Key terms and ideas

1
Solar System AstronomyExam 3 ReviewNovember 9
2004
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• Mars
• Orbit
• Inclination (24?) and rotational period (24.6 hr)
  very similar to Earth
• Orbit is eccentric causes different seasons
• Southern hemisphere has short hot summers
  (perihelion) and long, cold winters (aphelion).
• Northern hemiphere has longer mild summers,
  shorter, milder winters
• Atmosphere very thin (1 of Earths), mostly CO2
• Surface
• Arid, red color due to ferric oxide (rust)
• Polar caps mostly carbon dioxide, but some water
  ice
• Copious evidence of water erosion gt liquid water
  at early geologic time
• Valles Marinaris although probably caused
  initally by tectonic fault later evidence of
  water erosion
• Northern hemispheric ocean (?)
• Craters more craters indicate older surface
• Volcanoes None active now, but largest in solar
  system
• Olympus Mons (500 km across).

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Jovian Planets

• Jovian planetary atmospheres
• Zones-belts atmospheric clouds, colored by
  ammonia, compounds
• Uranus/Neptune blue haze caused by methane
• Storms -driven by ciruclation/Coriolis force.
  Example Juptiers Great Red Spot (long-lived
  storm, seen by Galileo in 1610)
• Differential rotation rotational period varies
  with latitude (equator rotates fastest)
• Jovian planetary interiors
• Mostly Hydrogen/helium (all jovian planets, also
  the Sun)
• Interior dense, hot gt liquid hdrogen (conducts
  electricity, causes magnetosphere)
• Planetary internal heating source of internal
  planets heat radioactivity (terrestrial
  planets), accretional (heat of formation) for
  Jovian planets
• Discovery
• Uranus discovered accidentally by Herschel
  1781
• Neptune discovered by mathematical prediction
  (perturbation of Uranus orbit by Adams/LeVerrier
  1846).

4

• Pluto and KBOs
• Discovered in 1931 (Tombaugh at Lowell Obs.)
• Currently not considered a planet why?
• Unusual orbital characteristics large
  eccentricity, orbital inclination
• Density higher than Jovian planets (not gaseous)
• Considered largest member of Kuiper belt objects
  (KBO)
• Kuiper belt
• Over 100 KBOs known
• Kuiper belt extends from 40 AU to 500 AU
• KBOs are (roughly) in ecliptic plane, prograde
  orbits
• Source of short/intermediate period comets (e.g.
  Halleys comet)
• Oort belt
• Spherical distribution centered on Sun
• Radius 50,000 AU
• Source of long-period comets

5

• Planetary satellites
• Tidal effects
• Occur on satellites close to planet (e.g. Io,
  Mimas)
• Causes internal heating (e.g. Io volcanos), 11
  spin-orbit coupling (same side faces planet, like
  our Moon)
• Also causes gaps in rings (e.g. Cassini
  division/Mimas)
• Triton satellite of Neptune, has retorgrade
  orbit captured?
• Planetary rings
• Seen around all 4 jovian planets
• extremely thin (few km)
• NOT solid surface - small (cm size) particles
  which rotate independently
• Gaps caused by tidal resonance with satellites
  (example Cassini division, caused by Mimas)
• Braids (thin ringlets) caused by sheparding
  satellites

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• Comets
• 3 classes, based on period
• Long period (Plt200y) - orbits randomly oriented,
  probbly from Oort cloud
• Oort cloud spherical, radius 50,000 AU
• Short/intermediate period (Plt200 y) usually
  prograde orbits, from Kuiper belt
• Kuiper belt disk of comets, planetoids near
  ecliptic plane
• Contains rocky/icy bodies, prime example Pluto
• Morphology
• Nucleus 10 km for large comets, mostly ice
  with darky carbon outside (low albedo), show
  ablation jets on Sunward surface dirty
  snowball model
• Coma 105 km surounds nucleus, ablated gases and
  dust
• Tails - up to 107 km long, only seen close to
  Sun ( Mars orbit
• Plasma or Ion tail - points directly away from
  Sun
• Dust tail points directly opposite direction of
  motion
• Halleys comet
• Intermediate period (76 y)
• Discovered to be periodic by Edmund Halley,
  predicted its return (in 1758)
• Visited by Giotto spacecraft 1986 first comet
  nucleus images
• Played key role in Norman invasion of 1066 AD