This research, published in 'Astrophysical Journal Letters', analyzed data from the Hubble Space Telescope and was led by Jorge Sanchez Almeida and Ignacio Trujillo from IAC and the Universidad de La Laguna (ULL). Collaborating with them was Angel Plastino from the Universidad del Noroeste de la provincial de Buenos Aires (Argentina).

A Different Kind of Matter
For decades, scientists have known that around 85% of the matter in the Universe is dark, meaning it does not emit radiation. This has made studying dark matter incredibly difficult, but by observing how ordinary matter, such as stars and gas, moves under the influence of dark matter, researchers have been able to infer its presence. Dark matter has traditionally been modeled as particles with mass that only interact through gravity, a theory known as the collisionless cold dark matter model.

However, despite its success in explaining how dark matter influences the formation of galaxies, this model does not explain what dark matter is or how it fits into the current understanding of particles. The new IAC study challenges this paradigm by showing that dark matter could interact in ways beyond gravity.

The Role of Low-Mass Galaxies
The research focused on ultra-faint dwarf galaxies-small galaxies with only a few thousand stars. These galaxies, with one-millionth the number of stars compared to the Milky Way, provide an ideal environment for testing dark matter theories because they are less affected by ordinary matter. The study's findings revealed that the distribution of stars in these galaxies does not accumulate toward the center, as would be expected under the existing model. Instead, the distribution remains constant, suggesting interactions beyond gravity.

"Using a novel technique based solely on the distribution of stars, we have been able to reject the collisionless cold dark matter model with high statistical significance," said Jorge Sanchez Almeida. He further explained that this discovery "provides a solid observational basis from which to explore more complex dark matter models."

Dark Matter's Unseen Forces
The researchers suggest that dark matter might behave similarly to ordinary particles that interact with each other, like billiard balls colliding. In contrast to the current model, where dark matter particles would pass through each other without interaction, this new study proposes that dark matter particles could collide and affect one another's paths.

Ignacio Trujillo commented, "All the galaxies studied have an identical stellar distribution. It seems that the galaxies have forgotten their own history. This can only be well understood if dark matter has erased these galaxies' past."

While the study does not yet answer the fundamental question of what dark matter is, it offers critical evidence that dark matter behaves differently than previously thought. "After this study, the question of 'what is dark matter?' remains unresolved, but we now know something essential: dark matter is not what we thought it was until now," added Sanchez Almeida.

Research Report:The Stellar Distribution in Ultrafaint Dwarf Galaxies Suggests Deviations from the Collisionless Cold Dark Matter Paradigm

Related Links
Instituto de Astrofisica de Canarias
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