Astrophysicists made a mysterious discovery while analyzing certain star clusters. The finding challenges Newton’s laws of gravity. Instead, the observations are consistent with the predictions of the alternative theory of gravity. (Fictional concept of strange attraction.)
The finding cannot be explained by classical hypotheses.
An international team of astrophysicists made a perplexing discovery while analyzing certain star clusters. The researchers write in their publication that the finding contradicts Newton’s laws of gravity. Instead, the observations are consistent with the predictions of the alternative theory of gravity. However, this is disputed among experts. The results have now been published in the Monthly Notices of the Royal Astronomical Society. The University of Bonn played a major role in the research.
In their work, the researchers examined open star clusters, which are loosely connected groups of several dozen to several hundred stars found in spiral and irregular galaxies. Open clusters are formed when thousands of stars are born in a short period of time in a giant cloud of gas. As newcomers to the galaxy “acclimate”, they blow away the remnants of the gas cloud. In the process, the cluster expands greatly. This creates a loose formation of several dozen to several thousand stars. The masses are held together by weak gravitational forces acting between them.
Prof. Dr. Pavel Kroupa of the Helmholtz Institute for Radiation and Nuclear Physics, University of Bonn. In the process, they regularly lose stars, which accumulate in two so-called “arrival tails”. One of these tails is pulled behind the cluster as it moves through space. On the contrary, the other comes forward like a spearhead.
Prof. Dr. Pavel Kroupa of the Helmholtz Institute for Radiation and Nuclear Physics, University of Bonn. Credit: Volker Lannert / University of Bonn
Dr. Jan Pflamm-Altenburg of the Helmholtz Institute for Radiation and Nuclear Physics. “So both tails should have about the same number of stars. However, in our work we were able to prove for the first time that this is not true: In the clusters we studied, the front tail always contains significantly more stars near the cluster than the back tail.”
A new method for counting stars has been developed
Among the millions of stars close to a cluster, it has been almost impossible to identify those belonging to its tail. “For this, it is necessary to look at the speed, direction of movement and age of each of these objects,” said Dr. Tereza Jerabkova. The co-author of the paper, who received a PhD in Kroupa’s group, recently transferred from the university. European Space Agency (ESA) to the European Southern Observatory in Garching. He was the first to develop a method that allowed him to accurately count stars in tails. “Five open clusters have been investigated in the vicinity so far, four of them by us,” he said. “When we analyzed all the data, we encountered a contradiction with the existing theory. Very accurate survey data ESA’s Gaia space mission it was necessary for this”.
In the Hyades (top) star cluster, the number of stars in the front tidal tail (black) is significantly higher than in the rear. A similar picture emerges in a computer simulation with MOND (below). Credit: AG Kroupa/Uni Bonn
Observational data, on the other hand, fit better with a theory that goes with the shortening THE WORLD (“Modified Newtonian Dynamics”) among experts. “Simply put, according to MOND, stars can exit the same cluster through two different gates,” Kroupa explains. “One leads to the rear tidal tail and the other leads to the front. However, the former is narrower than the latter – so the star is less likely to separate from the cluster through it. Newton’s theory of gravity predicts that both doors should be the same width.
Star clusters are shorter-lived than Newton’s laws predict
A team of astrophysicists calculated the expected stellar distribution according to MOND. “The results are surprisingly consistent with observations,” emphasizes Dr. Ingo Thies, who played a key role in the corresponding simulations. “However, to do this we had to resort to relatively simple computational methods. “We currently lack the mathematical tools for a more detailed analysis of modified Newtonian dynamics.” Nevertheless, the simulations matched the observations in another respect: They predicted how long open star clusters typically survive. And this period is much shorter than expected according to Newton’s laws. “It explains a long-known mystery,” Kroupa said. “Probably star clusters in nearby galaxies are disappearing faster than they should.”
However, the MOND theory is not without controversy among experts. Newton’s laws of gravity will not be valid under certain conditions, but as they must be changed, this will have far-reaching consequences for other areas of physics. “It still solves many of the problems facing cosmology today,” explains Kroupa, who is a member of the Transdisciplinary Research Areas “Modelling” and “Matter” at the University of Bonn. Astrophysicists are now exploring new mathematical methods for more accurate simulations. They can then be used to find further evidence that MOND theory is correct.
Reference: Pavel Kroupa, Tereza Jerabkova, Ingo Thies, Jan Pflamm-Altenburg, Benoit Famaey, Henri MJ Tidal Beffin, Jörcmouenai, Pflamm-Altenburg, “Asymmetric tidal tails of open star clusters: stars intersecting the práh of their clusters challenge Newtonian gravity”, Christian Boily, Hosein Haghi, Xufen Wu, Jaroslav Haas, Akram Hasani Zonoozi, Guillaume Thomas, Ladislav Šubr, and Sverre J Aarseth, 26 October 2022, Monthly Notices of the Royal Astronomical Society.
DOI: 10.1093/mnras/stac2563
In addition to the University of Bonn, the study included Charles University in Prague, the European Southern Observatory ([{” attribute=””>ESO) in Garching, the Observatoire astronomique de Strasbourg, the European Space Research and Technology Centre (ESA ESTEC) in Nordwijk, the Institute for Advanced Studies in Basic Sciences (IASBS) in Zanjan (Iran), the University of Science and Technology of China, the Universidad de La Laguna in Tenerife, and the University of Cambridge.
The study was funded by the Scholarship Program of the Czech Republic, the German Academic Exchange Service (DAAD), the French funding organization Agence nationale de la recherche (ANR), and the European Research Council ERC.
