François Bouchet

François Bouchet (born 16 July 1955) is a French astrophysicist and cosmologist.

A specialist in the cosmic microwave background (CMB) and the large-scale structure of the universe, he is an emeritus research director at the CNRS, based at the Institut d'astrophysique de Paris (IAP), which he directed from 2021 to 2023. He was one of the principal leaders of the European Space Agency's Planck mission: a member of ESA's Planck Science Team, initiator, scientific coordinator and deputy principal investigator of the consortium that built the satellite's High Frequency Instrument (HFI), and head of its data processing. His honours include, individually, the Émilie du Châtelet Prize (2016) and the Louis D. Foundation Grand Prize (2014), and, with the Planck team, the Gruber Prize in Cosmology (2018). He has been a member of Academia Europaea since 2019 and president of the Union rationaliste since 2025.

Biography Early life and education Bouchet is the son of the gallery owner Nadine Musté and the lawyer Paul Bouchet, whose second wife was the jurist Mireille Delmas-Marty. He graduated in 1980 from the ESPCI Paris and obtained a master's degree (DEA) in theoretical physics from Pierre and Marie Curie University, where he defended his doctoral thesis, Growth of primordial fluctuations and distribution of galaxies, in 1983 under the supervision of René Pellat. He received his habilitation in 1992.

Career After a research grant from the École Polytechnique (1983–1984), he joined the CNRS in 1984. From 1986 to 1989 he was a visiting astronomer in the United States, at the astronomy department of the University of California, Berkeley, the Lawrence Livermore National Laboratory, the Institute for Theoretical Physics in Santa Barbara and the astronomy department of Princeton University. Appointed a CNRS research director in 1993 (classe exceptionnelle in 2012), he spent his career at the IAP, which he directed from January 2021 to January 2023. In 2019 he was a Distinguished Visiting Professor at the Yukawa Institute for Theoretical Physics in Kyoto. He has been an emeritus CNRS research director since January 2024. His doctoral students include Stéphane Colombi, Éric Hivon, Stéphane Ninin, Olivier Doré and Anne Ducout, and he co-supervised several other doctoral candidates.

Research Bouchet's research concerns cosmology: the formation, evolution and characterisation of the large-scale structure of the universe and of anisotropies of the cosmic microwave background (CMB), and their implications for fundamental physics. According to the NASA ADS database he has authored more than 320 peer-reviewed papers, with an h-index of about 130. A regular invited speaker, he has given numerous plenary and review lectures at international conferences in Europe, India, South Korea, Japan and the United States, including plenary talks at ICHEP (Paris, 2010) and Lepton-Photon (San Francisco, 2013), the CERN General Colloquium (2015) and the opening talk of the Korean Physical Society meeting (2015).

Cosmic strings In the late 1980s, with David P. Bennett, Bouchet carried out numerical simulations of cosmic string networks that established a scaling solution for their evolution, and computed their imprint on the CMB, in work published in Physical Review Letters and Nature. One of these maps of the expected cosmic-string imprint on the CMB was the cover of Physics Today in March 1989, and the work was featured in Newsweek in June 1988.

Large-scale structure and simulations Among the first in France to develop numerical simulations of the large-scale structure of the universe in the 1980s, Bouchet contributed to several simulation codes, in particular a tree method developed with Lars Hernquist, and later to modelling galaxy formation within these structures (the GALICS code). He is, in parallel with Thomas Buchert, one of the originators of second-order Lagrangian perturbation theory (2LPT) of structure growth, which has become a standard tool of cosmology: generating the initial conditions of simulations, baryon-acoustic-oscillation reconstruction, and, more recently, as a fast forward model in machine-learning field-level inference.

Planck mission The cosmic microwave background map produced by Planck. Its data were generated at the HFI data-processing centre at the IAP. The Planck mission (2009–2013) of the European Space Agency produced the most precise map of the cosmic microwave background — the light emitted about 380,000 years after the Big Bang — pinning down with unprecedented precision the age, geometry and composition of the universe. From 1992 and for more than twenty-five years, Bouchet was one of its principal leaders. A member of ESA's Planck Science Team, he was an initiator and the deputy principal investigator of the international consortium that built the High Frequency Instrument (HFI) — whose principal investigator was Jean-Loup Puget — and its scientific coordinator throughout the project. He headed the French data-processing centre (2001–2018) and, from 2005, the entire HFI data processing, responsible for the production of the all-sky maps at the instrument's six frequencies, the CMB maps and derived products. The HFI data underpin Planck's determination of the standard cosmological model.

