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Spectroscopy of cosmic dust analogs: study of the interaction with polycyclic aromatic hydrocarbons

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A rare glimpse of the aromatic world

In the past, interstellar dust was an annoyance because it obscures objects astronomers want to observe. A new look at the dust permeating the Universe provided them with ways to identify organic matter created naturally by stars.

Climate Change and Environment

The composition of cosmic dust depends on where the dust is found. However, based on the wealth of observations from ground- and satellite-based telescopes, it has been well established that a significant component of dust grains and aggregates of dust grains is carbonaceous material. EU-funded scientists aimed to be considerably more precise in its detailed chemical and structural properties. Within the context of the 'Spectroscopy of cosmic dust analogs: Study of the interaction with polycyclic aromatic hydrocarbons' (PAHCNP) project, scientists simulated chemical processes that occur in astrophysical environments. Specifically, the absorption of polycyclic aromatic hydrocarbons (PAHs) by carbon particles was reproduced by mimicking conditions of astrophysical environments. These organic molecules are pervading space between stars. Containing only carbon and hydrogen, PAH molecules are called 'polycyclic' because of their many rings of carbon atoms and 'aromatic' because of the strong chemical bonds between them. On Earth, PAHs are formed during incomplete combustion of almost any organic material. In the laboratory, mixtures of PAHs and buckminsterfullerene (C60) were prepared by laser-induced pyrolysis of hydrocarbons like ethylene and acetylene. C60 has been recently confirmed as the largest molecule identified in space. Guided by observational evidence of the photochemical evolution of carbonaceous compounds upon strong ultraviolet irradiation, a series of experiments was conducted during the PAHCNP project. Their results shed light into the role of PAHs as both product and precursor of condensation processes ultimately leading to C60, a cage-like carbon molecule. In each photochemical evolution pathway, parameters such as temperature and intensity of ultraviolet irradiation influenced the condensation mechanism and, thus, the composition of by- and end-products. Different techniques were applied to obtain valuable information into alternative formation routes that are key to understanding the aromatic inventory in space. The PAHCNP laboratory studies offered a new look at what is believed by many to hold the key to life's origins — not just on our planet but also for the entire Universe.

Keywords

Interstellar dust, stars, cosmic dust, dust grains, carbonaceous, polycyclic, polycyclic aromatic hydrocarbons, hydrocarbons, carbon particles, astrophysical, buckminsterfullerene, pyrolysis, ultraviolet irradiation

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