The gravitational tug of a black hole makes it invisible to the naked eye because it swallows everything, including light.
But astronomers worked around the problem by observing a region of space where stars appeared to orbit an invisible object.
One such star caught the astronomers’ attention and its movements indicated it was racing around an object 70 times heavier than the Sun.
Until recently, astronomers have relied on X-ray emissions to pinpoint the locations of distant black holes.
Colliding black holes also offer clues to their whereabouts by releasing gravitational waves out into space.
But the detection of LB-1 is the first-ever discovery of a black hole by the “radial velocity method”.