This accidental find by a German team at the European Southern Observatory in La Silla, Chile, described last week in the review Astronomy and Astrophysics, shows that this so-called “inactive” black hole belongs to an astronomical system called HR 6819, and which we already knew as a binary system – composed of two stars.
Now it turns out that there are three of them. Astronomers were looking for the third thief, but rather expected to find a neutron star – a star resulting from the gravitational collapse of the hearts of some end-of-life stars. The mass of the new object, four times that of the Sun, turned out to be too large for a neutron star.
It is the first black hole spotted in a triple system. And besides being the closest black hole, one of the few inactive to have been discovered – a task all the more difficult than even in normal times, a black hole is by definition almost invisible – except when its activity generates a halo of particles.
So there may be many more in our galaxy, the Milky Way, not to mention the super massive black hole in the center. Astrophysicists estimate that it could be several thousand. And if they were evenly distributed, the closest one could be only 30 or 40 light years from us.
It’s far away if we had to go there, but it’s almost our backyard, if we remember that our galaxy measures about 100,000 light years from one end to the other.
A plethora of new minor planets beyond Neptune