New puzzling discovery challenges Newton’s laws of gravitation

Until now, it has been almost impossible to identify those that belong to its tails among the millions of stars near a cluster. To do this, you need to look at the speed, direction of movement, and age of each of these objects.

An international team of astrophysicists has made a puzzling discovery while analyzing certain star clusters that challenges Newton’s laws of gravitation. However, the observations agree with the predictions of the alternative theory of gravity. However, this is controversial among experts.

The so-called open star clusters have been a subject of study for scientists. These form when a large gas cloud containing thousands of stars rapidly spawns stars. The remnants of the gas cloud are blown away when the cosmic arrivals “ignite”. During this process, the cluster grows significantly. This results in a loose constellation of a few dozen to a few thousand stars. The cluster is held together by the weak gravitational forces between them.

Prof. Dr. Pavel Kroupa from the Helmholtz Institute for Radiation and Nuclear Physics at the University of Bonn said: “In most cases, open star clusters only survive for a few hundred million years before they disintegrate. They regularly lose stars, which accumulate in two so-called “tidal tails”. One of these tails is trailed behind the heap as it travels through space. The other, on the other hand, goes ahead like a spearhead.”

dr Jan Pflamm-Altenburg from the Helmholtz Institute for Radiation and Nuclear Physics said: “According to Newton’s laws of gravitation, it is a matter of chance in which tail a lost star lands. So both tails should contain about the same number of stars. However, in our work we were able to prove for the first time that this is not the case: In the clusters we examined, the front tail always contains significantly more stars in the vicinity than the back tail.”

By developing a new method, scientists were able to develop a method that allowed them to accurately count the stars in the tails for the first time.

dr Tereza Jerabkova, a co-author of the paper, said: “So far, five open clusters have been investigated in our vicinity, four of them by us. When we analyzed all the data, we encountered a contradiction with current theory. The very precise measurement data from the ESA space mission Gaia were indispensable for this.”

Kroupa said “The observational data, on the other hand, fits much better with a theory known in professional circles by the acronym MOND (“Modified Newtonian Dynamics”). Simply put, according to MOND, stars can leave a cluster through two different doors. One leads to the aft tidal tail, the other to the front. However, the first is much narrower than the second – so it’s less likely for a star to exit the cluster through it. Newton’s theory of gravity, on the other hand, predicts that both doors should be of equal width.”

dr Ingo Thies, who was significantly involved in the relevant simulations, said: “The results agree surprisingly well with the observations. However, we had to resort to relatively simple calculation methods. We lack the mathematical tools for more detailed analysis of modified Newtonian dynamics.”

“Nevertheless, the simulations agreed with the observations in another respect: they predicted how long open star clusters should typically survive. And this period of time is significantly shorter than expected according to Newton’s laws. This explains a long-known mystery. Star clusters in nearby galaxies seem to be disappearing faster than they should.”

Magazine reference:

1. Pavel Kroupa et al. Asymmetric tidal tails of open star clusters: Stars crossing their cluster’s Práh† challenge Newtonian gravity. Monthly Bulletins of the Royal Astronomical Society. DOI: 10.1093/mnras/stac2563