STRW local: Colloquia


Lifting the Veil on Aromatic Chemistry: Complex Carbon Across the Stellar Lifecycle

Date: 18-03-2019
Time: 15:30 h
Author: Brett McGuire

Up to 25% of interstellar carbon is ultimately fated to be locked up in polycyclic aromatic hydrocarbons (PAHs). These extremely large molecules play crucial roles in the star and planet formation cycle, not only as reservoirs and sinks of carbon, but as charge regulators, as sites of molecular hydrogen formation, and as the seeds of interstellar dust. In recent years, it has widely been believed that PAHs are the result of post-AGB stars essentially acting as sooting candles, ejecting large carbon species into the ISM as they age. It was therefore surprising when we recently detected the aromatic molecule benzonitrile (C6H5CN) in TMC-1, a quiescent dark cloud that is in the very infancy of its collapse to star formation. This detection suggests not only that the genesis of large aromatic molecules may be far, far earlier in the star-formation process than we had thought, but that we also must consider that these species could have a substantial driving influence on both the chemical and physical evolution of newborn stars and planets. In this talk, I will first discuss the initial detection of benzonitrile and describe our follow-up laboratory spectroscopic work to characterize its formation chemistry and relationship with the keystone aromatic molecule benzene (C6H6). I will then provide an overview of a Large Program (GOTHAM/ARKHAM) on the Green Bank Telescope to unveil this hidden chemistry in TMC-1 and expand our investigations to more evolved sources. Several early science results, including the discovery of benzonitrile in additional pre-stellar sources as well as the detections of five new interstellar carbon-chain molecules, will be presented and discussed in the context of the broader lifecycle of complex carbon throughout the star-formation process.