Physics

Astronomy

Hyperfine structure

Infrared

Organic chemistry

Astrochemistry

Atomic physics

Chemistry

Aromaticity

Interstellar medium

Hydrocarbon

Aromatic hydrocarbon

Polycyclic aromatic hydrocarbon

Nitrile

Benzonitrile

Molecule

Astrophysics

Photochemistry

Astrobiology

Galaxy

Science

Polycyclic aromatic hydrocarbons and polycyclic aromatic nitrogen heterocycles are thought to be widespread throughout the Universe, because these classes of molecules are probably responsible for the unidentified infrared bands, a set of emission features seen in numerous Galactic and extragalactic sources. Despite their expected ubiquity, astronomical identification of specific aromatic molecules has proven elusive. We present the discovery of benzonitrile ($c$-C$_6$H$_5$CN), one of the simplest nitrogen-bearing aromatic molecules, in the interstellar medium. We observed hyperfine-resolved transitions of benzonitrile in emission from the molecular cloud TMC-1. Simple aromatic molecules such as benzonitrile may be precursors for polycyclic aromatic hydrocarbon formation, providing a chemical link to the carriers of the unidentified infrared bands.

Detection of the aromatic molecule benzonitrile ( c -C 6 H 5 CN) in the interstellar medium