🔭 What if this was merely a pure concentration of dark matter?

The center of the Milky Way hosts a supermassive black hole: that's what the scientific literature tells us. Yet a recent study calls into question the very identity of Sagittarius A*.

The new hypothesis is based on the idea that Sagittarius A* could be an extremely dense cluster of dark matter. According to a team of researchers, this dark matter would be composed of ultralight particles from the fermion family, capable of forming a unified structure with the dark matter halo surrounding the Milky Way. In this way, the galactic core and its invisible environment would be one, explaining the fast orbits of nearby stars and the dynamics of gas sources known as G-sources.


Data from the Gaia mission, published in 2022, provided precise measurements of stellar motions in the galaxy's outskirts. Scientists detected a slowing of the rotation curve there, called a Keplerian decline. While the standard model of cold dark matter struggles to account for this observation, fermionic dark matter predicts a more compact halo that fits better. This offers a first clue in favor of this new proposal, linking very different galactic scales.

The famous image of Sagittarius A* unveiled by the Event Horizon Telescope in 2022 shows a bright ring surrounding a dark area at the center of the Milky Way. Interpreted as the shadow of a black hole, this silhouette could also come from a dense core of dark matter. Such a cluster, although invisible, would strongly bend light through gravity, creating a similar appearance without requiring an event horizon. Recent simulations confirm this possibility, making the model compatible with observations.

The researchers conducted a statistical comparison of their model with that of a supermassive black hole. The dark matter model reproduces the orbits of the S stars, the G sources, and the overall galactic structure. However, they emphasize the need for further evidence. Future observations with the Very Large Telescope will be able to search for photon rings, present only around a black hole, which will allow for directly testing this model by strictly distinguishing the presence of a black hole from that of a compact dark matter cluster.

This proposal is published in Monthly Notices of the Royal Astronomical Society.