SO Colloquium: The evolution of the accretion process: investigating the protostellar phase to constraints planet formation

The accretion process is responsible for the mass building during the star formation phase, but our knowledge of this phenomenon is still not totally understood. On one side, the magnetospheric accretion scenario describes the accretion on pre-main sequence (Class II/III) low-mass stars. However, most of the material is supposed to be accreted during the earliest stages, i.e. the protostellar phase (Class 0/I), when the forming star and its disk are embedded into a dusty envelope. The presence of the envelope and short lifetimes make the observations of these sources and their analysis challenging, preventing us from testing this and other scenarios during the early stages. On the other hand, the Gaia data alert project is increasing the number of the so-called "eruptive sources'' (FUor, EXors..), which were thought to represent only an exception in the accretion paradigm, suggesting their presence in the stellar mass building to be more important than we thought. In the last decade, thanks to new instruments and analysis techniques, we're starting to unveil the secrets of accretion on low-mass protostars, finding many similarities between these sources and the eruptive stars and finally being able to provide quantitative information about accretion parameters during the overall star formation evolution. In this talk I will present the most recent results about the stellar mass building during the early stages and how they impact the planet formation.