Polycyclic aromatic hydrocarbons (PAHs) are believed to be the most prevalent class of organic compounds in the universe, yet their lifecycle in interstellar media remains poorly understood. Recently, astronomers using NSF’s Green Bank telescopes identified cyanocoronene (C24H11CN), the largest PAH discovered in space, located within the starless cloud core TMC-1.
Cyanocoronene, composed of seven interconnected benzene rings and cyano groups, is a region known for its abundant chemistry and was discovered in the cold, dark molecular cloud TMC-1, recognized as a new cradle for star formation. Image credits: NSF/AUI/NSF/NRAO/P.VOSTEEN.
Cyanocoronene is a derivative of coronene, often regarded as a prototype compact PAH due to its stability and distinctive structure.
PAHs are thought to play a crucial role in the chemistry that captures a significant portion of the universe’s carbon and contributes to star and planet formation.
Until this discovery, only smaller PAHs had been identified in space, making this finding a significant leap in understanding size limits.
“Each new detection brings us closer to understanding the origins of the complex organic chemistry in the universe, and possibly the building blocks of life,” says Dr. Gabi Wentzel, an astronomer at the Center for Astrophysics at MIT and Harvard & Smithsonian.
Dr. Wentzel and her team first synthesized cyanocoronene in the laboratory and recorded its unique microwave spectrum using advanced spectroscopic methods.
Equipped with this molecular fingerprint, the astronomers searched data from the Green Bank telescope, the primary instrument for the Gotham project (GBT observations of TMC-1: GBT observations of aromatic molecules).
They identified several spectral lines of cyanocoronene, confirming its presence with a statistical significance of 17.3 sigma, a robust detection by astronomical standards.
Cyanocoronene is currently the largest individual PAH molecule found in interstellar space, featuring 24 carbon atoms in its core structure (excluding the cyano group).
The quantity of cyanocoronene detected is comparable to that of smaller PAHs previously identified, challenging the notion that larger molecules are rare in the universe.
This indicates that even more complex aromatic molecules may be prevalent in the cosmos.
“The presence of such a large, stable PAH lends support to the idea that these molecules can serve as significant reservoirs of carbon and potentially facilitate the formation of new planetary systems throughout their lifecycle,” the researchers stated.
“The quantum chemical analysis in this study reveals that the reaction between coronene and CN radicals enables the efficient formation of cyanocoronene in cold space conditions.
“This implies that even prior to star formation, there can be chemical processes that establish complex organic matter.”
“The discovery of cyanocoronene not only adds new chapters to the narrative of astrochemistry but also reinforces the PAH hypothesis. It suggests that these molecules are responsible for the enigmatic infrared emission zones scattered throughout the universe.”
“Additionally, it establishes a direct link between interstellar clouds, meteoroids, and asteroid chemistry, implying that organic molecules present in our solar system might have originated in similar environments long before the Sun was born.”
The scientists presented their Survey results on June 11th at the AAS246, 246th Summer American Astronomical Association.
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Gabi Wenzel & Gotham Collaboration. 2025. Discovery of 7-ring PAH cyanocoronene (C24H11CN) from Gotham observation of TMC-1. AAS246 Summary #75
Source: www.sci.news
