Sounding-rocket microgravity experiments on alumina dust.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 30232326.
- Also identified by DOI 10.1038/s41467-018-06359-y and PMC identifier 6145898.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Alumina (Al<sub>2</sub>O<sub>3</sub>) is believed to be the first major condensate to form in the gas outflow from oxygen-rich evolved stars because of the refractoriness and that α-Al<sub>2</sub>O<sub>3</sub> (corundum, most stable polymorph) is a potential origin of a 13 μm feature that appears close to stars. However, no one has directly reproduced the 13 μm feature experimentally, and it has remained as a noteworthy unidentified infrared band. Here, we report nucleation experiments on Al<sub>2</sub>O<sub>3</sub> nanoparticles monitored by a specially designed infrared spectrometer in the microgravity environment of a sounding rocket. The conditions approximate to those around asymptotic giant branch (AGB) stars. The measured spectra of the nucleated Al<sub>2</sub>O<sub>3</sub> show a sharp feature at a wavelength of 13.55 μm and comparable in width to that observed near oxygen-rich AGB stars. Our finding that α-Al<sub>2</sub>O<sub>3</sub> nucleates under certain condition provides a solid basis to elaborate condensation models of dust around oxygen-rich evolved stars.