“Billions of Planets in the Milky Way: The Quest for Earth-Twins and Maybe Life” Pro ISSI Talk with Prof. Michel Mayor (University of Geneva, Switzerland)


“Do there exist many worlds, or is there but a single world? This is one of the most noble and exalted questions in the study of Nature.”

Albertus Magnus (circa 1200–1280)

Are there other worlds in the universe? Does life exist elsewhere in the cosmos? The technology of our time has made it possible to transform this dream of antiquity into a fascinating field of current astrophysics.

Three decades after the discovery of a first planet orbiting a star like our Sun, a few thousand planetary systems have been discovered. These first discoveries revealed to us the astonishing diversity of these systems, very different from our solar system: orbital periods of a few hours, planets with very high eccentricity, ocean planets, rocky or gas giant planets with sometimes retrograde orbits, etc.

After the euphoria of these first discoveries, the era of studying the atmospheres of exoplanets is now beginning. Fascinatingly, despite the enormous contrast between the high luminosity of the star and the very weak light that is emitted by the planets, the analysis of their atmospheres begins now. It will benefit from space telescopes and giant telescopes on the ground (up to diameters of 39 m).

Does life exist in other places in the cosmos? – Vertiginous question – The analysis of planetary atmospheres may reveal biosignatures, these spectral characteristics induced by the development of life. Advances in spectroscopy studies of exoplanets make us think that the search for extraterrestrial life is possible.

This Talk was recorded on May 24, 2023