One of the most momentous discoveries in the history of astronomy was the discovery of QUASARS in 1963. Their incredible luminosity - more than million, million times the luminosity of the Sun - implied that their masses must be in excess of a billion solar mass. Another unexpected discovery was that their flux was 'variable'. It soon emerged that the 'central engines' that powered the Quasars must be supermassive black holes.
A parallel discovery was that of radio galaxies with their powerful relativeistic jets. Various observations led to the conclusion that all types of Active Galactic Nuclei are also powered by supermassive black holes. In the subsequent decades, X-ray observations revealed that all galaxies, and not just the more 'active' ones, have massive black holes in their centres.
This talk will review the evolution of our understanding of the realm of the supermassive black holes. It will be pedagogic in nature and will not assume any prior knowledge. The main thrust of the talk will be towards an understanding of the very recent result from the Event Horizon Telescope - an image of the shadow of the black hole at the centre of the giant galaxy M87.