Geology: Igneous Refers to igneous rocks that crystallized underground. Click on Term to Read More 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. Click on Term to Read More 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 Click on Term to Read More 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 Click on Term to Read More 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. Click on Term to Read More 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 Click on Term to Read More). In contrast to the classical planets, plutons typically have highly inclined orbits with large eccentricities.
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