Jean-Paul Zahn

It is with immense sadness that EDP Sciences announces the death of Jean-Paul Zahn, on the 15th of July. He was 80 years old.

After entering to Ecole Normale Superieure de la rue d’Ulm in 1955, he joined La Sorbonne and then the Institut d’Astrophysique de Paris where he defended his PhD under the supervision of Prof. E. Shatzman in 1966 on tides in binary stars. His study had a strong impact on that field of astrophysics. He was able to apply his discovery on tide dissipation to many systems such as exoplanets and planets of our solar system.

As a renowned expert in hydrodynamics, he played a central role all along in his career in our understanding of stellar and solar internal dynamics. He in particular developed theories on hydrodynamic instabilities in stellar interiors, demonstrating the key role played by rotation in shaping the evolution of stars. He made major contributions to the subjects of turbulent convection, angular momentum transport and the generation and excitation of internal gravity waves in stars. He made the first model explaining the existence of the solar tachocline, the thin intense shear layer at the base of the solar convection zone. He also was an active supporter of helio- and asteroseismology space missions.

Beside his impressive scientific production, Jean-Paul Zahn has had major administrative positions. After his arrival at the Observatory of Nice in 1966, he became in 1972 its director until 1981. Then from 1981 to 1988 he managed the Observatories of Pic du Midi and Toulouse (now Midi-Pyrennees). He also was one of the founders of Centre Europeen de Recherche et de Formation Avancee en Calcul Scientifique, better known as CERFACS. He could remove unnecessary impediments imposed by rigid bureaucracy by circumventing them in inventive, unconventional ways, yet always maintaining complete honesty and an ethical approach.

Jean-Paul Zahn joined the Observatory of Paris in 1993, becoming Emeritus in 2003, where he was actively continuing his research on stellar dynamics and tides.

He spent many years in USA (NASA Goddard Institute of Space Studies in New York, Columbia University, New York University, University of Colorado at Boulder).

Jean-Paul Zahn was also a great professor, teaching astrophysics and fluid dynamics at all levels. He was the head of the graduate school of astrophysics of Paris from 1995 until 1999 and organized many schools in les Houches and Aussois. He supervised many PhDs and many of his young colleagues are active in astrophysics and fluid dynamics, creating in effect a School in astrophysical fluid dynamics whose results and theory apply to subject from celestial bodies to laboratory experiments in fundamental fluid mechanics. Jean-Paul headed many French and international committees such as CNRS astrophysical hiring panels or the European Astronomical Society from 1997 until 2001.

He received many prizes all along his brilliant career both in France and Internationally.

EDP Sciences would particularly like to commend the Scientific Director of the EAS Publication Series, series which it had launched in 2001 and whose objective is the publication of the proceedings of conferences in astronomy and Astrophysics in Europe.

Jean-Paul was a great scientist with immense skills, an enthusiastic and fascinating teacher, and a charismatic coordinator and organizer. Jean-Paul was also known for his remarkable human qualities. We will always remember his kindness, his generosity and his great sense of humor.

All our thoughts are going to his wife and his relatives.