Does the Milky Way have two black holes at its core?
At the center of the Milky Way is a supermassive black hole call Sagittarius A* , with a mass of approximately 4 million suns. But is there another close to him? A new study has sought the answer and found nothing, but it has helped determine the possible mass if a medium-sized black hole is lurking there.
Scientists already know that Sagittarius A* does not have supermassive black holes as neighbors, nor stellar black holes, formed by the collapse of a star at the end of its life. However, there were still no studies looking for intermediate-mass black holes , the name given to those with between 100 and a few thousand solar masses.
Considered the missing link in supermassive evolution, these intermediate-mass objects are hard to find, although they may be more common than you might think. Some candidates have already been found by telescopes such as James Webb and Hubble , but they are still awaiting confirmation that they are indeed intermediate-mass black holes.
To probe the surroundings of Sagittarius A*, the authors of the study — which includes the winner of the Nobel Prize in Physics, for proving the existence of this black hole — used the orbit of the star called S2. As it orbits very close to the supermassive object, its path could reveal whether there is something else of considerable mass out there.
In other words, the presence of another black hole near Sagittarius A* would disturb S2’s orbit, especially if it’s an intermediate one, and even more so if it’s a supermassive one. The advantage of this approach is that this star completes a revolution around Sagittarius A* every 16 years and astronomers already have more than two decades of observational data on it.
Although they found no evidence of gravitational perturbations in the orbit of the star S2, the researchers think that the intermediate black hole could still exist there. Thus, they determined some restrictions:
If the putative intermediate black hole orbits Sagittarius A* beyond the orbit of S2, its mass would be between 1,000 and 10,000 suns. If it is closer to Sagittarius A* than the star, it will be up to 400 solar masses, no more.