An international team of researchers has identified the largest sulfur-containing molecule yet discovered in interstellar space, a finding published this week in *Nature Astronomy*. The molecule, 2,5-cyclohexadien-1-thione, was detected in a molecular cloud 20,000 light-years away near the Milky Way’s center, a region where stars and planetary systems are born. This discovery expands our understanding of the chemical complexity present in these stellar nurseries and offers new insights into the potential for prebiotic chemistry throughout the universe[[1]].
An international team of astrophysicists has detected the largest sulfur-containing molecule ever identified in interstellar space, a discovery that could shed light on the chemical origins of life. The molecule, known as 2,5-cyclohexadien-1-thione (C₆H₆S), was found in a dense molecular cloud near the center of the Milky Way – over 20,000 light-years from Earth.
This region is considered a crucial chemical “cradle” for prebiotic processes, a place where the building blocks of life may form. The findings, published in Nature Astronomy, represent a significant step forward in astrochemistry and our understanding of how complex molecules arise in the universe, independent of star formation.
Detecting molecules in space isn’t a straightforward process. Astronomers rely on radio spectroscopy, a technique that identifies compounds by their unique emission “fingerprints.” Essentially, the colors of these emissions reveal the molecule’s composition – a combination of rainbow and identification.
The team, including researchers from the Centro de Astrobiología (CAB) and the Max Planck Institute, first synthesized the C₆H₆S molecule on Earth using electrical discharges on precursors like thiophenol. They then measured its emission frequencies using a specialized spectrometer, effectively determining its spectral “fingerprint.” This profile was then compared to data collected by radiotelescopes observing the G+0.693–0.027 molecular cloud near the galactic center.
The result was a clear signal confirming the presence of C₆H₆S, a molecule containing 13 atoms in its ring structure – significantly larger than any previously detected sulfur-containing compound in space. From a chemical perspective, the molecule’s structure – a six-membered ring containing sulfur – is particularly noteworthy. Such closed rings, like benzene, are exceptionally stable and serve as foundational structures for more complex molecules.
Sulfur is an essential element in Earth’s biochemistry, present in amino acids like methionine and cysteine, which are the building blocks of proteins, and playing key roles in metabolic processes. The discovery of complex sulfur-containing molecules in interstellar space suggests that some of the essential components for life’s chemistry may have been available even before the formation of stars and planets.
“This is the first unambiguous detection of a complex sulfur-containing molecule in interstellar space and a crucial step towards understanding the chemical connection between the interstellar medium and the building blocks of life,” explains Mitsunori Araki, a scientist at the Max Planck Institute for Extraterrestrial Physics, in a statement.
Until now, only relatively small sulfur compounds (containing up to nine atoms) had been identified in space. The presence of more complex sulfur molecules suggests that chemically rich environments may be more common throughout the universe than previously thought. The detection reinforces the idea that a significant foundation for prebiotic chemistry could be established before planetary formation, potentially increasing the likelihood of life arising elsewhere.
