Is a region of spacetime that exists in such a gravitational field that nothing — no matter or even electromagnetic radiation like light — can escape it. . If the star is large enough there is no effect it can resist the increasing gravity, and it will collapse to a point of infinite density. The defining point of a black hole is the appearance of the event horizon - a boundary in time through which matter and light can only propagate in relation to the black hole's mass. Nothing, not even light, can escape from within the event horizon. The largest known black hole currently is the quasar TON 618, which has a mass 66 Billion times that of the Sun. The size of TON 618 limits the study of whether any larger black funds exist. found in most of the centers of large galaxies, such as our own Milky Way, or neighbors such as the Andromeda Galaxy, Messier 32 and beyond such as NGC 4395.