Chemical complexity and dust formation around evolved stars

Abstract

The outflows of asymptotic giant branch (AGB) stars are rich astrochemical laboratories, hosting different chemical regimes: from non-equilibrium chemistry close to the star, to dust formation further out, and finally photochemistry in the outer regions. Chemistry is crucial for understanding the driving mechanism and dynamics of the outflow, as it is the small-scale chemical process of dust formation that launches the large-scale stellar outflow. However, exactly how dust condenses from the gas phase and grows is still unknown: an astrochemical problem with consequences for stellar evolution. Disagreements between observations and the predictions of chemical models drive the development of these models, helping to understand the link between dynamics and chemistry and paving the way to a 3D hydrochemical model.