Puzzling astronomical observations support alternative theory of gravity questioning the existence of dark matter

Amazing stuff! Are we finally able to explain Dark Matter/Energy? For almost a century scientists got away explaining the universe using such obscure terms like Dark Matter for lack of better knowledge. 

Learn how the Phantom of Ramses code was involved in this study! Astronomers have too much fun! 😊

This work raises the interesting question whether the force of gravity is influenced by velocity or motion. 

"... An international team of astrophysicists had been investigating open star clusters, which contain thousands of young stars being born from a large cloud of dust and gas. These clusters have a relatively short lifespan before they dissolve, as the stars drift into two “tails” – one in front of the cluster and one behind.

“According to Newton's laws of gravity, it's a matter of chance in which of the tails a lost star ends up,” ... “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 true: In the clusters we studied, the front tail always contains significantly more stars nearby to the cluster than the rear tail.” ...

In the past it’s been tricky to determine which of a cluster’s stars belong to which tail, but the researchers on the new study developed a method to do so. They call it the Jerabkova-compact-convergent-point (CCP) method, and this was applied to data on four open star clusters gathered by surveys like the Gaia mission. To their surprise they found that in all four clusters, the leading tail had far more stars than the trailing one, in an apparent contradiction of Newton’s laws. ...
So, the team then simulated the movements of stars in these clusters according to a different hypothesis, known as Modified Newtonian Dynamics (MOND). Essentially, this model suggests that gravity’s effects are stronger at low accelerations than they are in Newton’s laws. And intriguingly, this model’s predictions lined up very well with the observations. ...
Another major implication of MOND could shake up astrophysics as we know it – if it was true, then dark matter wouldn’t exist. This mysterious substance was conjured up in the 1930s to explain discrepancies in the observed motion of stars and galaxies, which were seen to be moving much too fast for how much mass they apparently contained. Dark matter fills the gap by adding huge amounts of invisible mass, which scientists have been searching for ever since. Decades of experiments designed to detect dark matter particles have come up empty. ..."

"... "In most cases, open star clusters survive only a few hundred million years before they dissolve,"... In the process, they regularly lose stars, which accumulate in two so-called "tidal tails." One of these tails is pulled behind the cluster as it travels through space. The other, in contrast, takes the lead like a spearhead. ...
Until now, it has been almost impossible to determine from among the millions of stars close to a cluster those that belong to its tails. "To do this, you have to look at the velocity, direction of motion and age of each of these objects," ... She developed a method that allowed her to accurately count the stars in the tails for the first time. ..."

From the abstract:

"After their birth a significant fraction of all stars pass through the tidal threshold (práh) of their cluster of origin into the classical tidal tails. The asymmetry between the number of stars in the leading and trailing tails tests gravitational theory. All five open clusters with tail data (Hyades, Praesepe, Coma Berenices, COIN-Gaia 13, NGC 752) have visibly more stars within dcl≈50pc of their centre in their leading than their trailing tail. Using the Jerabkova-compact-convergent-point (CCP) method, the extended tails have been mapped out for four nearby 600–2000 Myr old open clusters to dcl>50pc⁠. These are on near-circular Galactocentric orbits, a formula for estimating the orbital eccentricity of an open cluster being derived. Applying the Phantom of Ramses code to this problem in Newtonian gravitation the tails are near-symmetrical. In Milgromian dynamics (MOND), the asymmetry reaches the observed values for 50 < dcl/pc < 200 being maximal near peri-galacticon, and can slightly invert near apo-galacticon, and the Küpper epicyclic overdensities are asymmetrically spaced. Clusters on circular orbits develop orbital eccentricity due to the asymmetrical spill-out, therewith spinning up opposite to their orbital angular momentum. This positive dynamical feedback suggests Milgromian open clusters to demise rapidly as their orbital eccentricity keeps increasing. Future work is necessary to better delineate the tidal tails around open clusters of different ages and to develop a Milgromian direct n-body code."

Puzzling astronomical observations support alternative theory of gravity

Astronomy: Observation puzzles researchers Finding cannot be explained by classical assumptions. 

Asymmetrical tidal tails of open star clusters: stars crossing their cluster’s práh† challenge Newtonian gravitation (no public access)

Asymmetrical tidal tails of open star clusters: stars crossing their cluster's prah challenge Newtonian gravitation (preprint, open access)

In the star cluster "Hyades" (top), the number of stars (black) in the front tidal tail is significantly larger than those in the rear. In the computer simulation with MOND (below), a similar picture emerges.