KARIM BENABED (1974-2025)

Photography of Karim Benabed taken
at IAP in March, 2014.
Credit: Sophie Rattier

Our colleague Karim Benabed died accidentally on 3 December 2025 at the age of 51. Karim had been an Astronomer at the Institut d’Astrophysique de Paris (IAP) since 2004. He taught at Sorbonne Université. He completed his PhD at the Institut de Physique Théorique (IPhT) under the supervision of Francis Bernardeau, followed by a postdoctoral stay at New York University (NYU).

After obtaining tenure in 2005, he joined François Bouchet’s Planck team at IAP, where he quickly became an essential pillar until the conclusion of the project in 2019. The Planck project, an ESA satellite, made it possible to measure the temperature and polarisation anisotropies of the cosmic microwave background with unprecedented precision. Within the project, he contributed in particular to the measurement of gravitational lensing effects, a topic he had already explored during his PhD. He also co-developed the core computational tools used for analysing and processing the collected data, and established the statistical tools needed for their cosmological interpretation. He was notably the principal architect of the paper on the likelihood of the cosmological parameters of our Universe. These exceptional contributions earned him the La Recherche prize in 2014, the AIAA Space Systems Award, awards from the Royal Astronomical Society, the Marcel Grossman Award in 2015, the Gruber Prize in 2018, and the Giuseppe and Vanna Cocconi Prize in 2019, as a member of the Planck scientific team.

Photography of Karim Benabed, together with Francis Bernardeau, taken at IAP on June 8, 2019, during the Astronomy Night, that he organised to celebrate CNRS' 80^th birthday.
Credit: Jean Mouette /IAP-CNRS-SU

From 2014 to 2020, he also served as Deputy Director of the IAP, and even assumed the duties of director for many months. In this role, he initiated numerous scientific and technical projects, as well as outreach activities that left a mark on the institute’s history, such as the Fête de la Science or the astronomy Nuit Blanche, which he founded. He later became involved in the Euclid project dedicated to measuring gravitational lensing effects, and especially in the South Pole Telescope experiment, aimed at measuring the polarisation of the cosmic microwave background on scales not covered by Planck.

Alongside his research and teaching duties, he supervised and mentored many interns, PhD students, and postdoctoral researchers, and was deeply committed to the future of French astronomy through his participation in CNAP selection committees and in the renovation project of the Palais de la Découverte.

Despite a career cut short, his distinctive way of approaching with brilliance the many facets of a researcher’s work will remain an undeniable source of inspiration for his colleagues. Karim Benabed was a role model for all, both through his deep humanity and his remarkable intelligence. The energy he devoted to astrophysics and to young scientists was matched only by his kindness toward all staff members. He also served on several joint promotion committees of the CNRS at the regional level, ensuring that he fully understood and represented the professional aspirations and career development wishes of the engineers, technicians, and administrative staff of the IAP.

Links

 Those who knew him can pay tribute to him on the site created for this occasion.

 These messages can be found on that website.

 You may also send a financial contribution to Karim's family.

 Recorded lectures and seminars, films, podcasts.

 Public conference (in French), October 2025, at “La Fête de la science” (Science festival) at IAP: “Tensions cosmiques - que nous apprennent les derniers résultats des grands relevés sur l’Univers ?”.

 Public conference (in French): “La mission Euclid” - 20 ans du PNR Millevaches, 2024.

 Colloquium at Collège de France (in French), 2020: “CMB et réionisation”.

 Public conference (in French) during the astronomy “Nuit Blanche” at IAP, 2019: “Le rayonnement cosmologique fossile”.

 Public conference (in French), 2015, Palais de la Découverte: “La première lueur de l'Univers”.

 Interview (in French), documentary movie, CNRS Images, 2015: “Planck: the First Light of the Universe”.

 Podcast (in French) Ciel et espace, 2015: “Karim Benabed, cosmologiste”.

 Public conference (in French), Cité des sciences, 2014: “Frissons dans le fond cosmologique”.

 “Out of atmosphere” - témoignage, by Laurence Honnorat, 2014.

 Interview (in French), documentary movie, CNRS Images, 2014: “PLANCK Mission: New results, 2014”.

 Presentation given at the 47^th ESLAB Symposium: “The Universe as seen by Planck”, 2013: “Lensing and ISW results from PLANCK”.

 A gallery of the many photographs taken by his colleagues over the years is available on this website (coming soon).

December 2025