Computer simulation of a merger of two stars
Computer simulation of a merger of two stars


“The radiation is the final and observable result of a complex fusion process that involves strong gravitation, heavy elements, neutrino physics, nucleosynthesis and radiation transport. Comparing our computer models with actual observations will help us to understand what really happens in such cosmic collisions,” says Stephan Rosswog, professor of astrophysics at Stockholm University.

The five-year project, which has been awarded funding of SEK 33.5 million from the Knut and Alice Wallenberg Foundation, brings together a number of different research areas to study different aspects of collisions between neutron stars. Stephan Rosswog, research leader of the project, has been studying colliding neutron stars for more than 20 years. He was one of the first to propose these collisions as sources of many of the heaviest elements around us, not least gold. 

In 2017, gravitational radiation and light were detected for the first time from a collision between two neutron stars and the periodical Science counted it as the year’s most important scientific breakthrough. This discovery confirmed many of Rosswog’s theories and part of the project is to continue this work.

The research group comprises scientists who are working on both theoretical modelling and observational studies. The results from a complete chain of computer models, starting at the moment of the merger and ending at the main electromagnetic emission weeks later, can be compared to actual observations. In this way the researchers hope to find out more about where and how the heaviest elements in the universe are created.

“This research field brings Einstein’s theory of relativity together with questions about the origins of the heavy elements. By combining supercomputer models with direct astronomical observations, we could learn how the heaviest elements in the universe are created,” says Stephan Rosswog.

Could give clues to the expansion of the universe

Another of the project’s objectives is to use these results to produce new tools for measuring distances in the universe, and thereby determine its expansion speed.
“This is fantastic news for our team! This funding will strengthen our multidisciplinary research collaboration. It also gives us the long-term security to be able to tackle the challenges that are found in this new area,” says Stephan Rosswog.

The research group for “Gravity meets light” also includes Anders Jerkstrand and Jesper Sollerman of the Department of Astronomy and Hiranya Peiris and Ariel Goobar of the Department of Physics.

About the grant
The Knut and Alice Wallenberg Foundation awards grants each year to research projects that are judged to have the potential to lead to a future scientific breakthrough. In 2019, the foundation has granted SEK 640 million to 20 research projects. Four of these grants, worth a total of around SEK 132 million, have gone to Stockholm University.