Polycyclic aromatic hydrocarbons and polycyclic aromatic nitrogen heterocycles are abundant throughout the Universe. They emit a characteristic set of emission features in the infrared, which are observed in many space environments. However, identifying precisely which aromatic molecules are present is very difficult.

Brett McGuire, National Radio Astronomy Observatory, Charlottesville, VA, USA, and colleagues have discovered benzonitrile in the interstellar medium. Hyperfine-resolved transitions of benzonitrile were found while probing a well-known nearby cloud of interstellar gas, the molecular cloud TMC-1 in the Taurus constellation, with the powerful Green Bank Telescope in West Virginia. This is the first time scientists have identified an aromatic molecule in space.

Molecules in space can be observed by looking with a telescope at the light they absorb or emit when the atoms in the molecule vibrate. The team used radio astronomy, so-called spectral-stacking procedure, to detect rotational transitions of benzonitrile. To confirm their data, the team compared these data with laboratory measurements of the different rotational transitions of the molecule. By this, they were able to observe nine different rotational transitions of benzonitrile.

• Detection of the aromatic molecule benzonitrile (c-C₆H₅CN) in the interstellar medium,
  Brett A. McGuire, Andrew M. Burkhardt, Sergei Kalenskii, Christopher N. Shingledecker, Anthony J. Remijan, Eric Herbst, Michael C. McCarthy,
  Science 2018, 359(6372), 202–205.
  https://doi.org/10.1126/science.aao4890