What, in mass, diameter or volume ?

At 10 times the mass it would be fat enough to ignite, if that's what you wanted to know. For the rest I have no idea because of the required mass

It's gases would expand. If it had 2x mass however there may be changes to SOL Systems...

I think the extra mass = more gravity = Jupiter shrinks.

The changes to the other planets would be very minor. How much do you really think that Jupiter has on the orbit of Mars, or Earth?

Isaac Newton is very disappointed in you.

I think more mass means bigger object that can interfere more with nearby asteroid belt, Jupiter moons, Saturn moons and Mars orbit around SOL. In short stuff of lesser mass nearby Jupiter may start moving towards Jupiter. Just as current Jupiter mass attracts comets and asteroids and possible moonlets.

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Jupiter would need to be about 80X it's mass to be the smallest possible red dwarf, so at 2X the mass we're still very far away from star territory. Oddly enough, though, it would be the roughly the same size as it is now, as Jupiter is about as large in terms of volume as a gas giant (or brown dwarf) gets.

As gas giants get more massive they run into an interesting situation in which the increase in gravity compresses the planet just as much as the planet increases in mass--so even though the mass increases the volume remains roughly the same. It just gets denser.

However, the additional mass likely would have drastically effected the evolution of our solar system. It may have flung the earth out of the solar system, or into the sun. It may have prevented as many water-rich asteroids and comets from hitting the earth, preventing it from ever accumulating enough water to support life.

Simulations would be required to figure out how, but it's safe to say that a Jupiter that is 2X the mass would have resulted in a solar system that looks very different from the one we see today.

The minimum mass that an object would need to initiate deuterium fusion in its core is about 13-14 times the mass of Jupiter. At that point it would be a brown dwarf star. The minimum mass to initiate hydrogen fusion is about 80x the mass of Jupiter. At 2x the mass, Jupiter is well below both limits and would not become a star.

As for the gravitational effect of doubling the mass of Jupiter on the remaining Solar System bodies - of course it would have an effect. Jupiter was (probably) the first planet to form out of the original Solar nebula. At double the mass, it would have had an influence on a larger area of the nebula, therefore pulling in more of the gasses. This would have a greater effect on the formation of the other gas giants. Exactly what that effect would be is up for you to speculate (or run your own Monte-Carlo models) on.

Jupiter is also cited as a major influence of the movement of the planetesimals which formed the inner (rocky) planets. Doubling the mass would certainly change that influence. Again, feel free to run your own Solar System simulations to figure out how that affects planetary formation, but the end game is that the Solar System would be different.

No, bigger doesn't mean more interference. The size of Jupiter is trivial compared with the distance to asteroids. More mass is what does it, not just more size.

And I'm sticking to my statement that with more mass, Jupiter would shrink. At least until it starts nuclear fusion, at about 80X current mass.

If Jupiter was 10X more massive, the near-by asteroids would change their orbit by less than 0.5 AU. They are already at least 4.2 AU from Jupiter. Earth's orbit would change by less than 0.05 AU, but that's still a huge impact on the seasons.

I think old Isaac would appreciate my understanding of how gases compress under pressure.

But not your understanding of additional mass within planetary systems.

> I'm sticking to my statement that with more mass, Jupiter would shrink.

You're almost right.

As you add mass to Jupiter, its diameter increases up until a mass of 3 x Jupiter, after which point the diameter starts to shrink because of the sheer amount of degenerate matter at the core.

Degenerate matter is weird stuff, a macro-scale substance only made possible by some obscure rules quantum physics. Prime among these rules is the Pauli Exclusion Principle, which states that, "no two electrons can exist in the same quantum state at the same time." Thing is, a quantum state is more than just position - it also includes momentum. You can have two electrons occupy the same position at the same time, so long as they're moving at different speeds through each other.

The above mechanism produces a very non-intuitive quality: the more material you add to an electron degenerate body, the smaller it gets in size, as electrons are forced to move faster and faster in speed. Counterintuitively, if you had an electron degenerate bookshelf, you'd have more room the more books you added.

Not only is this the case for really massive planets, but also brown dwarfs: the more massive it is, the smaller the radius.

Source: did my PhD researching Jupiter.

A real expert on Reddit? That’s a rare thing. Q: if the added mass was solid iron or silicon, so that it would sink to the core, I understand that the solid core would grow. But would the outer gassy layers also grow?

> if the added mass was solid iron or silicon, so that it would sink to the core, I understand that the solid core would grow. But would the outer gassy layers also grow?

That depends sensitively on "how much" and "what kind of stuff"...but generally electron degeneracy is electron degeneracy. You can't pack too much stuff too tightly or it goes degenerate, and starts expanding outwards into momentum space while shrinking in position space.

The resulting outer gassy layers are tricky, but there's a closely analogous phenomenon in stars: as an old main sequence star fuses up all the hydrogen at its core, it leaves behind a ball of helium "ash" that collapses under its own weight, supported only by electron degeneracy pressure. The central density in our Sun is already very high, about 160x greater than water, but this helium ash ball is closer to 16,000x denser than water. If you could stand on this ball, it would have enormous surface gravity - also meaning fresh hydrogen in a shell surrounding the degenerate helium ball is compressed, and fusion proceeds much more rapidly, expanding the outer layers into a red giant.

In the case of Jupiter, it's still a long way from the pressures / temperatures needed for any fusion, so the gassy layers would just get compressed by the increased density of a more massive, more degenerate core...and that's about it.