Webb detects the universe’s most distant complex organic molecules

Thanks to the capabilities of the recently launched James Webb Space Telescope.


Using the James Webb Space Telescope, an international team of scientists, in collaboration with the University of Illinois Urbana-Champaign and Texas A&M University, has identified complex organic molecules in a most distant galaxy. The galaxy is located more than 12 billion light-years away from Earth.

Scientists have been able to differentiate between infrared signals generated by some of the more massive and larger dust grains in the galaxy and those of the newly observed hydrocarbon molecules.

Dust grains absorb half of the radiation emitted by stars throughout the universe’s history. Polycyclic aromatic hydrocarbons (PAHs) are large organic molecules that trace millimeter-size dust grains and regulate the cooling of interstellar gas within galaxies.

In the latest study, gravitational lensing—which the researchers call “nature’s magnifying glass”—helped the JWST perform better. The team focused the JWST on SPT0418-47 – an object discovered using the National Science Foundation’s South Pole Telescope and previously identified as a dust-obscured galaxy magnified by a factor of about 30 to 35 by gravitational lensing.

Einstein ring
The galaxy observed by Webb shows an Einstein ring caused by a phenomenon known as gravitational lensing. Graphic courtesy S. Doyle / J. Spilker

The interstellar gas in SPT0418-47 that is shrouded, according to spectroscopic data from the JWST, is enriched in heavy elements, which suggests that previous star generations had already lived and died. The particular substance the researchers found belongs to a class of molecules known as polycyclic aromatic hydrocarbon, or PAH.

These molecules are present in combustion engines or forest fire exhaust on Earth. These organic molecules, composed of carbon chains, are considered the fundamental building blocks for the earliest forms of life.

Graduate student Kedar Phadke said, “What this research is telling us right now – and we are still learning – is that we can see all of the regions where these smaller dust grains are located – regions that we could never see before the JWST.”

“The new spectroscopic data lets us observe the galaxy’s atomic and molecular composition, providing very important insights into the formation of galaxies, their lifecycle, and how they evolve.”

Vieira said, “We didn’t expect this. Detecting these complex organic molecules at such a vast distance is game-changing regarding future observations. This work is just the first step, and we’re just now learning how to use it and learn its capabilities. We are very excited to see how this plays out.”

“It’s extremely cool that galaxies I discovered while writing my thesis would the JWST observe one day. I am grateful to the U.S. taxpayers, the NSF, and NASA for funding and supporting the SPT and the JWST. Without these instruments, this discovery could have never been made.”

Journal Reference:

  1. Spilker, J.S., Phadke, K.A., Aravena, M. et al. Spatial variations in aromatic hydrocarbon emission in a dust-rich galaxy. Nature (2023). DOI: 10.1038/s41586-023-05998-6


See stories of the future in your inbox each morning.