Recent observations create a puzzle for astrophysicists: since the big bang, less galaxy clusters have formed over time than was actually expected. Physicists from the university of Bonn have now confirmed this phenomenon. For the next three years, the researchers will analyze their data in even greater detail. This will put them in a position to confirm whether the theories considered valid today need to be reworked. The study is part of a series of 20 publications which appear in the professional journal «Astronomy and Astrophysics».