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Measuring Interstellar Reactions of Aromatics by Gas-phase Experiments

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Interstellar dust and planetary formation

Through cutting-edge laboratory techniques and international collaboration, one EU researcher investigated how aromatic molecules react at the very low temperatures of interstellar space – and what this means for newly forming, potentially habitable planets.

Space

The universe is a dusty place. Yet despite its prevalence, we know very little about interstellar dust, including how it is formed and the role it plays in creating, for example, new planetary systems. But this is starting to change, thanks in part to the recent discovery of the aromatic molecule benzonitrile in the Taurus Molecular Cloud (TMC), a large cloud of dust and gas about 450 light years from Earth. Due to a closed loop of electrons, aromatic molecules are defined by their special stability. “A plethora of aromatic molecules are found on Earth, but very few have been detected in space,” says Ilsa Cooke, a researcher at the University of Rennes 1. “Detecting these molecules in space and probing their chemistry in the lab can help us understand whether they are available to newly forming, potentially habitable planets.” With the support of the EU-funded MIRAGE project, Cooke is investigating how aromatic molecules react at the very low temperatures found in interstellar space.

International collaboration

The key goal of the project, which was undertaken with the support of the Marie Skłodowska-Curie Actions programme, was to understand how benzene, one of the simplest aromatic molecules, reacts with radicals and what this means for detecting other aromatic molecules in space. To do this, Cooke used cutting-edge laboratory techniques to investigate how fast benzene and other aromatic molecules react at the ultra-low temperatures found in space. These experiments aimed to simulate reactions that can occur in the depths of molecular clouds, hundreds of light years away. While this lab work was made more challenging by the COVID-19 pandemic, Cooke was able to conduct observations of interstellar space using the Green Bank Telescope, the world’s largest steerable radio telescope located in West Virginia, from her home in Rennes, France. Despite limited lab time and a shortened timeline, Cooke remained actively involved in an international collaboration that successfully detected the first polycyclic aromatic hydrocarbons (PAHs) in space. According to an article published in ‘Chemistry World’, this discovery challenges the scientific consensus that PAHs, which account for a significant portion of the universe’s carbon, only form in the hot atmospheres of dying stars. “These types of molecules had been predicted to exist in space for a long time but, until now, have always eluded detection,” explains Cooke.

Opening the door to new areas of research

Not only did the project help establish Cooke and the Rennes lab as key players in the study of how aromatic molecules react in space, it also opened the door to new areas of research. For example, in her new role as assistant professor of Chemistry at the University of British Columbia (UBC), Cooke plans to expand aspects of the project through continued collaboration with the University of Rennes 1. “We will continue to observe the chemical universe using radio telescopes to search for aromatic molecules at other stages of star-formation,” adds Cooke. “In doing so, we hope to unravel the mystery surrounding the origins and fate of interstellar PAHs.”

Keywords

MIRAGE, interstellar dust, aromatic molecules, space, planets, universe, planetary systems, benzene, Green Bank Telescope

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