Scientists think dark matter might come in two forms

New 'two-component' dark matter model could resolve a decade-long astrophysical mystery surrounding conflicting gamma-ray signals. | Contesto: cronaca

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• Scientists think dark matter might come in two forms

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Astrophysicists have proposed a radical new model suggesting the universe's elusive dark matter may be composed of two distinct types of particles that must interact to be seen, potentially solving a major puzzle in galactic observations. The theory, developed to reconcile conflicting data from the center of the Milky Way and its smaller satellite galaxies, challenges the long-held assumption that dark matter is a single, uniform substance. For over a decade, a persistent and unexplained excess of high-energy gamma rays emanating from the Milky Way's galactic center has tantalized researchers. This signal, detected by instruments like NASA's Fermi Gamma-ray Space Telescope, aligns with predictions of what might be produced if dark matter particles annihilated or decayed. Many considered it a prime candidate for the first indirect detection of dark matter, the invisible substance thought to constitute about 85% of all matter in the cosmos. However, this promising lead was undermined by a conspicuous absence. If the gamma-ray glow at our galaxy's heart was truly from dark matter, then similar, though fainter, signals should also be detectable in small, dense dwarf galaxies orbiting the Milky Way, which are believed to be heavily dominated by dark matter. Extensive searches have consistently failed to find such corroborating evidence, casting serious doubt on the dark matter interpretation of the galactic center signal and leaving a significant rift in the observational data. The newly proposed framework seeks to bridge this gap by moving beyond the standard single-particle paradigm. In this model, dark matter consists of two separate components. One component could be responsible for the overall gravitational effects that bind galaxies together, while the second interacts with it to produce the gamma rays. Crucially, the production of detectable radiation would require both types to be present and collide in specific densities and conditions. This two-component requirement naturally explains the discrepancy: the dense core of the Milky Way provides the right environment for this interaction, while the sparser dwarf galaxies do not. This "two-for-one" dark matter...

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Categoria: cronaca