Neil_Boekend wrote:It kinda weirds me out that objects don't really get bigger than Jupiter unless they have radiation pressure from fusion or become black holes. Add 1 Jupiter mass to Jupiter and the density almost doubles instead of the object getting significantly bigger. Add another Jupiter to the mix and the dang thing stays about the same size. Keep adding to get a total 13 Jupiter masses and you have an object with less than 2 times the volume of Jupiter. But freaking 13 times the mass!
So that made me think: going in the other direction, you can probably also take away significant mass from a Jupiter-like planet without it getting very much smaller?
Actually, there's a simple check possible, let's look up and compare the masses and sizes of Jupiter and Saturn.
Jupiter has a mass of about 1.9E27 kg (about 318 Earth masses), Saturn has 5.7E26 kg (about 95 Earth masses or 30% of Jupiter's mass).
Polar diametres: Jupiter 133,708 km, Saturn 108,728 km or about 81% of Jupiter.
Taking Saturn as a benchmark instead, Jupiter has about 3.34 times the mass of Saturn but only 1.23 times the diameter. Jupiter's density is nearly twice that of Saturn.
ETA: Uranus and Neptune, on the other hand, have masses of about 15% and 18% of Saturn's, respectively, and both about half the diametre, but also both densities similar to Jupiter's. I'm guessing that their compositions probably are significantly different from those of the two larger gas giants. So, without having done further research, I see myself forced to also drop the assumption that Saturn's composition should be comparable to Jupiter's, which appears to render the comparison of mass and size differences less significant than I originally thought.
