Planets: Difference between revisions
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There are three main categories of '''planets''': Solid planets, water giants and gas giants. [[Moons]] are also considered planets. | There are three main categories of '''planets''': Solid planets, water giants and gas giants. [[Moons]] are also considered planets. | ||
The term planet refers to celestial bodies orbiting a star with a gravity in a specific range. The gravity of a planet has to be strong enough to hold fluids in a stable state (hydrostatic equilibrium) which prevents them from escaping the planet and low enough to prevent nuclear processes to start as in stars. Some astronomical bodies, we call planets, are not considered as planets by this definition. Moons are natural satellites orbiting a planet and do not fall into the category of planets. However, some natural satellites are considered as planets because they fit their definition. | The term planet refers to celestial bodies orbiting a star with a gravity in a specific range. The gravity of a planet has to be strong enough to hold fluids in a stable state (hydrostatic equilibrium) which prevents them from escaping the planet and low enough to prevent nuclear processes to start as in stars. Some astronomical bodies, we call planets, are not considered as planets by this definition. Moons are natural satellites orbiting a planet and do not fall into the category of planets. However, some natural satellites are considered as planets because they fit their definition. | ||