"Is life possible there?" – Interview with space scientist Michele Cirasuolo

What can the ELT do better than today's telescopes?

The largest telescopes today are no more than 8 to 10 meters in diameter. The first telescopes were only a few centimeters, later one meter, then two meters. The progress was in doubling the diameter and was achieved most of the time about every few decades. Now, with the ELT, we will achieve a fivefold magnification, from eight to almost forty meters. That's a giant leap - and it brings with it other extraordinary challenges.

What are these challenges?

The entire telescope will be as wide as a football field and twice as tall as the football stadium "Allianz Arena" in Munich. To capture the light, we need the large mirror. The larger it is, the higher the precision of the control must be, otherwise the image will be blurred. So not only do we have to build numerous mirror parts and a main structure weighing around 3,500 tons to host them, but we also have to be able to control the shape of the mirrors very precisely (down to few nanometers level) as they move to observe targets across the sky.

Can you imagine moving the Allianz Arena with nanometer precision? Including all the surfaces inside it? And on top of that, we have to take into account the atmosphere with turbulence and temperature effects that distort the image. You are probably familiar with the very sharp images from the Hubble Space Telescope. In contrast, images from telescopes on Earth larger than Hubble appear blurrier. For several years, we have therefore been working on adapting the optics.
 

How exactly does this adaptive optics work?

Inside the telescope, we have built a special mirror with a two-millimeter-thin shell. Behind this shell, we install 5,000 magnets. These so-called actuators can change the surface of the mirror thousands of times per second. So this special mirror moves like crazy, compensating for what the molecules in the atmosphere distort. For example, we are observing a star. This star must be as sharp as possible for us - as if our telescope were in space. However, it is impossible to position such a large telescope in space. But with this technology, we can practically "remove" the atmosphere and capture the light as cleanly as possible. We are de facto creating a space telescope on Earth.

And that brings with it many other problems. Ensuring precise work for science requires calculating via super-fast computers and mirror controls, both on the main structure and on the instruments - all on top of a 3,000-meter mountain in windy conditions that affect the entire system. Every single aspect of our project is challenging and everything is unique. We have to develop something new for each aspect.

Let's talk about the motivation to build this telescope: What discoveries does science hope to make with the ELT?

Almost twenty years ago, we built the 8-meter-class telescopes. It was the largest of its time. We've pushed its capabilities to the limit: Among other things, we've discovered the first exoplanets, planets outside our solar system, distant galaxies, and black holes at the center of our Milky Way. About ten years ago, we realized that we could only push our discoveries further if we made a big leap forward. A larger diameter telescope (like the ELT) is first of all much more sensitive and therefore allows to observe much fainter and more distant astronomical objects, and at the same time it provides even sharper images to detect finer details. Only in this way can we get closer to the exoplanets so that we can also characterize their atmospheres. One question is particularly exciting: Is life possible there?

How can you detect life?

It sounds crazy, but imagine a star that we know is ten light years away. Now a planet during its orbits will pass in front of this star, and some starlight passes through the atmosphere of this planet on its way to us. Then, based on the deviations of the atmosphere from our previous measurements, we can see the composition of this planet's atmosphere. The ELT is so powerful that we can use the slightest irregularity to tell us whether this atmosphere contains oxygen or carbon and makes life possible or not.

But that is only the one scientific case. In another case, we are concerned with the far end of our universe. We know that the Big Bang occurred about 13.5 billion years ago and that the universe has been expanding faster and faster ever since. But we don't know how the first galaxies were formed. For that, we need a giant telescope like the ELT. We are doing archaeology in space: What are the galaxies, stars and the contents of the universe made of? Their atoms and molecules? How were they formed? How did they evolve? How does their light of 13.5 billion years reach us?
 

Why will the telescope be located there in Chile? Wouldn't there be many other places for it?

Yes and no. The best places for telescopes are really only two or three in the world. Our place on Cerro Armazones in the Atacama Desert is the best place in the world. Then there is a volcano in Hawaii and one on La Palma. For one thing, we need conditions that are as dry as possible, like in a desert. The more humidity there is, the more it absorbs light, our images become blurry and our observations more difficult. Secondly, the telescope should be as high as possible to have less atmosphere above it, which we have to compensate again. Chile offers us a very good compromise: We have the Andes mountains, and the complete ocean humidity is below. In the Atacama Desert, it only rains about once every ten years. In addition, the wind is ideal because it is very regular and few turbulences can disturb our observations.

What is your personal view: Will we find other life on other planets with this telescope?

Probably it is difficult to find life. However, it is very likely that a planet has the conditions for life and has the right balance between oxygen and other elements - just like our Earth. That's our goal: A planet where we have water in a liquid state, as well as an atmosphere where breathing is possible, and where we can find plants or microbes, for example.

To have more information about the telescope and the amazing science it will deliver please visit the website: elt.eso.org

Learn more about the transport of the ELT from Italy to Chile, please also read our LOOKOUT Interview with our colleagues Paolo Orsi and Benjamin Celis.