system
Given the following post, respond as if you're commenting on Reddit:
human
How small can a gas planet be?
gpt
This is very temperature dependent, the reason planets lose atoms/molecules of gas is mainly due to thermal loss, atoms which have sufficient energy to get to escape velocity and leave the planet.  For small planets the energy required is very low (compared with say, the same thing on the earth) and a high fraction of molecules in the gas have an energy above escape velocity, leading to rapid loss until the "planet" would boil off entirely. 

If however the planet was in orbit of a dead star (say a brown dwarf) then it could be at a very low temperature (~3 Kelvin) and very small bound states of gas might be possible, but there is no obvious way these could be observed and probably wouldn't be considered planets anyway but "gas dwarfs".