A rogue black hole spotted wandering 5,000 light-years from Earth

A rogue black hole has been found wandering through space aimlessly 5,000 light-years away from Earth, scientists have said. It is the first known isolated stellar-mass black hole. 

Moreover, their discovery also suggests that the nearest rogue black hole to Earth might be as close as 80 light-years away.

The astronomers spotted the lone stellar object through NASA’s Hubble Space Telescope. The black hole first revealed itself in 2011, when its gravity briefly magnified the light from a more distant star.

But at the time, its true nature eluded researchers. Now, two teams of astronomers—led by astronomers Casey Lam and Jessica Lu of the University of California, Berkeley—have analysed Hubble Space Telescope images to unmask the object’s identity — and have come to somewhat different conclusions.

But the new study suggests that it could be a neutron star, rather than a black hole, given the mass range of the object.

"This is the first free-floating black hole or neutron star discovered with gravitational microlensing," Lu told Science Alert.

"With microlensing, we're able to probe these lonely, compact objects and weigh them. I think we have opened a new window onto these dark objects, which can't be seen any other way."

Neutron stars and stellar-mass black holes form when massive stars — at least several times the heft of the sun — collapse under their own gravity at the end of their lives.

Astronomers believe that there are about a billion neutron stars and around 100 million stellar-mass black holes in our galaxy. But these objects aren’t easy to spot. Neutron stars are so tiny — about the size of a city — that they don’t produce much light. And black holes emit no light at all.

Even though it is yet to be detected whether that lone object is a stellar-mass black hole or a neutron star, it's, however, an interesting possibility that could allow for more accurate estimations of how many roaming black holes there are.