Lecture-7 - Lecture # 7: Formation of the Solar System...

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10/21/11 Physics 20 Lecture 7 1 Lecture # 7: Formation of the Solar System • Theories for the formation of the solar system • Formation of planets • Terrestrial and Jovian planets • comets and asteroids
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10/21/11 Physics 20 Lecture 8 2 A Formation Theory for the Solar System must explain: The pattern of motion of planets why planets have different compositions- rocky terrestrial (near the Sun) and Hydrogen rich jovian (farther out from the Sun) planets ? Why asteroids and comets exist and why they reside in special regions ? must explain all the observable patterns and those which are exceptions to the rules
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10/21/11 Physics 20 Lecture 8 3 Historical Theories for the Solar System Formation • Pierre-Simon Laplace (1795) and Immanuel Kant (1755) proposed that the solar system was formed from the gravitational collapse of an interstellar gas cloud (the nebular hypothesis) • Planets represent debris from near collision between the Sun and another star. They formed from gas that was gravitationally pulled out of the Sun (close encounter hypothesis)
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10/21/11 Physics 20 Lecture 8 4 The close encounter hypothesis was proved wrong as it could not explain the observations as how the planets are grouped the way they are and their motions. Also, given the vast emptiness in our neighborhood, it is hard to see how two stars could collide as was proposed in this scenario
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10/21/11 Physics 20 Lecture 8 5 Where does the Interstellar Gas Come From ? The gas which is needed in the nebular theory to collapse under its gravity and form the solar system came from re-cycling of material in stars. Light elements in stars are converted to heavier elements over the age of the universe. When a star dies, these material are released into space. These can then be re-cycled into new generation of stars. By the time our solar system was formed (4.6 billion years ago), this gas composed of 98% light elements and 2% heavier elements.
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10/21/11 Physics 20 Lecture 8 6 Solar Nebula Hypothesis • Galactic re-cycling: the interstellar matter re-cycle and produce heavier elements in stars through nuclear fusion. This material is then re-cycled into a new generation of stars
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This note was uploaded on 11/17/2011 for the course PHYSICS 20 taught by Professor Mubarek during the Spring '11 term at UC Riverside.

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Lecture-7 - Lecture # 7: Formation of the Solar System...

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