MEASURING THE SPIN OF A BLACK HOLE
Astronomers are able to measure the masses of black holes in a relatively straightforward way: watching how matter moves in their vicinity (including other black holes), affected by the gravitational field.
BLACK HOLE
A NEWFOUND BLACK HOLE IS THE CLOSEST ONE TO EARTH WE HAVE EVER FOUND
A newfound black hole may be the closest black hole to Earth, and you can spot its cosmic home in the night sky without a telescope.