Don't worry. We won't fall in.
A keen-eyed human in the southern hemisphere of planet Earth can spot two stars in the HR 6819 system with the unaided eye on a dark night by looking to the minor constellation Telescopium (named after a telescope). Now, that person will know she's looking toward a black hole.
A research team led by astronomers from the European Southern Observatory discovered a sneaky black hole lurking in HR 6819. The fact that the black hole's system could be seen with the naked eye came as a surprise. "This system contains the nearest black hole to Earth that we know of," said ESO's Thomas Rivinius in a release on Wednesday.
ESO said the black hole is located "just 1,000 light-years from Earth." That's cosmically close, but still incredibly far away in human terms.
The scientists used a telescope at ESO's La Silla Observatory in Chile to observe the system and discovered one of the stars orbits an invisible object while the second star practices a cosmic version of social distancing by hanging out away from the others.
The mysterious hidden object is the black hole, the end result of the collapse of a massive star.
The research team published its findings in the journal Astronomy & Astrophysics on Wednesday.
The inner, visible star's orbital behavior betrayed the identity of its companion, which has a mass at least four times that of our sun. For a black hole, it's pretty chill. "The hidden black hole in HR 6819 is one of the very first stellar-mass black holes found that do not interact violently with their environment and, therefore, appear truly black," ESO said.
Black holes are hard to spot for a reason. "A black hole is a place in space where gravity pulls so much that even light can not get out. The gravity is so strong because matter has been squeezed into a tiny space," NASA has elegantly explained. We can't just snap a photo of a black hole, though the pioneering Event Horizon project unveiled the first direct image of a black hole in 2019.
The black hole in HR 6819 hints at untold wonders. Astronomers are already scoping out another system, LB-1, that may be hiding a similar secret.
"There must be hundreds of millions of black holes out there, but we know about only very few. Knowing what to look for should put us in a better position to find them," said Rivinius.