This year's Nobel Prize

10 October 2019

As James Peebles, Michel Mayor and Didier Queloz are announced as the winners of this year’s Nobel Prize in physics, we look at the significance of their work.

The 2019 Nobel Prize in physics was awarded to James Peebles for his theoretical discoveries in physical cosmology and to Michel Mayor and Didier Queloz for their discovery of an exoplanet orbiting a solar-type star.

David Alonso, Associate Professor in Astrophysics at Oxford, shines a light on the significance of Professor James Peeble’s work: ‘It is fantastic to have cosmology recognised and profiled with the awarding of the Nobel Prize in physics to James Peeble. His work kick-started a large number of lines of research in cosmology: among other things, he played a role in predicting the Cosmic Microwave Background radiation, the first light emitted after the Big Bang, which has proven to be the most precise observable to determine the basic components that make up our universe. He also contributed to the theory of Big-Bang nucleosynthesis, which describes how the first atomic nuclei were produced in the early universe. He has had a transformative impact in how we understand structure formation: the process by which the small fluctuations in the cosmic density field generated after the Big Bang, grow through gravitational collapse to form the rich "cosmic web" of structures we observe around us.

An outstanding cosmologist

‘He is an outstanding cosmologist and has played a major role in transforming cosmology from a speculative branch of theoretical physics into a fully developed quantitative science that can be accurately compared with observational data.

‘Many of the experiments that several astrophysicists at Oxford are involved in, such as the Large Synoptic Survey Telescope, the Square-Kilometre Array, and the Simons Observatory, will be able to continue the lines of research initiated by Professor Peebles, achieving unprecedented sensitivities and using analysis methods inspired by those he developed.

‘Our current understanding of our place in the universe would probably be very different without Professor Peeble's contribution.’

Professor of Astrophysics at Oxford, Suzanne Aigrain, works on the modelling, detection and characterisation of exoplanets and considers the impact of Michel Mayor and Didier Queloz’s work: ‘Mayor and Queloz’s discovery of a planet orbiting another star like the sun in 1995 was a major astronomical achievement – the result of decades of innovative instrumentation, and years of painstaking observations. The planet which they found took everyone by surprise: it has a mass similar to Jupiter, but takes only a few days to orbit its host star: there is nothing remotely like it in our own solar system. Planets like it – now known as Hot Jupiters – continue to puzzle scientists to this day. But more importantly, that discovery was followed by many, many more, as a previously hidden component of the Universe is being revealed.

The profound importance of exoplanets

‘Compared to other astronomical objects like stars and galaxies, exoplanets may seem insignificant, but they are profoundly important not only because we live on one, but because the conditions on their surfaces are such that complex chemical reactions may occur, and give rise to interesting phenomena such as life.

‘Mayor and Queloz’s discovery kick-started an entire research field. Thousands of exoplanets have now been found around stars of all shapes and sizes, revealing a numerous and highly diverse population. Some of these planets are more similar to the Earth, and may be able to host life. There are hundreds of astronomers and planetary scientists – myself included – who dedicate their professional lives to searching for exoplanets studying them in detail, and understanding how they form and evolve. Oxford University is home to a large exoplanet research group whose members are searching for new exoplanets, building novel instruments on the ground and in space to characterise them, and modelling their formation and atmospheres. Find out more about our work at’

Image copyright: ESO/M. Kornmesser/Nick Risinger ( - ESO website, CC BY 4.0,