Jupiter is not even a brown dwarf which starts at about 13 times the mass of Jupiter. For upgrading Jupiter to a star, it would need 80 times its current mass.

Jupiter is not even a brown dwarf which starts at about 13 times the mass of Jupiter. For upgrading Jupiter to a star, it would need 80 times its current mass. There is nowhere else in the solar system enough mass to grow Jupiter but the Sun. Taking that mass from the Sun is in theory feasible but of course out of the range of our capabilities for quite some time. That's for natural nuclear fission though which would waste a lot of energy going into space and not where we would want to have it (the moons). It's probably more realistic to build small fission suns that orbit the moons that produce heat and light in a less wasteful, more directed manner. Still not possible today :-)