How small could a gas planet be? Can you have a gas planet smaller than Neptune?

Discussions about Neptune's interior seem to be in two camps-either it's a ball of liquid hydrogen, or a ball of superheated water. Neptune is approximately 30,000 miles in diameter. I wonder if planets like this can be smaller...

Could you have a planet that's twice the size of the earth that is a gas planet?

:-k

You could have a really heavy gas!

Jupiter et.al. have rocky cores. So you need to allow for a core. Figure on a certain maximum size that is allowed. So, make the core very dense.

Basically, you need to ensure that the percentage of gas that is fast enough to boil off is small enough to keep the planet around for the desired time frame. So, what is the thermal constant associated with the gas, and what is the mass of the particles? How hot is the body overall? How cold it may be depends on the boiling point of the intended gas.

So, given what you've said, is Neptune is about as small as you can get for a gas planet-assuming that it really fits that definition?

First, what's a "planet"?

What's a gas planet? I'm not being flippant, I'm really thinking that we think we know what they are because in our solar system there is such a visible difference between the inner and outer planets and yet, do we really know a definition?

If Jupiter has a rocky core and a thick atmosphere, and Venus has a rocky body and a thick atmosphere... what exactly would be the defining factors? Clearly there is a huge mass difference, but what else? Maybe the atmosphere is some large percentage of the total radius of the body?

I've also read where there is a distinction made between the gas giants Jupiter and Saturn, and the icy giants Uranus and Neptune -- that they are considered by some to be two different classes of bodies.

Re: the definition of "gas planet", dunno-maybe because planets like Jupiter and Saturn are basically giant balls of liquid hydrogen with a rocky center? :-? It's my best guess-I'm not going to pretend I know anything. :P

As to Uranus and Neptune, I've read conflicting info: either they are balls of liquid hydrogen, or some mix of water, ammonia and possibly liquid hydrogen. I admit to being frustrated at not knowing which one is the accepted theory. :x So-which is it??