His research involves Polycyclic Aromatic Hydrocarbons (PAH molecules). He was one of the first people to acknowledge the importance of these molecules in the universe. In 2012, Tielens was the most cited astronomer of The Netherlands and his work lies at the basis of current research.
Tielens’ research focuses mainly on the interstellar space and, in particular, on the Polycyclic Aromatic Hydrocarbons (PAH molecules) that are found in this space. His research made a significant contribution to the field of gas that is present in the photo-dissociation regions, interstellar dust and interstellar ice.
Tielens is also involved in the development of several satellites and telescopes including the SOFIA telescope and the European Herschel satellite.