Astronomers Discover Largest Aromatic Molecule in Deep Space

In a groundbreaking discovery in astrochemistry, a team of researchers has identified cyanocoronene, the largest polycyclic aromatic hydrocarbon (PAH) found in interstellar space to date. This significant finding, reported on June 12, 2025, was made in the cold molecular cloud TMC-1, known for its rich chemistry and role as a cradle for star formation.

Cyanocoronene, a complex molecule composed of seven interconnected benzene rings and a cyano group (C24H11CN), was synthesized in a laboratory before its unique microwave spectrum was measured using advanced spectroscopic techniques. According to Gabi Wenzel, a Research Scientist at the Massachusetts Institute of Technology (MIT) and the lead author of the research, “Each new detection brings us closer to understanding the origins of complex organic chemistry in the universe—and perhaps, the origins of the building blocks of life themselves.” This discovery adds a new chapter to the understanding of cosmic chemistry and the formation of planets.

Historically, polycyclic aromatic hydrocarbons have been recognized for their stability and role in the universe, acting as a significant reservoir of carbon. The discovery of cyanocoronene challenges existing theories that larger molecules should be rare in space, suggesting that even more complex aromatic structures may exist throughout the cosmos. The detection of this molecule was confirmed with a statistical significance of 17.3 sigma, a major threshold in astronomical standards.

The research team utilized data from the U.S. National Science Foundation Green Bank Telescope, a crucial tool in the GOTHAM (GBT Observations of TMC-1: Hunting Aromatic Molecules) project. By correlating synthesized data with observations, they successfully identified distinct spectral lines associated with cyanocoronene. The implications of this finding extend beyond mere molecular identification; they suggest that the processes involved in forming complex organics can occur even in the frigid environments of space.

As highlighted in the study published in IOP Science, the quantum chemical approach indicates that cyanocoronene can form efficiently under the cold conditions of space, further enhancing the understanding of chemical processes occurring prior to star formation. The presence of such stable, large PAHs supports the theory that these molecules might contribute to seeding new planetary systems with essential organic materials.

This discovery reinforces the 'PAH hypothesis,' which posits that these molecules are responsible for mysterious infrared emission bands observed across the universe. It also establishes a direct link between the chemistry of interstellar clouds and the organic molecules found in meteorites and asteroids, suggesting that the building blocks of life on Earth may have originated from similar cosmic environments long before the Sun's formation.

Looking ahead, scientists are eager to explore the potential for discovering even larger PAHs and their derivatives in space. The quest for understanding the origins and evolution of these molecules continues, promising to illuminate the pathways through which life may emerge in the universe. The Green Bank Observatory, operated under the National Radio Astronomy Observatory, remains a pivotal facility in this ongoing research, dedicated to advancing the study of astrochemistry and the mysteries of the cosmos.