Study Proposes Dark Matter Core at Milky Way's Center
Researchers suggest that the Milky Way's central mass may be a dense dark matter core, challenging the prevailing black hole theory.
For decades, the rapid orbits of stars near the Milky Way's center have been attributed to a supermassive black hole known as Sagittarius A*. However, a new study led by Dr. Valentina Crespi from the Institute of Astrophysics La Plata proposes an alternative explanation: a compact object composed of self-gravitating fermionic dark matter.
This model suggests that a dense dark matter core, surrounded by a diffuse halo, could replicate the gravitational effects observed in the orbits of the S-stars—stars that move at speeds up to several thousand kilometers per second near the galactic center. The researchers also note that this structure could account for the paths of nearby dust-enshrouded objects known as G-sources.
The study leverages data from the European Space Agency's Gaia DR3 mission, which mapped the Milky Way's rotation curve, revealing a slowdown in the galaxy's outer regions. This Keplerian decline aligns with the predictions of the fermionic dark matter model when combined with traditional mass components of ordinary matter.
Dr. Carlos Argüelles, a co-author from the same institute, emphasized the significance of these findings:
"This is the first time a dark matter model has successfully bridged these vastly different scales and various object orbits, including modern rotation curve and central stars data."
The researchers also highlight that their model is consistent with the 'black hole shadow' image captured by the Event Horizon Telescope, suggesting that the dense dark matter core can bend light similarly to a black hole. Dr. Crespi noted that the core's strong gravitational lensing creates a central darkness surrounded by a bright ring, mimicking the observed shadow.
While current data cannot definitively distinguish between the black hole and dark matter core scenarios, the study provides a unified framework that explains both the galactic center's dynamics and the overall structure of the Milky Way. The authors advocate for more precise observations from instruments like the GRAVITY interferometer on the Very Large Telescope in Chile to test their model's predictions.
The research was published in the Monthly Notices of the Royal Astronomical Society.