How laboratory astrophysics can help us understanding the formation of stardust. The case of silicon carbide.

Silicon carbide is a major component of stellar dust. Experimental simulations using the Stardust machine (ICCM-Madrid) have shown that silicon carbide nanograins can form from carbon and silicon atoms, and that this process involves the SiC₂ molecule, which has been identified spectroscopically in the reaction zone.

This is the first experiment to link molecular precursors to the formation of silicon carbide grains. It turns out that SiC₂ is also the most abundant molecule containing Si and C detected in the hot regions of the envelopes of carbon-rich evolved stars where dust forms. The experiments demonstrate that this chemistry requires the presence of molecular hydrogen (a very abundant molecule in these stellar envelopes), which allows for the formation of small hydrocarbons that lead to the formation of SiC₂. This proposal is supported by molecular analysis of the samples using the AROMA instrument (IRAP-Toulouse), which reveals the presence of numerous organosilicon species of the Si_nC_mH_l type.

This work is the result of interdisciplinary research conducted as part of the ERC Synergy Nanocosmos project between the CSIC and the CNRS. At IRAP, it involved Christine Joblin, Hassan Sabbah, and Sandra Wiersma (postdoctoral researcher, ANR GROWNANO project).

Further Resources

• Scientific paper : Tajuelo-Castilla, G., Santoro, G., Martínez, L. et al. The important role of hydrogen in the formation of silicon carbide in evolved stars. Nat Astron (2026). https://doi.org/10.1038/s41550-026-02854-1
• Press Release : « How cosmic dust forms from atoms in space » (C&EN)

IRAP Contacts

• Christine Joblin, christine.joblin@utoulouse.fr
• Hassan Sabbah, hassan.sabbah@utoulouse.fr