The first parts of the world's largest telescope are on their way to their final destination

An important stage has been reached in the construction of the world's largest telescope mirror: the telescope mirror Very large telescope (ELT). The first eighteen parts of the telescope's primary mirror have now been shipped to Chile.

After arriving in Chile, the parts will be transported to the European Southern Observatory (ESO) site in the Atacama Desert. The parts will then be boxed in preparation so they can be installed later. The telescope's primary mirror is so large that it cannot be made in one piece, and must instead be made from 798 separate pieces. With a diameter of more than 39 metres, this will eventually be the largest telescope mirror in the world.

Monster job
The construction of a telescope mirror can rightly be called a monstrous feat. For example, an entire building in central France was renovated specifically to polish only the mirror pieces. This is because the irregularities on the surface must be no more than 10 nanometers, which is less than a thousandth of the width of a human hair. To achieve this precision, Safran Riosek's executive team used a technique in which a beam of ions is passed over the cutting surface of a mirror to remove defects atom by atom. Now that the first 18 mirror pieces are on their way, the company still has 780 more to go. With a production speed of four, and soon five, mirrors per week, it will take at least three years (approximately) before all the pieces are ready for assembly. The telescope is therefore by no means cheap to build, with its final cost coming in at just over a billion euros.

Searching for a strange life
Of course, there is a good reason for all this international effort to build the largest telescope mirror ever. the sciences I actually spoke with Tim De Zeeuw, an astronomer and director general of the European Southern Observatory, in 2017. According to him, the telescope has three goals. The main goal is that this telescope mirror can better measure the atmospheric properties of Earth-like planets. Many exoplanets have been discovered in recent years. Some of these organisms appear to be quite capable of harboring life. But appearances can be deceiving, which is why scientists are looking for better ways to determine how habitable these planets are.

Look at the past
The second important reason for building a telescope mirror relates to the expectation that it can see “farther” than is currently possible. The idea is that this telescope can observe the edges of the visible universe. To show how amazing this is, these light sources are about 13 billion light-years away from Earth. This may allow us to conduct research on the first stars and galaxies that formed shortly after the Big Bang. The new telescope's precision is therefore essential: the ELT will be better able to split the light from these galaxies into the light from individual stars.

James Webb
This is not the first time that a giant mirror has been produced to study space. For example, we now have the James Webb Space Telescope, which has already been able to take many beautiful pictures of the universe. Despite this, there's still good reason to build an ELT as well, Di Zeeu explains. “Let me use Hubble as an example,” he said in 2017. the sciences. “The telescope produces beautiful, sharp images, and is not affected by atmospheric turbulence.” However, astronomers want more than just beautiful, memorable shots of distant planets. “You also want to measure the light from Earth and split it up, illuminate things a little longer, take a spectrum, and be able to say something about the composition of the matter or gas.” To do this, telescopes on Earth are needed. In this way, the ELT will complement the existing James Webb Space Telescope.

But we are still far from that. The eighteen polished mirror pieces left France last week, beginning a long journey of more than ten thousand kilometers to the ELT construction site in the Atacama Desert. The telescope will be operational at that site later this decade to meet the greatest astronomical challenges of our time and make unexpected discoveries.