Distorted galaxies defy gravity theory

(ORDO NEWS) — An international team of astronomers recently studied the galaxies in the Furnace Cluster to test the ΛCDM (or Lambda CDM) model – the standard model that describes the universe as homogeneous and isotropic, consisting of ordinary matter, dark matter and dark energy – and modified Newtonian dynamics (or MOND), a controversial alternative to the theory of general relativity.

They have identified perturbations in galaxy clusters of dwarf galaxies that point to a different theory of gravity.

Most astronomers believe that the mysterious dark matter underlying the ΛCDM model is the only way to explain certain phenomena, such as the mass and speed of galaxies, or simply their cohesion.

The Standard Model of Cosmology suggests that most galaxies are surrounded by a halo of dark matter particles capable of exerting a strong gravitational pull on nearby objects.

Despite decades of research, the existence of dark matter has never been proven, and various alternative theories have been proposed.

One of them is the modified theory of Newtonian dynamics (or MOND theory). To test these various models, a team of astronomers looked at dwarf galaxies in the Furnace Cluster, about 62 million light-years from Earth.

Dwarf galaxies are small, faint galaxies that are often located in or near large galaxies or clusters of galaxies.

Due to their low surface brightness, they are particularly sensitive to tidal forces generated by more massive galaxies, making them ideal objects for testing gravity theories.

“We present an innovative way to test the Standard Model based on the extent to which dwarf galaxies are perturbed by the ‘gravitational tides’ of large neighboring galaxies,” Elena Asensio, doctoral student at the University of Bonn and first author of the study reporting the discovery, explains in a press release.

The degree of disturbance expected for these galaxies depends on the assumed law of gravity and the presence or absence of dark matter.

Observations show that many of the dwarf galaxies in the cluster have undergone significant deformation, as if the environment of the cluster has disturbed them.

This completely contradicts the Standard Model, since in the theory the dark matter halo of dwarf galaxies should partially protect them from the tidal forces created by the surrounding galaxy cluster.

First, the team examined the expected level of destruction of dwarf galaxies, which can be determined by their intrinsic properties and their distance from the strong gravitational center of the cluster.

For example, large galaxies with low stellar mass, as well as galaxies located close to the center of the cluster, are more easily destroyed or even destroyed.

The researchers compared their results with the scale of the disturbances seen in images taken with the European Southern Observatory’s Very Large Telescope. This is where the inconsistency arose.

“The comparison showed that if we are to explain the observations with the Standard Model, then the dwarfs in the Furnace cluster should already be destroyed by the gravity of the center of the cluster, even if the tides it causes in the dwarf galaxy are 64 times weaker than the gravity of the dwarf galaxy itself!” – Elena Asensio explains.

The scientist notes that this conclusion is not only counterintuitive, but also contradicts several studies that have shown that the external force required to destroy a dwarf galaxy is approximately equivalent to its own gravity.

If these dwarf galaxies don’t have a halo of dark matter, how did they come about? And above all, how could they resist the surrounding forces of attraction?

Since the standard model is not suitable to explain the observed phenomenon, the team decided to apply another theory, the MOND theory, which is based on a modification of Newton’s second law (which relates the mass of an object to the acceleration it receives when forces are applied to it).

He rules out the presence of dark matter halos, but suggests a correction that gravity “boosts” at very low accelerations.

This model proved to be much more consistent. “Our results show remarkable agreement between observations and MOND expectations for the perturbation level of the Furnace Cluster dwarf galaxies,” said Dr. Indranil Banik, a researcher at the University of St. Andrews and co-author of the study.

The team notes that this is not the first time that a study testing the influence of dark matter on the dynamics and evolution of galaxies has challenged the theory.

“The number of publications showing the incompatibility of observations and the dark matter paradigm is growing every year.

It’s time to start investing more resources in more promising theories,” says Dr. Pavel Krupa, head of the Stellar Populations and Stellar Dynamics research group at the University of Bonn.

These results obviously have serious implications for fundamental physics. The team continues their research and expects to find other highly perturbed dwarf galaxies in other clusters of galaxies, inviting other research groups to explore this direction.

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