How black holes were first theorised and detected
In 1783, British scientist John Michell theorised that it may be possible for a star to have such size, and strong gravity, that even light couldn’t escape. He referred to this phenomenon as a Dark Star.
He also suggested that, as it wouldn’t be directly visible, that it’s gravitational effects on nearby objects may betray its presence.
The idea remained fringe, until 1915 when Albert Einstein produced his general theory of relativity, which added theoretical weight to the idea, not by describing a large object, but rather, a dense object, which would warp time/space to such an extreme amount that nothing beyond a certain boundary could escape (event horizon).
In 1916 German astronomer Karl Schwarzschild took Einsteins work and produced proofs for how a singularity could occur and the size of that event horizon.
J. Robert Oppenheimer and Hartland Snyder in 1939 first theorised how such an object could be created, by the collapse of a sufficiently dense star, describing for the first time what we today would call a Stellar Black Hole.
It was another 25 years (1964) before this idea received a name ‘Black Hole’ printed in a science newsletter by reporter Ann Ewing who noted she’d heard the term being used in Cleveland science meeting, the term was then later popularised by the physicist John Wheeler.
In 1973 a paper suggested that an object designated Cygnus X-1 which had been seen to produce large X ray bursts, may in fact be a Black Hole responding to matter falling into it. A year later Physicist Stephen Hawking famously laid a bet with physicist Kip Thorne, that the X ray bursts would eventually be proven not be from a black hole, so that, if Hawkins own work on Black Holes later were found to be invalid, he at least get second prize by knowing the X-Ray burst was not from a black hole. The bet was settled in 1990, Hawkins work remaining valid.
Astronomers Bruce Balick and Robert Brown in 1974 noted strong radio signals coming from an object at the centre of our galaxy, known as Sagittarius A*, this has since been found to be a supermassive black hole.
1978 M87 at over 50 million light years away from our sun, and a massive elliptical galaxy, was found to have the largest ever central black hole, and recently was the target of the first attempts to picture a black hole.
In 2008 the first real confirmation of a black hole existence at the centre of our own galaxy, with the mapping of objects around it in motion and followed up by 2016 and the first detection of gravitational waves from such objects.
Finally, in 2019, the first image of the black hole at the centre of M87
Source : https://www.sciencenewsforstudents.org/article/short-history-of-black-holes
