The POLAR-2 project is an international scientific mission aimed at studying gamma-ray bursts (GRBs) by measuring the polarisation of their radiation. The instrument will be installed on the Chinese Space Station. On the Polish side, the project is led by Prof. Agnieszka Pollo, and Dominik Rybka, MSc Eng., is responsible for coordinating the technical packages. Both are scientists from the National Centre for Nuclear Research.

POLAR-2 is one of six experiments selected in 2019 as part of a joint competition announced by the United Nations Office for Outer Space Affairs (UNOOSA) and the China Manned Space Agency (CMSA). The project is being carried out by an international consortium of institutes from Poland (the National Centre for Nuclear Research, NCBJ), Switzerland (the University of Geneva), Germany (the University of Tübingen) and China (the Institute of High Energy Physics of the Chinese Academy of Sciences, IHEP).

In November this year, meetings and events related to the POLAR-2 project were held in Beijing with the participation of the Polish delegation. Prof. Agnieszka Pollo, Dominik Rybka, MSc Eng. and Grzegorz Łubian, Eng. held talks on, among other things, the progress of work on the construction of the instrument and the scientific use of data, and visited selected research and technical centres.

The main objective of the POLAR-2 mission is to precisely measure the polarisation of cosmic gamma-ray bursts (GRBs) — some of the most powerful explosions in the Universe, associated with the final stages of the evolution of massive stars, such as hypernova explosions or neutron star collisions. - In recent years, interest in GRBs has grown because these phenomena are also the source of observed gravitational waves. Despite the growing observational base, the mechanism of gamma-ray burst formation is still not fully understood. A key piece of missing information remains the measurement of radiation polarisation, which may explain, among other things, the role of the magnetic field in the source of the burst. Existing measurements are scarce and do not allow for clear conclusions. We estimate that once in orbit, POLAR-2 will record about 250 gamma-ray bursts per year, of which about 30 will have high-quality polarisation measurements - says Professor Agnieszka Pollo.

The series of meetings in November allowed for intensive discussions, exchange of experiences and presentation of the research competences of the teams participating in the experiment. It was an opportunity to discuss not only further activities within the POLAR-2 mission, but also possible future joint scientific and technological initiatives.