| Feb 09, 2026 |
Scientists discovered that galaxy clusters are about twice as heavy as previously assumed. The additional mass comes mainly from neutron stars and stellar black holes and also explains the observed quantities of heavy elements.
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(Nanowerk News) Galaxy clusters are the largest gravitationally bound structures in the universe, but their mass and composition have not yet been fully researched. A new study led by Prof. Dr. Kroupa investigated how stellar populations and matter are distributed in the clusters. Using the Integrated Galaxy-wide Initial Mass Function (IGIMF) theory developed in Bonn, realistic star populations were calculated and the total masses of the clusters were determined.
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The study (Physical Review D, “Revisiting the missing mass problem in MOND for nearby galaxy clusters”) shows that galaxy clusters are about twice as heavy as previously assumed. The newly determined masses are in good agreement with the predictions of Milgrom’s theory of gravity (MOND). Newton’s theory with dark matter, on the other hand, does not provide correct results, as the amount of dark matter required for this is only about half as much as previously assumed.
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| The Abell 209 galaxy cluster – at a distance of 2.8 billion light-years. (Image: ESA/Hubble & NASA, M. Postman, P. Kelly)
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For the study, the researchers had to compile a large amount of observational data on numerous galaxy clusters, including data from gravitational lens measurements and detailed information about the individual galaxies. On this basis, the star populations of each galaxy had to be recalculated in order to finally determine the total mass of the clusters.
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The results provide a new understanding of the connection between space-time and matter, which could potentially lead to new technologies in the future.
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In addition to the Helmholtz Institute for Radiation and Nuclear Physics at the University of Bonn, the Astronomical Institute of Charles University in Prague and the Institute for Advanced Studies in Basic Sciences (IASBS) at the University of Zanjan, Iran, were also involved in the study.
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