At the galactic center lies the enigmatic supermassive black hole, Sagittarius A*. Some researchers propose that this may not be a black hole at all, but rather clusters of dark matter.

Dark matter, which comprises about 85% of the universe’s matter, does not interact with light or normal matter outside of gravitational forces. Despite its significance, our understanding of dark matter is limited. As Valentina Crespi from the National University of La Plata (UNLP) notes, “While we know dark matter exists at the galaxy’s edge, the core remains a mystery.”

Crespi and her team developed a model of a galactic nucleus made of dark matter consisting of light particles called fermions. Their findings suggest that fermion dark matter can clump in ways that resemble supermassive black holes from afar.

“From Earth, this scenario appears akin to what one would expect from a black hole; however, a spacecraft could pass through without any issues,” explains Carlos Arguelles, part of the UNLP research team. “Even if you were swallowed by a black hole, you wouldn’t perish; you would pass through safely.”

The researchers base their model on the orbit of a star near Sagittarius A* and a small gas cloud, aligning with observations of galaxy rotation and imagery from the Event Horizon Telescope (EHT) from 2022. This imaging reveals a glowing ring of superheated matter around Sagittarius A*, potentially influenced by a dark matter core.

However, observation support for the dark matter theory does not confirm its validity. Gaston Gillibet from New York University stresses, “While this simple explanation aligns with the evidence, I still believe the central object is likely a black hole.” He emphasizes the necessity of remaining open to all possibilities in this fascinating debate.

Concerns arise regarding the model’s applicability to observations near the event horizon. Shep Doeleman from Harvard University notes that the distinctive spiral pattern of the magnetic field in this region corresponds closely with black hole characteristics.

Moreover, fermion dark matter’s clumping is limited to about 10 million times the Sun’s mass. Although this could explain the majestic size of supermassive black holes, images of M87*—a black hole substantially larger than Sagittarius A*—complicate this theory as M87* closely resembles Sagittarius A* despite its size of approximately 6.5 billion solar masses.

Researchers admit that both dark matter and black hole theories hold equal plausibility. Crespi notes, “While we have enhanced tools today, confirming the nature of these phenomena is still not foolproof.” Achieving the necessary image resolution for this identification would extend far beyond the capabilities of even the next-generation EHT, indicating that definitive answers may be decades away.

If Sagittarius A* is indeed a manifestation of dark matter, it would profoundly impact our understanding of the universe. Fermion dark matter, which current cosmological models do not predict, could revolutionize not only our comprehension of black holes but also our entire cosmic paradigm.

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