Didier Queloz: the inside story of Pegasi 51 B

For someone who believes in alien life, that climate change will wreak havoc without major societal change, and who is unfazed by the myriad discoveries yet to be made beyond our galaxy, Professor Didier Queloz is surprisingly upbeat.

Professor Queloz on hearing the news he had won the Nobel Prize. Photo: Nick Saffell

The Nobel Laureate, Cavendish Laboratory Professor and Trinity Fellow seems to fizz with energy and enthusiasm – particularly when it comes to teaching students and talking to the public about science.

Didier Queloz moved from the University of Geneva to Cambridge in 2013 where he is now Professor of Physics at the Cavendish Laboratory. He shared the 2019 Nobel Prize in Physics with Professor James Peebles and Professor Michael Mayor for their pioneering advances in physical cosmology and for discovering an exoplanet.

At the time, says Professor Queloz, ‘exoplanet research was a very small field. I think there were about 50 of us and we were seen as weirdos.’ Last year’s Nobel Prize changed all that. Professor Queloz is still getting used to his rock star status in the scientific world.

‘I have to sign autographs and there is a lot of interest and a lot of students want to talk to me,’ he says. ‘I am still a student of the Nobel Laureate world.’ The other Nobel effects are more subtle with, for example, scientists in other fields who might have been skeptical, now take exoplanet research seriously.

Astronomers had speculated about the existence of these distant worlds but until Professors Queloz and Mayor’s discovery, no planet other than those orbiting the sun had been found.

Professor Queloz himself took some convincing when he first noticed something unusual in his results. ‘At that time I didn’t think at all it was a planet, I thought I had just found something that was wrong, and I had better sort it out. After some time when it continues to be wrong …you think maybe it is not wrong at all, maybe it is a planet.’

photo: Silas Sanders

Detecting planets is ‘quite difficult’, says Professor Queloz without irony, because of their proximity to bright stars. But new instrumentation, including the development of spectrographs by the Professor himself, have improved the precision of the Doppler technique.

‘When a planet is orbiting its star, the star is wobbling, changing location a little bit and what we can do is track the change of the speed of the star. The speed is quite easy to measure because we can use the Doppler effect, which is the slight change in the wavelength of the colour of the stars.’

Then there are eclipses, when a planet travels in front of its star, creating a shadow. ‘From this we can learn quite a lot about the mass of planet and we can even learn something about the atmosphere on some of these planets,’ he said.

A fraction of the exoplanets Professor Queloz and others have discovered ‘kind of look like the Earth but we have not found yet what is called an Earth twin – that is a planet that is exactly the mass, the size and the orbit of the Earth.’

To non-scientists this might sound complicated and distant, literally and metaphorically, to our everyday lives. Compared to Earth, Pegasi 51 B, is very hot – more than 1000 Centigrade – very heavy and 50.9 light years away (a light year is the distance light travels in a year – about six trillion miles).

But says Professor Queloz compared to scientist working on the Higgs Bosun or quarks, for example, engaging the public is easy. ‘Talking about origin of life and solar systems, it’s very profound. By its essence it is interesting.’

Telling this story is fun, refreshing – and important, he says.

‘As a scientist if you don’t give to society what is your purpose? We have a very privileged position and we should definitely engage with society. I think science does not engage enough. Society tends to be a bit skeptical and often people don’t understand what scientists do, so I think we should do a better job here. Every scientist should have this activity as part of their portfolio.’

Engaging with students and the public in Cambridge is made easy by its small size, public events series and College traditions.

Cambridge attracts the best of the best. You have clever people everywhere in the world but here they are more intense because they are together. You are exposed to so much brainpower, going to College and meeting colleagues for lunch or a good chat over a nice coffee, that is very special, it’s unique with this kind of city.

It was just such a chat with Professor John Sutherland, at the MRC Laboratory of Molecular Biology, that sparked a collaborative research project to investigate the chemical origins of life.

‘We are back to something very simple: the origin of the universe. What the universe is made of that is still something about which there are a lot of unknowns. We don’t know what dark matter is for example. Then there is the origin of the galaxy – why do have galaxies and stars and planets? We don’t know. Then there is life. It’s all about understanding where we sit, from the farther away, the biggest, to the microscopic, which is life.’

You can watch Professor Queloz’s Nobel Prize Lecture at Trinity College, 26 February 2020.

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