Ch 15 – The Formation of the Solar System

Modeling the origin of the solar system

Model Requirements•Each Planet is relatively isolated in space

•The orbits of the planets are nearly circular

•The orbits of the planets all lie in nearly the same plane.

•The direction in which the planets orbit the sun is the same as the direction in which the sun rotates about its axis.

•The direction in which most of the planets rotate is roughly the same as the direction in which the sun rotates.

•The comets are primitive, icy fragments that do not orbit in the ecliptic plane and reside primarily at large distances from the sun.

•The asteroids are very old and exhibit a range of properties not characteristic of either the inner or outer planets(except Pluto) or their moons

•Our planetary system is highly differentiated. (the inner terrestrial planets are much different than the outer Jovian planets)

Condensation Theory

Large, rotating dust cloud gravitationally collapses

The Solar nebula flattens into a spinning disk Angular momentum is conserved

Nebular gas is expelled by the strong solar wind (T-Tauri phase)

Finally, after approximately 100 million years, the protoplanets have formed. A billion years more were required for the solar wind to “sweep” out much of the left over solar debris.

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