He is the corresponding author of several of the collaboration's reference papers, in particular those describing the HFI data processing, the CMB power spectra and likelihood, and the overview and cosmological-legacy paper of the final data release. He gave the first presentation of Planck's inflation results at ESA's first data-release meeting, and the main talk on Planck's CMB results in a dedicated session at the International Astronomical Union General Assembly in Honolulu (2015).

Earlier he had taken part in the balloon-borne experiment Archeops, a precursor of Planck, of which he was secretary of the steering group (1998–2005). He later co-proposed to ESA, with Jacques Delabrouille and Paolo de Bernardis, several post-Planck satellite concepts dedicated to CMB polarisation (COrE, CORE).

Recent work After Planck, Bouchet continues to study the CMB within the international SPT-3G collaboration, which operates the South Pole Telescope. Together with the Atacama Cosmology Telescope (ACT), this experiment reaches a precision comparable to Planck's on several cosmological parameters, based on different observables (polarisation and small angular scales). He is a co-author of its publications, including measurements of CMB gravitational lensing from the combination of the ACT, SPT and Planck surveys and the determination of cosmological parameters from SPT-3G data, and contributes to the search for the imprint of primordial gravitational waves in CMB B-mode polarisation. He also takes part in the preparation of the Japanese satellite LiteBIRD, dedicated to this search.

Scientific and institutional roles Throughout his career Bouchet helped to structure the development of physical cosmology in France, serving on numerous scientific bodies: member of the scientific council of the national Cosmology research group (1989–1997); member of the Astronomy commission of the Institut national des sciences de l'Univers (1997–2003) and of the Astronomy panel of CNES (2001–2010); chair of the science council of the French National Cosmology Programme (2003–2006), then of the CNRS "Particles and Universe" interdisciplinary programme (2007–2011); chair of the inter-agency (CEA, CNES, CNRS) committee that produced the French roadmap for CMB science (2015–2016, updated 2017–2018); director of the Institut d'astrophysique de Paris (2021–2023); elected member of the Governing Board of the CMB-S4 collaboration (2018–2020); member of the External Advisory Committee of the Kavli Institute for the Physics and Mathematics of the Universe, University of Tokyo (since 2024).

In 2026 he retraced the history of the cosmology sessions of the Rencontres de Moriond at the conference celebrating their 60th anniversary (Collège de France), a programme that also featured the Nobel laureates Barry Barish, Takaaki Kajita and Giorgio Parisi. He has been president of the Union rationaliste since 2025 and of the association Physique Outremer, and is vice-president of the Institut Paul Bouchet.

Public engagement Bouchet is a regular communicator of cosmology to the general public, especially around the milestones of the Planck mission, appearing in national media and giving an interview to Le Monde on the mission's final results. His expertise has been sought by Sciences et Avenir, Le Figaro, the CNRS Journal and the Financial Times. He is the editorial director (responsable de la rédaction) of the mission's public-outreach website public.planck.fr. He has given many public lectures in France and abroad, including the Bunyan Lecture at Stanford University (2015), lectures at IUCAA in Pune and at the Bangalore planetarium (2019), and at the University of British Columbia (2018).

Awards and honours Gruber Prize in Cosmology, to the Planck team (2018) Group Achievement Award in Astronomy of the Royal Astronomical Society, to the Planck team (2018) Marcel Grossmann Award, to the Planck team (2018) Giuseppe and Vanna Cocconi Prize of the European Physical Society, to the WMAP and Planck collaborations (2019) Émilie du Châtelet Prize of the French Physical Society (2016) Louis D. Foundation Grand Scientific Prize (Institut de France), €450,000 (2014) ARRI Prize for French international standing (2011) Grand Prize of the Association Aéronautique et Astronautique de France, to the Planck–Herschel team (2010) Prize of the French Society of Astronomy Specialists (1993) Elected member of Academia Europaea (2019)

Selected publications Cosmic velocity fields (ed., with Marc Lachièze-Rey), Éditions Frontières, 1993. "CMB: A, B, C, …, W and beyond (P!)", Comptes Rendus Physique, 2003. Inflation cosmique (ed., with Jean-Philippe Uzan), Comptes Rendus Physique, 2015. "Planck 2015 results and inflation", Comptes Rendus Physique, 2015. Planck and the fundamentals of cosmology (ed., with David Wiltshire), Classical and Quantum Gravity, 2016.