Astronomers using the James Webb Space Telescope have identified an unexpectedly rich inventory of small organic molecules inside the heavily obscured nucleus of a nearby ultraluminous infrared galaxy. The study, led by Dr. Ismael García Bernete of the Center for Astrobiology in Spain, with contributions from researchers at the University of Oxford and collaborating institutions, provides new evidence that deeply buried galactic cores can function as active chemical environments rather than chemically dormant regions.
García-Bernete, I., Pereira-Santaella, M., González-Alfonso, E., Agúndez, M., Rigopoulou, D., Donnan, F. R., Speranza, G., & Thatte, N. (2026). Abundant hydrocarbons in a buried galactic nucleus with signs of carbonaceous grain and polycyclic aromatic hydrocarbon processing. Nature Astronomy. https://doi.org/10.1038/s41550-025-02750-0
The team focused on IRAS 07251–0248, a galaxy whose central region is concealed by dense gas and dust. In visible wavelengths, this material blocks most radiation emerging from the supermassive black hole and surrounding star forming activity. Infrared observations, however, can penetrate these layers. By analyzing spectroscopic data from Webb’s NIRSpec and MIRI instruments across wavelengths from roughly 3 to 28 microns, the researchers were able to identify molecular fingerprints within the hidden nucleus.
Dr. Ismael García Bernete from the University of Oxford stated,
“We found an unexpected chemical complexity, with abundances far higher than predicted by current theoretical model. This indicates that there must be a continuous source of carbon in these galactic nuclei fueling this rich chemical network.”
The observations revealed high abundances of small hydrocarbons, including benzene, methane, acetylene, diacetylene, and triacetylene. The methyl radical was also detected, marking its first confirmed identification beyond the Milky Way. In addition to gas phase molecules, the spectra showed evidence of carbon rich dust grains and icy components such as water ice embedded within the surrounding material.
What stands out is not simply the presence of these compounds, but their concentration. According to the authors, the observed abundances exceed what current chemical models predict for such environments. Standard explanations based on high temperatures, shocks, or turbulent gas do not fully account for the molecular richness.
To interpret the results, the researchers used theoretical models of polycyclic aromatic hydrocarbons developed at the University of Oxford. These large carbon based molecules are common in space and are known to emit distinctive infrared signatures. The analysis suggests that intense cosmic ray fields within the galactic nucleus may be interacting with carbonaceous grains and polycyclic aromatic hydrocarbons. Collisions with energetic particles can fragment larger carbon structures, releasing smaller hydrocarbons into the surrounding gas.
The team also compared their findings with similar obscured galaxies and found a correlation between hydrocarbon abundance and indicators of cosmic ray ionization. This supports the idea that cosmic rays, rather than thermal processes alone, are driving the chemistry in these compact, dust embedded regions.
Although the detected molecules are relatively simple, they are considered building blocks in broader organic chemistry networks. Small hydrocarbons such as acetylene and benzene are intermediates in reactions that can lead to more complex carbon based structures. While this does not imply biological activity, it does demonstrate that the raw ingredients for advanced chemistry can accumulate in extreme galactic environments.
The work highlights Webb’s capability to probe regions previously inaccessible to observation. Earlier infrared missions lacked the sensitivity and spectral resolution required to disentangle overlapping molecular features in such dusty systems. With Webb’s instruments, astronomers can now quantify both the composition and temperature of molecular gas in nuclei that were once effectively hidden.
Beyond the immediate chemical implications, the findings contribute to a larger question in galaxy evolution. Buried nuclei like IRAS 07251–0248 are common in the early universe, where intense star formation and black hole growth often occur within dust rich environments. If these regions routinely act as production sites for organic molecules, they may influence the chemical enrichment of their host galaxies over time.
The study, published in Nature Astronomy, suggests that extreme galactic cores are not chemically suppressed by their obscuration. Instead, they may operate as concentrated chemical factories, reshaping carbon bearing material through cosmic ray processing and redistributing organic compounds into the interstellar medium. As Webb continues to survey similar systems, researchers expect to refine models of how organic chemistry evolves under the combined influence of radiation, dust, and energetic particles on galactic scales.
Adrian graduated with a Masters Degree (1st Class Honours) in Chemical Engineering from Chester University along with Harris. His master’s research aimed to develop a standardadised clean water oxygenation transfer procedure to test bubble diffusers that are currently used in the wastewater industry commercial market. He has also undergone placments in both US and China primarely focused within the R&D department and is an associate member of the Institute of Chemical Engineers (IChemE).
