Alexander Godfried Gerardus Maria (Xander) Tielens (born 1953) is a Dutch astronomer. He is Adjunct Professor at the University of Maryland, College Park and Emeritus Professor at Leiden Observatory, Leiden University, in the Netherlands. He previously worked at NASA Ames Research Center, California and the University of California, Berkeley, and was previously a professor at the University of Groningen. In 2012, Tielens received the highest distinction in Dutch science, the Spinoza Prize, and he was the most cited astronomer in the Netherlands.
Biography Tielens has contributed significantly to several fields of astronomy, including interstellar physics and astrochemistry. NASA ADS Citation report He is mostly known for his work on large aromatic molecules (PAHs) in space Review on PAHs and on photodissociation regions. He is also the author of a reference textbook on the interstellar medium.The Physics and Chemistry of the Interstellar Medium
Tielens is the project scientist of the HIFI instrument on board of the Herschel Space Observatory. He used to be the NASA Project Scientist of the Stratospheric Observatory for Infrared Astronomy.
Since 2012 Tielens has been a member of the Royal Netherlands Academy of Arts and Sciences.
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