Infinite Space
We tend to think of black holes as some kind of cosmic vacuum cleaner, constantly sucking in all the material around it. And while it’s true that if you managed to very carefully drop an object into a black hole, YOU'D never ever get that object back, under normal circumstances, black holes are actually remarkably bad at pulling material that close.
Black Holes
We tend to think of black holes as some kind of cosmic vacuum cleaner, constantly sucking in all the material around it. And while it’s true that if you managed to very carefully drop an object into a black hole, YOU'D never ever get that object back, under normal circumstances, black holes are actually remarkably bad at pulling material that close.
Here's Why..black holes AREN'T actually attractive to anything for any reason other than gravity. Much like our solar system is in a stable orbit around the sun, the vast majority of a galaxy is in a stable orbit around the black hole, with no real reason to go plunging towards the very centre of the galaxy.
black holes are bad at being astronomical vacuum cleaners because THEY'RE really, really, inefficient at getting material close enough to them to cross the event horizon and add to the mass of the black hole. Even small black holes, which exist in great numbers in a galaxy, are much better at tearing a companion star apart than they are at actually growing their own size by consuming the other star. Our Black HoleThe Milky Way’s central black hole, for instance, seems to be surrounded by stars, but almost no gas, so there’s no accretion disk around our black hole. In order to be shredded by a black hole, a star would have to come very, very close to the black hole. The star that orbits the black hole in the CENTER of the Milky Way orbits once every fifteen years and WE'VE been able to watch it move around the black hole. It comes within a light-day of the event horizon, and that’s still not close enough to get torn apart or sucked in. (There are videos of the orbiting stars. Go watch them. Here’s the actual data.
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Size..The fastest way for a black hole to grow in size - at least, as far as we know right now - is by crashing into another galaxy. When that happens, after things settle down, the heaviest objects will wind up in the centre, which for two galaxies will be the two black holes. Over time, the two black holes will lose enough energy while orbiting each other to merge into a single black hole. If the other galaxy was about the same mass as the original galaxy, this should double the mass of the black hole in one fell swoop - much more efficient than than by trying to build mass with gas.
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