For decades, the scientific community maintained almost without discussion that at the center of Milky Way inhabits a supermassive black hole. That object, known as Sagittarius A (Sgr A)is located about 26 thousand light years from Earth, in the constellation of Sagittarius, and would have a mass equivalent to four million times that of the Sun.
However, an international team of astrophysicists—with the key participation of Conicet researchers—has just published a work that challenges that paradigm. The research was published in the scientific journal Monthly Notices of the Royal Astronomical Society and proposes an alternative explanation: Instead of a black hole, there could be a compact, super-dense core of dark matter.
A black hole is a region of space with gravity so intense that nothing can escape, not even light. The evidence of its existence in the galactic center is supported by the observation of stars that orbit at very high speeds around an invisible point.
But the new model suggests another possibility never before thought of until now. According to the study, a particular type of dark matter, which would be composed of subatomic particles called fermions, could form a structure with two parts:
This “core-halo” would act as a single continuous entity. The inner core would be so massive that it would imitate the gravitational force of a black hole, which explains the movement of the so-called “S stars”, which rotate around the center at thousands of kilometers per second. At the same time, the outer halo would help understand how the most distant stars in the galaxy rotate, something that was measured with great precision by the European Space Agency’s Gaia mission.
“The new study demonstrates that a specific model of dark matter composed of fermions, that is, light subatomic particles, can create a unique cosmic structure: a compact, superdense core surrounded by a vast, diffuse halo. This core-halo configuration acts as a single and unified entity,” the specialists indicated in an article published on the official Conicet website.
“This is the first time that a dark matter model manages to connect these very different scales and the orbits of several objects, including modern data on rotation curves and central stars,” explained Carlos Argüelles, Conicet researcher at the IALP and Argentine co-author of the study.
“We are not simply replacing the black hole with a dark object. We are proposing that the central supermassive object and the dark matter halo of the galaxy are two manifestations of the same continuous substance”, added the researcher.
The hypothesis does not automatically eliminate the existence of a black hole in the center of the Milky Way, but it opens a new discussion that the scientific community will have to face at a global level. If future observations confirm this theory, the understanding of the structure of our galaxy could change radically and be a completely Argentine discovery.
