In the Milky Way there should be between 10 and 1,000 million stellar-mass black holes , moving quietly through the galaxy. What happens is that, unless they manage to trap some material passing through their gravitational field, they are essentially invisible.
And the fact that it is basically invisible does not mean that it cannot be detected. Now, a team of astronomers claims to have detected and measured, for the first time in history, an isolated stellar-mass black hole.
Located just under 5,200 light-years from Earth and with a mass about 7.1 times that of the Sun, this black hole is moving through the Milky Way at a speed of 45 kilometers per second.
An isolated and nomadic black hole
The team of researchers, led by Kailash Sahu, from the Space Telescope Science Institute (STScI), in the United States, documents their finding in The Astrophysical Journal , which will be available soon (it can already be consulted on the arXiv preprint server).
The errant black hole has been detected thanks to a method or phenomenon known as gravitational microlensing that is used to identify small, faint objects that would otherwise be too difficult for our telescopes to detect. Gravitational microlensing occurs when an object with a gravitational field passes almost exactly in front of a distant star. That gravitational field causes a curvature of space-time that can be detected.
“We report the first unequivocal detection and mass measurement of an isolated stellar-mass black hole,” explain the paper’s authors.
So far, all of the stellar-mass black holes detected to date have existed in binary systems with companions, such as neutron stars. But this black hole wanders alone in the galaxy. “No one had been able to find an isolated black hole before,” says Sahu.
And what has most caught the attention of scientists is that it not only wanders alone through the galaxy, but also out of control (remember that it moves at about 45 kilometers per second). And it was probably ejected into space when its parent star exploded in a supernova.
Thanks to this detection, we already know that they exist and that there must be many in our cosmos.
Referencia: An Isolated Stellar-Mass Black Hole Detected Through Astrometric Microlensing. Kailash C. Sahu, Jay Anderson, Stefano Casertano , Howard E. Bond, Andrzej Udalski , Martin Dominik, Annalisa Calamida, Andrea Bellini , Thomas M. Brown , Marina Rejkuba , Varun Bajaj , Noe Kains , Henry C. Ferguson , Chris L. Fryer , Philip Yock , Keith Horne , Iain A. Steele et al.Solar and Stellar Astrophysics (astro-ph.SR); Astrophysics of Galaxies (astro-ph.GA); High Energy Astrophysical Phenomena (astro-ph.HE) arXiv:2201.13296 [astro-ph.SR] 2022
