A planet, often called a world, was a celestial body that was in orbit around a star, was neither a binary star nor a moon, and had cleared out the area around its orbit as it formed by causing all other smaller bodies in its orbit to accrete with it. As a consequence, it would not share its orbital region with any other bodies of significant size, except for moons or those collected later under its gravitational influence.

"Homeworld" was a term used to describe the original home of a species, organization, or person.


Planet Class

  • Gas giant: Often large in size, gas giants have little or no solid surface. Instead, they consist largely of swirling gases—mainly hydrogen and helium—in a dense atmosphere.
  • Ice giant: Unlike gas giants, ice giants are composed of heavier elements—such as carbon, nitrogen, oxygen and sulfur—in solid or liquid form.
  • Terrestrial world: Terrestial planets or rocky planets have a solid metallic core with a surrounding silicate rock mantle. The deeper parts of the mantle may or may not be molten, but the outer surface of the planet is solid.
  • Desert world
  • Ice world
  • Water world
  • Irregular world
  • Jungle world
  • Lava world


Type I atmospheres: Breathable

Type I atmospheres had appropriate levels of oxygen, nitrogen, and hydrogen to be breathable by the majority of species in the galaxy. Some contaminants or other trace gases could have had long-term detrimental effects. Planets with these types of atmospheres almost always had some form of indigenous life. Plant life or some analog that frees oxygen was present on all planets with a Type I atmosphere—all oxygen in the atmosphere would have been bound to other elements within a matter of months without such life to free it up. Most heavily populated planets, such as Alderaan and Coruscant, had Type 1 atmospheres.

Type II atmospheres: Breath mask Suggested

Type II atmospheres usually had appropriate levels of atmospheric oxygen and nitrogen. Due to lack of sufficient pressure or the presence of contaminants and/or of other trace gases, however, these atmospheres usually caused detrimental effects to Humans and most other species over a shorter period of time. Many species could breathe Type II atmospheres without any trouble depending on physiology. Planets with a Type II atmosphere usually supported some form of indigenous life. Mustafar's volcanism gave it a Type II atmosphere.

Type III atmospheres: Breath mask Required

Within Type III atmospheres, due to either the lack of appropriate levels of atmospheric oxygen, nitrogen, sufficient pressure, the presence of contaminants and/or of trace gases, a breath mask had to be worn. For Humans and most other species, these atmospheres caused immediate or eventual impediments or even incapacitation. Some species could breathe these types of atmospheres depending on physiology and biology. Planets with a Type III atmosphere sometimes supported native life, such as Goroth Prime and Dorin.

Type IV atmospheres: Environment Suit Required

Type IV atmospheres were either toxic, flammable, extremely high pressure, or nonexistent; these types of atmospheres caused immediate incapacitation or death in most species of the galaxy. Few species could breathe in this type of atmosphere; planets with a Type IV atmosphere rarely supported life. Most asteroids had Type IV atmospheres.

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