March 22, 2023

Are Newton’s Laws of Gravitation Wrong: Mysteries of Researchers’ Observations

Astrophysicists made a puzzling discovery while analyzing some star clusters. This discovery defies Newton’s laws of gravity. Instead, the observations are consistent with the predictions of an alternative theory of gravity. (The technical meaning of extraterrestrial gravity.)

The discovery cannot be explained by classical assumptions.

An international team of astrophysicists made a puzzling discovery while analyzing some star clusters. This discovery defies Newton’s laws of gravity, the researchers write in their publication. Instead, the observations are consistent with the predictions of an alternative theory of gravity. However, this is controversial among experts. The results have now been published in the Monthly Notices of the Royal Astronomical Society. The University of Bonn played an important role in the study.

In their work, the researchers investigated so-called open star clusters, unconnected groups of a few dozen to a few hundred stars found in spiral and irregular galaxies. Open clusters form when thousands of stars are born within a short period of time in a huge cloud of gas. When “ignited,” the galactic newcomers eject the remnants of a gas cloud. During the process, the mass expands significantly. This creates a loose formation of several tens to several thousand stars. The mass is held together by the weak gravitational forces acting on each other.

“In most cases, open star clusters live only a few hundred million years before they melt,” explains Professor Dr. Pavel Krupa from the Helmholtz Institute for Radiation and Nuclear Physics at the University of Bonn. In the process, stars are regularly lost, which accumulate in so-called “tidal tails”. One of these tails is pulled back by the block as it travels through space. In turn, the other takes the lead like a spearhead.

Pavel Krupa

Prof. Dr. Pavel Krupa from the Helmholtz Institute for Radiation and Nuclear Physics of the University of Bonn. Credit: Volker Lanert/University of Bonn

“According to Newton’s laws of gravity, it is a matter of chance which of the tails ends up in the lost star,” explains Dr Jan Pvalam-Altenberg of the Helmholtz Institute for Radiation and Nuclear Physics. “So both ends should contain roughly 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 more near-mass stars than the back tail.

A new method for calculating stars was developed

Among the millions of stars close to the mass, it has been almost impossible to determine which ones belong to their tail – until now. “To do this, you need to look at the speed and direction of movement and the age of each of these objects,” explains Dr. Teresa Yarabkova. The study’s co-author, who received her Ph.D. in the Kroupa group, recently moved from the European Space Agency (ESA) to the European Southern Observatory in Garching. She developed a method that allowed her to accurately measure the stars in their tails for the first time. “So far, five open clusters have been investigated near us, including four of us,” he says. “When we analyzed all the data, we encountered the contradiction with the current theory. The highly accurate survey data from the European Space Agency’s Gaia mission is essential for this.”

A history of frontal tides from the Hyades star cluster

In the Hyades star cluster (top), the number of stars (black) in the front tidal tail is much larger than in the back. In a computer simulation with MOND (below), a similar picture emerges. Credit: AG Kroupa / Uni Bonn

Instead, the observational data best fits the theory for short MOND (“Modified Newtonian Dynamics”) among experts. “Simply put, according to MOND, stars can leave a cluster through two different doors,” Krupa explains. “One leads the tail tidally back, the other forward. However, the former is much narrower than the latter – so it’s unlikely that the star will leave mass through it. On the other hand, Newton’s gravitational theory predicts that both doors should be the same width.’

Star clusters have shorter lifetimes than Newton’s laws predict

The 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 respective simulations. However, we had to resort to relatively simple numerical methods to do so. We currently do not have the mathematical tools to perform more detailed analyzes of Modified Newtonian dynamics.” However, the simulations also matched observations from the other side: they predicted how long normally open star clusters should remain. This time period is much shorter than expected according to “This explains a known mystery,” notes Krupa. “In particular, star clusters in nearby galaxies appear to be disappearing faster than they should.”

However, the MOND theory is not undisputed among experts. Since Newton’s laws of gravity would not be valid under certain conditions, but would have to be modified, this would have far-reaching consequences for other areas of physics. “Again, it solves many of the problems that cosmology faces today,” explains Krupa, who is also a member of the Interdisciplinary Research Areas of Modeling 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 more evidence about whether the MOND theorem is true or not.

Reference: “Asymmetric Tidal Tails of Open Stars: Brah Cluster Crossing Stars Defy Newtonian Gravity” by Pavel Karpa, Teresa Yarabkova, Ingo Theis, Jan Pvalam-Altenberg, Benoit Famy, Henry MJ Boffin, Jörg Beccario, Giacom, , Christian Boyle, Hossein Hajji, Zuven Wu, Jaroslav Hass, Akram Hosni Zunuzzi, Guillaume Thomas, Ladislav Uber and J Arsith Ambassador, 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.

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