Lecture 17. Solar System Debris

A. Class Business

  1. Late Night Planet Viewing?
  2. Reading for Wednesday -- Ch. 14, Ch. 15
  3. Write Ups

B. Satellites & Rings

  1. Moons
    • most orbit CCW (counterclockwise) from NCP (North Celestial Pole) -- error in text?
        cf., p.230 & p.277
    • two Jovian moons of note:
      • Europa -- seas of water ice beneath frozen surface? (life?)
      • Io -- volcanically active; due to Jupiter's tidal forces
  2. Rings
    • Formation
      1. moon(s) break up -- tidal forces
      2. moon(s) never even formed!
      3. small moon(s) formed, but broken up in collision(s)
    • almost all are within tidal stability limit (fig. 11.15)
      -- no large moons there
    • Structure -- clumpiness due to satellites*








C. Debris

  1. Comets
    • "DIRTY SNOWBALL" is accepted model
      1. we know there's "snow"
        -- water ice (dry ice, CO2, and CO, too)
      2. Q: what's the "dirt"?
        -- satellites say it's "dirt": hydrocarbons
      3. nucleus a few km across
      4. Sun "bakes" gas off, resulting in huge cloud
    • The Comets Three Fates:
      1. Chewed Up -- fragments and/or hits planet,
        a la Shoemaker-Levy 9
      2. Spit Out -- knocked out of closed orbit, never returns
      3. Toyed With -- in ever-decaying orbit 'til it boils away, fragments, or hits something (see 1.) -- 1000 passes tops
    • A Tale of Two Tails* -- point in different directions
      • ION (charged!) tail flows away from Sun, along direction of solar wind
      • DUST tail is debris left along orbital path;
        follows Keplerian orbital path
    • Comets' Origins -- two main sources
      • Oort Cloud -- from 50,000 AU, 10 trillion,
        primordial: have been in deep freeze since beginning
      • Kuiper Belt -- 50 AU




  2. Stones from the Sky
    • METEORS in the sky,
      METEORITES on the ground
    • FALLS (tracked) vs. FINDS (serendipity)
    • most meteors are small -- pea sized, 1 g
    • meteor showers = enhancement of meteor frequency
      1. comets' debris fuels -- new passes recharge
      2. named for constellation of radiant
    • Compostion -- meteorites are STONES or IRONS
      • DIFFERENTIATED or PRIMORDIAL
      • carbonaceus -- complex molecules: amino acids

D. Solar System Formation