Detection of the Aromatic Molecule Benzonitrile ($c$-C$_6$H$_5$CN) in the Interstellar Medium

TL;DR

This paper reports the first detection of benzonitrile, a simple nitrogen-bearing aromatic molecule, in the interstellar medium, supporting theories about the prevalence of aromatic compounds in space.

Contribution

It provides the first observational evidence of benzonitrile in space, linking aromatic molecules to unidentified infrared bands and suggesting their role as precursors to polycyclic aromatic hydrocarbons.

Findings

Detected benzonitrile in the TMC-1 molecular cloud

Observed hyperfine-resolved emission transitions of benzonitrile

Supports the hypothesis that aromatic molecules are widespread in space

Abstract

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.