In the last year, the exoplanets with the best conditions to be habitable have been discovered. ESO and its director have been behind these findings.

Tim de Zeeuw, during his visit to Madrid.

The European Southern Observatory (ESO) is a complex of telescopes located in the Atacama desert, Chile. In the last year they have been protagonists for having discovered the Proxima b exoplanets and the TRAPPIST-1 system, until now the main candidates to be able to host life outside our planet. The ESO director, Tim de Zeeuw from the Netherlands, was in Madrid this week to give a conference at the BBVA Foundation, where he explained the challenges of finding a new planet to live in and the scientific challenges that arise along the way.

NASA recently published a new study that warns that the atmosphere of these discovered planets could lose too much oxygen to be truly habitable. Are hopes beginning to fade or does it enter into expected?

I would look at it on the bright side, after the discovery of Proxima b last year, in which an ESO telescope discovered that the closest red dwarf has a rocky planet in what could be a habitable zone with a planet with fields. magnetic and all that, then came the other discovery, that of the seven planets of the TRAPPIST-1 system, seven rocky planets. If several of them are in a potentially habitable zone and three of them can contain liquid water, it does not prove that it will be a ‘second Earth’ but it is a necessary condition, since we do not know how to create life without liquid water. It is normal for people to look for what else is necessary to be able to live, this time it seems that it will not be as simple as it seems, but this is how science works.

Is it too early yet?

Every time we discover a new planet, we get closer to the goal that we really pursue. It’s obvious, even within the Solar System: Mars and Venus are within the habitable zone and could have had liquid water, but we don’t know where it may have gone.

You may have gotten used to it, but it is incredible that we are able to know the composition of the atmosphere of a planet that is billions of miles away. Do you still have that sense of wonder?

Yes. In the end, they are precision measurements and, in most cases, it works with what we call planets in transition. There is the star, there is the planet that revolves around it and that, for a moment, passes in front of the star turning off its light a little, the planet blocks part of the light. So if you take a spectrum with and without the planet in front of the star, the differences are very small. That light is passing through the planet’s atmosphere and the elements in that atmosphere give themselves away. The concept is not complicated, but measuring these elements is because the signal is very small. It is impressive that we are able to do those calculations, yes, and determine if an atmosphere contains ozone or methane.

You began by investigating why some galaxies are elliptical and others are not. Does the shape of a galaxy give clues as to what may be inside?

What we were trying to do, in general, in astronomy, was to use elsewhere the laws of physics that we have tested and developed on Earth. Although we cannot fly to these galaxies, we at least assume that the same laws govern there. Thus we see that the Milky Way has its stars rotating in a disk, that there is a center defined by the gravity of all orbiting bodies. In other parts very confused galaxies are seen, not in a spiral but with beautiful symmetrical structures, we cannot always study the light that comes from these stars, sometimes it is very difficult due to their structures, or because all the stars move in the same gravitational field, how can that galaxy be stable?

If we can know so much about an exoplanet, applied to our own galaxy it must be milk, right?

In our galaxy and in other nearby ones, we can not only measure movement, but by looking at spectral lines, we can also study the colors or a precise composition of stellar atmospheres, not only that of planets, but also that of suns. Are there many metals or not so much? In the Milky Way we can observe, for example, that there are a number of stars that are more or less in the same orbit with the same chemical composition, and others that trace another orbit and are composed in a different way, and that means that they have other parents. It’s very exciting, and if I think back to the days when I was a student, technology has changed so much that it seems almost science fiction to me.

Before telescopes were named as a tribute to famous astronomers, for example Hubble, now you call yours a Very Large Telescope or Extremely Large Telescope. How do these fashions work?

A number of telescopes in the US ended up having a name, usually after someone famous who helped build it died, then changed when the James Webb Space Telescope, named after the NASA administrator. ESO does not usually name its telescopes after people’s names, we called our telescope “the 3.6 meter” or “the new technology”. Then the Very Large Telescope arrived, which has 8.2-meter mirrors, and in reality the four telescopes of which it is composed have names from the Mapuche language, but nobody uses them. I like the name, because it is very boring. The next is going to be the Extremely Large Telescope, in part because it will follow the same boring tradition. [Risas]

Someone once asked me the same question that you have asked me, it was Barbara, the daughter of Albert Broccoli, who was the director of the production company that makes the James Bond films. This was in 2008, when they came to Bern to shoot Quantum of Solace and she said, “Tim, why do you give these boring names to telescopes?” and I said “well Barbara, I would love to call it the James Bond Telescope” and she said “no, no, no!” because I knew if I did that, they would have to pay for it. I don’t know, I’m quite neutral in that regard and, what’s more, I prefer to continue with this very unexciting tradition of ours.