Webb Telescope Detects Complex Organic Molecules in Distant Galaxy

The James Webb Space Telescope (JWST) has detected a diverse array of complex organic molecules in the nucleus of the ultra-luminous infrared galaxy IRAS 07251–0248. This discovery provides new insights into the chemical processes occurring in extreme cosmic environments.

The study, led by researchers from the Center for Astrobiology (CAB), CSIC-INTA, and utilizing modeling techniques from the University of Oxford, focused on IRAS 07251–0248, a galaxy whose nucleus is obscured by substantial amounts of gas and dust. Traditional telescopes have struggled to study such regions due to the absorption of radiation by this material. However, JWST's infrared capabilities allow it to penetrate the dust, revealing the chemical composition of these hidden areas.

Using spectroscopic data from JWST's NIRSpec and MIRI instruments, the team identified several small organic molecules, including benzene (C₆H₆), methane (CH₄), acetylene (C₂H₂), diacetylene (C₄H₂), and triacetylene (C₆H₂). Notably, the methyl radical (CH₃) was detected for the first time outside the Milky Way. In addition to these gas-phase molecules, the researchers found significant amounts of solid molecular materials, such as carbonaceous grains and water ices.

Lead author Dr. Ismael García Bernete, formerly of Oxford University and now a researcher at CAB, stated that the team found an unexpected chemical complexity, with abundances far higher than predicted by current theoretical models. This suggests a continuous source of carbon in these galactic nuclei fueling this rich chemical network.

The presence of these molecules could be crucial as fundamental building blocks for complex organic chemistry relevant to life. Co-author Professor Dimitra Rigopoulou from the University of Oxford noted that although small organic molecules are not found in living cells, they could play a vital role in prebiotic chemistry, representing an important step towards the formation of amino acids and nucleotides.

The analysis indicates that the observed chemistry cannot be explained solely by high temperatures or turbulent gas motions. Instead, the results point to cosmic rays, abundant in these extreme nuclei, as fragmenting polycyclic aromatic hydrocarbons (PAHs) and carbon-rich dust grains, releasing small organic molecules into the gas phase. A clear correlation between hydrocarbon abundance and the intensity of cosmic-ray ionization in similar galaxies supports this scenario.

These findings suggest that deeply obscured galactic nuclei could act as factories of organic molecules, playing a key role in the chemical evolution of galaxies. The study opens new avenues to explore the formation and processing of organic molecules in extreme space environments and demonstrates JWST's potential to investigate previously hidden regions of the universe.