James Webb Space Telescope detects ancient carbon-rich dust in the early cosmos for first time

“I’ve studied galaxies in the first billion years of cosmic time my entire career and never did we expect to find such a clear signature of cosmic dust in such distant galaxies,” said co-author Dr Renske Smit from Liverpool John Moores University, in an official release. 

The study, led by the University of Cambridge, hypothesizes that there were likely specific sources that boosted carbon activity in the chaotic early universe. Until now, it was considered that heavier elements, such as carbon, evolved much later in the timescale of the universe. 

Observing 10 early galaxies 800 million years after the Big Bang

Carbon-enriched dust was identified in the light spectrum data of 10 young, distant galaxies 800 million years after the Big Bang.

Webb's advanced and highly sensitive instrument, the Near-Infrared Spectrograph (NIRSpec), enabled the observation of early galaxies at such a nascent stage, thanks to its capability of providing infrared spectroscopy.

Surprisingly, the existence of carbon-rich dust occurred considerably earlier than estimated by the current models.

This recent discovery can potentially alter general scientific knowledge of the universe's chemical evolution. This is because, unlike what JWST has witnessed in such early years, the processes that spew heavier elements normally require hundreds of millions of years to build dust in galaxies. 

The authors suggest two possible theories

Having uncovered the existence of carbon-rich matter within early galaxies, astronomers are now faced with the task of unraveling the mechanism responsible for its production.

The researchers propose two plausible explanations for the existence of carbon in the dust of the early cosmos. 

The first suggests that supernova explosions could have expelled these elements into space. Subsequently, as the gas from these explosions expanded and cooled, it might have led to the formation of dust particles enriched with the star's heavy elements. However, the authors also propose that the powerful forces of such explosions could have potentially destroyed a significant portion of this newly formed dust during the early years.

Another potential explanation stems from Wolf-Rayet stars, which are short-lived stars known for rapidly shedding mass.

Cosmic dust is a crucial component in the evolution of galaxies and the formation of the next generation of stars. Another JWST-based study has also predicted that supernovae dust played a key role in the formation of new stars.

The recent discoveries could transform scientists' understanding of the universe's evolution, encompassing aspects such as the formation of the first stars and the development of young galaxies. By utilizing the JWST, astronomers have only just scratched the surface in their endeavor to construct a more comprehensive image of the enigmatic early universe.

The findings have been published in the journal Nature.

Study Abstract:

Large dust reservoirs (up to ~108 M⊙) have been detected1-3 in galaxies out to redshift z ∼ 8, when the age of the universe was only about 600 Myr. Generating significant amounts of dust within such a short timescale has proven challenging for theories of dust formation4,5 and has prompted the revision of the modelling of potential sites of dust production6–8 such as the atmospheres of asymptotic giant branch (AGB) stars in low-metallicity environments, supernovae (SNe) ejecta, and the accelerated growth of grains in the interstellar medium (ISM). However, degeneracies between different evolutionary pathways remain when the total dust mass of galaxies is the only available observable. Here we report observations of the 2175 Å dust attenuation feature, well known in the Milky Way (MW) and galaxies at z ≲ 39–11, in the near-infrared spectra of galaxies up to z ∼ 7, corresponding to the first billion years of cosmic time. The relatively short timescale implied for the formation of carbonaceous grains giving rise to this feature12 suggests a rapid production process, likely in Wolf-Rayet (WR) stars or SN ejecta.