Nearest stellar-mass black hole revealed
Giving off no radiation, it was only discovered by its gravitational effects
Astronomers have discovered a black hole just 1,000 lightyears from Earth, making it the closest black hole known to date. It’s the first stellar-mass black hole observed which isn’t interacting with its environment, making it truly black.
All other black holes we know of in our Galaxy cause great disturbances in the surrounding gas, which then emit bright radiation, revealing the otherwise invisible objects to astronomers. However, this black hole has no such bright emission, and was only discovered as gravitationally bound to two stars in the system HR6819, one of which looks as if it’s being pulled on by an unseen companion.
“An invisible object with a mass at least four times that of the Sun can only be a black hole,” says Thomas Rivinius from the European Southern
Observatory (ESO), who led the study. “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.”
The black hole, or at least its home system, is bright enough to be seen in the Southern Hemisphere constellation of Telescopium using just the naked-eye, meaning that astronomers around the world could soon be casting their gaze towards our newly discovered neighbour.
“We were totally surprised when we realised that this is the first stellar system with a black hole that can be seen with the unaided eye,” says Petr Hadrava from the Academy of Sciences of the Czech Republic in Prague. www.eso.org