For several years, the scientific consensus is that the dark mass in the middle of the Milky Way, designated Sagittarius A*, is a black hole - and a new study is challenging the widely accepted notion.
Researchers from the International Center for Relativistic Astrophysics (ICRA) have found "hints" that Sagittarius A* sitting in the middle of our own galaxy might not be a black hole after all, but an incredibly large mass of dark matter. In their report titled "Hinting a dark matter nature of Sgr A* via the S-stars," researchers present evidence of why this is so and how the new theory holds up against tests.
Sagittarius A* at the Center of the Milky Way
While it is largely believed to be a black hole, Sagittarius A* has never been directly verified so far. More accurately, it is a very bright astronomical radio source sitting at the galactic center of the Milky Way. Back in 2013, astronomers using the NASA Chandra X-Ray Observatory were able to take an image of the space object in unprecedented resolution. A composite image released by the space agency was built using X-ray imaging from Chandra, appearing in blue spots, combined with infrared emissions captured by the Hubble Space Telescope in red and yellow hues. The effort explained why material around the supposed black hole is extraordinarily faint in conventional X-Ray imaging methods.
However, a year later, the astrophysics community encountered a conundrum: a galactic cloud designated G2 has drifted a little too close to Sagittarius A*. While it should've been pulled and disintegrated by the supermassive black hole, if it was, the G2 gas cloud simply continued drifting without any significant changes to it.
A previous study published in 2017 monitoring the interaction between the G2 gas cloud and the Sagittarius A* suggested that, based on the lack of impact, G2 was not just an ordinary gas cloud. They explain that at least two components had to be present to allow the cloud to pass through that close to the "black hole" without being devoured. One is an extended, cold, and low-mass gas cloud and the other is a very compact segment like a dusty object that dominated the detected emission from G2 as it passed by.
However, for the ICRA team, it might be another thing: that Sagittarius A* might not even be a black hole after all.
Hinting at Being a Mass of Dark Matter
Intrigued by the possibility of the center of the Milky Way being a mass of dark matter instead, researchers first developed a simulation of our galaxy. This model, however, had Sagittarius A* characterized as a mass of dark matter and ran the simulations. Throughout the simulations, researchers discovered that the Milky Way galaxy exists and functions in almost the same way, even with the replacement done in its galactic center. Nearby S-stars, or those associated with the radio source that is Sagittarius A*, exhibited the same behavior, same with the rotational curve in the outer halo of the Milky Way.
Taking their inquiries one more step, they suggest that the mass at the middle of the Milky Way might be made up of darkinos, which are in the same class as fermions. If darkinos clump together into a huge mass, they would have the same characteristics as a black hole, aside from its extreme features such as devouring everything around it.
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