your theory is full of holes
if Saturn is a sun then so is Jupiter. it's bigger it is going to have a much higher self produced internal energy d/t gravity.
and if your using that loose of a definition the moon is a sun and every other celestial body big enough to "walk" on, They all have gravity which increases pressure on the core which causes energy independent of our sun.
technically all of the matter here was produced by other suns and novas elsewhere. so the gravitational/pressure energy made by jupitor and saturn was produced by a distant star. Matter is a battery they may or may not ever run out on it's own. it has not been observed…. that i know of. nukes work by turning matter into energy so it's "artificially" possible.
It might be a worthwhile experiment to see if krakatoa was 100% pressure from the mantle blowing thru the surface of if the pressure was high enough to cause fission or fusion and that was the bulk of the surface explosion.
all of that is based on some things we can't verify without going in a space ship and looking for yourself or trusting known liars.