We have detected a “wandering” black hole in our galaxy. surely not the only one

This year the black holes have given much to talk about, and although the photos of supermassive black holes are the ones that have generated the most attention, the smaller ones are also important. A team from UC Berkeley has confirmed the sighting of a stellar black hole roaming our galaxy, perhaps the smallest black hole sighted to date.

An 11-year study.
The team, led by researchers from the University of California at Berkeley, has independently confirmed this finding whose history dates back to 2011, but which we have not been able to confirm until 11 years later.

It was in 2011 when Hubble’s detectors picked up a distant star shine strangely. This phenomenon was collected in two independent surveys focused on a phenomenon, microlenses (or microlensing). This phenomenon occurs when a massive object such as a star or a black hole exerts its gravitational attraction on a beam of light from another body, usually a star, deflecting it as if it were a lens.

Independent confirmation.
News of this black hole first reached the public earlier this year, when a team led by Kailash Sahu of the Hubble Telescope Institute published as a preprint in the arXiv repository the results of your analysis. Now the team led by Casey Lam and Jessica Lu of Berkeley has independently confirmed the finding. Both papers are in the process of being published in the journal The Astrophysical Journal Letters.

The black hole.
The studies carried out allow us to know some characteristics of this black hole. It would be about 5,000 light years from us (with a range between 2,200 and 6,200 light years), through the constellations of Keel and Sagittarius. It would be a stellar mass black hole, those that form at the end of the life of some stars, those that are larger than our Sun.

The teams disagree on the speed at which this “errant” hole would be moving. While the first study estimated a speed of 45 km per second (162,000 km/h), the second calculated that it was traveling at 30 km per second (just under 108,000 km/h).

The key is in the dough.
From here comes the perhaps most important discrepancy. According to the first calculations, the mass of the black hole would be 7.1 times that of the Sun, while the most recent study places it between 1.6 and 4.4 solar masses.

Case closed?
This difference in mass is important. While in your article the first team writee that his work “[muestra] that the lens does not emit detectable light, which, added to the fact that its mass is greater than that possible for a white dwarf or a neutron star, confirms its nature as a black hole dome”.

But the mass estimated by the second team does not completely rule out the possibility that it is a neutron star, but it opens another possibility, that we are facing the smallest black hole ever detected. Astronomers speak of the low-mass gap to refer to the fact that black holes less than five times the mass of the Sun have never been detected. Until now.

One of many in our galaxy.
Detecting black holes is a very complicated task. Some can be seen thanks to the accretion disk that shines around them due to the radiation emitted by the particles accelerated by the gravity of the ultra-heavy body.

It is estimated that there between 10 and 1,000 million black holes “swarming” through our galaxy, waiting to be discovered. These black holes would shoot out at the birth of their supernova, hence their wandering nature.

The future of exploration.
Like the exoplanets that are discovered passing in front of their star, these black holes could be “seen” by highlighting steps. Although these techniques to see what is invisible to the human eye differ in fundamental aspects, the parallelism is also evident.

Astronomers are confident of finding new cases of wandering black holes in our galaxy. The information we collect from similar objects will give us new clues about the hole that we have already observed. In addition, scientists already plan to try to search for this black hole with X-ray telescopes to locate a hypothetical accretion disk that it might have gained on its interstellar journey.

Image | POT