An image of the supermassive black hole Sagittarius A* in polarised light, captured by the Event Horizon Telescope
EHT Collaboration
One of the most intriguing mysteries of our galaxy is the supermassive black hole at its center known as Sagittarius A*. However, a team of researchers has put forth a controversial theory suggesting that Sagittarius A* and similar black holes may not be black holes at all, but rather clumps of dark matter.
Dark matter, a mysterious substance that makes up a significant portion of the universe’s mass, remains elusive as it does not interact with light or regular matter except through gravity. Valentina Crespi from the National University of La Plata (UNLP) in Argentina explains, “We know it has to be at the outskirts of galaxies, but we don’t know what happens at the very center.”
Crespi and her team have proposed a model where the galactic core is composed of dark matter in the form of fermions, extremely light particles. Their simulations suggest that this fermionic dark matter could aggregate into a dense and massive clump that closely resembles a supermassive black hole when observed from a distance.
Carlos Argüelles, also from UNLP, adds, “From Earth, you would see something very similar to what you would see in the black hole scenario – but if we went in a ship towards the centre, we could go through with no problem. You will not die by being eaten by the black hole; you will go through peacefully.”
While the model aligns with the orbits of stars and gas clouds near Sagittarius A*, as well as the data from the Event Horizon Telescope (EHT), which captured an image of the black hole, skeptics like Gaston Giribet from New York University caution that the simpler explanation of a black hole might still be more plausible.
Shep Doeleman, from Harvard University and the EHT project, raises concerns about the model’s ability to explain observations close to the event horizon of the black hole, particularly the spiral pattern of magnetic fields. Additionally, the limited size of clumps that fermionic dark matter can form poses a challenge when considering larger supermassive black holes like M87*.
Despite these challenges, the researchers acknowledge that definitive proof of Sagittarius A* being dark matter is currently beyond reach. Crespi notes, “Nowadays, with the instruments available, it is not yet possible to 100 per cent discriminate if it’s indeed dark matter or not.” Nonetheless, if Sagittarius A* does turn out to be dark matter, it would revolutionize our understanding of the universe and the nature of supermassive objects.
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