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The Solar System

The Solar System. Ingredients?. The Solar System. Ingredients?. 1 Star: the Sun 8 Planets + a few “minor planets” 126 moons around these planets Asteroids, meteoroids, comets A lot of nearly empty space. Questions.

william-blevins
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The Solar System

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  1. The Solar System Ingredients?

  2. The Solar System Ingredients? • 1 Star: the Sun • 8 Planets + a few “minor planets” • 126 moons around these planets • Asteroids, meteoroids, comets • A lot of nearly empty space

  3. Questions • What percentage of the total mass of the solar system does the Sun contribute? • How is the solar system laid out in space? Spacing between planets? Orbital directions?

  4. Sun, Planets and Moon to scale Sun accounts for 99.9% of solar system mass!

  5. Two Kinds of Planets "Terrestrial" Mercury, Venus, Earth, Mars "Jovian" Jupiter, Saturn, Uranus, Neptune Distance from Sun? Size? Composition? Density? Rotation Rate? Number of moons? Rings? Heavy or light Elements?

  6. Two Kinds of Planets "Terrestrial" Mercury, Venus, Earth, Mars "Jovian" Jupiter, Saturn, Uranus, Neptune Far from the Sun Large Mostly Gaseous Low Density Fast Rotation (0.41 - 0.72 days) Many Moons Rings Main Elements H, He Close to the Sun Small Mostly Rocky High Density Slow Rotation (1 - 243 days) Few Moons No Rings Heavier Elements

  7. Origin of Pluto Large member of a class of objects in the outer reaches of the Solar System: The Kuiper Belt Objects 100's found since 1992. Orbits tend to be more tilted, like Pluto's. Leftover planetesimals from Solar System formation?

  8. Questions • What are some of the smaller objects (or debris) found in the solar system? • What information do they contain that the planets and moons do not? • (Hint: What effects do erosion, geological activity, vulcanism, etc. have on a planet?)

  9. Questions • What are some of the smaller objects (or debris) found in the solar system? • Comets, asteroids, meteoroids • What information do they contain that the planets and moons do not? • Solar system debris is unevolved => gives direct evidence of conditions during solar system formation!

  10. Solar System Debris Comets Comet Hale-Bopp (1997) Comet Halley (1986) Short Period Comets Long Period Comets Few times 105 or 106 year orbits Orbits have random orientations and large ellipticities Originate in Oort Cloud 50-200 year orbits Orbits prograde, close to plane of Solar System Originate in Kuiper Belt

  11. Oort Cloud is a huge, roughly spherical reservoir of comets surrounding the Solar System. ~108 objects? A passing star may redirect Oort cloud objects, creating long period comets. Kuiper Belt object can be redirected by Neptune, creating a short-period comet.

  12. Question • What causes the tail of a comet? • (Hint: The tail always points directly away from the sun.)

  13. Comet Structure Coma and tail due to gas and dust removed from nucleus by the Solar Wind. Far from Sun, comet is a nucleus only. Nucleus: ~10 km ball of ice, dust Coma: cloud of gas and dust around nucleus (~106 km across) Tail: Always points away from Sun.

  14. Comet Trajectory

  15. Meteor Showers Comets break up when near Sun - solar wind, evaporation, tidal force. e.g. Halley loses 10 tons/sec when near Sun. Will be destroyed in 40,000 years. Debris spreads out along comet orbit. Intersection of orbits => meteor shower

  16. Asteroids Most in Asteroid Belt, between Mars and Jupiter. If a potato represents an asteroid in the asteroid belt how far away on average (using the same scale) is the next nearest potato?

  17. How did the Solar System Form? What must be explained? • Solar system is very flat. • Planetary orbits are nearly circular. • Almost all moons and planets (and Sun) rotate • and revolve in the same direction. • Planets are isolated in space. • Terrestrial - Jovian planet distinction. • Leftover junk (comets and asteroids).

  18. Nebular Theory • Nebula: Cloud of interstellar dust and gas about a light-year across • Condensing cloud heats up - star forms at center • But why is solar system rotating and flat?

  19. Nebular Theory • Nebula: Cloud of interstellar dust and gas about a light-year across • Condensing cloud heats up - star forms at center • But why is solar system flat? • Conservation of Angular Momentum! • Ang. Mom. = mass x rotation speed x “size”

  20. Conservation of angular momentum(Demo)

  21. So, as nebula contracted it rotated faster. It became a flattened disk, like a pizza crust. (Centrifugal hoops demo)

  22. But, clumps in rotating gas tend to disperse. Need modified theory. Solar Nebula: 98% of mass is gas 2% in dust grains Condensation theory: 1) Dust grains act as "condensation nuclei. Also radiate heat => help to cool gas => faster gravitational collapse. 2) Accretion: Clumps collide and stick 3) Gravity-enhanced accretion: objects now have significant gravity => faster growth

  23. Asteroid Belt Perhaps a planet was going to form there. But Jupiter's strong gravity disrupted the planetesimals' orbits, ejecting them out of Solar System. The Belt is the few left behind. And Finally . . . Remaining gas swept out by intense period of solar wind activity.

  24. Planetary Ejection

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