Beyond the Event Horizon

It is common understanding that all black holes have event horizons — the point beyond which nothing, not even light, can escape the gravitational pull exerted by the densest known objects in the universe. But not all theorists agree that such a phenomenon — the event horizon — exists; they argue instead for something far stranger that is based on modifications made to Einstein’s General Theory of Relativity.
According to the widely accepted theory of black holes, based on Einstein’s relativity theory, black holes, including their supermassive variants, form when a star with a mass approximately great than 20 suns, collapses onto itself after running out of energy to support itself. The resulting dense concentration of matter has gravity so strong that it accretes everything that comes within its gravitational sphere, growing in mass all the time. Since everything includes light, a black hole is not directly visible, earning it its name. The concept of event horizons, while accepted by a large number of people, has not yet been proven, however.

Do event horizons really exist around black holes?