>>9549463Gravity is what determines how varying pressure cells will react to each other.
In a vacuum you don't really get high and low pressure coexisting. A vacuum is a (near) 0 pressure cell, effectively so in a vacuum you can't have a high pressure cell without some other force acting.
Vacuum has no attractive force, pressures just want to equalize. This is part of the reason our atmosphere stays put but decompression is a danger in space. There is no force acting on the air inside the station to keep it inside if you open the door, so it equalizes with the low pressure outside.
Matter, including gases, have mass and thus gravitational influence. This is why clouds of gas condense and form stars, bursting into life as their sheer mass causes the hydrogen in their cores to start fusing into helium.
In a way stars also demonstrate this same phenomenonin reverse. The high pressure cell created by the fusion in the core overcomes the force of gravity attempting to condense the star into a much smaller object.
