QUESTION: If there is a supermassive black hole at the center of each galaxy then would it be fair to assume that eventually of trillions of years that all of the stars and planets and all mass would be turned into Black-Body radiation? What would the universe be like then?
ANSWER: No, it would not be fair to assume that. Why would you assume that at all? At what temperature? There are many larger issues there, that's kind of a crazy assumption.
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QUESTION: Well if nothing can escape a black hole's pull and if the stars and planets are in it's pull already. It's not a crazy assumption. Then in time all of the stars and relative planets will be pulled into the black hole and then it'll release Black-Body Radiation. I don't know how far a supermassive black hole's pull goes but that's why I'm asking questions.
Still crazy, which is why you were right to ask an expert. Black holes do not emit blackbody radiation, they emit Hawking radiation (which is quite different). You can use the formula for the Schwarzchild radius of a black hole to figure out the radius of the pull from which light cannot escape. And just because something feels the pull of gravitation far away doesn't mean that it will get pulled in. The Earth has been orbiting the Sun for billions of years. Your question appears to be mostly based on words like "black" which are mismatched with their actual meaning in this case. No offense is intended, but you should study what black holes really are and what blackbody radiation really is (it just means that an object emits radiation without preference to a frequency) before you start matching up terms and meanings. People usually make that mistake with the world "particle." Try not to make that mistake with black body and black holes (totally unrelated).