Geology: Igneous Refers to igneous rocks that crystallized underground. body that forms when Molten silicate (rock) beneath the surface of a planetary body or moon. When it reaches the surface, magma is called lava. is injected into host rocks and solidifies. Plutons occur in the Outermost layer of a differentiated planet, asteroid or moon, usually consisting of silicate rock and extending no more than 10s of km from the surface. The term is also applied to icy bodies, in which case it is composed of ices, frozen gases, and accumulated meteoritic material. On Earth, the of asteroids undergoing A process by which a generally homogeneous chondritic body containing mostly metal, silicates and sulfides will melt and form distinct (differentiated) layers of different densities. When the melting process continues for a long enough period of time, the once chondritic body will re-partition into layers of different composition including or planets. Named after Pluto, the Roman god of the underworld. Plutonic rocks are the rocks found within a pluton.
Astronomy: Category of The term "planet" originally comes from the Greek word for "wanderer" since these objects were seen to move in the sky independently from the background of fixed stars that moved together through the seasons. The IAU last defined the term planet in 2006, however the new definition has remained controversial. including all planets with orbital periods >200 years (Pluto, Charon, and Generally, small bodies found in the Kuiper Belt. The largest Kuiper Belt Object (KBO), Eris, is <3000 km in diameter. Image source: http://en.wikipedia.org/wiki/File:EightTNOs.png). In contrast to the classical planets, plutons typically have highly inclined orbits with large eccentricities.
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