A black hole is a region of spacetime where gravity is so strong that nothing can escape from it, similar to a vacuum. Instead of swallowing gobs of dust, black holes suck up stars, which is how some stars end their “lives”. The black hole in HR 6819, a triple star system, is one of the very first black holes found that do not interact violently with their surroundings and is actually black. Currently, Astronomers have only discovered about twelve black holes in total, and finding one in a triple star system and is able to be seen with the naked eye is unusual and rare.
This black hole has a whole mass of 4 times that of the Sun. Astonishingly, one black hole at the core of supergiant elliptical galaxy Messier 87 has a mass of 7 billion times the mass of the Sun. Four times the mass of the Sun is already heavy enough, but seven billion times, that is way over the top!