Valentina Crespi et al.
Artist’s depiction of the Milky Way, where the innermost stars move at near-relativity speeds around a dense core of dark matter, with no black hole at the center
Our galaxy, the Milky Way, may not have a supermassive black hole at its center, but rather a huge clump of mysterious dark matter exerting the same gravitational influence.
In a new study, astronomers suggest that the dark matterthe invisible substance that makes up most of the universe’s mass, can explain both the violent dance of stars just light hours from the galactic center and the smooth, large-scale rotation of all matter on the Milky Way’s outskirts.
This was presented in an article published last week in the magazine Monthly Notices of the Royal Astronomical Society.
The findings challenge the prevailing theory that Sagittarius A* (Sgr A*), o supposed black hole in the heart of our galaxyis responsible for the observed orbits of a group of stars, known as S stars, that rotate at tremendous speeds of up to a few thousand kilometers per second.
The international team of researchers proposed, alternatively, a different idea – that a specific type of dark matter made up of fermions, or light subatomic particles, can create a unique cosmic structure that also fits with what we know about the Milky Way’s core.
In theory, it would produce a superdense and compact nucleus surrounded by a halo vast and diffuse, which togetherwould act as a single entity unified.
The inner core would beso compact and massive which could mimic the gravitational pull of a black hole and explain the orbits of S stars that have been observed in previous studies, as well as the orbits of dust-shrouded objects known as G sources, which also exist nearby.
Of particular importance to the new research is the latest data from the European Space Agency, which has meticulously mapped the rotation curve of the Milky Way’s outer halo, showing how stars and gas orbit far from the center.
The study authors observed a rotation curve deceleration of our galaxy, known as Keplerian decay, which researchers say can be explained by outer halo of your dark matter model when combined with the traditional mass components of the disc and bulge of common matter.
This, they add, reinforces the “fermionic” model by highlighting a fundamental structural difference. While traditional Cold Dark Matter halos spread following a extended “power law”the fermionic model predicts a more compact structure, leading to more concentrated halo tails.
“This is the first time that a dark matter model has managed to establish a bridge between these vastly different scales and several orbits of objects, including modern data on the rotation curve and central stars”, stated Carlos Argüelles, researcher at the Instituto de Astrofisica de La Plata and co-author of the study, in .
“We’re not just replacing the black hole by a dark object; we are proposing that the supermassive central object and dark matter halo of the galaxy are two manifestations of the same continuous substance.
Crucially, this fermionic dark matter model had already passed a significant test.
A 2024 study by Pelle et al., also published in MNRAS, showed that when an accretion disk illuminates these dense dark matter cores, they cast a shadow-like feature surprisingly similar to that captured by the Event Horizon Telescope (EHT) collaboration for Sgr A*.
“This is a crucial point“, he stated Valentina Crespiresearcher at the La Plata Astrophysics Institute and lead author of the study.
“Our model not only explains the star’s orbitssea rotation of the galaxy, what is it like consistent with the famous ‘black hole shadow’ image‘. The dense core of dark matter can mimic shadow because it bends light so intensely, creating a central darkness surrounded by a bright ring.”
