Modelling of dust formation and chemistry in AGB outflows and disks

In their twilight years, solar-like stars in the asymptotic giant branch (AGB) phase enrich the interstellar medium (ISM) with fresh material (gas and dust) for new stars and planets.

AGB stars lose their outer layers to the ISM through a stellar outflow or wind, forming an extended circumstellar envelope (CSE). The wind is thought to be dust-driven, with dust grains forming close to the star.

State-of-the-art observations have revealed the composition of the inner CSE, allowing the first identification of gas-phase seeds for dust grains, and the presence of disks around AGB stars.

Despite major knowledge gains over the past three decades, it is still not fully understood how dust forms, grows, and drives the stellar wind, limiting our understanding of both stellar evolution and the chemical enrichment of the ISM.

Moreover, the structure and chemistry of AGB disks is unknown; if similar to protoplanetary disks, second generation planet formation may be possible therein.Solving these puzzles requires new and sophisticated models that connect dust formation with chemistry and couple gas and dust chemistry throughout the wind and in the disk.

With ‘ICE and Dust Reactions in AGB Gaseous Outflows and disks with Nucleation’ (ICEDRAGON), we will develop the first models that link the chemistry throughout the whole CSE and the first chemical model of an AGB disk.

The novel models will allow us to study, for the first time, the organic refractory feedback of dust grains delivered to the ISM and the role of dust formation on the gas-phase chemistry throughout the CSE.

This is necessary to deduce the physics behind the wind launching mechanism, that is encoded in the observed composition. The AGB disk model will provide the first answers to the viability of secondary planet formation.

The synergy between fellow and host is ideal for this astrochemical (and fundamentally interdisciplinary) project, as it combines their respective expertise in chemical modelling.