Fermionic Dark Matter: A New Contender for the Heart of the Milky Way

In a groundbreaking development published in the February 2026 edition of the Monthly Notices of the Royal Astronomical Society, an international team of astrophysicists has proposed a provocative new theory. Their research challenges the long-standing assumption that Sagittarius A* (Sgr A*), the gravitational powerhouse at the center of the Milky Way, is a supermassive black hole. Instead, the scientists suggest that the intense gravitational effects observed in the galactic core might stem from an incredibly dense concentration of fermionic dark matter rather than a traditional singularity.

This innovative model was spearheaded by Valentina Crespi and Carlos Argüelles, researchers affiliated with the Institute of Astrophysics of La Plata. Their hypothesis posits that the ultra-dense core of dark matter, composed of lightweight subatomic particles known as fermions, and the broader dark matter halo of the Galaxy are essentially two manifestations of the same substance. This unified framework aims to provide a consistent explanation for various phenomena across different galactic scales, most notably the rapid orbits of S-stars, which circle the center at velocities reaching several thousand kilometers per second.

A primary strength of this fermionic proposal lies in its alignment with recent observational breakthroughs. The model demonstrates remarkable consistency with data from the European Space Agency’s Gaia DR3 mission, which provided a comprehensive map of the Milky Way's outer halo rotation curve. Furthermore, the authors contend that their theoretical structure is entirely compatible with the famous shadow of the black hole image of Sgr A* captured by the Event Horizon Telescope (EHT) collaboration in 2022. Valentina Crespi emphasized that a sufficiently dense dark matter core can effectively mimic the gravitational lensing of light, producing a central dark region surrounded by a luminous ring.

Historically, the existence of Sagittarius A* as a black hole was inferred from a gravitational field requiring approximately four million solar masses to be packed into a volume smaller than the orbit of Pluto. The proposed alternative structure, composed of fermions, successfully replicates these massive gravitational effects without the necessity of a physical singularity. Additionally, this hypothesis addresses a lingering discrepancy in traditional galactic models: the observed lack of expected dark matter concentration at the very center of galaxies, a problem this new model inherently resolves.

While the theoretical advantages are compelling, the research team acknowledges that current data regarding internal stellar dynamics are not yet precise enough to definitively rule out the black hole scenario. The scientific community is now looking toward future observational milestones to settle the debate. High expectations are placed on the upcoming data from the Cherenkov Telescope Array (CTA), which is scheduled for launch in 2026. This ongoing intellectual conflict represents a pivotal moment in our understanding of the universe, potentially reshaping the fundamental nature of galactic centers.