Can we corroboratively compare facts about (1) our solar system; (2) gaseous outer planets and their moons; and (3) earth-like bodies in exospace?
The history of science records research of scientists who believed that Jupiter and Saturn were once part of a triple star (Lyttleton, ORIGIN OF THE SOLAR SYSTEM, ed. Robert Jastrow and A.G.W. Cameron, pages 186, 398n.51; cited in N. A. Watanabe, BELOVED IMAGE, Rowman and Littlefield, pages 186, 398n.51). E.M. Drobyshevski wrote a paper titled "Was Jupiter the Protosun's Core?" (NATURE 250, pages 35-36; cited Watanabe, pages 187, 398n.56). Jupiter and the sun have "identical chemical compositions" (Joseph Veverka; cited Watanabe, pages 187, 398n.57). A Pioneer 10 probe shows Jupiter "emits twice the heat it receives from the sun" and "behaves like a miniature sun" (Paolo Maffei, BEYOND THE MOON, page 75; cited Watanabe, pages 188, 398n.58). L. Mestel asserts that "the sun in fact formed rotating rapidly," and "the protoplanetary material had angular momentum right from the start" ("Stellar Magnetism and Rotation," STELLAR EVOLUTION, ed, Hong-Yee Chiu and Amador Muriel, MIT, page 718; cited Watanabe, page 190, 399n.62).
Nancy Ann Watanabe
I've read a few of Ververka's works - but I'm not familiar with the quote that you use which states the Sun and Jupiter have" identical chemical compositions ".
One can be fairly certain that they cannot have identical compositions - chemistry isn't possible in the Sun (compounds dissociate and ionize readily) and so there can be nowhere in the Sun which is rich in ammonia, methane, or more complex compounds - which are visible in the jovian atmosphere.
So I'm rather surprised that Ververka, normally so precise with his writings, would have stated that.
By "chemistry", I think the intent is to say that they have similar elemental abundancies (metallicity) which is not unreasonable if they formed from the same nebula, like a rather lop-sided binary.
Jupiter does emit some excess heat but that is just the remnant of the heat generated by gravitational contraction during its formation, there is no fusion occurring within Jupiter, its mass is much too small. The smallest mass for a brown dwarf star would be around 35 times greater than Jupiter.
George Dishman Indeed. Elemental make-up, unlike chemical make-up, is unaffected by the thermal 'distillation column' of the early protosolar nebula.