If a galaxy is the accretion disk for a supermassive black hole, how can it be a shape other than disk?
closed as unclear what you're asking by AccidentalFourierTransform, ZeroTheHero, garyp, ahemmetter, user191954 Dec 3 '18 at 12:44
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Because it is not an accretion disk. Accretion disks occur when matter orbits a massive object in such a way that it interacts with itself, losing energy through frictional heating and converging into a hot disk. A galaxy consists of stars orbiting their mutual center of mass, without any appreciable friction or other violent interactions. There may certainly be a black hole at the center, but it is much smaller. A galaxy can be elliptic or irregular, depending on the orbits.
In a galaxies early stage it’s not disc shaped and doesn’t necessarily have a black hole. When two galaxies collide they can disturb each other so much they become sphere shaped and start forming a disc all over again.