Open star clusters and their asymmetrical tidal tails

TL;DR

This study tests the symmetry of tidal tails in open star clusters using Gaia data and finds strong evidence against Newtonian symmetry, supporting alternative gravitational theories like Milgromian dynamics.

Contribution

The paper provides the first empirical test of tidal tail symmetry in open clusters, challenging Newtonian gravity and supporting Milgromian dynamics based on Gaia observations.

Findings

Leading tails are more populated than trailing tails in observed data.

Newtonian symmetry hypothesis is falsified at 8 sigma confidence.

Milgromian dynamics are consistent with the observed asymmetry.

Abstract

Stars that evaporate from their star cluster by the energy equipartition process end up either in a leading or a trailing tidal tail. In Newtonian gravitation and for open star clusters in the Solar vicinity, the tidal threshold, or prah, for escape is symmetrical, such that the leading and trailing tails are equally populated. The data by six independent teams that applied the convergent point method to map out the tidal tails of four open clusters (the Hyades, the Praesepe, Coma Berenices and COIN-Gaia13) using Gaia DR2 and DR3 are here applied to test for the expected symmetry. All tidal tails contain more stars in the leading tail. The combined confidence amounts to an 8 sigma falsification of the prah symmetry. The same test using Milgromian dynamics leads to consistency with the data. More effort needs to be exerted on this matter, but the data indicate with high confidence that the tidal prah of an open star cluster is asymmetrical with the corresponding confidence that Newtonian gravitation is falsified. Open star clusters depopulate more rapidly in Milgromian than in Newtonian dynamics and the COIN-Gaia13 cluster is here found to be nearly completely dissolved. In view of these results, the wide-binary star test and the Keplerian Galactic rotation curve finding are briefly discussed.