The world’s largest telescope gets a little closer to the stars

The Extremely Large Telescope (ELT), the most powerful optical instrument ever built that will greatly increase the observation power of astronomers, is slowly emerging from Earth in northern Chile, one of the best places to look at the stars.

This new “eyes on the sky”, which will be added from 2027 to the powerful observing instruments already in service in the Atacama Desert, will make it possible to multiply the current observing capacity by 5,000, directing a look at what were hitherto unknown places to answer questions Still open about the origins of the universe.

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

“Astronomy is always running on the edge of technology, on the edge of discovery, and on the edge of everything these amazing tools can provide,” he says.

Current observing instruments, such as the Very Large Telescope (VLT) – the most powerful instrument currently operating – and ALMA, the world’s largest radio telescope, both located in northern Chile, are able to answer the questions scientists have been asking themselves. Three decades ago.

But the limits of knowledge slipped, forcing the construction of more efficient instruments, such as the ELT, which will be installed at an altitude of more than 3,000 meters on the Armazones Hill, about twenty kilometers from the VLT. Owned by ESO in the middle of the desert.

The ELT, whose construction began in 2017, will consist of a basic mirror with a diameter of 39 meters, made up of 798 small hexagonal mirrors. It will be located in a huge hemispherical dome with a diameter of 85 meters and a height of 74 meters above the ground. Two circular doors will open sideways to allow for nighttime observation.

“It’s a huge technical achievement to be able to get the levels of resolution needed to be able to use these telescopes to the fullest extent (…), something that pushes back technology barriers,” Luis Chavarria is excited.

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

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

“ELT is an evolution of VLT (…) it is clearly a very different scale than anything that has been done before, so it has very different (technological) requirements” hence the time required to act, site manager Guido Veccia, AFP .

Existing optical telescopes, with a diameter of 8-10 meters, made it possible, above all, for scientists to discover exoplanets, these planets orbit other stars where the search for traces of life is focused.

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

With a diameter of 39 meters, the ELT will collect 15 times more light than the optical telescopes in operation today and will provide images 15 times sharper than those found in the Hubble Space Telescope, according to ESO, the intergovernmental organization for astronomy in Europe, funded annually to the tune of 198 million euros by 16 European member states.

“This is a project for the future that will enable us to reach further distances in the universe,” notes Susie Solis, geologist and technical assistant for ELT Building.

The climatic characteristics of the Atacama Desert and its dry weather, which allow observations in absolutely clear skies, make it a particularly suitable place for astronomical observations.

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