Is our galaxy's heart a black hole or a dark matter clump?

Space · Published 22 October 2026 Swipe more like this →

In short: For decades, we assumed Sagittarius A* was a supermassive black hole anchoring the Milky Way. However, new research suggests this central powerhouse might actually be a massive, compact clump of dark matter—a single unified structure that could explain everything from local stellar orbits to the galaxy's outer rotation.

The prevailing model identifies Sagittarius A* (Sgr A*) as a supermassive black hole. Alternatively, Carlos Argüelles from the Institute of Astrophysics La Plata and his colleagues suggest that ultra-light fermionic dark matter makes up the core. This specific type of dark matter can form a structure featuring a super-dense, compact core with a mass equivalent to 4.6 million suns. This core would mimic the gravitational effects of a black hole, accounting for the 'S-stars' that race around the galactic center at speeds up to 30,000 kilometers per second (about 10% of the speed of light).

What makes this theory compelling is its ability to explain two different scales of motion simultaneously. The compact core accounts for the violent 'dance' of nearby stars and dust-shrouded bodies known as G-sources. Simultaneously, this same dark matter distribution extends outward into a vast, diffuse halo. This halo shapes the large-scale rotation of the Milky Way's outskirts, creating a specific slowdown in the rotation curve known as the Keplerian decline.

The research team argues that these two structures—the core and the halo—are not separate entities but manifestations of the same continuous substance. This model is supported by data from the European Space Agency's Gaia mission, specifically the third data drop released in June 2022. While Dr. Becky Smethurst focuses on how supermassive black holes influence galaxy evolution and star formation, this new research challenges the fundamental identity of the object at our own galactic center.

Such a replacement remains viable solely if the fermion family's ultra-light particles constitute the dark matter. Other recipes of dark matter cannot replicate this specific dual structure. If proven, it would mean that what we perceive as a central black hole is actually part of a unified dark matter architecture spanning the entire galaxy.

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