I am Professor in Astronomy at Leiden University. My research focuses on extrasolar planets, worlds that orbit other stars than our Sun. While distances are enormous, making exoplanets extremely faint, our group devise techniques to study their properties. Longterm goals are to understand how planets form, how common our Solar System is, and to find out whether other life-bearing planets like Earth exist. The hope is that all these worlds, very far away, will teach us something about ourselves. How common is life, or are we alone in the Universe?


Our group develops observation and data-analysis techniques for ground-based telescopes to characterize atmospheres of extrasolar planets. These involve transit techniques, but also high-contrast imaging. Important successes have been reached using high-dispersion spectroscopy in which the planet light is separated from the much brighter starlight using its unique spectral features combined with time-differential and/or spatial separation techniques. In this way, atmospheric gases can be observed, global wind patterns, planetary rotation, and even specific isotopes.

Most of the time, the telescopes on La Palma (Canary Islands, Spain) and those from the European Southern Observatory (ESO, Chile) are used for this research. Most excitingly, the countries united in ESO are constructing the Extremely Large Telescope - with 39 meters diameter, by far the largest optical/near-infrared telescope in the world. In a few years from now, we can start studying nearby rocky planets, and find out how much they are like our own world.

mail: snellen@strw.leidenuniv.nl
twitter: @ignassnellen
visit: Leiden Observatory, J.H. Oortgebouw (rm 439), Niels Bohrweg 2, Leiden, NL