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Moons, Rings, & Dwarf Planets

Moons, Rings, & Dwarf Planets. Solar System Astronomy Chapter 11. In the Solar System:. Dozens of worlds Rock & ice Diverse properties, only partially understood Offers insight into our ideas/theories of planet formation. Moons. Most larger moons formed with planets Regular moons

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Moons, Rings, & Dwarf Planets

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  1. Moons, Rings, & Dwarf Planets Solar System Astronomy Chapter 11

  2. In the Solar System: • Dozens of worlds • Rock & ice • Diverse properties, only partially understood • Offers insight into our ideas/theories of planet formation

  3. Moons • Most larger moons formed with planets • Regular moons • Some are captured objects • Usually in retrograde orbits • Irregular moons

  4. Major Moons • Four gas giants • Earth • Some are geologically active • Others show evidence of past activity

  5. Many Moons

  6. Formation of Large Moons • The largest moons formed the same way the terrestrial planets did • Major processes: accretion and differentiation • Biggest difference with the terrestrials: composition • more ices (frozen water, methane, &c) • less rock (silicates)

  7. Rings • All four gas giants have ring systems • Swarms of tiny moons • Saturn’s are the largest and brightest • Particles orbit according to Kepler’s laws • orbits are circular • collisions or ring gravity keep them that way

  8. Saturn’s Rings • Very complicated system • thousands of ringlets • bright and dark rings, and “gaps” • gaps are not empty • brightness/darkness indicates amount of material in each • ring system is extremely thin

  9. Rings • Rings don’t contain much material • mass of all the ring particles is about the same as a small, icy moon • Can be distorted by the gravity of nearby moons

  10. Origin of Rings • Ring material is from disrupted moons • Large moons are broken up within Roche limit • Tidal forces • Other sources of ring material • Volcanoes • Impacts • Saturn’s rings formed from an icy moon • Uranus’ and Neptune’s are very dark • Body rich in carbon

  11. Moons & Rings • Rings don’t last forever • Collisions and sunlight would destroy them • Small, nearby shepherd moons can help stabilize • Moons also create gaps • orbital resonance: • orbital period is in a ratio with the moon period

  12. Titan • Saturn’s largest moon • deep, nitrogen-rich atmosphere • Currently being explored by the Cassini spacecraft • Huygens lander revealed icy “rocks” and a soil rich with organic compounds

  13. Titan • Saturn’s largest moon • deep, nitrogen-rich atmosphere • methane and ethane can condense and lead to rain of methane and ethane • Methane is gradually converted to ethane in the atmosphere • Renewed in active geology

  14. Then there’s poor Pluto… • Very small • 1/6 the mass of Moon • Binary planet: moon Charon • properties like comets • eccentric orbit • icy composition (probably) • member of the Kuiper Belt Objects (KBO) • Probably not even the largest

  15. Discovery of Pluto • 1930 Clyde Tombaugh • Existence predicted from disturbances of Neptune • Though it’s too small…

  16. Discovery of Pluto

  17. Discovery of Pluto • Venetia Burney • 1930 • 2007 • Venetia Burney Phair • died April 30, 2009

  18. Pluto • Orbit • 2:3 resonance with Neptune • Comes closer to Uranus than Neptune

  19. Dwarf Planets • Small numbers, but increasing • Pluto • Charon, Nix, Hydra • Eris • Dysnomia • Ceres • Haumea • Hi’iaka, Namaka • Makemake

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