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Radiometric dating
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The process of determining the age of a rock
(ex: the time since it solidified) by comparing the present amount of
radioactive substance to the amount of its decay product
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Half-life
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The time it takes for half of the
nuclei in a given quantity of a radioactive substance to decay.
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Terrestrial planet
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Rocky planets similar in overall composition to Earth. (Mercury, Venus, Earth, and Mars)
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Jovian planet
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Giant gaseous planets similar in overall composition to Jupiter. (Jupiter, Saturn, Uranus, and Neptune)
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Extrasolar planet
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A planet orbiting a star other than our Sun,
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Radial velocty technique
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The portion of any object's total velocity that is directed toward of away from us. this part of the velocity is the only part that we can measure with the Doppler effect,
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Transit
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An event in which a planet passes in front of a star (or the Sun) as seen from Earth. only Mercury and Venus can be seen in transit of our Sun. the search for transits of extrasolar planets is an important planet detection strategy.
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Core (of a planet)
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The dense central region of a planet that has undergone differentiation.
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Core (of a star)
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The central region of a star, in which nuclear fusion can occur.
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Mantle
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The rocky layer that lies between a planet's core and crust.
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Crust
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The low-density surface layer of a planet that has undergone differentiation.
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Lithosphere
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The relatively rigid outer later of a planet; generally encompasses the crust and the uppermost portion of the mantle.
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Differentiation
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The process by which gravity separates materials according to density, with high-density materials sinking, and low-density materials rising.
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Conduction
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The process by which thermal energy is
transferred by direct contact from warm material to cooler material.
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Convection
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The energy transport process in which warm
material expands and rises while cooler material contracts and falls.
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