Stellar physics is a field of astrophysics that has undergone both topical and methodological revolutions over the last two decades. These have given a strong momentum to the field, made possible by the combination of a very rich instrumental context, the rapid development of digital technology, and the contribution of laboratory physics. The major scientific questions in the field of stellar physics are of course related to the ‘star object’, in particular the study of hydrodynamic processes and microphysics in stellar interiors. In addition, there is the question of magnetism and stellar activity, for which high-precision spectropolarimetry and photometry have enabled us to make a considerable leap forward in recent years. The interaction of stars with their environment and in particular the consideration of multiple interactions (star-planet/star-disk/star-stars/star-circumstellar environment) are scientific questions that are also becoming increasingly important, and that will become central in the years to come. In addition, the interplay between our field, and other areas in astrophysics have become undeniable. For instance, the question of stellar ages is quite illustrative because it transcends stellar physics alone and its precise and accurate determination becomes key in the study of planetary systems or in galactic archaeology.

Without going so far as to pretend that Paris Observatory’s teams cover the entire field of stellar physics, there is a topical and methodological continuity that is quite unique in the national and international landscapes. In addition to this, these teams are sometimes drivers (e.g. Gaia, PLATO, UV spectropolarimetry, etc.) in projects that are structuring and will structure the community in the decades to come. There is therefore a remarkable potential that only needs to be exploited, provided that the interfaces are structured and brought to life.

Hence, the purpose of this incentive action of Paris Observatory scientific council is to gather, coordinate, stimulate the stellar physics community at Paris Observatory.