News interview: Didier Queloz: "This telescope is a sublime intellectual gesture"

Didier Queloz: "This telescope is a sublime intellectual gesture"

For the astrophysicist and Nobel Prize winner Didier Queloz, co-author with Michel Mayor of the first discovery of an exoplanet, the James Webb Telescope is a new window on the universe which will allow perhaps revolutionary discoveries.

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- Relieved that the launch and then the high-risk deployment of this space telescope went perfectly? - Didier Queloz: Yes, because operations of such complexity inevitably raise concerns. But so far everything is going smoothly and it's a huge satisfaction. That said, even if the most delicate stages have already passed, we still have to wait a few months before being completely certain that this instrument will work as expected. Space is a hostile environment, which tends to destroy all instruments in it.

- What are the unique advantages of the James Webb compared to previous space telescopes?- The first thing to keep in mind with this telescope is that it is designed to observe the universe in the infrared. That is, what we call “heat”. This has huge advantages. And then the sensitivity of the James Webb is much greater than that of Hubble and other space telescopes. Because it is first larger and therefore captures more light. But also because it is optimized, in particular with its gold-coated mirrors, an ideal material for transmitting infrared to instruments. In addition, we moved it as far as possible from Earth, unlike Hubble, which is very close. This distance, corresponding to three times the Earth-Moon distance, makes it possible to considerably reduce terrestrial thermal effects, effects that disturb observations.

>> Read also: How two Romands discovered an exoplanet

- Until now, we could only measure the size, mass or type of orbit of exoplanets. What more can we learn about these cousins ​​of the Earth thanks to the James Webb? - As all objects that have a colder temperature than a star emit a lot of infrared - the Earth for example - the James Webb is a ideal instrument for the study of extrasolar planets. We therefore hope to be able to observe and measure the atmospheres of these planets. Some of them, in transit in front of their star, are very interesting because we know that they are of a size comparable to the Earth and that it will be possible to highlight their atmosphere. But this will require very different atmospheres from the Earth's atmosphere, which is very thin. It will take super-atmospheres of planet-oceans, atmospheres of several hundred km. It may sound like science fiction, such planets, but it is nevertheless quite plausible. And we will also be able to observe planets forming in their protoplanetary disk.

>> Read also: Michel Mayor: "I fell into astrophysics by chance"

- You will have direct access, with your teams from ETHZ or Cambridge, to this instrument? - All scientific teams working on study objects in which this new telescope performs can hope to have access to this instrument. For the ETHZ, this is special insofar as this school participated directly in the design of certain on-board instruments. The ETHZ will therefore be privileged. But the observation time is also divided between different teams of international researchers, Swiss and European in particular, according to a process of competition. Teams with privileged access to certain objects of study will be entitled to observation time with the James Webb. For example, our international team which, with Belgian colleagues, discovered the famous Trappist planetary system will have the right to take advantage of this new telescope. These are planets orbiting around very small stars. We believe that one of these exoplanets has a very large atmosphere. We will finally be able to verify if our hypothesis is true.

- Can we already say that we should not expect spectacular images with the James Webb and that its observations will be especially savored by scientists? - The James Webb is indeed not designed to produce images at high resolution due to the fact that it works in the infrared, that is to say wavelengths which cause loss of resolution given the limited size of the telescope. Hubble, whose instruments detect visible light, had made it possible to make spectacular images. But we can still expect images that will be beautiful and that will fascinate the general public, even if the shock of the Hubble images will probably not be as strong.

- On the beginning of the universe, can we hope to be fascinated by what we are going to find? - Yes, because the James Webb was initially designed for that, to observe the deep universe, at more than 10 billions of light years in the past. It was only later, when we proved the existence of planets revolving around stars other than the Sun, that we adapted it to also study observable exoplanets which are, for the most part, distant from a few tens to a few thousand light-years. But for its initial objective, purely cosmological, this telescope should make it possible to determine in particular when the first stars were lit. Today, we don't know. To find out, it was necessary to be able to observe the first galaxies. But they are extremely far from us, therefore very dim and are only visible in the infrared due to the expansion of the universe which creates a shift of light towards the infrared. This telescope should therefore allow us to determine when the first stars were born, a major question for understanding the genesis of our universe.

- Why is it so important to somehow know the date of birth of the first stars?- This will help to better understand how and how quickly the first galaxies evolved to create the ingredients of the cosmological picture from which life became possible. It all starts with a lot of hydrogen, a little helium and bits of lithium, to end up very quickly, on a cosmic time scale, with all the elements of Mendeleïev's famous table, elements which then allowed biochemistry .>> Read also: Didier Queloz: "To have the Nobel is first of all a huge emotion"

- And to fill these gaps in the knowledge of the universe, means of observation are needed? Theory is not enough? - Of course, because science is not made of theory, but of the confrontation with observation. Science needs data. We can develop the best of theories, if you can't compare it to a result, it has no value.

- These two great cosmological mysteries that are dark matter and dark energy, will this telescope allow if not to elucidate them, at least to know more? - When we suddenly have a new instrument like this telescope , we can be sure that it will allow us to have surprises. But which ones? No one can tell. So you have to keep your eyes open. The question of dark matter is interesting, because by observing the first galaxies, we will be able to know if there was already as much dark matter at the time as there is now, if it has evolved since these first ages of the universe. As for dark energy, I'm not sure we'll get a lot of new stuff as we would need to be able to observe even older times than the James Webb will have access to. But I will be the first to be happy that my pessimism is contradicted.

- Could the surprise(s) that this instrument has in store for us be such that they force us to completely change our way of mentally inscribing ourselves in the universe? - What is magnificent in science is never know when the next surprise will arrive. With Elodie, the innovative spectrograph we had developed, we never imagined that we would change astrophysics by proving the existence of planets outside the solar system. And yet that is what happened. When you have a new window on the universe, you have to expect to see something revolutionary. To see galaxies forming during the adolescence of the universe, between 300 million years and 1 billion years after the big bang, will be unheard of. Will these observations upset our cosmological models? Impossible to say. But the wonder at this unprecedented spectacle will be guaranteed.

- So is the James Webb an absolutely amazing toy? - Our species has succeeded, with this telescope, in sending an instrument of incredible complexity into space and positioning it three times further than the Moon. For me, it is a feat of a beauty comparable to the cathedrals of the Middle Ages. It is a sublime intellectual gesture on the part of a species that is unfortunately also capable of doing terrible things. This international project brought together the best minds in the world. It is the fruit of our thought and our curiosity. In our time, which tends to value the irrational, it seems very valuable to me that this kind of project exists and brings communities together around fundamental questions. Journalists, in my opinion, have a responsibility to publicize this kind of magnificent project as widely as possible.

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