Planet

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A planet (from the Greek πλανήτης, planetes or "wanderers") is a body of considerable mass that orbits a star and that produces very little or no energy through nuclear fusion.

Planets are thought to form from the collapsing nebula that a planet's star formed out of, aggregating from gas and dust that orbits the protostar in a dense protostellar disk before the star's core ignites and its solar wind blows the remaining material away.

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[edit] Classification

  • Terrestrial or rocky: Planets that are largely composed of rock.
  • Jovian or gas giant: Those with a composition largely made up of gaseous material.
  • Neptunian or ice giant: Are a sub-class of gas giants, distinguished from true Jovians by their depletion in hydrogen and helium. This objects are mainly made up of ice but much bigger that icy planets
  • Icy: Sometimes a third category is added to include bodies whose composition is primarily ice; this category of "icy" bodies also includes many non-planetary bodies such as the icy moons.
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