The event horizon and the Swarzchild radius are two different things. The Swarzchild radius is the amount of force that an object must be squeezed into to create a black hole. The Event Horizon is the point where light can not escape the black hole.
To the people demanding "more intelligent" answers than star stuff. It is a (well) known expression. Not just a definition of what we are made of. Otherwise the answers could be quite divers, blood and bones, atoms, carbon etc etc. (like on another quiz, what do you count when you want are trying to fall asleep. well you could basicly count anything, beer bottles works well.. but the expression is sheep)
only 35% got ursa major :o that totally surprised me. I really wonder why so few people knew that one ( usually the percentages do not really surprise me, and if they do I can usually come up with a plausible reason, this is the first time I really wondered why it is this low I would have expected about 60%). I think it is the most known one
They are very different things.
accept "stellar material" from smarter people