Artist’s animation of the triple system with the closest black hole

This animation shows the orbits and movements of the objects in the HR 6819 triple system. This system includes an inner binary with one star (orbit indicated in blue) and a newly discovered black hole (orbit indicated in red). As we move away from this inner pair, we see the outer object in the system, another star in a much wider orbit (in blue). 

The team originally believed there were only two objects, the two stars, in the system. However, as they analysed their observations, they were stunned when they revealed a third, previously undiscovered body in HR 6819: a black hole, the closest ever found to Earth. The black hole is invisible, but it makes its presence known by its gravitational pull, which forces the luminous inner star into an orbit. The objects in this inner pair have roughly the same mass and circular orbits.

The observations, with the FEROS spectrograph on the 2.2-metre telescope at La Silla, showed that the inner visible star orbits the black hole every 40 days, while the second star is at a large distance from this inner pair.