Researchers from the GOTHAM project have identified specific polycyclic aromatic hydrocarbon (PAH) molecules in the cold molecular cloud TMC-1, which has not even started star formation yet.

According to scientists, it was previously thought that a significant part of the carbon in space is in the form of large molecules of polycyclic aromatic hydrocarbons (PAHs). Studies have found confirmation of this, however, it was impossible to understand what exactly these compounds are.

Such large PAH molecules on Earth are formed only at high temperatures: as by-products of burning fossil fuels. They can be found, for example, in charring marks on grilled food.

During the search for PAHs, the authors of the new work studied the TMC-1 nebula, part of the Taurus Molecular Cloud, using the Green Bank Radio Telescope (GBT) in the United States. In order to conduct the research more efficiently, they developed a technology for extracting elusive signals from noise by summing and processing the observation results through special filters.

As a result, in a cold interstellar cloud with a temperature of 10 degrees above absolute zero, the authors identified about 12 specific PAH molecules. They described two of them – these are 1- and 2-cyanonaphthalene – compounds consisting of two condensed benzene rings with an attached nitrile group.

We stumbled upon a whole new set of molecules, different from anything we’ve seen before, and this completely changes our understanding of how these molecules interact with each other. It is believed that polycyclic aromatic hydrocarbons contain up to 25 percent of the carbon in the universe. Now, for the first time, we have a direct window into their chemistry, which will allow us to study in detail how this massive carbon reservoir evolves.

Brett McGuire, first author of the article, assistant professor of chemistry and principal investigator of the GOTHAM project