Dr. Henry Throop / University of Colorado Astronomy 1110 June 22, 2000 Lecture 13: Little Bits: Comets, Asteroids, Pluto, and Dust Announcements ------------- Exams Retrograde is _not_ the spin, but the orbit Moon balls HW #3: due now July 3: vacation on monday? Class poll? Observing: 26-Jun-00, Monday Walker Ranch, 8 miles w. of bldr Carpool -- meet in front of Planetarium @ 9:00 Bring barbecue, cookies, froot, beer, chair, blanket/towel, etc? Mtn. Biking -- the _first_ walker ranch trail, not 2nd Mars press conference Minute essays --- Pluto Asteroids --------- Mostly in asteroid belt Mostly potato shaped Mostly rocky About the size of a small planet (moon/merc) if put all together in mass Think of it as a big planetary ring. Collisions Tidal forces Resonances Producing dust Can't stick together, since these resonances keep tearing them apart Resonances In Jupiter system, resonance between Io/Europa/ganymede keeps them all squeezed In Asteroid belt, resonance keeps them broken up. Asteroids are interesting, since so small, and old: nothing's happened to them in age of SS. So, they're little bits that were left around. Other than that, asteroids are boring. They're interesting only for their history of the past. Little woodchips on the floor. No geology now, no volcanoes, no atmospheres, etc. Meteorites: most come from asteroid belt. Kepler's laws don't quite work! Close interactions between asteroids: 'kick' one in or out. Can hit the Earth, Jupiter, or anything it wants to. Changes its orbit. Comets ------ In Kuiper belt or Oort cloud Long, long periods -- not quite keplerian See about -- maybe 10 comets/year. See most comets a few times. Basically, bigger asteroid belt -- much much further out. When we see a comet, it's basically like an asteroid that's been kicked in from asteroid belt -- but dfft. Icy Demo Pic of Oort cloud. Comets Roids --------------------- Icy Rocky 1000 AU 3 AU Oort/Kuiper Asteroid belt Primordial Primordial few km few km atmo near sun no atmo Perturbed orbits Perturbed, complex orbits (mostly circular, but kicked out into elliptical orbits) Produce dust Produce dust QB1's ----- Out beyond Pluto Dust ---- Pluto ----- Is it a planet? Round History of discovery size atmosphere moons like other planets Demo: dry ice + ammonia + bucket + gloves + dirt + water + hammer + bags Demo: christine lavin song VG: turner photo VG: asteroid field VG: Grade dist VG's: from book VG: few comet photos, to point at tail Minute Essays