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image Stellar formation, evolution and ISM image Stellar formation, evolution and ISM image Stellar formation, evolution and ISM image Stellar formation, evolution and ISM

Stellar formation, evolution and ISM
To understand the cycle of matter in the Galaxy, all stages of the life of stars and planets will be investigated. To begin, Arago will investigate stellar formation and, in particular, the role of magnetic fields in accretion. Arago will characterise magnetospheric accretion in pre-main sequence (PMS) stars, i.e. T Tauri and Herbig Ae/Be stars. This is crucial to determine their initial angular momentum and the properties of their inner circumstellar disc at the time of planet formation, as well as the interplay between stellar activity, through the chromosphere and accretion, and the global evolution of discs affected by forming planets and stellar irradiation. The truncation and composition of the inner parts of discs, in particular, has consequences for the migration of giant planets, and it can only be understood by studying magnetic fields.
Moreover, Arago will characterise the structure, geometry, and dynamics of stellar environments across stellar evolution, and quantify stellar mass loss and angular momentum loss during various evolutionary phases. This will be done primarily through 3D mapping of magnetospheres and chromospheres over the stellar rotation period. Magnetic fields, mass loss, and accretion of matter have a strong but poorly understood impact on stellar structure and evolution in any type of stars. To investigate this phenomenon, Arago will study circumstellar discs (e.g. of PMS or Be stars) and winds escaping from stars, including circumbinary discs and colliding winds in binary systems. In cooler stars, Arago will allow users to characterise the physical conditions in chromospheres and their magnetic activity. Similarly, Arago will investigate the role of mass and momentum transfer in binary systems throughout their evolution and explore how these processes shape the progenitors of supernovae and gamma-ray bursts.
Careful attention will be given to late stages of stellar and planetary evolution, including red giants, supergiants, Wolf-Rayet stars, Luminous Blue Variables (LBV), white dwarfs (WDs), and supernovae, and their impact on associated planets. These objects yield radiation, momentum, and chemical outputs, which in turn feed the ISM and impact the next generations of stars and planets. Moreover, WDs accreting the debris discs of evolved planetary systems, and catastrophically disintegrating planets, provide the opportunity to investigate the bulk composition of terrestrial and giant exoplanets.
To close the loop of the cycle of matter, Arago will investigate the gas, dust grains, and magnetic field in the ISM to understand the building blocks of stars and planets and the initial conditions of their formation.