The black hole that isn’t there

In 2020, the discovery was announced that within the HR 6819 star system, located just a thousand light years from Earth, a black hole had been observed, thus becoming the closest to our planet ever discovered.

In recent days, however, a new study was published based on observations conducted with the VLT that refuted the discovery of 2020: HR 6819 had initially been interpreted as a system composed of two stars and a black hole, But now it’s become clear that it’s actually a system of two stars in very tight orbits around each other.

The initial error is amply justified since HR 6819 is in an unknown and very fast evolutionary phase, known as stellar vampirism, of which few examples have been observed before.

The name "vampirism" is not accidental: one of the stars of the system has just finished ripping away the atmosphere of the secondary, leaving it without the outer shell.

It will be interesting now to try to understand how this little-known phenomenon of vampirism can influence the evolution of the two stars. It is known that for the conservation of angular momentum the primary component must begin to rotate faster, but we now want to try to understand if this phenomenon also has consequences on gravitational waves or supernova explosions.

Credit: ESO, VLT.