A black hole is the ultimate prison. It is impossible to exit from the interior of its event horizon even at the speed of light. For those freedom-lovers who are worried about the risk of entering a region where no escape is possible, there is one existential question: how large is the mouth of the most massive black hole in the universe?
The record holder is the quasar TON 618 with a mass of forty billion suns, detected at a redshift of 2.2 when the universe was merely 3 billion years old. A quasar is a supermassive black hole that shines brightly as a result of the viscous heating of gas that drains into it. The mouth of TON 618 is a thousand times bigger than the Earth-Sun separation.