In Class:
Question to Ponder
Which of the following bodies has the lowest mass?
- a) Mercury
- b) Our Moon
- c) Pluto
- d) Triton
The Kuiper Belt
- Small planetesimals mainly made of ice
- Located just beyond the orbit of Neptune (30-50 A.U.)
- predominantly orbit in the ecliptic plane
- Some people claim that Triton, Pluto, and Charon are just the
largest of these objects (rather than planets and moons in their own
right).
- Probable source of periodic comets (i.e., thoses with 200 year or
less periods).
The Oort Cloud
- Much farther out (10,000-50,000 A.U.)
- Probably a spherical shell surrounding the Solar System
- Objects similar in composition to Kuiper Belt objects
-- mainly ice.
- Source of long period comets (i.e., w/ periods of millions of
years)
Comets
- Icy planetesimals that stray too close to the Sun
- Once they're inside the orbit of Jupiter, they start to sublime.
- Gas and dust sputter off their surfaces
- Creates a large (~1 million mile wide) coma of dusty fog.
- Large coma reflects sunlight, and make the comet noticeable in
the night sky.
Comet Tails
- Radiation pressure from sunlight pushes on dust particles
in the coma.
- gently "blows" the dust material away from the Sun.
- Dust tail forms not behind the comet, but in the direction
away from the Sun.
- The ion tails forms from ionized gas particles in the coma.
- These particles are charged, and feel the magnetic field from the
Sun.
- They become trapped in the solar magnetic fields, and stream
directly away from the Sun.
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