Apart from thermo-nuclear reactions in the Sun, (and in hydrogen bombs and other methods developed by scientists) does nuclear fusion occur naturally in the planets? If not, why?
Also, do the Sun and the Outer planets - Jupiter through Neptune - have rocky cores similar to the Earth (consisting of iron, nickel, silicon etc) in addition to the gases? I have read that there is not much of hydrogen or helium in the inner planets because of their low escape velocities and the solar winds from the Sun. Hence only the heavier elements remained.