Picture of Garrelt Mellema

Garrelt Mellema

Studierektor, professor

Visa sidan på svenska
Works at Department of Astronomy
Telephone 08-553 785 52
Visiting address Roslagstullsbacken 21, C 6 & D 6
Room C6:3055
Postal address Institutionen för astronomi 106 91 Stockholm

About me

I am a professor at Stockholm University working at the department of Astronomy and the Oskar Klein Centre. In this profile I give an overview of my various work-related activities.



Undergraduate education

In recent years my educational activities have been at the organisational level as I have been director of studies for the department of astronomy. This means that I have the overall responsibility for the courses taught at the first and second level, which means our Bachelor courses, Master courses and our introductory courses.

During my time as director of studies I have not been teaching any courses. However, in the past I taught

And was also one of the teachers on


Graduate courses

Graduate students can take this numerical assignment which I designed:



My main research focus is on the period in the history of the Universe when the first stars and galaxies formed, several 100s of millions of years after the Big Bang, or 13 billion years ago. We do not know much about this period as even the largest existing telescopes are barely powerful enough to detect the galaxies from this time.

However, efforts are underway to detect and map the distribution of matter during this era by using a new generation of radio telescopes. These radio telescopes operate at low frequencies (below 200 MHz) and can pick the signal produced by the neutral hydrogen in the Universe. The distribution of neutral hydrogen will teach us much about the state of the Universe in this watershed period when the first stars and galaxies formed.

The two radio telescope project I am involved in are LOFAR (Low Frequency Array), a European collaboration involving Sweden together with the Netherlands, Germany, Great Britain, France, Poland and Ireland, and SKA (Square Kilometre Array), a global project also involving Sweden. LOFAR is currently collecting data and the SKA is in its design phase and will start operations after 2020.

My contributions to these projects consist of detailed numerical simulations of what the signal from neutral hydrogen will look like and how we can use it to extract detailed information about the first stars and galaxies. These numerical simulations are among the most advanced in the world and are performed using the largest supercomputers in the world. Courtesy of the Swedish National Infrastructure for Computing (SNIC) I make for example use of the beskow supercomputer at the PDC Center for High Performance Computing at the KTH Royal Institute of Technology. I have also used European supercomputers through PRACE (Partnership for Advanced Computing in Europe)

Last updated: February 6, 2020

Bookmark and share Tell a friend