In 2012, humanity first captured light reflected by a terrestrial planet outside the solar system. It was called 55 Cancri e and was about 40 light years away. A robotic probe would take about 180,000 years to get there. 55 Cancri is so close to its sun that a year lasts just 18 hours. The radiation is so intense that the rock is completely molten forming a huge lava ocean at 1,700 degrees. The observations indicate that this world is a super earth with several times the mass of our planet, but less than gaseous worlds like Neptune. The most interesting thing is that, judging from the list of 4,100 exoplanets discovered to date, these super-earths are much more common than planets like ours. The strangers are us.
55 Cancri e is going to be one of the first planets whose radius is going to be measured in unprecedented detail by the European space telescope Cheops, which has just been put into orbit. This measurement may clarify for the first time if it is a truly rocky planet or if it is gaseous on the contrary. This is what Didier Queloz (Geneva, 1966), astrophysicist, scientific director of the European mission and winner of the Nobel Prize in Physics 2019 together with his mentor Michel Mayor for discovering the first exoplanet orbiting a star like the Sun, in 1995. a gas giant similar to Jupiter but with very high temperatures due to the proximity of its star. At first it also seemed a rarity almost impossible to believe, but now we know that these worlds are abundant in the vicinity of the solar system.
All these discoveries, says Queloz, are essential to begin to understand our true place within the universe and know what is necessary for life to arise in the exoplanets. A few hours before the successful launch of the Soyuz rocket that put the telescope into orbit Cheops, Queloz explains the long path of astronomical exploration that lies ahead before finding inhabited worlds. That, he warns, expecting that our civilization does not destroy itself before.
Question. What has led to the discovery of more than 4,000 extrasolar planets in just a quarter of a century?
Reply. It is a revolution in our vision of the universe. It is the continuation of the Copernican revolution that made us see that the Earth is not the center of the solar system. The discovery of exoplanets helps us now to know that ours is one among many other solar systems. The diversity of exoplanets is fascinating because nobody expected it. For obvious reasons we know our solar system very well and we had a model to explain its origin and formation that worked very well. But now we see that it cannot explain many of the planets we are discovering. We are just one system among many and now we must understand them all.
P. What kind of questions will you answer Cheops?
R. For example, now we talk about supertierras and minineptunos, two types of exoplanets, but we really don’t know what they are, nor what they are made of. Cheops It is the first mission that will address this question and increase our understanding of the true nature of these worlds. First it will measure its size, which in turn can tell us something about its structure, especially if we also know its mass, what it would tell us if we are facing a rocky world like Earth.
P. What would be the next step?
R. If the star’s light is reflected on those planets, the amount they reflect will tell us what its surface is like, whether it is gas or rock and if those rocks are dark or light. This is a great step forward that prepares us for the next. Thanks to two instruments that will start working in the coming years, the space telescope James Webb and the Extremely Large Telescope in Chile, we will be able to study the light spectrum of planetary atmospheres when they pass in front of their star. All this will clarify the history of all known solar systems.
God is a psychological concept, I don’t need it to explain the universe
P. When do you think life will be discovered in an exoplanet?
R. It is very difficult. Before clarifying it, we must answer two other questions. It is not clear that life beyond the solar system is as we know. We are the product of a specific chemistry and that chemistry led to life forms as we know, but it is possible that there are other types of chemistry that leads to other living forms. I speak nothing of anything exotic, but with the same bases, water, carbon. You have to be very cautious, I don’t think we learn anything looking for life like the one we know or even try to hear signs of extraterrestrial civilizations. If we really want to learn we must start from scratch, understand what are the fundamental elements of life.
P. How do you address that goal?
R. You have to approach the planets as a whole, understand their nature, their chemistry, their rainfall. All this helps us to elaborate a theory of the origin of life that could be applied both to the Earth and to other stars and their planets. We are far away yet. The study of exoplanets is not a new field, it is a new science. It is astrophysics, but also chemistry, biology and other disciplines. We have to start forming a new generation of exoplanet search engines that combine knowledge of astrophysics and chemistry, for example. Maybe in 50 years, in 100 years, we have the technical means and knowledge to confirm that life in the universe is everywhere.
We will not be able to reach any of these exoplanets in the next 1,000 years
P. Are you skeptical of projects like SETI that are looking for signs of extraterrestrial civilizations?
R. I’m not. But I don’t think he tells us anything about the origin of life. What it tells us is whether there is a possibility that advanced societies will survive themselves without destroying themselves. It is something very interesting. How long does it take since a civilization develops nuclear weapons until it begins to use them without causing their total destruction? We have spent 50 years. Can we continue 500 years?
P. When do you think we can reach an exoplanet?
R. We cannot reach any of these planets in the next 1,000 years. The technology to do so simply does not exist. In addition, humans are not biologically designed for that trip. Maybe we can send a robotic probe at some point, but the distances are so huge, we would have to reach such a high speed, that today this barrier cannot be broken.
P. In addition to looking for planets similar to Earth, Cheops it will allow to observe in detail very different worlds, such as 55 Cancri e.
R. We know many solar systems like that of this star, which has five planets. We call them compact supertierras systems. They are called that because the planets are extremely close to their star and it is very common to find several planets together. In the case of 55 Cancri, the planet is slightly larger than Earth. We think it is rocky. We are still not sure if it lacks atmosphere, but there are enough indications that it has already lost it and the planet is covered by an ocean of lava. The heat of its sun has melted the rocks of this planet. It is an infernal, extreme world, but we think that this type of planets is very abundant. More than half of all stars can have planets like this and the most interesting thing is that we don’t even understand how these worlds can form, how they evolve. That is why this will be one of the main objectives of Cheops.
P. One day after winning Nobel laureate Michel Mayor, he told this newspaper that God does not need to explain the universe. What do you think?
R. I think that is not science. Science is based on facts and based on them rational theories are formed that can be demonstrated. God has no fit in this, it is something that exists only within you. You have to believe in him. Science does not need you to believe in it. God is a psychological concept. I personally do not need a God to explain the universe.
We are just one solar system among many and now we must understand them all
P. When will we have the first results of Cheops?
R. If all goes well, in a couple of months we will start with the observation program. We already have a couple of clear objectives. One of them is a world that spins so fast that it is deforming, flattening. I hope that by summer we have the first scientific results.
P. How close and how far can you see this telescope?
R. We are going to look at stars that are very close, about 10 light years away, and we can reach up to 200 light years. These are our closest regions. Remember that the space telescope Kepler I looked at planets that are about 2,000 light years away. Here we are exploring our nearest neighborhood.