It seems that the nearest galaxy to a black hole does not have a black hole

In 2020, a team led by astronomers from the European Southern Observatory (ESO) will report the presence of a black hole in the star system HR 6819. Only 1,000 light-years away, it will be the closest black hole. However, their discovery has been disputed by other researchers, including an international team from KU Leuven. Both teams now jointly agree that HR 6819 does not contain a black hole: it is a binary star that undergoes a rare and short-lived phase of evolution.

The original research article on HR 6819 received a lot of attention from both the press and scientists. Chilean ESO astronomer Tomas Rivinius, lead author of the paper, was not surprised by the reaction of the astronomical community to their discovery of the black hole. “Not only is it natural, but it is also necessary to look at the results critically, especially if the result is making the headlines,” he says.

2 stars

Rivinius and colleagues believe that the best explanation for the data they obtained with the 2.2-meter MPG/ESO telescope is that HR 6819 is a three-star system, consisting of a star orbiting a star in 40 days. A second star in a much wider orbit around it. But research led by Julia Bodensteiner, a doctoral student at KU Leuven, suggested a different explanation based on the same data: HR 6819 could also be a system without a black hole, made up of just two stars that orbit each other in forty days. . This alternative scenario would require one of the stars to be “disassembled”, meaning that it lost a lot of its mass to the other star in the recent past.

To solve this mystery, the two teams collaborated to obtain new and more accurate data from HR 6819 using ESO’s Very Large Telescope (VLT) and Very Large Telescope Interferometer (VLTI). It has now been established that there is no clear moderator in a wide orbit in HR 6819. HR 6819 simply consists of two stars separated by only 50 million km.

Astronomers believe that this compact binary star was the scene of a “stellar vampire”: a single star that “sucked up” the atmosphere of its companion. As the “donor star” lost some of its material, the receiving star began to rotate even faster. To further investigate the evolution of this particular binary star, the joint research team wants to take a closer look at it using VLTI.