In planetary classification, a class A gas giant is a type of planet. As the name describes, the planet is generally composed of a tenuous gas concentration, with or without a more solid subsurface or core. In many cases, methane composes a significant amount of the planetary atmosphere. In particular among gas giant planets, the class A worlds of this type are radiant of heat and some energy, differing in this respect from the class B gas giant. Jupiter is an example of a class A radiant gas body. Some notations on this classification list worlds of this type as being similar to unborn stars that have failed to ignite into nuclear fusion. (ST references: Star Trek Maps, The Worlds of the Federation)