A coffee with… René Doyon | The hunt for extraterrestrial life gets complicated

Are we alone in the universe ? Among the fundamental questions that haunt human beings, it is certainly one of the most intriguing (tied with the future of the ménage à trois among Habs goalkeepers).

René Doyon devotes his career to trying to answer them. This professor from the University of Montreal is director of the Trottier Institute for Research on Exoplanets (iREx), a group of around sixty researchers and students driven by a mission: to discover new worlds beyond the solar system and check if they support life.

For more than two years, hunters for extraterrestrial life have been able to count on the formidable space telescope James Webb, which searches the cosmos with unparalleled precision. I wanted to go to the news. Are the researchers on the right tracks? Or is the quest proving more difficult than expected?

“It’s the second option. And, honestly, I’m not surprised. Reality always catches up with us. It’s always more complicated than you think! », replies René Doyon with a smile.

While I endure some disappointment, the researcher attacks a piece of cherry pie, accompanying it with a sip of cappuccino. He arranged to meet me at Caffè Italia in Montreal, near his home.

I obviously did not expect to emerge from our meeting with an international news story and an article titled “Extraterrestrial life confirmed!” “. But I hoped that Professor Doyon would entertain the possibility of a discovery in the not-so-distant horizon. This is not the case.

“When we created iREx, I said that we were a few decades away from finding a biosignature. And it’s been almost a decade. So it remains consistent! », he tells me.

Looking at the researcher’s eyes shining behind his glasses, I understand that he is not in the least bit daunted by the difficulties that face his quest. And I’m going to have a great time listening to it.

Hunting for extraterrestrial life as practiced by René Doyon and his collaborators is much more complex than looking through a telescope hoping to come across green men.

“It’s tricky, what we’re trying to do,” he reminds me.

First step: discover an exoplanet, a planet orbiting a star other than the Sun. This is achieved by capturing the small drop in brightness that occurs when a planet passes in front of its star, hiding part of its light.

In this regard, hunting is prolific. Since the first detection of an exoplanet in 1995, researchers have identified around 5,000.

The problem is that the vast majority of them are not very conducive to life, at least in a form as we know it on Earth. They are either too close or too far from their star for water to be found there in liquid form.

René Doyon and his group focus their research on small, rocky planets similar to Earth. The researcher says he has three targets in particular in the short and medium term: an exoplanet called LHS 1140b, as well as two planets located in the habitable zone of the star Trappist-1.

“They will keep me very busy over the next few years,” he says.

When an exoplanet seems suitable for life, the second challenge arises: checking whether it is surrounded by an atmosphere, then analyzing its composition.

It’s anything but obvious.

“The atmosphere is a few tens of kilometers thick and the planet is located several tens of light years from Earth,” explains René Doyon.

This atmosphere causes tiny variations in the star’s brightness, which researchers try to capture. “It’s like trying to detect at night the passage of a firefly in front of the equivalent of two car headlights… on the high ground,” he compares.

The researchers’ hope is to detect a “biosignature” in these atmospheres – a proportion of oxygen, carbon dioxide or methane which would betray the presence of life.

The telescope James Webb, which floats in space 1.5 million kilometers from Earth, is best placed to detect these atmospheres. Except that the task turns out to be more complex than expected.

“The results that reach us are deduced from very complex data,” says René Doyon. Even before interpreting them, we do not completely agree on the results. There’s a lot to learn about how to extract the data, but I’m confident we’ll get there. »

Another difficulty: James Webb showed that the presence of spots on the surface of certain stars can generate “ghost signals” that can lead people to believe that the planets orbiting around them have atmospheres… when this is not the case.

The researcher has just requested observation time on James Webb in order to clarify this. But this time is fiercely debated among the planet’s scientists: barely one request in seven will be accepted for the next cycle of observations.

René Doyon does not know when we will be able to detect life elsewhere in the Universe. But he has doubts about how it will play out. A team will describe the composition of the atmosphere of an exoplanet which will suggest the possibility of life.

“It’s going to be controversial. There won’t be the word biological in the title – that much you can be sure of. It will be mentioned in the scientific article, but it is sure that it will be debated,” he predicts.

“The way we will convince ourselves of this is through a convergence on the part of theorists who will come to say that life is the most plausible explanation,” he says.

So forget about encounters of the third type. The exoplanets are too far away to go there. Even sending signals there would take decades at best. There is also nothing to say that these will be forms of intelligent life. Even simple bacteria would arouse enthusiasm.

Another possibility is that those looking for life within the solar system itself are outpacing exoplanet hunters. Europa and Enceladus, moons of Jupiter and Saturn respectively, are currently the candidates attracting the most interest.

In any case, René Doyon is convinced that there is indeed life elsewhere in the Universe.

“We know that the chemical elements that allowed life are present elsewhere,” he says. The ingredients are there, you just need the right conditions. Thinking that we are alone, there is something religious about that. I have a lot of trouble imagining that. »