James Webb Detects Silicon Carbide, Iron Dust in 2 Sextans A Stars
Updated
Updated · spacedaily.com · Jul 18
James Webb Detects Silicon Carbide, Iron Dust in 2 Sextans A Stars
1 articles · Updated · spacedaily.com · Jul 18
Summary
Six stars observed by Webb in Sextans A yielded two standout dust signals: carbon star 90428 showed a confirmed 11.3-micrometre silicon-carbide feature, while oxygen-rich star 90034 was best fit by metallic-iron dust.
That is unexpected because Sextans A contains only about 1% to 7% of the Sun’s metal abundance, where models generally predict silicon-carbide and iron-bearing dust should become scarce.
The iron result is indirect rather than a line-by-line identification: 90034’s smooth infrared excess lacked normal silicate features, and model comparisons favored an iron-dominated wind with less than 1% silicate dust.
The finding makes Sextans A the lowest-metallicity galaxy known to host a star with detected SiC dust, but the study covered just six asymptotic giant branch stars and does not show such dust is common there.
Because higher-mass AGB stars can return dust within roughly 30 to 50 million years, the results point to a possible early dust source that current galaxy-evolution models may undercount.