What's Really at the Centre of the Milky Way?

The center of the Milky Way hosts Sagittarius A (Sgr A), a supermassive black hole with about 4 million solar masses. This conclusion stems from decades of observations, including star orbits like S2’s, which trace a compact massive object, and the 2022 Event Horizon Telescope image showing its shadow. Recent hypotheses propose a dense fermionic dark matter core instead. A February 2026 study suggests this core could mimic black hole effects on star motions, rotation curves, and even the shadow image through extreme light bending. Scientific consensus still favours the black hole. These dark matter ideas remain speculative, requiring future tests like sharper photon ring imaging or precision GRAVITY/Gaia data to distinguish them.
 
Stars like S2 orbit Sgr A* in tight, relativistic paths, completing cycles every 16 years at speeds up to 3% of light speed. Their trajectories reveal a 4.3 million solar mass object confined to a radius smaller than our solar system, consistent only with a black hole. Further, the 2022 EHT image shows Sgr A*‘s shadow, a dark central region ringed by glowing plasma, matching general relativity predictions for a black hole’s event horizon and photon ring. The GRAVITY/VLT observations in 2018 detected gas clumps at 30% light speed and bright flares from hot electrons near the event horizon, aligning with black hole accretion models. And the Chandra X-ray data confirms a jet-like structure impacting surrounding gas, with spectra typical of supermassive black hole outflows; magnetic fields spiral gas inward, keeping emissions low.
 
However, a February 2026 study proposes that a dense core of fermionic dark matter, rather than Sagittarius A, powers the Milky Way’s center. The lead author Lic. Valentina Crespi from the Institute of Astrophysics La Plata, and collaborators, including Dr. Carlos R. Argüelles, model this as a compact core mimicking black hole gravity for S-stars and G-sources, surrounded by a halo explaining the galaxy’s rotation curve slowdown (Keplerian decline) per GAIA DR3 data. This was published in Monthly Notices of the Royal Astronomical Society (DOI: 10.1093/mnras/staf1854). It unifies central orbits, large-scale dynamics, and the EHT shadow image via strong light bending, without photon rings unique to black holes.
 
Key Model Features
Fermionic dark matter (light subatomic particles) forms a continuous core-halo structure, unlike traditional cold dark matter’s extended tails;
Fits inner relativistic star speeds (thousands km/s) and outer halo motions with ordinary matter components; and
Builds on 2024 Pelle et al. work showing accretion disk shadows match EHT observations.
 
Future GRAVITY/VLT data and photon ring searches could distinguish it from black hole models, as current data cannot yet rule either out.
 
References
Chu, J. (2022, May 12). Astronomers Snap First-Ever Image of Supermassive Black Hole Sagittarius A*. MIT Department of Physics.
 
Mohon, L. (2013, November 290). NASA’s Chandra Helps Confirm Evidence of Jet in Milky Way’s Black Hole. NASA.
 
Tonkin, S. (2026, February 5). Dark Matter, not a Black Hole, Could Power Milky Way’s Heart. Royal Astronomical Society.
 
(2026, January 14). What is the Center of Our Galaxy Like? NASA. https://science.nasa.gov/mission/webb/science-overview/science-explainers/what-is-the-center-of-our-galaxy-like/
 
(2026, April 5). Galactic Center. In Wikipedia, https://en.wikipedia.org/wiki/Galactic_Center
 
(2026, April 15). Sagittarius A*. In Wikipedia, https://en.wikipedia.org/wiki/Sagittarius_A*