Oh I wasn't disagreeing with you there kara, it was directed at Lib's bad science comments on the previous page. I was reinforcing what had already been stated. On brown dwarfs, you are correct; they are stellar masses but don't actually have the working fusion powerplant of a star. I was thinking of Red dwarfs, which do still have a small fusion reaction ongoing in their cores. They degenerate into brown dwarves IIRC, once their fuel supplies have been completely exhausted.

However, I don't think the heat generated by Jupiter is due to gravitational compression alone, there's something else causing it. It's a conservation of energy thing, something is causing Jupiter to not only heat up to higher temperatures than it should be reaching from the sunlight it recieves, it is actually emmitting more energy into space than it collects. Which is the opposite of any other planet in the solar system. Gravity fields can't do that.

Gravity fields can't do that.

I think they do, actually. Gravity causes pressure, and pressure releases heat. A good example of how it would release heat, is by observing alumnium blocks placed in presses. When a block of iron or alumnium is placed on a press, and subjected to high pressure, the pressure alone causes the block to heat up. I know because i worked in one. The Jupiter gravity is so powerfull, that the matter within gets subjected to unbelivable pressures, wich releases heat, by the rearrangement of atoms or some such technobabble. Then the atmosphere acts as a greenhouse, trapping the heat inside. Wich causes more pressure, and subsequentially more heat. There will come a time that Jupiter will become so dense that it colapses on itself. Kinda like a sun, at a smaller scale.

However, we should keep in mind that we still have very little idea as to what really exists inside Jupiter. No probe ever managed to reach the surface, they melt away long before. So all this is still just pretty much theoretical. Some say the surface of Jupiter is actually a sea of mercury and other heavy metals in a liquid and gaseous state, others say it´s an iron core. We just don´t know for sure yet.

You're on the right track Swamp Thing. As a jovian planet cools the atmospheric pressure decreases. This causes the planet to contract increasing the pressure on the core which then heats up.

*does quick web search* It's called the Kelvin Helmholtz mechanism if you're interested.

Strat I don't think red dwarfs become brown dwarfs. As far as I can see brown dwarfs were never big enough to sustain fusion of hydrogen where as red dwarfs were big enough to do it slowly.

As for jupiter current theries are mostly based on a metallic hydrogen core (either liquid or solid). Of course it will be hard to tell for certain since any probe that gets too close to jupiter gets fried or squashed long before it gets close enough to tell us the answer.

Somebody, Clarke I think, theorized a core of crystalized carbon(diamond) the size of Earth.

That's an interesting question, what kind of properties would solidified hydrogen possess? It can't exist in a normal enviroment, it requires intense pressures found only in the lower altitudes of a jovian/super-jovian class planet.

That's an interesting question, what kind of properties would solidified hydrogen possess? It can't exist in a normal enviroment, it requires intense pressures found only in the lower altitudes of a jovian/super-jovian class planet.

Actually it can't form in a normal enviroment. Once formed there is a good possibility that it's stable.

Metallic hydrogen would probably be one of the best building materials ever seen. Extrapolation of it's properties from other chemically similar elements predicts that it would be as strong as aluminium but incredibly light.

From what I'd heard, because Hydrogen bonds so tightly to itself, it would quite possibly be a stronger material than diamond.

And can I just ask, how did this thread get from Sentry Guns to Elemental reactions within Jovian planets? That's quite a leap, even for us