrument currently in operation- and ALMA, the world’s largest radio telescope, both located in northern Chile, are capable of answering the questions that were raised scientists three decades ago.

But the limits 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 Armazones, about twenty kilometers from the VLT. ESO property in the middle of the desert.

The ELT, whose construction began in 2017, will consist of a primary mirror 39 meters in diameter, made up 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 laterally to allow night observations.

“It is an enormous technological feat to be able to have the necessary levels of precision to be able to use these telescopes to the maximum (…), something that pushes back the barriers of technology”, enthuses Luis Chavarria.

– “Image 15 times sharper” –

The construction cost of the huge 2,800-tonne complex is estimated at 1.3 billion euros.

The “major civil engineering works” phase is currently 40% complete, with the construction of the perimeter wall that supports the dome that will support the mirror panel.

“The ELT is the evolution of the VLT (…) Obviously it is a completely different scale to anything that has been done before, so it has very different (technological) requirements”, hence the time required for the work, Guido Veccia, site manager, told AFP.

Today’s optical telescopes, with a diameter of 8 to 10 meters, have made it possible above all to discover exoplanets, those planets in orbit around other stars where the search for traces of life is concentrated.

But to deepen their knowledge, more precise observation instruments are needed, and therefore larger ones, capable of collecting a greater amount of light.

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

“This is a project for the future that will allow us to reach other distances in the Universe,” says Susy Solís, geologist and technical assistant for the construction of the ELT.

The climatic characteristics of the Atacama Desert and its arid climate, which allows a very high proportion (90%) of the nights of the year to be observed in a perfectly clear sky, make it a particularly suitable place for astronomical observations.

One of its final objectives will be, according to ESO, 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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