An international astrophysics team discovered a puzzling phenomenon when analyzing some star clusters . The study has been published in the monthly report of Royal Astronomical Society, and the discovery challenges the universal law of gravity of Newton . , however, this discovery is controversial among experts.
The team mainly studied open star clusters, which are loose combinations of dozens to hundreds of stars, and are present in spiral galaxy and irregular galaxy . When thousands of stars are born in huge gas clouds in a short time, they form open clusters.
When they "ignite", the newcomer of Milky Way blows away the remnants of the gas cloud. In this process, the cluster expands greatly. This forms a loose structure of dozens to thousands of stars. The clusters are held together by the faint gravity acting between them.
Professor Pavel Kroupa from the Helmholtz Institute of Radiation and Nuclear Physics, University of Bonn, explained: "In most cases, the scattered cluster can only survive for hundreds of millions of years before it is disbanded." During evolution, open clusters often lose stars, which accumulate in two so-called "tidal tails". As it travels through space, one of its tail is pulled behind the cluster. In contrast, another "Tidal Tail" takes the lead like a leader.
Dr. Jan Pflamm-Altenburg of the Helmholtz Institute for Radiation and Nuclear Physics explained: "According to Newton's law of gravity, it is a coincidence that a lost star will eventually appear on which tail, so the two tails should contain about the same number of stars. However, in our work, we were able to prove that this was not true for the first time: in the clusters we studied, the front tail always contained more stars near the cluster than the back tail".
When millions of stars begin to approach the cluster, it is almost impossible to determine who will join a certain "tidal tail". "To do this, you have to look at the speed, direction of motion and age of each object. So far, we have surveyed five open clusters nearby, four of which we surveyed ourselves. When we analysed all the data, we encountered a contradiction with the current theory. Very precise survey data from the ESA Gaia space mission is essential for this work."
In contrast, the observation data are more in line with the theory of the acronym MOND ("corrected Newtonian dynamics") in the expert. “In short, according to MOND, stars can leave a cluster through two different gates,” Kroupa explains. "One leads to the tidal tail behind, and the other leads to the front. However, the first one is much narrower than the second -- so it is unlikely that the star will leave the cluster through it. Newton's theory of gravity on the other hand predicts that the widths of the two doors should be the same."
