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Black holes are characterized by extreme gravity, which is so strong that not even electromagnetic radiation can escape. Within Einstein's Theory of General Relativity, such objects could exist if enough mass/energy is comprised in a sufficiently small volume. While black holes have no clear boundary, one often uses the event horizon to determine the size of a black hole. The event horizon characterizes the distance at which nothing (not even light) can escape from the black hole. The event horizon radius of our sound would be about 2.95km, i.e., tiny compared to the sun's real size of 700000km.

On 10 April 2019, the first direct image of a black hole from M87* (see the image below)