The first image of a black hole was captured in 2019 by the Event Horizon Telescope (EHT) collaboration. Before that, the first observational evidence was discovered in 1964 with the detection of the X-ray source Cygnus X-1, which was later interpreted as material accreting onto a black hole from a companion star. In 1971, Cygnus X-1 was proposed as the first robust observational evidence of a black hole by astronomers Tom Bolton and Louise Webster.