the outer parts rotate more slowly than the inside.
The natural laws dictate that. any particles not having the right energy, potential or dynamic, will exit, fall until it finds the correct distance. look at the fast inner, and slow, outer planets here.
The arms in galaxies are not rotating but are standing waves through which the material flows, rotates. More stars are born in star nurseries in the the denser arms,
Big stars die young, small stars live longer. if only the sun were smaller, everlasting life on an everlasting planet under an everlasting sun would be longer. As it is, we are half done.