Gas giant

A Gas Giant is a type of planet that can be seen in the Space stage. They can't be visited by the UFO, according to the game they are "too dangerous". This is probably because Gas Giants don't have a solid surface, and the atmospheric pressure would crush and destroy the UFO. However, some of them have moons that can be visited, mostly ice or lava planets. From lower down on these moons, at certain times of the day, the gas giant covers most of the sky and blocks out the sun, creating an artificial night.

On the list of planets while viewing the star, the moon(s) are listed, but not the Gas Giant that they orbit. Most home systems have a Gas Giant, though it normally doesn't have a moon. The Gas Giants come in many colours and some have rings while others do not. Some Gas Giants appear to be tilted at an angle.

Occasionaly, a glitch can occur, and they may be inhabited by an AI empire, and the planet will produce rather strange White spice. Inhabited Gas Giants can be bought, but not captured or entering, as a result it can be irritating to own a Gas Giant because a player cannot protect their colonies.

It is somewhat ironic that the player cannot land on gas giants, even though they can withstand the enormous pressure in a black hole, which would make the pressure in a gas giant seem tiny by comparison.

In real life
Jupiter, Saturn, Uranus and Neptune of the Sol System are Gas Giants. They have many moons and the "surface" is mainly gas. The huge mass of these planets makes them attract a lot of matter with gravity, this is what makes the moons. They also have the tendency to "release" small fractions of their matter in massive explosions every few dozen million years. This is what creates the rings. Many other known extraterrestrial planets in real life are Gas Giants, with moons orbiting them.