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View submission: Ask Anything Wednesday - Engineering, Mathematics, Computer Science
There's nothing about a black hole, even a supermassive one like Sagittarius A*, that magically sucks in objects from all over. A black hole is just an extremely dense, strong source of gravity. In the same way that planets can orbit the sun without falling into it, stars can also orbit a black hole. And indeed, all the stars in our galaxy basically orbit that supermassive black hole, and will continue doing so unless something else directly pushes them closer to it.
The part of a black hole from which nothing can escape is called the Event Horizon, and it only exists at a certain distance from the center of the black hole. Anything that crosses closer than that distance can never come back out, but anything outside that distance can continue orbiting undisturbed, and can move away from the black hole given enough of a push. The accretion disk is a region around the black hole, just outside the event horizon, where lots of matter (mostly gas and dust) is getting all smushed together as it orbits very fast. Because it's getting smushed together, it gets hot and emits light (in the same way that a lightbulb or a "red hot" piece of metal does). This is the light that we can observe "coming from" black holes, but as you say it's not coming from within the black hole's event horizon itself (because it can't), but rather from all the stuff nearby.
We don't really know what happens to all the stuff that does fall into a black hole and cross the event horizon, but it doesn't get expelled in a traditional sense. It just becomes part of the black hole, adding to its mass, in the same way that a meteorite which strikes Earth becomes part of the planet. If something in the accretion disk gets pushed around enough that it can escape from that close orbit, nothing particularly special happens to it; it will probably either enter a new, higher orbit around the black hole, or keep flying away until it hits something else.
There's nothing here!