Black hole or neutron star? Astronomers wonder what is the wandering object in the Milky Way

Over a month since Event Horizon Telescope captured the first image of the black hole at the centre of the Milky Way, astronomers have come across another object in the universe-- a free-floating black hole.

The With the help of gravitational microlensing this phenomenon was spotted in the deep space.

Gravitational microlensing is the process used by astronomers to observe light from a star far behind the black hole, which brightens momentarily before being deflected by an object that passes in front of it. The object is the black hole.

Astronomers from UC Berkeley estimate that the mass of this invisible compact object could be somewhere between 1.6 to 4.4 times that of the sun.

There is another opinion among astronomers that the object could be a neutron star rather than a black hole. Neutron stars are dense, highly compact objects, but their gravity is balanced by internal neutron pressure, which prevents further collapse of a black hole.

“This is the first free-floating black hole or neutron star discovered through gravitational microlensing. 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,” Jessica Lu, a UC Berkeley associate professor of astronomy, and lead author said in a statement.

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The wandering black hole lies about 5,000 light-years away, in the Carina-Sagittarius spiral arm of our galaxy. Its discovery though has paved a way for astronomers to believe that the nearest black hole to Earth might be as close as 80 light-years away.

Two teams observed the microlensing event, one from Berkley and another from the Space Telescope Science Institute (STScI) in Baltimore.

The STScI team led by Kailash Sahu estimates the black hole is traveling across the galaxy at an incredibly fast speed of 1,60,000 kilometers per hour. At that speed, one can reach Earth from the Moon in less than three hours.