Scientists have tried for years to identify the matter that exists between stars. Now a Stanford University research team may be closer to reaching that goal.

The group exposed polycyclic aromatic hydrocarbons in ice to ultraviolet radiation under astrophysical conditions. Next, they analyzed the products using IR spectroscopy and mass spectrometry. Peripheral carbon atoms underwent oxidation, producing aromatic alcohols and ethers. These were reduced, producing partially hydrogenated aromatic hydrocarbons, molecules that account for interstellar emissions at 3.4 µm.

Because polycyclic aromatic hydrocarbons are abundant throughout the solar system, the team said the research demonstrates that the photochemistry of these molecules in interstellar ices could be a contributor to interstellar organic chemistry.

Furthermore, complex organic molecules similar to the ones produced in the experiment have been found in meteorites, along with oxidized polycyclic aromatic hydrocarbons. Details of the work appear in the Feb. 19 issue of Science.