Astronomers have spotted what might be the first known solitary stellar-mass black hole in the Milky Way — or it might be an unusually heavy neutron star.
— a mere two to four times the weight of our nearest star — and therefore either an unusually lightweight black hole or a curiously hefty neutron star, another group reports in a study in press in theNeutron 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.
To detect these kinds of objects, scientists typically observe how they affect their surroundings. “The only way that we can find them is if they influence something else,” says Kailash Sahu, an astronomer at the Space Telescope Science Institute in Baltimore. But finding black holes in binary systems doesn’t paint a whole picture of the black hole kingdom. Because these objects are continually accreting matter, it’s challenging to determine the mass at which they formed. And since birthweight is a key characteristic of a black hole, that’s a significant drawback to looking at binary systems, Sahu says. “If we want to understand the properties of black holes, it’s best to find isolated ones.