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Astro 10-Lecture 6: Formation and Structure of the Solar System. What are the properties of the solar system? How are these properties explained by theories of the formation of the solar system? Why are the planets different from one another?.
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What are the properties of the solar system?
How are these properties explained by theories of the formation of the solar system?
Why are the planets different from one another?
1. All of the planets orbit in the same direction and in the same plane. (Within a few degrees) This plane corresponds with the equator of the sun.
2. Most of the planets rotate in the same direction and have their equators roughly aligned with the plane of the solar system.
3. Orbits of moons around planets are in the planet’s equatorial plane.
4. Two (three?) types of planets…
Small and Rocky. Crust mainly composed of Silicon and Oxygen (Silicates).
Atmosphere ranges from none to thick. Atmosphere
Near to the sun. (< 5 astronomical units)
Small and Rocky. (From 0.1 to 1 Me)
Cratering is common on the surface of terrestrial planets.
From the ages of the craters, we can tell that impacts were much more common early in the history of the solar system
Atmosphere ranges from none (Mercury) to thick (Venus).
Typically have no moons.
Primarily composed of hydrogen (H2) and Helium (He)
Massive (15 to 300 Me)
Low density (0.7 to 1.8x the density of water)
Small rocky core surrounded by huge ocean of liquid hydrogen.
All are found more distant than about 5 astronomical units from the sun.
Rings! All Jovian planets have them.
Moons! Jovian planets tend to have very many
5.Three types of space debris:
1. & 2. Collapse to a disk explains the concentration in the plane of the solar system, and why almost everything moves in the same direction.
3. The giant planets had disks of their own so their moons orbit in their equatorial plane
4a. Because the inner solar system was hot, only rock and metal could condense which resulted in terrestrial planets
4b. The outer solar system was cold enough for ices to condense and for hydrogen gas to be captured by a massive enough body. This resulted in Jovian planets.
4c. If an object in the outer solar system wasn’t massive enough to capture hydrogen gas, it remained as a small icy body. (Pluto, the outer planet moons, comets)
4d. The terrestrial planets released their atmospheres from their interiors. The Jovian planets captured theirs. The icy planets weren’t massive enough to capture one, or hot enough to release one.
4e. The inner structure of the planets is explained by differentiation. Heavier elements sink to the core. Lighter ones float to the surface.
5. Asteroids and comets are left over planetesimals. Meteors are bits of dust that have fallen off of comets
6. Everything is the same age because it all formed at about the same time.
What about the exceptions?