Au revoir Yannick! It is with greatest sadness that we have to announce the passing of Yannick Mellier, lead of the Euclid Consortium since 2011. Yannick has worked tirelessly to steer Euclid’s development from before its adoption as a mission by ESA to the first science results in 2025. Much of what the Consortium is today bears his mark – and the first flagship paper introducing the first Euclid science results is, and will be, a ‘Euclid Collaboration: Mellier et al.’
Yannick Mellier received his doctorate in astrophysics from the University Toulouse III Paul Sabatier in 1987, where he studied distant galaxy clusters with spectroscopy. Since 1996 he is heading a group on gravitational lensing at the Institut d’astrophysique de Paris. He received the Prix Jean Ricard by the French Physics Association in 2005, the French-German Gay-Lussac-Humboldt Prize in 2006, and the Médaille d’argent du CNRS in 2009. He is author of more than 400 publications in scientific journals.
In 1986/87 he was part of the team first proving gravitational lensing by a galaxy cluster, showing an arc they discovered in Abell 370 was indeed the lensed image of a more distant galaxy. In 2000 he led one of the teams that first detected a cosmic shear signal. Gravitational lensing has been the center of his work – from ground based observations all the way to Euclid.
In 2011 Yannick took on the role of Euclid Consortium Lead. He headed the expanding consortium that created final designs of the two instruments onboard Euclid and then constructed and tested them in subsequent years. He also oversaw the organisation of the consortium’s science team, a structure that set more than a thousand scientists in motion to turn the exceptional capacities of the mission into a scientific reality. He facilitated the frequent communication with ESA and the discussions with international partners to provide the ground-based survey data needed for Euclid cosmology science.
While having been at the forefront of weak gravitational lensing research to study dark matter and dark energy, Yannick was about the most kind-hearted person you could find. Friendly to his fellow scientists and colleagues, always giving credit for people’s contributions and wanting others to be recognized and seen. He was integrative and supportive – and to many people a good friend.
Yannick, you will be greatly missed!
Francis Bernardeau (Euclid Deputy Lead) & Marc Sauvage (Chair Euclid Board)
