A detection of sulfur-bearing cyclic hydrocarbons in space

TL;DR

This paper reports the first astronomical detection of a sulfur-bearing cyclic hydrocarbon in space, specifically in a galactic molecular cloud, using laboratory spectroscopy for identification.

Contribution

It provides the first identification of a six-membered sulfur cyclic hydrocarbon in the interstellar medium, linking interstellar chemistry to prebiotic molecules.

Findings

Detection of 2,5-cyclohexadien-1-thione in space

Laboratory measurements enabled unambiguous identification

Largest interstellar sulfur-bearing molecule discovered

Abstract

Molecules harbouring sulfur are thought to have played a key role in the biological processes of life on Earth, and thus, they are of much interest when found in space. Here we report on the astronomical detection of a six-membered sulfur-bearing cyclic hydrocarbon in the interstellar medium. Observations of the Galactic Centre molecular cloud G+0.693-0.027 reveal the presence of 2,5-cyclohexadien-1-thione, which is a structural isomer of thiophenol ($c$-C$_6$H$_6$S). For the astronomical identification, we first performed precise laboratory measurements of the thiophenol discharge products system. These measurements, conducted in the radio band using a chirped-pulse Fourier transform microwave spectrometer, enabled us to characterize this highly polar molecular species and provided unambiguous fingerprints needed to identify this organosulfur compound in space, which now ranks as the largest interstellar sulfur-bearing molecule. These results herald the discovery of a family of prebiotically relevant sulfur-bearing species, which potentially act as a bridge between the chemical inventory of the interstellar medium and the composition of the minor bodies of the Solar System.