The first results of astrophysical relevance obtained with the Stardust machine evidence a prevalence of non-aromatic species in the inner regions of circumstellar envelopes
This work is part of the results obtained in the framework of the European project ERC Synergy Grant “Gas and dust from stars to the laboratory: Exploring the NANOCOSMOS”. In particular, this study represents the first results of astrophysical relevance obtained with Stardust, an ultra-high vacuum equipment which combines atomic gas aggregation with advanced in situ characterization techniques. Stardust was designed to simulate cosmic-dust formation and processing in the circumstellar regions of evolved stars. This work explores the nature of the carbonaceous cosmic dust formed from low-pressure gas-phase condensation of carbon atoms in a hydrogen atmosphere, in a ratio of carbon to molecular hydrogen similar to that reported for evolved stars. The results suggest the formation of amorphous carbon nanograins and aliphatic carbon clusters, although polycyclic aromatic hydrocarbons (PAHs) and fullerenes might not be efficiently formed during gas-phase growth in circumstellar envelopes. Nevertheless, the species that are deposited on dust grains are susceptible to further processing, and dust can catalyse the formation of aromatic species on thermal activation, which could take place as a result of the substantial rise in dust temperature that occurs in highly UV-irradiated environments.
Prevalence of non-aromatic carbonaceous molecules in the inner regions of circumstellar envelopes, Lidia Martínez, Gonzalo Santoro, Pablo Merino, Mario Accolla, Koen Lauwaet, Jesús Sobrado, Hassan Sabbah, Ramón J. Pelaez, Victor J. Herrero, Isabel Tanarro, Marcelino Agúndez, Alberto Martín-Jimenez, Roberto Otero, Gary J. Ellis, Christine Joblin, José Cernicharo & José A. Martín-Gago, Nature Astronomy (2019)