Imaging a black hole
Black holes are either rather small or very large and far away. There are two supermassive black holes with the largest apparent event horizons: SgrA* at the center of the Milky Way and M87 in the center of the Virgo A galaxy. The apparent size of these black holes is comparable to the size of an apple on the moon, as seen from the earth. Imaging these thus required a very high resolution, which was obtained by combining telescopes around the world to form a virtual telescope (the Event Horizon Telescope) the size of the Earth using VLBI. An idea first proposed by Radboud University professor Heino Falcke in 2000. In 2019, the EHT consortium presented the first ever picture of a black hole.