Home page of Floris van der Tak

Submillimeter Scientist in the Astrophysics programme of the Netherlands Institute for Space Research (SRON)

and Professor of Submillimeter Astronomy at the Kapteyn Astronomical Institute of the University of Groningen.

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Radiative transfer
   Radex on-line
   Radex off-line
   Ratran program
   LAMDA database

Astrophysical web sites
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   Ground-based telescopes
   Space-based telescopes

   Interstellar Medium
  Star and Planet Formation

Inaugural lecture
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Research Interests

Physics of the interstellar medium and star formation

The stars that we see in the night sky have not always been there, and will not remain forever. They are part of a cycle of matter in galaxies, which includes clouds of gas and dust between the stars, the so-called interstellar medium (ISM). At the end of their lives, stars return much of their mass to the ISM, from which then new generations of stars are born. How exactly this process works and what determines the numbers, masses, and other properties of stars and planets is a question that my research focuses on. Click here to read more.


The gas in interstellar clouds is mostly hydrogen, but also contains traces of other molecules. Some of these are commonly known on Earth, such as carbon monoxide (CO), ammonia (NH3), and methanol (CH3OH), while others only occur under special laboratory conditions, such as formyl (HCO+). Some species were even found in space before they were known on Earth! The chemical composition of interstellar gas clouds reveals a great deal about their physical properties, and at the same time tells us about basic chemical processes that are hard or impossible to study on Earth. My research focuses on two specific areas: the ionization rates of interstellar clouds, and their temperature history. Click here to read more.

Molecular spectroscopy and radiative transfer

Astronomers use a technique called spectroscopy to observe specific molecules in space, and interpreting these observations requires specialized computer programs. My group develops such tools, in particular the fast non-LTE solver RADEX for clouds with a simple slab geometry, and the sophisticated Monte Carlo program RATRAN for spherical and cylindrical objects such as protostellar envelopes and disks. The molecular input data for both programs are collected in a database called LAMDA. Click here to read more.

Exoplanets and astrobiology

Since 1995, thousands of planets have been discovered around nearby stars; probably there are more planets than stars in the Universe. About 1% of planets resemble the Earth in size, composition, and temperature, which makes them candidates for habitable worlds. My research focuses on the question which conditions are required (and optimal) for life to originate (or at least survive) on planets, and how we may recognize signs of such life. Click here for my 2018 blog (in Dutch) about the prospects for life on the recently discovered TRAPPIST-1 planetary system.

Last update: July 27, 2018