“It has already completed its main existence, but because the exterior has been removed and only the core is visible, it has comparable temperature and brightness to a young star,” says Kareem El-Badry, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. El-Badry was not involved in the new study, but he suggested in 2021 that HR 6819 is a binary system.

Black hole system. Elements of this image furnished by NASAThe core color and brightness of this siphoned star might lead astronomers examining the older data to believe it was a young star with ten times as much mass. It appeared at first to be orbiting something enormous but undetectable – a black hole.