a1_09_ss_origin

a1_09_ss_origin - Origin of the Solar System Comparison of...

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Origin of the Solar System
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Comparison of Terrestrial and Jovian Planets Terrestrial Planets Smaller size and mass Higher density (rocks and metal) Solid surface Closer to the Sun and hence warmer Few (if any) moons and no ring system(s) Jovian Planets Larger size and mass Lower density (light gases and hydrogen compounds) No solid surface Farther from the Sun and hence cooler Extensive rings systems and many moons
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Any formation model must explain… Large Scale Properties 1. the planets are isolated in orderly intervals 2. orbits are nearly circular 3. orbits are roughly in the same plane 4. all planets revolve prograde Small Scale Properties 1. most planets rotate prograde 2. terrestrial planets have high densities, rotate slowly, have thin or no atmospheres, and are poor in ices and H/He 3. Outer SS objects are ice and rock
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The origin of the Solar System: Four Challenges 1. Explain why the motions in the Solar System are generally so ordered. 2. Explain why the inner and outer Solar System planets divide so neatly into two classes. 3. Explain the existence and general properties of the large number of asteroids and comets. 4. Must allow for exceptions to the rule, i.e., objects that don’t fit the above patterns.
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The idea of the “Solar Nebula” Origin Immanuel Kant (1755) pictured a rotating disk of gas which eventually formed into the Solar system. There is lots of evidence for gaseous disks around young stars (T-Tauri stars) located in dense molecular clouds. These disks have been imaged directly by the Hubble Space Telescope “proto-planetary disks” “proplyds”
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How does the Solar Nebula collapse? Collapses under its own gravity, but the collapse might be initiated by a pressure wave (shock wave) from a nearby supernova. The temperature increases as the cloud collapses. Hottest at its center where the young “protosun” is forming. Due to the conservation of angular momentum, the nebula rotates faster and faster as it collapses more and more. The nebula begins to flatten into a disk -- a proto-planetary disk. It continues to grow (accrete) mass, forming an “ accretion disk ”.
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98% H and He.
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a1_09_ss_origin - Origin of the Solar System Comparison of...

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