While they may look similar, the two black holes imaged by the Event Horizon Telescope (EHT) Collaboration are actually very different. Sagittarius A* (Sgr A*), the black hole at the centre of the Milky Way, is over a thousand times smaller than the black hole at the centre of the galaxy M87. The reason they appear the same size is because of their relative distances from Earth. This animation demonstrates their massive differences in size by showing what the M87 black hole would look like if it were closer to Earth. The final frame shows the sizes of the two black holes if they were both at the same distance from Earth as Sgr A*.
ESO/M. Kornmesser, EHT Collaboration
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