Molecules play a key role in controlling the physics and chemistry of the Interstellar Medium – the space between the stars. Molecules impact on the distribution of energy in the Interstellar Medium and this in turn controls where and when stars and planetary systems form. One class of molecules, the polycyclic aromatic hydrocarbons or “PAHs”, play a particularly important role. Close to 15 % of all of the carbon in interstellar space exists in a PAH molecule. PAHs play key roles in the ionization balance and heating of the interstellar gas, and thus influence the phase structure of the interstellar medium. Everywhere you point a telescope in space, you will observe the presence and influence of PAHs. PAHs are also central to the chemical complexity of space and the organic inventory of regions of star and planet formation. The PAH molecules present when planetary systems are forming may influence the chemical species that evolve on that planet. Understanding PAHs and their role in the Universe is thus a key question in astrophysics.
EUROPAH brought together, astronomers, astrophysicists, astrochemists, biologists, social scientists and plasma physicists to create an interdisciplinary research and innovation environment. Our aim was to use cutting edge experimental and computational approaches to gather fundamental research data in laboratory settings, to understand how PAH molecules behave in the Interstellar Medium. The data from the EUROPAH network will help astronomers to interpret the data from their observations, and offers a firm understanding to the observations made using past, present and future telescopes. On Earth, PAHs are predominantly known as carcinogenic pollutants, as found, for example, in motor vehicle exhaust fumes and petroleum‐related pollution. Some of the methods used to understand the chemistry of PAHs in the Interstellar Medium may also help us understand the behaviour of PAHs on our own planet.
A new generation of 18, diverse researchers were recruited and trained to be capable of interacting and working together in a multidisciplinary world. They demonstrated many new aspects in the physics and chemistry of PAH molecules. Infrared spectra of PAH species is the core means of identifying these molecules via observational astronomy. EUROPAH produced IR spectra of a vast array of PAH molecules, in various chemical states and developed the computational methods necessary for understanding these spectra and predicting how other PAH species might be identified in the ISM. The interaction of PAHs with ionising radiation demonstrated how these molecules can recycle energy in the Interstellar Medium to generate new chemical species. PAHs interact with interstellar nano‐scale dust grains both on Earth and in the ISM, and EUROPAH researchers demonstrated how PAHs interact with other chemical species, such as ices, dust grain surfaces, nanoparticle, and atomic H and O to generate larger but also smaller chemical entities; identifying some species that might act as precursors for the chemistry building blocks we think of as essential for life on Earth. Finally, we learned how incorporation of interactions with the public as a compulsory part of our researchers’ learning experience provided a step towards a different culture of research.
