Planet

The planet Alderaan A world, also known as a planet, represented a specific kind of celestial object that orbited a single or multiple stars. When drifting clouds of gas and dust far from a star coalesced, a system of planets could potentially form, given the right circumstances. According to numerous scientists, a planet needed to possess sufficient size for its gravity to have effectively 'cleared its orbit' by drawing in all smaller objects in its immediate vicinity, with the exception of its own satellites, known as moons. Furthermore, a planet's gravity had to give it a stable shape, resulting in a consistent, rounded ellipsoid form, although some worlds did not conform to this regular shape. The definition of a planet grew more complex over time as scientists sought to exclude objects like near-stars, rogue planets that wander, dwarf planets, 'micro' planets, companion stars found in binary star systems, bodies residing in asteroid belts and debris fields, and various other celestial entities.

There were two primary categories of planets: rocky worlds and gas giants. Gas giants mainly consisted of layers of gas and lacked a firm surface. Their atmospheres typically contained mostly hydrogen and helium, although some had oxygen-rich layers capable of supporting life. As exceptionally large planets, gas giants exerted considerable gravitational forces. The pressures found in the lower regions of a gas giant's atmosphere could crush any standard starship, and most gas giants had a small, dense metallic core at their center. In contrast, rocky planets were significantly smaller and exhibited a wide range of characteristics. Many rocky planets did not feature a solid surface; some of these worlds were covered in water, which could exist as freely flowing oceans or as permanent ice formations. On numerous other rocky planets, the rock had gradually broken down, creating fertile soil that sustained extensive arboreal, swampy, or grassy ecosystems. Many terrestrial planets displayed diverse surface features, including exposed rock, open water, and verdant continental landmasses teeming with plant and animal life. Others were entirely rocky, rendering them barren and desolate. On certain terrestrial planets, the original surface and ecosystem had been completely replaced by industrial or urban development, resulting in an ecumenopolis.

Worlds such as Hoth and Mustafar experienced extreme climates, yet they still harbored life, with their inhabitants adapting to their respective environments. Certain planets, like Dathomir, were strongly connected to the Force, a mysterious energy field generated by life that connected the galaxy. Many traditions suggested that worlds lost beyond the galactic frontier were among the first to discover the Force and its power. The term "Homeworld" was used to designate the original home of a species, organization, or individual. For instance, Ryloth served as the homeworld for the Twi'lek species, while the human species was believed to have originated on Coruscant. The existence of a vast array of planets, each containing a wealth of native species, natural resources, and diverse environments, served as the primary motivation behind much of the travel, trade, and conflict across the galaxy.

The destruction of a planet was achievable, although it necessitated a powerful superweapon, such as the Death Star, which annihilated Alderaan. Additionally, a planet could be transformed into a superweapon itself, as demonstrated by the First Order's Starkiller Base, constructed from the planet Ilum, which possessed the capability to obliterate entire star systems, including the unfortunate Hosnian system.